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RISK ASSESSMENT
AND
RISK MANAGEMENT
OF
NON-FERROUS
METALS
Realizing the Benefits and
Controlling the Risks
HAZARD
IDENTIFICATION
EXPOSURE
ASSESSMENT
DOSE-RESPONSE
EVALUATION
RISK
CHARACTERIZATION
RISK
MANAGEMENT
ICME
RISK
COMMUNICATION
A Publication by the International Council
on Metals and the Environment
RISK ASSESSMENT
AND
RISK MANAGEMENT
OF
NON-FERROUS
METALS
Realizing the Benefits
and
Managing the Risks
ICME
A Publication by the International
Council on Metals and the Environment
Dedication
T
his document is dedicated to the memory of Marcel Valtat, the founder and head
of Communications Économiques et Sociales with corporate headquarters in
Paris, France. He brought ICME to the realization that this publication was an
important initiative and led the way in proposing its purpose, scope and content.
Marcel Valtat was born in Paris on March 6, 1923. He spent his childhood in the Morvan,
a rugged and poor region in central France. In 1940, he suspended his studies to join the
French Resistance alongside his parents. Imprisoned by the Nazis for a year, he eventually escaped in 1944. Following the liberation of France, Mr. Valtat became “chef de cabinet” for another Resistance fighter, Charles Tillon, while he was Minister of Air
(1944-1945), Minister of Armaments (1945-1946) and later Minister of Reconstruction
(1947). Mr. Valtat then took a job as a journalist, which he eventually abandoned for reasons of conscience.
In 1957, Marcel Valtat founded the public relations department of the advertising agency
Synergie. In 1964, he set out on his own, establishing the firm Communications
Économiques et Sociales where he quickly put to work interactive methods of communication. Throughout his career, he was admired for his very personable style and
demand for high quality, and for the scrupulousness with which he treated all matters
entrusted to him.
Marcel Valtat passed away in Paris on December 20, 1993.
2
TABLE OF CONTENTS
Foreword
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Acknowledgements
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Executive Summary
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ix
CHAPTER 1. Introduction
......................................... 1
CHAPTER 2. Non-Ferrous Metals: Uses, Properties and Attributes
.5
Typology of Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
What are Metals? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Types of Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Production of Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Occurrence and Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Processing and Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Use of Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Current and Future Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Properties of Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Physical Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Important Properties for Risk Assessment and Risk Management . . . . . . . . . . . . . .13
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
CHAPTER 3. Hazard Identification of Non-Ferrous Metals
The Risk Assessment Framework and Hazard Identification
Data for Hazard Identification . . . . . . . . . . . . . . . . . . . . . .
Epidemiology of Non-Ferrous Metals . . . . . . . . . . . . . . . .
Toxicology of Non-Ferrous Metals . . . . . . . . . . . . . . . . . .
Ecotoxicity of Non-Ferrous Metals . . . . . . . . . . . . . . . . . .
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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CHAPTER 4. Towards Sound Risk Assessment of
Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Dose-Response Evaluation . . . .
Threshold Substances . . . . . .
Non-Threshold Substances . .
Ecotoxicology Dose-Response
Exposure Assessment . . . . . . . .
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Table of Contents
i
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.38
.39
.44
.46
.48
Risk Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
General Principles of Sound Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
CHAPTER 5. Balancing the Risks, Benefits and Costs of
Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Risks . . . . . . . . . . . .
Life Cycle Analysis
Acceptable Risk . .
Benefits . . . . . . . . . .
Costs . . . . . . . . . . . .
Conclusion . . . . . . . .
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.64
.66
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.76
CHAPTER 6. Risk Management of Non-Ferrous Metals
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Risk Management Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
Risk Management Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
Health Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
Joint Industry-Government Environmental Projects . . . . . . . . . . . . . . . . . . . . . . . .83
Pollution Control Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
Phase-Out of High-Risk Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Voluntary Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Worker Health and Safety Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
Risk Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
Pollution Monitoring and Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
Environmental Mangement Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
Product Stewardship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
Technology Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
“Green Design” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94
Future Risk Management of Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Industry-Government Cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Setting Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Matching Risks with Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Innovative New Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Reasonable “Stopping Points” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
CHAPTER 7. Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . 103
CHAPTER 8. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
CHAPTER 9. Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . .
Risk Assessment and Risk Management of Non-Ferrous Metals
ii
113
TABLES, FIGURES, AND BOXES
Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page
1.
2.
3.
4.
Uses of Some Common Non-Ferrous Metals . . .
Some Common Attributes of Non-Ferrous Metals
IARC Carcinogen Classification Scheme . . . . . . .
Standard Safety Factors . . . . . . . . . . . . . . . . . . .
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.11
.14
.31
.41
Figures
1.
2.
3.
4.
A Coordinated Framework for Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x
A Coordinated Framework for Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Example of Dose-Response Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Example of U-Shaped Dose-Response Curve for an Essential Metal . . . . . . . . . . . . .40
Boxes
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12.
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26.
27.
The Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Use of the Term “Metal” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
The Numerous Compounds of a Non-Ferrous Metal . . . . . . . . . . . . . . . . . . . . . . . . . .6
The Future Supply of Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Environmentally Beneficial Uses of Non-Ferrous Metals . . . . . . . . . . . . . . . . . . . . . .12
Essential Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Hypothetical Example of Information Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Example of Confounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Chromium Epidemiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Metals Classified as Possible Carcinogens by NTP . . . . . . . . . . . . . . . . . . . . . . . . . .30
The Example of Copper Ecotoxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Alternative Dose-Response Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Metal Toxicity and Deficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Genotoxic vs. Non-Genotoxic Carcinogens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
The Canadian Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
Ecotoxicity Adjustment Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
Bioavailability and Metals Speciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Importance of Site-Specific Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Principles of Sound Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Bioaccumulation of Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
The Distributional Approach to Risk Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
Example of Metal Toxicity from Industrial Source . . . . . . . . . . . . . . . . . . . . . . . . . . .64
Example of Toxicity from a Metal Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Natural Sources of Metals in the Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
The Relationship Between Release and Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Facility Decommissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
The Importance of Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
Table of Contents
iii
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
Cost Analysis — Three Basic Questions . . . . . . . .
Risk-Risk Tradeoffs . . . . . . . . . . . . . . . . . . . . . . . .
Indirect Health Consequences . . . . . . . . . . . . . . .
Recently Proposed Risk Management Frameworks
Quantitative vs. Qualitative Weighing . . . . . . . . . .
List of Risk Management Strategies . . . . . . . . . . . .
The Belgian Cadmibel Study . . . . . . . . . . . . . . . . .
Emissions Reduction Case Studies . . . . . . . . . . . .
The Leaded Paint Example . . . . . . . . . . . . . . . . . .
Product Labels . . . . . . . . . . . . . . . . . . . . . . . . . . .
Industry-Sponsored Recycling Program . . . . . . . . .
ICME and Product Stewardship . . . . . . . . . . . . . .
A Risk-Based Priority-Setting Approach . . . . . . . .
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Risk Assessment and Risk Management of Non-Ferrous Metals
iv
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Foreword
T
he public is confronted with increasingly numerous and complex messages
regarding the risks they face in their daily lives. Individuals are left with the challenge of making decisions on whether the risks are worth the benefits.
Information provided to the public is variable in quality, and the individual is usually illequipped to determine the validity of the case being communicated in the popular press.
The International Council on Metals and the Environment (ICME) is an advocate of the
use of sound science and analysis with respect to information on the safe production,
use, recycling and disposal of metals. The methodologies used to determine the health
and environmental risks posed by metals have been largely established as an adjunct to
those developed for the assessment of synthetic organic chemicals, based on three primary criteria: toxicity, persistence and bioaccumulation. While these criteria have
served well in defining organic chemicals which require close scrutiny in order to assess
risks and provide appropriate risk management systems, the direct application of these
criteria to metals fails to address the special characteristics of metals.
The late Marcel Valtat of the Paris-based company Communications Économiques et
Sociales encouraged ICME to advance the understanding and knowledge of risk assessment for metals through an easily readable publication. Subsequently, ICME commissioned recognized authorities in risk assessment and disciplines related to minerals and
metals to prepare a book on risk assessment and risk management of non-ferrous metals. Dr. W. G. Jeffery has had a distinguished career in science, engineering and policy
development in both industry and government. Dr. George Gray is Deputy Director of
the Harvard Centre for Risk Analysis of the Harvard School of Public Health. Dr. Gary
Marchant is a scientist and lawyer specializing in environmental matters with the firm
of Kirkland & Ellis in Washington, DC.
A “working draft” was first issued in September 1995 and entitled Risk Assessment and
Risk Management of Non-Ferrous Metals: Realizing the Benefits and Controlling the Risks.
It was sent out to nearly 500 individuals for review and comment. Many comments were
received, notably from the research and academic communities, and were taken into
account in preparing this book for final publication. As well, the editorial structure has
been changed to provide the reader with a general overview and to select salient points
throughout the book without having to study the book at length.
Foreword
v
This book should give both the novice and the professional insights and guidance in
undertaking risk assessment and risk management of metals. It introduces sources, production, properties and uses of metals as a basic introduction to their unique characteristics. The disciplines required in hazard identification, dose-response, exposure and
risk analysis are described in sufficient detail for a good understanding of the process
and its application to metals. The options for risk management are outlined and the role
of proper risk communication is addressed.
Hopefully, this publication will be seen as a substantial contribution to the better understanding and practice of risk assessment and risk management, particularly as they
apply to metals. It should appeal to both those knowledgeable in the field and to those
seeking further insights into risk assessment. It can also provide a valuable guide to
those engaged in policy and decision making related to the control and regulation of
non-ferrous metals.
Readers are encouraged to read and use this book in addressing their own requirements
in the field of risk assessment. They are also encouraged to review the text critically and
comment directly to ICME. ICME would like to incorporate the views and ideas of the
readership in a revised edition as required to achieve a level of quality that can serve the
risk assessment/risk management community for years to come.
Gary Nash
Secretary General
ICME
Risk Assessment and Risk Management of Non-Ferrous Metals
vi
Acknowledgements
T
he expertise, professionalism and energy of the three principal authors — Dr.
George M. Gray, Dr. William G. Jeffery and Dr. Gary E. Marchant — have been
central to the completion of the process that has led to this publication. Their
background is provided on the inside back cover of this book.
ICME would like to extend particular thanks to Ms. Bette Meek, Health Canada; Dr.
Richard Gaunt, RTZ Corporation (UK); Dr. Peter Chapman, EVS Environment
Consultants (Canada); and, Dr. B.K. Davison, BKD Consultants (UK), who read and commented extensively on the draft text. Appreciation is also extended to a number of others who provided insightful comments on the “working draft” of this ICME publication,
including Dr. Joel Barnhart, Harcross Chemical Group (USA); Ms. Marcia Blanchette,
Natural Resources Canada; Dr. John H. Duffus, The Edinburgh Centre for Toxicology
(UK); Dr. John K. Fawell, Water Research Centre (UK); Dr. W. F. Forbes, Statistics
Canada; Dr. Herman Gibb, U.S. Environmental Protection Agency (USA); Dr. Janet D.
Gough, Lincoln University (NZ); Dr. Bev Hale, University of Western Ontario (Canada);
Dr. Michael S. Johnson, University of Liverpool (UK); Dr. S. M. McGill, University of
Leeds (UK); Dr. Colin F. Mills, Rowett Research Institute (UK); Mr. Bob Riley, US
Department of Commerce (USA); and Dr. John Shortreed, Institute for Risk Assessment,
University of Waterloo (Canada).
Special appreciation is expressed for the contribution of Dr. Stuart Dobson of the
Institute for Terrestial Toxicology (UK) who strengthened aspects of environmental risk
assessment in the light of discussions at the International Workshop on Risk Assessment
of Metals and Their Inorganic Compounds in Angers, France, November 13 – 15, 1996.
Acknowledgements
vii
Executive Summary
L
ike all materials, non-ferrous metals have the potential to present risks to public
health and the environment. Those risks must be accurately assessed and properly managed. Much progress has already been achieved in reducing the risks
from non-ferrous metals. Industry, governments, scientists and others are pursuing
additional strategies for managing the remaining risks. All sectors of society now recognize that the production and use of metals, both for existing and new applications,
must be environmentally acceptable.
This publication presents an overview of the risk assessment and risk management of
non-ferrous metals. Techniques and principles of risk assessment and risk management
must take account of the special properties of non-ferrous metals. Risk assessment and
risk management should apply an even-handed, scientifically sound approach to the
variety of substances, products and activities that present risk in today’s society, while
recognizing and accounting for unique properties.
Non-ferrous metals have many special properties, summarized in Chapter 2. For example, non-ferrous metals in one form or another are ubiquitous in the environment, occurring naturally in soil, plants, water and the atmosphere. Each non-ferrous metal can
exist in many different physical and chemical forms (or species) with very different
bioavailable and toxic characteristics. Some non-ferrous metals are essential for life, and
thus too little of such metals can be as hazardous as too much. Metals are elemental
materials that are never created or destroyed by chemical means, but only transferred
from one environmental compartment to another. Metals are also recyclable, which has
a benefits-multiplier effect when the same unit of metal is used over and over again for
different applications. Because of these and other special properties of non-ferrous metals, each application of a non-ferrous metal presents a unique risk and benefit profile.
A key prerequisite to the effective risk management of non-ferrous metals is to accurately assess the risks from specific metal applications. A general paradigm for the risk
assessment process has been provided by the National Research Council, the research
arm of the US National Academy of Sciences. The European Union (EU) uses a similar
framework. The four steps of risk assessment are: (1) hazard identification; (2) doseresponse evaluation; (3) exposure assessment; and, (4) risk characterization. Figure 1
shows these steps and their relation to risk management, the process that uses the output from risk assessment as an input for decision making, along with economic, equity
and legal considerations. Figure 1 also indicates the need for feedback from the risk
Executive Summary
ix
FIGURE 1.
A Coordinated Framework for Risk Assessment
manager to the risk assessor in order to provide some guidance on the level of complexity of analysis required.
The first step in the risk assessment process is hazard identification, which uses sciences
such as toxicology, epidemiology, occupational medicine and ecology to identify the
adverse health and environmental effects associated with exposure to a substance.
Chapter 3 reviews the hazard identification process, including factors that must be considered in applying the traditional hazard identification methods and assumptions to
non-ferrous metals. Hazard identification of non-ferrous metals varies not only by metal,
but also by the specific metal species and route of exposure involved. Hazard identification of non-ferrous metals must also consider that deficiencies of essential metals can be
as hazardous to human health or the environment as excessive levels.
Hazard identification is only the first step in risk assessment, and does not provide an
estimate of risk under identified exposure scenarios. A usable risk assessment also
requires dose-response evaluation, exposure assessment and risk characterization —
which are reviewed in Chapter 4. Sound risk assessment requires at each step in the
process the consideration and weighing of all relevant evidence, acknowledgement of
the assumptions and uncertainties, and presentation of the results in a clear and usable
format. Normally, the uncertainties will be such that a range of risks will be described.
Risk Assessment and Risk Management of Non-Ferrous Metals
x
Risks are only one side of the equation in the risk management of non-ferrous metals.
Benefits must also be considered, as well as the costs of replacing or limiting specific
uses. Chapter 5 summarizes the weighing of the risks, benefits and costs relevant to risk
management of non-ferrous metals. A common theme in evaluating these parameters is
that they are all highly context-specific and depend on the specific metal species and
application at issue. Reasonable decision making requires the balancing of risks, benefits and costs associated with specific uses of non-ferrous metals.
Risk management is the decision-making process which seeks to minimize risks and
costs while maximizing the benefits associated with a substance. Chapter 6 begins by
identifying a series of risk management approaches that have been applied to non-ferrous metals and which have cumulatively achieved major reductions in the risks presented by non-ferrous metals. These risk reductions have resulted from the combined
effects of industry initiatives, government regulation, scientific and technological
advances, and increased public expectations and corporate accountability.
The second part of Chapter 6 addresses some principles to guide future risk management of non-ferrous metals in order to achieve additional risk reductions at acceptable
cost to society. First, cooperative efforts between industry, governments and other interested parties, which utilize the resources and expertise of each, are generally more
effective in achieving efficient risk reduction than unilateral or adversarial approaches.
Second, every potential hazard cannot be addressed simultaneously, and therefore riskbased priorities for future action will need to be established and followed. Third, in
choosing from the hierarchy of possible risk management approaches, it will be important to choose the option that best matches the problem that is being addressed. Fourth,
creative and flexible newer approaches, such as product stewardship and green design,
will be necessary to deal effectively with remaining risks from non-ferrous metals.
Finally, there is need to balance costs, benefits and risks to define reasonable stopping
points for risk management efforts. The wasteful pursuit of zero risk is futile and counterproductive, and no longer considered credible by experts in government, industry and
academia. Rather, the record of the past quarter-century demonstrates that realistic and
scientifically credible risk management goals are most effective in promoting public
health and the environment, as well as the productivity and the general well-being of
society.
Executive Summary
xi
CHAPTER 1
Introduction
P
eople throughout the world use and benefit from a multitude of non-ferrous metals in their daily lives. Copper is used in electrical wiring, zinc is used to protect
cars and other products against corrosion, and aluminum is used to make soft
drink cans. Coins are commonly made of nickel, copper or zinc. Batteries for starting
automobiles are made of lead, while nickel-cadmium batteries power tools, computers
and communications devices. But perhaps even more important are the myriad “behindthe-scenes” roles that metals play in manufacturing, construction, communications,
defence and transportation applications. Today, metals are being used extensively in the
expanding spectrum of “high technology” fields, and more sophisticated uses are being
developed for the future. These uses may not be obvious to most of the general public,
but they are essential to the infrastructure and functioning of today’s society.
Box 1: The Non-Ferrous Metals
The most important non-ferrous metals in terms of production and value are aluminum, copper, lead, nickel, tin and zinc. Along with their extraction there is also
substantial production of gold, silver, platinum, cobalt, selenium, cadmium, bismuth, and a number of other minor metals.
The growing use of non-ferrous metals has been accompanied by an evolving understanding of the potential health and environment effects of metals. Like all materials,
metals have the potential to pose risks to health and the environment. Those risks are
highly context-specific, varying substantially depending on the metal, its particular form,
and the circumstances of its use. Each metal application involves its own unique profile
of risks and benefits.
In common usage, the term “metals” refers to substances with a distinctive lustre, high
specific gravity, good conductivity of heat and electricity, and which are often ductile and
malleable under heat and pressure. It is these properties of metals that generally make
them so commercially useful. But in assessing and managing the risks of non-ferrous
metals, it is important to consider not only the metallic forms in which these materials
Chapter 1 - Introduction
1
exist in commercial use, but also the various chemical compounds in which they usually exist in the environment and in living organisms.
Box 2: Use of the Term “Metal”
The term “metal” usually refers to the metallic form of an element such as aluminum, copper, lead, nickel or zinc. Most commercial and industrial applications
of these elements involve the metallic form. In nature, however, few non-ferrous
metals occur in their elemental form, and then only in very small amounts. Most
metallic elements exist in nature as chemical compounds which do not exhibit
metallic attributes as, for example, oxide and sulphide minerals. Most environmental exposures to non-ferrous elements involve exposures to metal compounds
or ions rather than the elemental metal, and the various compounds of a given
metal often differ significantly with respect to bioavailability and toxicity. Although
for convenience the term “metal” is often used broadly to include a metal and all
its compounds, including in this book, it is important to remember that each chemical substance involving a metal element in its composition, including the elemental form itself, must be considered individually because of its very different
properties.
Given the importance of context in the assessment and management of risks from nonferrous metals, it is critical to clearly differentiate the terms “risk” and “hazard.” Hazard
is the intrinsic property of a substance to cause an adverse effect at some dose.
Assessment of dose-response and exposure is necessary to characterize whether a risk
is significant or not. Risk is the likelihood and magnitude of adverse effects under
defined exposure conditions. Because the potential of a given non-ferrous metal application to cause harm varies greatly depending on the specific form and exposure conditions involved, it is necessary to base risk management decisions on real-world
assessments of risk rather than more abstract hazard identifications.
All sectors of society now recognize that the production and use of metals, both for existing and new applications, must be environmentally acceptable. Governments and industry have key roles in ensuring that metals are produced and used safely. Governments
have accumulated substantial experience in environmental regulation, and industry has
assumed greater accountability for the environmental performance of its facilities and
products. But neither government nor industry can rely solely on regulatory compliance
to ensure levels of risk that are acceptable to society. Rather, new approaches and strate-
Risk Assessment and Risk Management of Non-Ferrous Metals
2
gies are needed to supplement regulation and to ensure that metals are produced, used
and disposed in environmentally sound ways.
Much progress has been achieved in reducing the risks from non-ferrous metals. Many
of the remaining environmental problems can only be solved at a cost acceptable to society if government, industry and other interested parties combine their respective
resources and expertise in search of common solutions. There will continue to be legitimate differences on some issues, but there is growing consensus that effective environmental stewardship requires greater flexibility and cooperation by both government and
industry.
Risk Assessment and Risk Management of Non-Ferrous Metals has been prepared by the
International Council on Metals and the Environment (ICME) to further these goals.
ICME represents the commitment of each of its members to operate their businesses in
the non-ferrous metals industry in an environmentally responsible manner. This ICME
publication has been prepared in order to advance the understanding of the special characteristics of metals, the information needs to support appropriate risk assessment and
risk management of metals, and an understanding of the relevant scientific, regulatory
and management processes.
This publication may be of interest to executives, managers, scientists, engineers, regulators, medical professionals, economists, lawyers, regulators and the media. The intent
is to offer a relatively concise overview of the principles, methodologies and applications
of sound risk assessment and risk management as applied to non-ferrous metals. While
some of the traditional tools and approaches of risk assessment and risk management
apply to non-ferrous metals as they do to other materials, such application must reflect
the special properties of non-ferrous metals. This publication focuses, where appropriate, on the aspects in which non-ferrous metals differ from other regulated materials
such as organic chemicals.
Because risk management and risk assessment involves a wide scope of disciplines and
specialist input, the different chapters of this publication may be of varying interest and
familiarity to a given reader depending on his or her own areas of expertise. The
Executive Summary, together with the Acronyms and Glossary sections at the back of the
book, may be most useful to the media and to busy managers. Chapter 2 is for those who
are unfamiliar with the fundamentals of non-ferrous metal production, trade and uses.
Chapters 3 to 6 are intended for management and professionals with an interest in nonferrous metals who seek an understanding of the steps to be considered in risk assessment and risk management. Hopefully, the publication as a whole contributes a
balanced presentation of the “science and art” of environmental management of non-ferrous metals that will be of benefit to today’s global society.
Chapter 1- Introduction
3
CHAPTER 2
Non-Ferrous Metals: Uses,
Properties and Attributes
This chapter describes non-ferrous metals and their uses,
attributes and special properties. Each non-ferrous metal offers a
unique combination of useful attributes — such as strength,
hardness, malleability, and electric and thermal conductivity.
Past, present and future applications of non-ferrous metals are
based on the attributes of each metal. In addition to these physical
attributes, non-ferrous metals have special properties that
distinguish them from many other regulated substances. These
properties — including that non-ferrous metals are ubiquitous in
nature, exist in many different forms or species, are highly
recyclable, and are in many cases essential nutrients — must be
taken into account in the risk assessment and risk management of
non-ferrous metals.
N
on-ferrous metals are used by society in many different applications. To maximize the net benefits from those applications, non-ferrous metals must be produced, used and disposed safely through sound assessment and management of
the potential risks associated with each application. Both the benefits and risks of nonferrous metals are, in large part, a function of their many special properties. This second chapter therefore describes non-ferrous metals and their production, uses and
properties, and reviews those key aspects of such metals that are important for risk
assessment and risk management.
Typology of Metals
What are Metals?
Technically, the majority of the elements in the periodic table are classified as “metals”
based on scientific criteria for their chemical properties. In everyday use, and in this
book, the term “metal” is used to characterize a more limited class of substances all of
which at room temperature, except mercury, are crystalline solids in their elemental
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
5
form. These materials are readily recognized by their distinctive lustre, high specific
gravity, good conductivity of heat and electricity, and their general malleability under
heat and pressure. A substance that exhibits these metallic properties in its elemental
form is defined as a metal. As discussed in the Introduction, the term “metal” is often
used broadly, including in this book, to include all chemical forms and compounds in
which an element with metallic properties exists, with the important caveat that different physical forms of the same metal often present very different properties.
Various metals can be combined with other elements to form alloys that have different
properties than their individual constituents. For example, copper alloys with tin to form
bronze, with zinc to make brass, with aluminum to form aluminum brasses and bronzes,
and with silicon or nickel to form a variety of alloys. Modern alloys are carefully
designed by varying the proportions of constituents to obtain a material with specifically desired physical properties. Thousands of alloys are currently available as industrial
materials, most precisely defined according to international standards. Ongoing
research and development efforts are continually identifying new alloys with improved
characteristics.
In addition to alloys, metals can react chemically with other substances to form an array
of compounds that have vastly different physical and chemical properties. Many of these
metal compounds are intentionally produced for important industrial uses.
Furthermore, metals are also present in nature in various ionic chemical forms or
species. As discussed in subsequent chapters, the different species in which a metal may
exist can have important consequences for the metal’s bioavailability and toxicity.
Box 3: The Numerous Compounds of a Non-Ferrous Metal
Each non-ferrous metal can exist not only in the metallic form, but also as an ion
in solution and in a number of different compounds. For example, cadmium exists
in a number of distinct inorganic chemical compounds displaying different characteristics, including the following:
•
•
•
•
•
Cadmium
Cadmium
Cadmium
Cadmium
Cadmium
oxide
cyanide
fluoride
chloride
sulphide
•
•
•
•
Cadmium
Cadmium
Cadmium
Cadmium
formate
fluorosilicate
iodide
sulphate
Risk Assessment and Risk Management of Non-Ferrous Metals
6
Types of Metals
Metals are often classified into different categories, such as ferrous and non-ferrous metals. The term “ferrous” is derived from the Latin word “ferrum” for iron, which is the
fourth most abundant element by weight in the Earth’s crust. Ferrous metals are those
containing a major amount of iron, such as the many types of steel. Common usage
applied to ferrous metals in industry also includes the metals chromium, nickel, manganese and molybdenum since their dominant use is in the manufacture of steel and
steel alloys. However, they are often co-products of the extraction of non-ferrous metals, and do have other uses unrelated to steel production.
Non-ferrous metals do not contain significant amounts of iron. The major industrial
non-ferrous metals include aluminum, copper, lead, nickel, tin and zinc. Minor non-ferrous metals include bismuth, cadmium, titanium, selenium and many others. Another
category of metals is the precious metals, which include gold, silver and the platinum
group metals. Precious metals are extracted and processed for their own intrinsic value,
but they are also recovered as by-products from many non-ferrous metal mining and
metallurgical operations.
Production of Non-Ferrous Metals
Occurrence and Extraction
All metals are extracted from the Earth’s crust, the thin outer shell that is accessible to
mining and quarrying. Non-ferrous metals occur naturally, usually in the form of compounds with other substances, throughout the rocks of the Earth’s crust in very small
quantities. For example, the metal content of igneous and sedimentary rocks can range
from 2 to 200 parts per million (ppm) for copper, 1 to 150 ppm for lead, 2 to 3,600 ppm
for nickel, and 2 to 1,500 ppm for zinc.1
A few metals are stable in their elemental form, the most well-known being copper and
gold, but the elemental forms are generally rare occurrences in the natural environment.
The bulk of the metallic elements exist within many different minerals that comprise
chemical combinations with more abundant elements to form silicates, oxides, sulphides, sulphates and the like. Each mineral has its own crystalline form and specific
chemical and physical characteristics.
1
Thornton, Iain. 1996. Metals in the Global Environment: Facts and Misconceptions. International Council on
Metals and the Environment. Ottawa, Canada.
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
7
The normal process of weathering of rocks and the chemical breakdown of their minerals disperses metals into soils, waters and the air. Consequently, all metals are an inherent part of the natural environment, occurring in a great variety of forms or species.
They are found in the geosphere (rocks, soils), the hydrosphere (surface and ground
waters, oceans), the atmosphere (though volcanic eruptions, dust and fires), and the
biosphere (which defines the environmental circumstances where metals come into
contact with living organisms, including humans). Metals are therefore a fundamental
and natural part of all life forms, and an inherent part of the food chain of all organisms.
Indeed, many are, at certain levels of concentration, essential nutrients for healthy life
forms. Apart from the natural occurrence of metals, society’s industrial and modern
agricultural practices have led to the introduction of additional metals into the environment, and these are described as anthropogenic sources.
The extraction of metals from the earth is economically feasible only from highly
enriched occurrences of metals that are sufficiently large to make mining feasible. The
degree of concentration of the metal in the rocks is termed the grade. Where the grade
and the mass of the mineralization are such that extraction appears to be economically
viable, the material is defined as ore, and the mine is developed on the basis of the ore
body. Deposits of non-ferrous metals usually contain a combination of metals, called a
poly-metallic mineral deposit. Some typical naturally occurring combinations of metals
include lead with zinc, copper with zinc, and nickel with copper.
The first step in metal extraction is mineral exploration, the process of discovering mineral deposits. Exploration is essential for maintaining an inventory of reserves, and
therefore mining companies invest significant resources in exploring for new mineral
deposits. The techniques involved are many and varied, but essentially include the study
of rocks and crustal structures (geology), the detection of mineralization by searching for
the physical characteristics such as magnetism or conductivity of the minerals or species
(geophysical), and the identification of enrichments of naturally occurring metals in surface waters and plant life (geochemical). Once a promising deposit has been identified,
the cost and feasibility of developing the deposit must be evaluated.
Mine development is a capital-intensive undertaking that requires long-term, front-end
investment. It usually takes two to six years to develop a mine before the first returns
are available to the investors, with costs ranging from approximately $US100 million to
over $US1,500 million. Because mines must be located where ore bodies are found,
which often are in remote areas, substantial investments are required for the infrastructure needed to support a mine, such as roads, rail, airstrips, water supply, power supply,
housing, and community facilities. Long-term planning is complicated by evolving technologies, new material standards, changing transportation modes, demographic trends,
new government taxes and legislation, and fluctuations in the economy that affect costs,
prices and demand. Concern for local, regional and global environmental and human
Risk Assessment and Risk Management of Non-Ferrous Metals
8
health impacts has also become an integral part of the planning process, and uncertainties about future regulatory requirements also increase the risks of mine development.
Box 4: The Future Supply of Non-Ferrous Metals
Over the centuries, known reserves of non-ferrous metals have continued to
expand as a result of new exploration, improved exploration technologies (such as
remote sensing and sophisticated geochemical and geophysical methods to
detect ores), and new techniques to economically mine ore and extract metal from
lower grade deposits. According to the US Bureau of Mines, known world
reserves have increased over the past 40 years by 622 percent for copper, 387
percent for lead and 546 percent for zinc. The growth of estimated reserves has
thus far outstripped the growth of primary metals production, and there have been
no commercial shortages of non-ferrous metals — despite occasional predictions
of impending mineral exhaustion, such as those by the Club of Rome. These predictions have consistently proven to be unfounded, and there is no reason to
believe the future will be any different (Crowson 1992). While there appears to be
no risk that the world will run out of metals in the foreseeable future, common
sense dictates that full use should be made of reserves. One problem is that the
imposition of excessive costs on a mining operation can lead to “high grading,”
which results in leaving lower grades of ore in the ground. The imposition of such
costs can therefore be contrary to conservation goals.
Processing and Manufacturing
After the ore is mined, it is crushed and milled, usually at or near the mine site. The
milling process involves the grinding, separation and concentration of metal-bearing
mineral from the waste rock to form concentrates. Whereas mined ore often has a metal
concentration of less than one percent, concentrates usually have metal contents (in the
form of metal sulphides or oxides) of over 10, and up to 70, percent. These metal sulphide or oxide concentrates are shipped to smelting facilities for further separation and
purification of the metal using pyrometallurgical and electrolytic processes. Refined
metals are produced to standard industrial specifications of purity. An extremely high
degree of purity can be achieved at additional cost for certain small-volume specialty
uses. The refined metal is provided to fabricators or specialty chemical manufacturers
for production of alloys, intermediate shapes or industrial chemicals, or shipped directly to manufacturers for production of a variety of industrial and consumer products.
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
9
Recycling
An important aspect of non-ferrous metals is their recyclability. As elements, metals can
be salvaged and recycled repeatedly, especially from products in which the metal is not
released to the environment in significant quantities during product use. The supply of
metals thus involves two streams: (i) the production of primary metal from mining; and,
(ii) the secondary production of refined metal and alloys through recycling of industrial
and post-consumer scrap. To be recycled, scrap metal must be separated, sorted, compacted, remelted and/or re-refined and recast. These combined steps are generally
more labour-intensive, but less energy- and capital-intensive, than the primary production of metals. Recycling significantly reduces the quantity of primary metal that must
be mined and processed to meet demand.
Use of Non-Ferrous Metals
History
The use of non-ferrous metals is prevalent throughout human history and around the
world. Copper, lead and tin have been in circulation since antiquity. They were used by
early societies to make better implements for hunting and warfare. As human civilization advanced, metals assumed an increasingly prominent role. Indeed, it was the discovery of an admixture of copper and tin to form the alloy bronze that helped bring about
the advances in the era appropriately termed the “Bronze Age.” The Roman Empire further expanded the use and reliance on non-ferrous metals, including tin imported from
England, copper from Cyprus and lead from Spain.
From the dawn of the industrial age, non-ferrous metals have played a central role in
activities that include manufacturing, transportation, defence, agriculture and construction. In addition to the traditional metals and alloys that have been used for many centuries, “new” metals such as nickel, aluminum and magnesium were “discovered” as a
result of advances in the chemical separation of mineral compounds. The uses of nonferrous metals have continued to expand throughout the years, and today non-ferrous
metals are used in tens of thousands of different applications.
Current and Future Uses
The versatility of non-ferrous metals is demonstrated by the continuing discovery of new
applications. Aggregate use of non-ferrous metals has increased steadily for the last 100
years despite substitution by plastics and other materials in some individual applications.
Non-ferrous metals have continued to be used in increasingly sophisticated applications
in the traditional metal-using industries, and have provided many lasting aesthetic ben-
Risk Assessment and Risk Management of Non-Ferrous Metals
10
efits through their use in adornments, sculptures, memorials and other architectural features. In addition, many essential applications of non-ferrous metals have developed in
rapidly emerging high-technology industries such as microelectronics, computers, medicine and telecommunications.
TABLE 1.
Uses of Some Common Non-Ferrous Metals
Non-Ferrous Metal
Major Applications
Aluminum
•
•
•
•
•
•
Transportation
Building and Construction
Containers and Packaging
Electrical
Consumer Durables
Machinery and Equipment
Copper
•
•
•
•
•
Electric/Electronic Equipment and Wiring
Building Construction
Industrial Machinery and Equipment
Autos and Other Transportation
Others - Pigments, Agriculture, Medicine,
Preservatives, Water Purification
Lead
•
•
•
Lead-Acid Batteries
Protective Radiation Shielding
Electronics
Nickel
•
Stainless Steels used in Chemical, Petroleum
and Transportation Industries
Plating
Foundries
Batteries and Fuel Cells
Catalysts
Coinage
•
•
•
•
•
Zinc
•
•
•
•
Galvanized Coatings used for Autos, Wire Ropes, etc.
Assembly Line Die-Casts used in Engines, Auto Trim,
Light Equipment and Tools
Brass used in Heat Exchange Equipment, Plumbing
and Hardware
Others - Batteries, Chemical Catalysts, Agriculture,
Cosmetics and Medicine
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
11
The uses and markets for non-ferrous metals are highly varied and depend on the specific metal. Nickel goes primarily to the steel industry for production of stainless steel
and to manufacturers of consumer and industrial batteries. Some nickel is also used in
chemical plating and jewellery, and by many other consuming industries. The major
uses of zinc are in galvanizing steel and in die casting. Lead is sold primarily to battery
manufacturers and to producers of ammunition, solder and fabricated lead products.
Copper has a wide range of applications in capital goods, housing and consumer
durables. Current uses of some common non-ferrous metals are summarized in Table1.
Box 5: Environmentally Beneficial Uses of
Non-Ferrous Metals
The central risk management issue for most products, including those made with
non-ferrous metals, is whether they present risks to the environment and public
health that are acceptable to society. For some applications of non-ferrous metals, however, the very purpose of the product is to help protect human health and
the environment. For example, non-ferrous metals are a major component of a
new generation of high energy density batteries for electric vehicles which are
expected to play a key role in achieving clean air and energy conservation goals.
The leading candidate for first-generation electric vehicle batteries is the
advanced lead-acid battery, while other emerging battery technologies rely on
zinc, nickel and other metals. Other examples of new uses of non-ferrous metals
for environmental and human health protection include the recent development of
a sheet-lead radon barrier for use under buildings to protect against radon exposure, the use of aluminum foil for food preservation, and the use of nickel in
advanced air pollution control equipment such as flue-gas scrubbers. The extensive use of chromium and nickel in stainless steel for household kitchens and in
industrial food processing has decreased the possibility of bacterial infection due
to improved cleaning properties.
The uses of non-ferrous metals have evolved throughout history — and the many attributes of these materials suggest that they will continue to have important roles in the
future. While some uses of metals have been phased out because of the availability of
better substitutes, the consequences of changing technology or environmental concerns,
an ever-expanding spectrum of new, environmentally sustainable uses of non-ferrous
metals are appearing that take advantage of the physical and chemical attributes of these
materials. For example, some new applications of non-ferrous metals will help to reduce
Risk Assessment and Risk Management of Non-Ferrous Metals
12
pollution and protect human health (see Box 5). Additional new uses of non-ferrous metals that may be increasingly important in the future include computer and video equipment microelectronics, superconductors, medical diagnostic technologies, improved
corrosion protection, “smart” military technologies such as guidance and sensing systems, new metal alloys with applications in a variety of industrial and consumer products, lead-lined shields for nuclear waste disposal applications, and new power
generation technologies using liquid metal magneto-hydrodynamics.
Properties of Non-Ferrous Metals
Physical Attributes
The many uses of non-ferrous metals is a reflection of the many attributes that these
materials provide. Each non-ferrous metal and alloy offers its own unique combination
of properties and characteristics that make it well-suited for particular applications.
For example, the high specific gravity and malleability of lead, as well as its electrochemical properties, make it useful for many applications in a variety of industries.
Copper is valued for its superior electrical and thermal conductivity, great tensile
strength and resistance to corrosion. Zinc has a low melting point and is very fluid, and
is useful for its “galvanic” action that can protect iron and steel from corrosion in the
presence of moisture. Nickel as a ferro-alloy provides toughness, strength and ductility
over a wide range of temperatures. Aluminum provides a unique combination of
strength with exceptional lightness. A list of some of the useful attributes of various nonferrous metals and alloys is provided in Table 2.
Important Properties for Risk Assessment and Risk Management
Non-ferrous metals have a number of special characteristics that must be considered in
risk assessment and risk management, including the following:
1. Elemental Substances: Non-ferrous metals are usually marketed and used in their
metallic (elemental) form with varying degrees of purity, unlike most regulated substances that are manufactured chemical compounds, polymers or composite materials.
As elements, metals cannot be created or destroyed by chemical means. Metals are not
added to or removed from the environment — they are only transformed from one form
to another and transferred from one environmental compartment to another, which can
dramatically affect the availability and thus potential risks from the metal.
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
13
TABLE 2.
Some Common Attributes of Non-Ferrous Metals
Attribute
Description
Example2
Appearance
Castability
Corrosion Resistance
Electrical Conductivity
Energy Efficiency
Attractive colour and lustre
Ability to take up the detail of a mould
Resistance to corrosion from air/water
Ability to conduct electricity
Contribution to energy savings through
material substitution
Hardness
Magnetic Properties
Resistance to deformation
Ability to generate magnetic field
Malleability
Strength
Ability to undergo shaping or
mechanical working without rupture
Resistance to applied stress
Brass
Zinc
Copper
Copper
Aluminum
(e.g., lighter
vehicles)
Nickel
Nickel
alloys
Lead
Thermal Conductivity
Ability to conduct heat
Nickel
alloys
Copper
2. Ubiquitous: Non-ferrous metals are naturally occurring elements that are ubiquitous in soils, waters and the atmosphere, mostly in oxide and sulphate forms. Many nonferrous metals are present in significant quantities in the Earth’s crust.3 Aluminum is by
far the most prevalent and accounts for 8 percent by weight of the Earth’s crust as a constituent of the silicate and oxide minerals that form various rock types. Through weathering and other natural processes, metals in one form or the other from the Earth’s crust
are continually redistributed in soils, waters and the atmosphere. Humans and all other
organisms have therefore always been, and will always be, exposed to metals through
natural processes. Indeed, biogeochemical exploration techniques are used to measure
minute metal concentrations in plants and surface waters in the search for potential ore
bodies.
2
3
Although only a single metal example is given for each property, many of the properties are exhibited by several different metals.
Wedephol, K.H. 1991. The composition of the upper Earth’s crust and the natural cycles of selected metals.
Metals and Their Compounds in the Environment: Occurrence, Analysis, and Biological Relevance. E. Merian,
ed. Weinheim, New York, NY.
Risk Assessment and Risk Management of Non-Ferrous Metals
14
3. Speciation: Non-ferrous metals exist in many different chemical and physical forms.
The bioavailability, solubility, environmental distribution and toxicity of metals depend
very significantly on the type of metal species involved. Unlike organic chemicals, where
the total amount of the substance in the environment is a relevant factor for determining risk, the total amount of a metal in the environment is much less relevant than the
quantity of different metal species present and their bioavailability. For example, aluminum exists in different forms depending on the pH and other factors, with substantial
differences in toxicity. While the significance of metal speciation has been recognized in
the scientific community for many years, it has usually not been given adequate emphasis in risk assessment and risk management, often because of insufficient data on specific metal species. New research is helping to distinguish the different risks that are
associated with different metal species, which should permit increased attention to metal
speciation in regulatory decision making.
4. Essential Nutrients: Many non-ferrous metals are essential nutrients for humans
and other organisms. As one recent review summarized, “all living species are absolutely dependent on the presence of metal salts in their food in order to maintain their life
and reproductive capacity. The reason for this resides in the evolutionary development
of the organisms. The first living cells probably developed in a ‘primeval soup’ which
contained, in dissolved state, all elements present in the Earth’s crust at that period.”4
Because non-ferrous metals are abundant constituents of the Earth’s crust, it is not surprising that life forms have become dependent on many metals. Inadequate availability
of essential metals can lead to serious health or environmental problems as much as can
an over-abundance of the same metals.
5. Bioavailability: The bioavailability of a non-ferrous metal, which is the pathway
from the environment to life forms, is greatly affected by the many different degrees of
chemical stability, solubility and mobility of the myriad mineral and chemical forms in
which a metal can occur. Metal species (particularly those in solution) are inherently
labile, in that they have a tendency to change form in different environmental conditions.
Metals are subject to a variety of physico-chemical processes, including complexation
and disassociation, oxidation and reduction, precipitation and dissolution, and adsorption and desorption. In addition, some metals may undergo microbial transformations,
such as oxidation/reduction or methylation/demethylation reactions. These transformations are reversible and can either increase or decrease the availability of metals,
depending on local physico-chemical conditions. Unlike organic compounds which
remain soluble in the environment, many metal species have a tendency to convert over
4
Kieffer, S. 1991. Metals as essential trace elements for plants, animals, and humans. Metals and Their
Compounds in the Environment: Occurrence, Analysis, and Biological Relevance. E. Merian, ed. Weinheim, New
York, NY.
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
15
time to less soluble and immobile forms that are not bioavailable. The bioavailability
and hazard potential of a given metal can vary greatly between different types and
species of metals. The bioavailability of a metal species, rather than the total quantity
present in the environment, is therefore the critical factor determining exposure potential.
Box 6: Essential Metals
Non-ferrous metals essential for humans and other animals include:
Cobalt
Molybdenum
Copper
Selenium
Manganese
Zinc
Non-ferrous metals essential for plants include:
Copper
Nickel
Manganese
Zinc
Molybdenum
6. Recyclability: Metals can be recycled, and are one of the few materials that do not
degrade or lose their chemical and physical properties in the recycling process. The
market price for metals usually provides sufficient economic incentives for recycling,
although some countries have chosen to subsidize recycling industries either by direct
subsidy or by regulation that transfers to the consumer the cost and labour associated
with collection and segregation of post-consumer scrap. Recyclability acts as a benefitmultiplier for purposes of risk management, because each unit of metal produced can be
used over and over for a variety of applications.
7. Co-Production: Many non-ferrous metals are produced jointly as a by-product or
co-product of other metals that are found together in poly-metallic mineralized deposits.
For example, zinc and lead are often produced jointly from the same mines. The economic viability of operating a mine will often depend on obtaining adequate revenues
from each of the metals produced by that mine. A market downturn or regulatory
restriction for one metal may therefore make an entire mining operation uneconomical.
Accordingly, regulatory proposals for metals should not only consider the reduced benefits that may result from directly or indirectly limiting a specific metal, but also the
increased costs and reduced benefits that may result from less co-product production.
Risk Assessment and Risk Management of Non-Ferrous Metals
16
8. Commodities: Non-ferrous metals are commodities rather than proprietary chemicals like many other regulated substances. In other words, there are in principle no
characteristics to distinguish one unit of a pure metal (such as copper) from another
unit, although in practice metal quality does vary to some degree, and the grades of
metal produced by some producers may be preferred over others. As commodities, metals are primarily sold and brokered on international markets. The commodity nature of
metals has several consequences. A competitor that does not have to comply with strict
regulations for manufacture of metals or metal-containing products in its country of production can export its products into markets where domestic competitors must comply
with stricter regulations governing the production process. Such disparities do not warrant less environmental protection in the nation with stricter regulations, but they
demonstrate that industry and government in regulated nations have a common interest
in ensuring that regulation achieves its protective goals as cost-effectively as possible to
minimize the international competitive impact of regulation. The commodity nature of
metals also makes it difficult to track and control the downstream use of metal produced
by an individual metal producer. Accordingly, industry-wide action and coordination is
necessary to best promote the safe use of a given metal.
Conclusion
Non-ferrous metals offer a variety of attributes and properties that make possible a multitude of applications. While the uses of non-ferrous metals have changed over time,
non-ferrous metals continue to perform many vital applications now and in the future in
both developing and developed nations. Each non-ferrous metal is unique, and the risks
and benefits of each application of a particular metal must be evaluated separately to the
extent permitted by available data. Nevertheless, non-ferrous metals share several
important properties in common. For example, all non-ferrous metals are elemental
substances found ubiquitously in nature in many different chemical and physical mineral forms or species. Other important properties of non-ferrous metals are that they are
recyclable and in many cases are essential nutrients to all life forms. As discussed in
subsequent chapters, several of these characteristics of non-ferrous metals differ from
other regulated substances such as organic chemicals, and must be taken into account
in the risk assessment and risk management processes.
Chapter 2 - Non-Ferrous Metals: Uses, Properties and Attributes
17
CHAPTER 3
Hazard Identification of
Non-Ferrous Metals
Like all materials, non-ferrous metals can present risks to human
health and the environment in specific contexts and applications.
A key prerequisite to the effective management of the risks from
non-ferrous metals is to identify and quantify those risks using
sound science. The first step in this risk assessment process is
hazard identification, which uses sciences such as toxicology,
epidemiology, ecology and occupational medicine to identify the
adverse health and environmental effects potentially associated
with a substance. This chapter reviews the hazard identification
of non-ferrous metals, including special characteristics of nonferrous metals that must be considered in applying traditional
hazard identification methods and assumptions. Hazard
identification of non-ferrous metals should focus on specific metal
species, and must take into consideration that both excesses and
deficiencies of essential metals can be hazardous.
M
etals are of keen interest in the world of science. Many non-ferrous metals are
essential nutrients for humans, animals, plants and microorganisms — playing
an important role in growth and development, the generation of energy from
food, and protection from harmful substances and diseases. Metals can also cause
adverse effects under certain circumstances, some of which have been recognized and
studied for at least 2,000 years. Scientists have found that different metal compounds
have different toxic potentials, that route of exposure is often important in determining
adverse effects of metal exposure, and that metals have the potential for enhancing, or
damaging, the functioning of natural ecosystems. The ways in which humans use and
manage metals, in addition to natural sources of exposure, are key factors influencing
potential health and environmental risks.
The widespread use of metals and known examples of metals toxicity have stimulated
efforts to assess the health and environmental risks of non-ferrous metals and to develop appropriate protective strategies. The large scientific database that now exists for
Chapter 3 - Hazard Identification of Non-Ferrous Metals
19
many metals, and the relative ease with which metals can be detected and measured,
have resulted in intense scrutiny by scientists and regulators. The potential hazards of
many metals in air, soil, drinking water, sewage discharge, the food chain, and plant and
animal tissues have been widely studied. Despite this, the demand for assessing the
risks of non-ferrous metals will probably only increase in the future, and additional data
will be needed to support such assessments. In addition to adequate data, sound risk
assessment of non-ferrous metals must be based on the scientifically based principles
discussed in this chapter and the next.
The Risk Assessment Framework and
Hazard Identification
Risk assessment is the scientific process by which risks are identified, estimated and
evaluated. A general framework for risk assessment has been provided by the US
National Research Council, a committee of the National Academy of Sciences.5 The
European Union (EU) uses a similar framework.6 The four steps of risk assessment are:
FIGURE 2.
A Coordinated Framework for Risk Assessment
5
6
National Research Council. 1983. Risk Assessment in the Federal Government: Managing the Process. National
Academy Press, Washington, DC.
See, for example, Commission Regulation 1488/94, especially Article 3, §1 Laying Down the Principles for
Assessment of Risks to Man and the Environment of Existing Substances in Accordance with Council Directive
67/548/EEC.
Risk Assessment and Risk Management of Non-Ferrous Metals
20
(1) hazard identification; (2) dose-response evaluation; (3) exposure assessment; and, (4)
risk characterization. These four steps of risk assessment and their relation to risk management and risk communication are shown schematically in Figure 2. The dotted line
denotes the need for feedback to the risk assessor for guidance as to the scope of analysis required for the risk management.
This chapter addresses hazard identification of non-ferrous metals, the first step in risk
assessment, while the next chapter reviews the subsequent steps of the risk assessment
process. Hazard identification is defined by the US National Academy of Sciences as “the
process of determining whether exposure to an agent can cause an increase in the incidence of a health condition (cancer, birth defect, etc). It involves characterizing the
nature and the strength of the evidence of causation.”7 As the starting point for risk
assessment, hazard identification is a key step in the evaluation of health and environmental risks. But because it is only the first step in risk assessment, and does not provide information on the existence and magnitude of either exposure or risk, hazard
identification is an inappropriate basis for regulatory decisions. However, it may provide
a useful screening tool to identify substances that should be further evaluated in the subsequent steps of risk assessment and is used as a basis on which to classify and establish
precautionary information for those who might be exposed in the course of handling or
using such substances.
A risk assessment will only be as good as the hazard data that are available and used in
the initial hazard identification step. It is therefore imperative that hazard identification
utilize the highest standards of scientific rigour. The most difficult issue in hazard identification is how to compare and combine different types of data, including data from animal and human studies, studies with different routes of exposure, studies of different
quality, and studies with conflicting results, including both those with positive and negative findings. To avoid excluding relevant evidence, hazard identification should be
based on the overall weight of the evidence, with the greatest weight given to data that
are most relevant to humans or the ecosystem being studied. The remaining part of this
chapter reviews the major types of data relevant for hazard identification and their application to non-ferrous metals.
Data for Hazard Identification
Metals exert their effects on living organisms primarily through specific interaction with
various cellular biochemical systems. Some of these interactions may be beneficial or
even essential, while other interactions may be detrimental. For instance, some metal
7
National Research Council. 1983. Risk Assessment in the Federal Government: Managing the Process. National
Academy Press, Washington, DC.
Chapter 3 - Hazard Identification of Non-Ferrous Metals
21
ions can interact in a positive or negative way with important functional sites of enzymes.
Others may compete with essential metals for uptake or incorporation into proteins. In
this way, a metal may be toxic by causing a deficiency of another metal or, through incorporation, preventing the proper functioning of a protein. The mechanism of some effects
of metals is not as well understood. Different species of the same metal often result in
different interactions with biological systems, and therefore hazard identification should
focus on specific metal species. The objective of hazard identification is to identify the
existence, magnitude and, to the extent possible, the mechanism of effects associated
with a specific metal species or compound, using the types of scientific data reviewed
below.
Epidemiology of Non-Ferrous Metals
Epidemiology is the study of the distribution and determinants of diseases and injuries
in human populations.8 The presence of disease is compared between people exposed
and not exposed to the agent under study. Because epidemiology evaluates human
rather than animal data, it has the potential to be particularly informative for human
hazard identification.9 There is no need for extrapolation of effect or dose across species,
and therefore concerns about anatomical, physiological, metabolic and genetic differences between the test species and humans do not arise.
Notwithstanding the potential advantages of epidemiology, there are important limitations to the use of epidemiology for hazard identification and risk assessment. Ideally,
epidemiology requires that exposure be accurately determined, and that the relationship
between exposure and risk be reliably established at all exposure levels. In practice, this
is rarely achievable because of the lack of precise data on historical exposures.
Moreover, even a consistent finding of a relationship between a particular exposure and
a disease in humans does not by itself establish a causal relationship. Causation can be
established only if other possible explanations of the observed relationship can be discounted. Some of these additional issues that must be considered in evaluating epidemiology data — such as bias, confounding and exposure evaluation — are summarized
below.
Bias is a systematic error which tends to overestimate or underestimate the hazard. For
example, selection bias occurs when the control population differs from the study population because people with exposures or the disease at issue are more likely to participate in the study. Information or classification bias exists when people who have been
8
9
While the term “epidemiology” usually refers to human data, and is used here with that meaning, the emerging field of environmental epidemiology uses studies on free-living organisms in the environment to make
inferences about potential environmental hazards. Environmental toxicology is addressed later in this chapter.
Other types of human data are also important for hazard identification, including data obtained from the fields
of occupational medicine and industrial hygiene.
Risk Assessment and Risk Management of Non-Ferrous Metals
22
exposed to the agent being studied are classified as non-exposed (or vice versa). This
bias can also occur if people who really have the disease are classified as not having it
(or again, vice versa). An example of an information bias would be if a study of workplace exposure to a specific metal ignored the fact that the general population, used as
the control group, is also exposed to the metal. In this case, if the metal truly did
cause the disease, the estimate of occupational risk would be biased because the disease
rate in the general population is already increased due to exposure outside the workplace.
Box 7: Hypothetical Example of Information Bias
Information bias will occur if, for example, metal exposures are not considered in
the general population used as the control population in an epidemiological study.
Consider a hypothetical example in which the prevalence of a particular type of
cancer is 5 percent in the general population and 10 percent in workers at a facility processing metal species X. Occupational exposure studies indicate that
workers at the facility are exposed to metal species X at an average concentration of 10 parts per million (ppm). Assuming other sources of exposure and possible confounding factors are eliminated as possible explanations of the results,
the researcher may conclude that the 10 ppm exposure to metal species X
appeared to cause a 5 percent increase in cancer in the workers. This conclusion
would be erroneous, however, if it did not consider background exposures to
metal species X in the general population. If the background exposure was 5
ppm, the incremental increase in workplace exposures would only be 5 ppm (not
10 ppm), and thus the effect per unit of exposure of metal species X would be
twice as large as previously estimated. Thus, in this hypothetical case, information bias would lead to a substantial underestimation of risk. Other types of information bias can cause an overestimation of risk.
Confounding is a special type of bias in which another factor is associated with both the
agent and the effect under study. For example, if factory workers who are the subject of
an epidemiological study are more likely to smoke cigarettes than the control group
(e.g., the general population), some or all of an observed increase in lung cancer in the
workers is likely attributable to the confounding effect of smoking rather than occupational exposures. Without carefully controlling for such confounding, the effects attributable to the agent being studied can be erroneous, either significantly exaggerated or
masked. An important limitation of epidemiology is that it may be impossible to know
all potential confounders in advance of a study. Nevertheless, because significant con-
Chapter 3 - Hazard Identification of Non-Ferrous Metals
23
founding factors are known to exist for many metal exposures, it is important that epidemiological studies be examined with potential confounding in mind.
Box 8: Example of Confounding
Confounding factors are an important factor that must be taken into account in epidemiological studies of metal compounds. Studies that attempt to demonstrate
and quantify the effects of lead exposure on childhood IQ provide an example
where confounding factors are important. A recent review of lead-IQ studies
found that “[i]n every study the unadjusted results indicated stronger evidence of
an inverse association than did the more informative results after adjustment for
confounders.” In several studies, adjustment for parental and social confounding
factors only reduced the estimated impact of lead by less than 1.5 IQ points but,
in other studies, the adjustment had a much larger effect. For example, in one
study, adjusting for confounding reduced the estimated detrimental impact of
increasing blood levels from 10 to 20 g/dl from 12.1 to only 1.1 IQ points, a 91 percent reduction in the measured effect after adjusting for confounding. The review
authors suggest that the large confounding effect in that study was because half
of the children in the study had alcoholic mothers. This example therefore demonstrates that confounding can significantly bias results if not taken into account,
and that confounding varies from study to study based on the unique circumstances of each study group.
Pocock, S.J., M. Smith and P. Baghurst. (1994). Environmental lead and children’s intelligence: A systematic review of the epidemiological evidence. British Medical Journal. 309: 1189–1197.
Exposure evaluation problems can make accurate quantification of exposure levels difficult or impossible, which in turn can prevent reliable evaluation of a dose-response
relationship that is important for establishing causation. An important exposure evaluation problem for metals is that the concentration of metals is often determined for the
total amount of metal present, without regard for the different chemical or physical
forms (speciation) of the metal, which can greatly affect bioavailability and toxicity.
Another problem is that the long-term use of metals results in the availability of epidemiological data going back many years, but estimates of historic exposure levels are
particularly imprecise and could therefore significantly bias the data. The fact that metals are naturally occurring elements and are used in a broad range of applications also
makes analysis of exposure attributable to particular industrial or workplace processes
more difficult, because of the variability of background exposures. For example, a study
Risk Assessment and Risk Management of Non-Ferrous Metals
24
of occupational exposures to cadmium may be complicated by the fact that heavy cigarette usage elevates blood cadmium values.
In evaluating epidemiological data, it is essential that all available data be considered,
allowing the weight of evidence from both positive and negative studies to influence a
judgement of causality. Since statistically significant results can arise by chance and
because some negative studies may have insufficient power to refute positive studies, it
is important to evaluate the statistical bases of epidemiological studies in isolation and
together. Several public and private entities have produced guidelines for good practices
in interpreting epidemiological data.10 Important factors in making a causal inference
from the complete set of available epidemiological data include the following:
1. Number of Studies: A large number of studies producing similar results provides
greater confidence in drawing conclusions about the presence or absence of a causal
relationship because it is less likely that the same confounders and biases affected each
study. This is especially true if the studies involve different exposure settings, different
types of epidemiological analyses, and different researchers to ensure the robustness of
the findings.
2. Strength of Association: Epidemiological studies use well-defined statistical measures, such as relative risk or a standardized mortality ratio (SMR), to represent the
strength of an observed association between an exposure and an effect. Higher relative
risks or SMRs make epidemiologists more certain of cause and effect because it is less
likely that the observed results were due to chance. Note: The power of the studies —
which is a statistical measure of how sensitive the study is for detecting the disease — is
another important consideration in interpreting epidemiological data. As a general rule,
the larger the study group, the greater the power of the study.
3. Dose-Response Relationship: Evidence for a dose-response relationship is considered by toxicologists and epidemiologists to be important in establishing a causal link.
Scientists expect the frequency or severity of effects to increase as dose (or exposure)
level increases. Poor exposure information often means that dose-response is very difficult to evaluate within and across epidemiological studies, yet it is a crucial factor in
hazard identification.
10 For example, the International Agency for Research on Cancer (IARC) and the US Environmental Protection
Agency (EPA) have published criteria for interpreting epidemiology studies. IARC. 1987. IARC Monographs on
the Evaluation of Carcinogenic Risks to Humans, Overall Evaluations of Carcinogenicity: An Updating of IARC
Monographs Volumes 1 to 42 (Supplement 7); US EPA. 1996. Proposed Guidelines for Carcinogenic Risk
Assessment, 61 Fed. Reg. 17960 (Apr. 23, 1996). The US Chemical Manufacturers Association (CMA) has also
published epidemiology guidelines. CMA Epidemiology Task Group. 1991. Guidelines for good epidemiology
practices for occupational and environmental epidemiologic research. Journal of Occupational Medicine 33:
1221-1229.
Chapter 3 - Hazard Identification of Non-Ferrous Metals
25
4. Biological Plausibility: Biological plausibility means that there is a logical scientific reason to think that an exposure and a disease could be related. This may be because
a similar disease has been produced in animals by the same substance. Or it may be that
scientific and medical theory can provide a logical explanation for a relationship
between an exposure and disease. An observed relationship between exposure and
effect that does not appear to be biologically plausible indicates that the results should
be interpreted with caution until confirming data or a biological explanation are available.
Box 9: Chromium Epidemiology
The epidemiology of chromium demonstrates some key issues in metal epidemiology, including the difficulty of attributing effects to a specific metal in multi-exposure occupational settings, the importance of focusing on specific metal
compounds and the importance of route of exposure. Most epidemiological studies of metals use occupational data because exposures tend to be higher, and it
is easier to define a population of exposed individuals, in the workplace.
Numerous epidemiological studies had shown excess risk for lung cancer in workers in the chromate production industry, but it was difficult to attribute this risk to
any particular type of chromium because workers in this industry are exposed to
a variety of forms of chromium, including chromium [VI] and [III] compounds.
However, when these results are considered along with data from chromiumexposed workers in other industries, a clearer picture emerges. For example,
workers in the chromium plating industry also have an excess of lung cancer, and
exposures in this industry are primarily to inhalation of soluble chromium [VI]
compounds. There are insufficient data to demonstrate a significant increase in
lung cancer among ferro-chromium workers, who are primarily exposed to chromium [III] compounds and to metallic chromium. Based on these and other epidemiological data, IARC concluded that there is sufficient evidence in humans for
the carcinogenicity of chromium [VI] compounds inhaled by workers in certain
industries, but not for chromium [III] compounds or chromium metal. In contrast
to the epidemiological evidence that the inhalation of certain chromium compounds can cause lung cancer at high exposures, evidence does not support a
similar carcinogenic risk from other routes of exposure to chromium, such as
ingestion. Chromium carcinogenicity therefore appears to be specific to both the
type of chromium and the route of exposure involved.
Risk Assessment and Risk Management of Non-Ferrous Metals
26
Despite the limitations and cautions associated with epidemiological data, epidemiology
can provide the most direct evidence of an association between human exposure and a
disease in appropriate circumstances where ample, reliable data are present.
Epidemiology has played an important role in the understanding of the potential health
effects of exposure to many non-ferrous metals. For example, the relationship between
exposure to hexavalent chromium (but not trivalent chromium) and lung cancer was
first identified by epidemiology. Epidemiology also documented the adverse kidney
effects caused by high doses of cadmium. There has been a great deal of epidemiological study of metals because large populations of workers with long-term exposure potential are available to be studied. Of course, as with any epidemiological study, care must
be taken in interpreting the available data because of the potential pitfalls identified
above.
Toxicology of Non-Ferrous Metals
Given the limitations of epidemiology and the desire to identify hazards before a problem becomes manifest in human populations, experiments are conducted with animals
to identify agents that are potential human toxins. Toxicology is the science of identifying potential hazards or other health effects, usually involving controlled studies in living organisms, isolated tissues, cells, or cellular components.
The toxicology of metals and metal compounds is relatively well-developed because
metals have been studied for many years. The natural origin and widespread distribution of metals in the environment, however, means that special care must be taken when
using toxicological data in hazard identification and risk assessment. Moreover, the
evaluation of the potential effects of metal exposure to humans and the environment
must be approached on a compound by compound basis. This is primarily due to two
key characteristics of metals and the various species in which they are found discussed
earlier: special biochemical properties and differences in bioavailability. While a substantial database on metal toxicity has now been accumulated, the data needed to properly account in risk assessment for issues such as the speciation, bioavailability and
essentiality of metals are in many cases inadequate or unavailable.
Another problem is the scarcity of diagnostically specific pathological responses, or in
other words observable health effects that can be unambiguously attributed to metal
exposures. For example, mild neuropathological changes from lead exposures are difficult to detect, because individuals with such effects are not easily distinguishable from
the general population. Another example is that a general malaise is frequently the
characteristic response to an excess of many non-ferrous metals in domestic animals or
human subjects, but such malaise can also be caused by many other factors, including a
deficiency of some essential non-ferrous metals. Another area for which better information is needed is the effects of metal compounds in mixtures, as many exposures to
Chapter 3 - Hazard Identification of Non-Ferrous Metals
27
metals involve exposures to a mixture of specific metal compounds, each with their own
unique properties.
In at least some countries, the greatest emphasis in regulatory toxicology in recent years
has been on carcinogenicity, with relatively less attention given to other types of potential toxicity such as reproductive and developmental toxicity, neurotoxicity, immunotoxicity, ecotoxicity and systemic effects. Some of these other types of toxicity are more
difficult to study than carcinogenicity in rodents, because the symptoms and effects of
such toxicity are not as easily detected and defined as tumours in cancer. For example,
small but nevertheless important decrements in IQ are often difficult to detect and assign
to specific causes, and variations in immunological function may be of unknown biological significance. For many non-ferrous metals, cancer is not a health effect of significant concern, but rather other types of potential toxicity such as ecotoxicity or
neurotoxicity are more important. Nevertheless, because much of the attention and regulatory guidelines for hazard identification and the other steps in risk assessment have
focused on carcinogenicity, the discussion below primarily uses carcinogenicity as an
example to illustrate the types of issues encountered in toxicology and hazard identification of metals. Many of the same or similar issues apply to hazard identification for
other types of toxicity that may be more relevant for many metal compounds.
The most commonly used toxicological test for human carcinogen identification is the
long-term rodent bioassay. This type of test is based on the assumption that a rodent carcinogen may also be a human carcinogen.11 Rodent tests also play a prominent role in
identifying other health effects such as teratogenicity and reproductive toxicity. In addition, short-term laboratory tests of the biological properties of chemicals in isolated tissues, cells or subcellular components provide information which may help inform
judgements concerning the potential for human hazard by identifying the mode of
action.
Several protocols for carcinogenesis bioassays have been published, including those by
the Organization for Economic Cooperation and Development (OECD) and the US
National Toxicology Program (NTP). In a standard NTP animal carcinogenesis bioassay,
50 animals of each sex of two species, usually rats and mice, are exposed to each dose
level of the suspected carcinogen for virtually their entire lives. Although this animal
test is designed specifically to find tumours, the test is fairly insensitive. For example, if
a dose of a carcinogen causes an increased lifetime cancer risk of one chance in 100, a
test with only 50 animals is unlikely to detect a single tumour-bearing animal. For this
reason, high-dose levels are chosen to compensate for the limited sample sizes that are
11 Huff, J., J. Haseman, and D. Rall. 1991. Scientific concepts, value, and significance of chemical carcinogenesis studies. Annual Review of Pharmacology and Toxicology. 31: 621-652.
Risk Assessment and Risk Management of Non-Ferrous Metals
28
practical. The dose levels selected are the maximum tolerated dose (MTD) and usually
fractions thereof, such as MTD/2 and/or MTD/4.
All other toxicological studies are conducted at much lower exposure levels. The goal of
these tests is to identify exposure levels both below and above the experimental response
threshold. High-dose studies, like the carcinogenesis bioassay, are only useful in cases
in which one knows that there is no response threshold. Even in carcinogenesis the nothreshold assumption is contentious.12
Inherent in the use of rodent bioassays to predict human carcinogenicity are many critical assumptions, including that: (1) humans respond in a manner similar to rodents; (2)
the results at high doses for the relatively short lifetimes of animals are functionally
equivalent to low-dose exposures for the longer human lifetimes; and, (3) animal doses
in the tests can be scaled appropriately to reflect human exposure.13 These assumptions
are increasingly the subject of controversy within the scientific and regulatory communities because, for example, there are known cases of carcinogenic responses in rodents
that are not relevant to humans.14 There is increasing recognition of the importance of
obtaining and evaluating data on the mechanisms of tumour induction in animal studies
in order to evaluate their relevance for humans. Moreover, there is controversy about
whether results from rodent bioassays performed at or near the MTD are applicable to
the much lower levels of exposure typically faced by humans.15 Many scientists believe
that toxic effects which alter animal responses to the test chemical, or which induce cell
proliferation, may induce tumours at high doses which have no relevance to lower exposures that may be more representative of human exposures.16
Several hundred chemicals, including some non-ferrous metal compounds, have been
shown to have carcinogenic potential in animals, often with little or no information from
studies in humans. This includes certain compounds of five non-ferrous metals classified by the US National Toxicological Program (NTP) as “reasonably anticipated to be
carcinogens” (Box 10). Even within this group of animal carcinogens the evidence
varies. Some substances have caused increased tumours in every animal group tested
12 Upton, A.C. 1988. Are there thresholds for carcinogens? The thorny problem of low-level exposure. Annals of
the New York Academy of Sciences. 534: 863-883.
13 Huff, J., J. Haseman, and D. Rall. 1991. Scientific concepts, value, and significance of chemical carcinogenesis studies. Annual Review of Pharmacology and Toxicology. 31: 621-652.
14 The best described situation in which chemicals cause increases in tumours in animals through a mode of
action which does not occur in humans involves a number of hydrocarbons which bind to the male rat-specific protein a 2-globulin. See, for example, US EPA. 1991. Alpha 2-Globulin: Association with Chemically
Induced Renal Toxicity and Neoplasia in the Male Rat (EPA/625/3-91/019F).
15 National Research Council. 1993. Issues in Risk Assessment. National Academy Press, Washington, DC.
16 Carr, C.J., and A.C. Kolbye Jr. 1991. A critique of the use of the maximum tolerated dose in bioassays to assess
cancer risk from chemicals. Regulatory Toxicology and Pharmacology. 14: 78-87; Gold, L.S. 1993. The importance of data on mechanism of carcinogenesis in efforts to predict low-dose human risk. Risk Analysis. 13: 399402.
Chapter 3 - Hazard Identification of Non-Ferrous Metals
29
(e.g., male and female mice and rats), while others cause tumours only in one or some
groups. Some substances cause many different tumour types, some cause tumours in
sites which rarely get cancer in control animals, and others increase the number of only
one type of tumour which may be very common in control animals. Some compounds
are genotoxic and some are not. Genotoxic substances interact with and alter deoxyribonucleic acid (DNA), which is thought to be an important first step in cancer formation.
Most metals of concern for carcinogenicity have little evidence of genotoxicity in standard short-term tests.
Box 10: Metals Classified as Possible Carcinogens by NTP
The US National Toxicology Program classifies substances as “known” carcinogens and substances “reasonably anticipated” to be carcinogens. The only nonferrous metals classified as “known” carcinogens are “chromium and certain
chromium compounds” and thorium dioxide. Certain compounds of five non-ferrous metals are classified as “reasonably anticipated” carcinogens, including:
beryllium and certain beryllium compounds; cadmium and certain cadmium compounds; lead acetate and lead phosphate; nickel and certain nickel compounds;
and, selenium sulphide.
National Toxicology Program. 1994. Seventh Annual Report on Carcinogens. US Department of Health and
Human Services.
Many governmental and international bodies have established carcinogen classification
schemes which identify compounds suspected of being carcinogenic and rate the degree
of evidence. For example, IARC (see Table 3), the US EPA, the EU, the US NTP, the
American Conference of Governmental Industrial Hygienists (ACGIH), and the national
bodies of countries such as Canada, Norway and Germany have each developed their
own carcinogen classification schemes. Several of these carcinogen classification agencies, including IARC, the US NTP and the US EPA have recently begun to give greater
weight to data that evaluate the human relevance of the mechanism and mode of action
of cancer causation in animal studies. Under the auspices of the Intergovernmental
Forum on Chemical Safety (IFCS), initiatives have been undertaken to harmonize classification on a common and coherent basis for hazard identification and risk assessment
for metals and metal compounds.
Risk Assessment and Risk Management of Non-Ferrous Metals
30
An important consideration in evaluating carcinogenic potential of metals is the route of
exposure in experimental animals and in humans. Some metal species cause tumours
only through a single route of exposure that may not be relevant to humans. For example, many positive findings for metals in animal bioassays are the result of experiments
in which the metal is injected into the muscles or lung cavity of animals. The utility of
these experiments for normal metal exposure routes is questionable both on toxicological grounds17 and because these methods of administration are not normally associated
with environmental or occupational exposure. Consideration of the human relevance of
the mechanism and route of exposure that results in cancer in experimental animals is
therefore an important step in identifying potential human carcinogens.
Even with consideration of mechanistic data, the various classification schemes represent only hazard identification, the first step of risk assessment, because they do not consider the exposure and dose-response inputs that are necessary for evaluating risk. As
TABLE 3.
IARC Carcinogen Classification Scheme
Category
Description
Criteria
Group 1
The agent is carcinogenic
to humans.
Sufficient evidence of
carcinogenicity in humans.
Group 2A
The agent is probably
carcinogenic to humans.
Limited evidence of
carcinogenicity in humans and
sufficient evidence in animals.
Group 2B
The agent is possibly
carcinogenic to humans.
Limited evidence of
carcinogenicity in humans and
inadequate evidence in animals.
Group 3
The agent is not classifiable
as to its carcinogenicity.
When an agent does not fall into
any other group.
Group 4
The agent is probably not
carcinogenic to humans.
Evidence suggesting lack of
carcinogenicity in humans and
animals.
17 Theiss, J.C. 1982. Utility of injection site tumorigenicity in assessing the carcinogenic risk of chemicals to
man. Regulatory Toxicology and Pharmacology. 2: 213-222.
Chapter 3 - Hazard Identification of Non-Ferrous Metals
31
such, cancer classifications are not intended to form the direct basis for regulatory programs, but rather are intended to identify potential cancer hazards for further evaluation
and risk assessment by regulatory agencies. For example, the IARC carcinogen classification monographs expressly state that the classification scheme “represents the first
step in risk assessment” which “may assist national and international authorities in making risk assessments and in formulating decisions concerning any necessary preventive
measures.”18 Similarly, the US NTP’s Annual Report on Carcinogens (now the Biennial
Report) expressly cautions that “[t]he listing of a substance in the Annual Report ... does
not establish that such substance presents a risk to persons in their daily lives.”19
In addition to carcinogenicity bioassays, many other types of subchronic and chronic toxicity testing are frequently undertaken and may be more relevant for most metal compounds. Other types of testing include tests for genotoxicity, reproductive toxicity,
developmental toxicity, neurotoxicity and systemic toxicity. There are also limitations
and potential problems in extrapolating the animal test results for these types of toxicity
to humans, just as there are for extrapolating animal carcinogenicity findings.
For example, potential neurotoxicity is an issue of research and regulatory concern for
some non- ferrous metals and many other industrial substances.20 Neurotoxicity focuses
on the effects of substances on the central nervous systems, resulting in behavioural
effects such as aggression, irritability, depression, passivity and impairment of learning,
thinking, memory and motor activity. Many fundamental issues in understanding and
applying neurotoxicity remain unresolved, such as how to define and measure an
“adverse” neurological effect, and how to design and extrapolate to humans the results
of animal tests for neurotoxic effects.
Ecotoxicity of Non-Ferrous Metals
The hazard identification process is also concerned with potential adverse ecological
effects on organisms other than humans. There is a fundamental difference between
hazard identification for human health and for the environment. Human health hazard
identifiation is concerned with effects at the level of individual humans, while ecological
hazard identification addresses effects at the level of populations and community structure.
18 IARC. 1987. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Overall Evaluations of
Carcinogenicity: An Updating of IARC Monographs Volumes 1 to 42 (Supplement 7).
19 National Toxicology Program. 1994. Seventh Annual Report on Carcinogens. US Department of Health and
Human Services.
20 International Council on Metals and the Environment. 1994. A Guide to Neurotoxicity: International Regulation
and Testing Strategies. Ottawa, ON; US Office of Technology Assessment. 1990. Neurotoxicity: New
Developments in Neuroscience. Washington, DC.
Risk Assessment and Risk Management of Non-Ferrous Metals
32
For environmental hazard identification, test populations of organisms, usually of standard species, are evaluated and the no-observed-effect concentrations (NOEC) are established. Then for risk assessment, the NOEC for the test population is translated into a
NOEC for populations in the wild. Furthermore, for metals, natural background and
essentiality of some metals need to be considered. This is taken into account by the application of uncertainty factors which consider the limited number of tests, the limited
range of organisms and the extrapolation from acute to chronic effects.
Box 11: The Example of Copper Ecotoxicity
Copper is an example of a metal with low mammalian toxicity but considerable
toxicity to some aquatic species. For copper to be toxic to aquatic organisms,
however, it must be soluble and bioavailable. It has been found that even very
high levels of copper in sediments may have little adverse effects on the aquatic
environment, presumably because the copper is not bioavailable. Another important factor influencing toxicity is the solubility of different oxidation states and
chemical complexes of the copper ion. These are often a function of other properties of the water such as hardness or CO3 content.
By far the greatest biological hazard related to copper is the occurrence of copper deficiency adversely affecting ruminant animals in agricultural systems. Here
again the issue is one of copper availability in which metabolic interactions with
molybdenum (from either natural or anthropogenic sources) modify the form of
copper presented to the digestive tract in a way that reduces the animal’s intake
of copper. This problem does not arise in other animals such as humans, pigs or
rodents.
These effects of concern include toxicity to aquatic vertebrate and invertebrate species,
terrestrial vertebrate and invertebrate species, plant species and microorganisms. For
instance, the European Commission (EC), in its Risk Assessment of Existing Substances;
Environmental Risk Assessment of Existing Substances Technical Guidance Document,
identifies which ecotoxicity studies must be included in the “base set” for a substance:
acute toxicity to fish, acute toxicity to Daphnia, growth inhibition tests on algae, and bacterial inhibition tests if the compound may influence biodegradation. Further tests on
the terrestrial environment, including plants, earthworms and other species, may be
required. Under various national and international schemes, toxicity to birds, plants, terrestrial vertebrates and invertebrates, and other species may also be required. This does
highlight one important feature of ecotoxicology, that studies are frequently conducted
Chapter 3 - Hazard Identification of Non-Ferrous Metals
33
on the species of interest or closely related species. A critical question in ecotoxicology
tests is how to present the test organism with forms of the element which reflect, both
physically and chemically, those found in the natural environment.
For some metal species, ecotoxicity may be a major factor in a risk assessment because
low levels of the metal may be a greater potential hazard to a sensitive ecosystem than
to human health. Given the enormous number of organisms in the environment, it is not
surprising that some organisms can be very sensitive to certain metals. In evaluating
these potential effects, it is imperative that hazard identification focus on the physical
and chemical form of the metal which will be encountered in the environment. The solubility, particle size and bioavailability of different metal species should be evaluated in
hazard identification when relevant data are available.
Another important factor for metal ecotoxicity analysis is the type of organism used for
toxicity testing. Tests involving organisms that are not indigenous to the environment of
interest have the potential to produce inappropriate results, such as recommended levels that are below natural levels in a particular environment. This is particularly a problem for essential metals, if strict limits on metal concentrations to ensure no toxicity to a
non-indigenous test organism result in a deficiency of an essential metal for indigenous
species. To overcome this problem, the choice of test organism is crucial. Both the
species and the sources of test population will affect the conclusions drawn from laboratory tests. Many different populations exist in the wild, each having a different history of prior exposure to metals and, therefore, different sensitivity. The combination of
geochemical maps, including definition of soil type, may give an indication of the
bioavailable concentration of metals which, combined with distribution maps for organisms using geographical information systems, offers one method by which test organisms might be chosen.
Conclusion
Scientific information provides the basis for hazard identification. Epidemiological studies and toxicological studies of potential health and environmental hazards must be used
in hazard identification with an understanding of their scientific strengths and weaknesses. In the case of metals, several important factors are crucial. First, metals are
found in a wide range of chemical and physical forms with different toxicological properties. It is critical that different metal compounds are not combined or otherwise confused, and that the necessary data be generated and considered to permit hazard
identification of metals on a compound-by-compound basis. Data generation requires
the involvement and commitment of industry, governments and research groups in order
to ensure data availability for risk assessment. Second, the toxicology of many metals,
Risk Assessment and Risk Management of Non-Ferrous Metals
34
like many other substances, may be route-specific. For example, a metal compound may
be dangerous by inhalation but pose no threat when ingested. Finally, metals are elements and as such have been part of the natural environment for all time. Biological systems use metals in many biochemical processes and many have evolved methods to
balance and control the level of many metals. In fact, for some metals a deficit of exposure may be as harmful as too great an exposure. These unique characteristics and
properties of non-ferrous metals are critical for sound hazard identification, as well as
the subsequent steps of risk assessment discussed in the next chapter.
Chapter 3 - Hazard Identification of Non-Ferrous Metals
35
CHAPTER 4
Towards Sound Risk Assessment of
Non-Ferrous Metals
Hazard identification, addressed in the previous chapter, is only
the first step in risk assessment, and does not provide an estimate
of risk under identified exposure scenarios. A usable risk
assessment also requires dose-response evaluation, exposure
assessment and risk characterization — which are reviewed in
this chapter as applied to non-ferrous metals. Sound risk
assessment requires each of these risk assessment steps to consider
and weigh all relevant evidence, acknowledge the assumptions
and uncertainties inherent in risk assessment, and present the
results in a clear and usable format.
A
n essential prerequisite to effective risk management of non-ferrous metals is the
accurate identification and evaluation of the potential health and environmental
risks from specific metal applications. While scientific risk assessment by itself
will not resolve many of the controversies relating to risk management, it is surely the
case that risks that are unknown or inadequately characterized will be managed poorly,
inefficiently or not at all. The first step of risk assessment is hazard identification, which
was addressed in the previous chapter. The output of hazard identification should be a
portrait of the adverse effects that a specific substance is capable of causing. Hazard
identification is, however, only the initial step in the risk assessment process, not an end
in itself. Simply stating that a substance is a reproductive toxin or a carcinogen, with no
discussion of dose-response or exposure, is misleading and scientifically incomplete.
Other important factors such as exposure, dose-response and potency must be combined
with hazard identification to provide a meaningful evaluation of the magnitude and distribution of risk, and indeed whether any significant risk exists at all.
It is a well-established scientific axiom that “the dose makes the poison,”21 and therefore
information showing that a substance is capable of causing some adverse effect under
certain circumstances is only part of the story. To truly understand the risk, it is impor21 Ottoboni, Alice M. 1991. The Dose Makes the Poison. Second Edition. Van Nostrand Reinhold, New York, NY.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
37
tant to also consider the dose at which the adverse effect occurs, the likelihood and magnitude of any such effect under real-world exposure conditions, and information on the
mechanism by which such an effect occurs. Regulatory and personal decisions on risk
avoidance should therefore be based on an assessment of risk, rather than simply on
hazard identification. The remaining steps of the risk assessment process — which
include dose-response evaluation, exposure assessment and risk characterization — are
the subject of this chapter.
An important caveat to the following discussion of risk assessment issues is that while
several pitfalls and suggestions for improvements in risk assessment are identified, the
recommendations that follow will not necessarily resolve all problems. In some cases,
data limitations preclude a reliable assessment of risks. In other cases, methodological
and theoretical issues need to be resolved to reduce major uncertainties in risk assessment. While further work in these areas should continue, the knowledge and data that
are available today do permit useful estimates of risk to be derived for many applications
of non-ferrous metals. This information can provide the basis for rational risk management based on scientifically sound risk assessment.
Dose-Response Evaluation
Dose-response is a fundamental tenet of toxicology, exemplified by the oft-quoted phrase
from Paracelsus that: “All substances are poisons: there is none which is not a poison.
The right dose differentiates a poison and a remedy.” So important is this principle that
many scientists consider the presence of a dose-response relationship to be critical in
establishing a causal relationship between an exposure and disease.22 The process of
dose-response evaluation evaluates the hazard associated with exposure to different
amounts of a substance. Dose-response evaluation for human risk assessment often distinguishes between non-threshold and threshold substances.
Non-threshold substances are believed to be capable of causing adverse health effects
(such as genotoxic carcinogenicity and mutations) at any exposure level, and therefore
there is no threshold for adverse health effects. A threshold substance, in contrast, is
believed to have a concentration below which no adverse effect occurs. The presence of
this threshold is commonly believed for most substances. For many substances, the
available data do not definitely demonstrate that a substance does or does not exhibit a
22 Hill, A.B. 1965. The environment and disease: association or causation? Proceedings of the Royal Society of
Medicine. 58: 295-300.
Risk Assessment and Risk Management of Non-Ferrous Metals
38
threshold for a particular health effect. In the absence of such data, substances are identified as a threshold or non-threshold substance based primarily on assumptions and theoretical considerations, which have been the subject of much debate. In addition to
reviewing dose-response evaluation for threshold and non-threshold substances, the following section also evaluates dose-response methodology for ecotoxicology, which is
particularly relevant for many non-ferrous metals.
Threshold Substances
Determination of what dose of a chemical is non-hazardous and what is harmful has
been the practice of toxicologists for many years. The data from these dose-response
relationships have been used in occupational health, environmental protection, nutrition
and medicine to protect people against the toxic effects of chemicals. Central to this science of poisonous compounds is the concept of a response threshold.
A threshold is the dose of the toxicant below which it is believed that there will be no
adverse effect on nearly all exposed individuals. Above the threshold, some portion of the
population will exhibit adverse effects. The dose-response relationship for a chemical is
usually determined by evaluating the effects observed at a variety of doses of the compound. The lowest dose producing an adverse effect is called the lowest observed adverse
effect level (LOAEL), and the next tested dose below the LOAEL is the no observed
adverse effect level (NOAEL). The terms “lowest observed effect level” (LOEL) and “no
observed effect level” (NOEL) were used in the past, but most toxicologists now recognize that “adverse” effects are more appropriate for defining a threshold. The threshold
FIGURE 3.
Example of Dose-Response Curve
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
39
dose is somewhere between the LOAEL and the NOAEL and is often estimated as the
geometric mean of the NOAEL and the LOAEL, although its exact value is unknown.
This relationship is shown graphically in Figure 3.
In the case of metals essential for life and health, the dose-response curve is actually Ushaped because both very low and very high doses are associated with adverse health
effects (Figure 4). At both ends of the curve, there exists 100 percent mortality or morbidity. The optimum for intake and exposure includes a range of doses in the trough of
the curve. Because doses that are too high or too low will result in adverse effects, great
care must be taken in assessing the risks of essential metals, such as zinc, selenium, copper and iron. It is not enough to ensure “safe” levels of uptake of such metals, but rather
the objective should be “safe and sufficient” uptake levels.
The traditional approach for evaluating the dose-response of non-carcinogens that are
assumed to have a threshold is called the safety factor method. Under this methodology,
the NOAEL (or the LOAEL in the absence of a NOAEL) is modified by safety factors 23 to
account for potential differences in response between humans and animals, to protect
potentially sensitive portions of the human population, and to account for lack of knowledge of human response when there are little or no human data. The goal is to estimate
the human population threshold for adverse effects. Factors of 10 are often used as stan-
FIGURE 4.
Example of U-Shaped Dose-Response Curve for an Essential Metal
23 Safety factors are also sometimes called application factors, adjustment factors or uncertainty factors.
Risk Assessment and Risk Management of Non-Ferrous Metals
40
TABLE 4.
Standard Safety Factors
Extrapolation
Safety Factor
Animal to Human (H)
10
Average to Sensitive Human (S)
10
Sub-Chronic to Chronic Study (C)
10
LOAEL to NOAEL (L)
10
Data Quality (MF)
1 - 10
dard safety factors for each area of uncertainty, although these values are generally
based on convention, rather than objective data.24
For example, the NOAEL from a chronic animal test is generally divided by 100 — a combination of a factor of 10 to account for potential differences between humans and the
tested animal, and a factor of 10 to protect potentially sensitive human groups. Factors
of 10 are thought to be conservative, minimizing the chance of setting an acceptable dose
above the human population threshold. In recent years, there has been increasing
recognition of the need for greater flexibility in the application of safety factors to take
account of the specific characteristics of the substance being evaluated. For example,
lower safety factors have been used in the case of essential elements, which include
some non-ferrous metals. Likewise, the International Programme on Chemical Safety
(IPCS) has endorsed an approach in which safety factors can be subdivided and partially replaced by appropriate data on toxicodynamics and toxicokinetics where such data
exist.25
The safety factor approach is used in setting a number of numerical standards to protect
human health, including the World Health Organization’s (WHO) tolerable intakes (TIs),
the US EPA’s reference doses (RfDs) and reference concentrations (RfCs), and the US
Food and Drug Administration’s (FDA) acceptable daily intakes (ADIs) for pesticides.
These standards based on the safety factor approach are assumed to be an estimate of a
safe dose. For example, an RfD is defined as “an estimate (spanning perhaps an order
24 Dourson, M.L., and J.F. Stara. 1983. Regulatory history and experimental support of uncertainty (safety) factors. Regulatory Toxicology and Pharmacology. 3: 224-238.
25 IPCS. 1994. Assessing Human Health Risks of Chemicals: Derivation of Guidance Values for Health-Based
Exposure Limits. WHO, Environmental Health Criteria 170.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
41
of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.”26
Box 12: Alternative Dose-Response Approaches
New approaches for evaluating the dose-response of threshold substances are
currently being considered. One such approach is the benchmark dose method.
This approach uses statistical models to estimate the dose that produces a specified percentage increase in the adverse effect of interest above the control level.
The goal is to use all of the experimental data to more precisely define the starting point for extrapolation. The major advantage of the benchmark dose method
is that it uses data from the entire experimentally tested exposure range, rather
than simply from the NOAEL or LOAEL. Additionally, this method takes into
account the number of animals in study groups and the variability in the data.
Another new approach, under active study, is probabilistic modelling of the human
threshold dose, which attempts to estimate a probability that the substance will
cause an adverse effect at a given dose or exposure level.
Crump, K. 1984. A new method for determining allowable daily intakes. Fundamental and
Applied Toxicology 4: 854-871; US EPA. 1995. The Use of the Benchmark Dose Approach in
Health Risk Assessment (EPA/630/R-94/007); S.J.S., Baird, J.T., Cohen, J.D., Graham, A.I.,
Shlyakhter, and J.S., Evans.1996. Noncancer risk assessment: A probabilistic alternative
to current practice. Human and Ecological Risk Assessment. 2:79-102.
Several important issues arise in dose-response evaluation of non-ferrous metals for
threshold (i.e., non-cancer) effects. One of the most prominent is the essentiality of several metals for proper nutrition. For example, zinc is an essential component of more
than 200 enzymes in the human body. The FDA has established recommended dietary
allowances (RDAs) for zinc. Standard procedures for establishing an RfD for zinc results
in a value close to, or below, the RDA.27 Thus, with essential metals such as zinc, the concept of zero exposure, or indeed an RfD using the standard safety factors, could be just
as harmful to human health as exposures that are too high.28 This illustrates the prob26 Barnes, D.G., and M.L. Dourson. 1988. Reference dose (rfd): Description and use in health risk assessment.
Regulatory Toxicology and Pharmacology. 8: 471-486.
27 Abernathy, C.O., R. Cantilli, J.T. Du, and O.A. Levander. 1992. Essentiality versus toxicity: some considerations
in the risk assessment of trace elements. Hazard Assessment of Chemicals, Volume 8, J. Saxena, ed. Hemisphere
Publishing, New York, NY.
28 International Life Sciences Institute. 1994. Risk Assessment of Essential Elements. W. Mertz, C. Abernathy & S.
Olin, eds. ILSI Press, Washington, DC.
Risk Assessment and Risk Management of Non-Ferrous Metals
42
lem with using a regimented approach to all substances and not utilizing all scientific
information in characterizing the risk. To make more credible risk assessment of metals, lower bounds on “safe doses” should be established based on background levels in
the environment and minimal nutritional requirements. The establishment of such safe
dose lower bounds has been hampered in many cases by inadequate data on minimal
nutritional requirements.
Box 13: Metal Toxicity and Deficiency
The importance of ensuring that exposures to essential metals are both not too
high and not too low is demonstrated by a recent report of zinc ecotoxicity in the
Netherlands. The report concluded that “[t]he risks associated with the current
concentrations of zinc in the environment appear to be negligible for man, and limited and localized for animals and plants.” The report nevertheless recommended lower “desirable levels” for zinc based on a finding that zinc presented a
serious threat to the aquatic environment in the Netherlands. The recommended
zinc levels were so low, however, that a number of aquatic organisms would suffer from zinc deficiency at such concentrations. Natural levels of zinc in many
waters appear to be higher than the recommended “desirable level”*
*Van Tilborg, W.J.M. and F. van Assche. Integrated Criteria Document. Zinc. Industry Addendum. Report for
‘Projectgroep Zink’ of BMRO-VNO.
Another problem, although not unique to non-ferrous metals, is the definition and differentiation of a toxic effect. The toxic effects of metals have been widely studied for
many years. This means that there is a very large database from which to draw in risk
assessment. It is known that non-ferrous metals often have toxicological effects by mimicking or replacing other necessary minerals in the body. Therefore, exposures which
result in systemic or organ toxicity are frequently preceded by a number of minor and
reversible enzymatic or biochemical changes which may be of questionable clinical significance. Some of these biomarkers may provide a useful early warning of more serious deleterious effects that could occur at higher exposures. The problem is that the
biomarker, rather than the more significant toxic effect that occurs at higher doses, may
end up serving as the critical effect for risk assessment using the safety factor approach.
These minor, reversible effects are then placed on the same footing as those derived for
other compounds for more serious toxic effects. Even if the biomarker is a good predictor of more serious health effects at higher exposures, it is inappropriate to apply the
same safety factor to a minor, reversible effect that is applied to a more serious or nonreversible endpoint. Human health benchmarks such as an ADI, TI or RfD that are cal-
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
43
culated using the safety factor approach must therefore give appropriate weight to the
severity of the critical effect upon which the benchmark is based.
Another relevant issue is the influence of nutritional state and nutritional adequacy on
the tolerable limits of exposure to non-ferrous metals. Individuals with adequate and
well-balanced nutrition have much higher tolerable limits of exposure than individuals
with inadequate diets. Observation of pathological effects in socially deprived populations with exposures to non-ferrous metals and other potentially toxic materials may
therefore reflect in large part the nutritional state of exposed individuals. These relationships between metal toxicity and nutritional status raise difficult issues about how
they should be factored into dose-response and risk assessment estimates, as well as the
relative effectiveness and priorities of reducing exposures versus improving the nutritional status of under-nourished populations.
Non-Threshold Substances
For non-threshold substances such as genotoxic carcinogens, dose-response evaluation
seeks to estimate the increased probability of an adverse effect rather than attempting to
estimate a safe exposure level. Much of carcinogen dose-response evaluation, especially as practised in the USA, relies on probabilistic risk assessment. The linear no-threshold model, which is prominently used in probabilistic cancer risk assessment, postulates
that cancer can arise from a single change to the DNA of a single cell in the body. In
other words, it is assumed that a single molecule of a carcinogen has a non-zero probability of causing cancer. In addition, environmental and occupational carcinogens are
seen as adding to a background process of cancer formation which, theoretically, means
that no threshold should be expected.29 For this reason, it is assumed in cancer risk
assessment that any dose of a carcinogen, however small, increases the probability of
tumour formation.30
The non-threshold assumption is a rather controversial theory for at least some (particularly non-genotoxic) carcinogens.31 The logical implications of this theory for metals,
which have natural background levels in the environment and in foods, is that some proportion of any cancer risk from metals must be attributed to natural sources. This theory also does not take account of the likelihood that living organisms have developed
defence mechanisms to the low levels of natural exposure to non-ferrous metals that
have existed since the beginning of life on the planet. Various mechanisms and process-
29 Crump, K.S., D.G. Hoel, C.H. Langley, and R. Peto. 1976. Fundamental carcinogenic processes and their implications for low dose risk assessment. Cancer Research. 36: 2973-2979.
30 Anderson, E., et al. 1983. Quantitative approaches in use to assess cancer risk. Risk Analysis. 3: 277-295.
31 The US EPA has recently proposed new guidelines for carcinogen risk assessment that would allow use of nonlinear or threshold models for some carcinogens. 61 Fed. Reg. 17960-18011 (April 23, 1996).
Risk Assessment and Risk Management of Non-Ferrous Metals
44
es in the body, such as biotransformation, sequestration and DNA repair, suggest that
organisms may be able to accommodate some level of exposure to most substances without serious adverse effects.
Box 14: Genotoxic vs. Non-Genotoxic Carcinogens
Many non-US agencies, including the European Union (EU), the United Kingdom
(UK) Department of Health and the Health Council of the Netherlands, divide
potential carcinogens into genotoxic and non-genotoxic categories. Doseresponse evaluation for non-genotoxic carcinogens utilizes the NOAEL and safety factor approach, based on the assumption that a threshold exists for such
carcinogens. For genotoxic carcinogens, the EU and UK are in the process of
developing methods for estimating dose-response, while the Netherlands relies
on a probabilistic risk assessment methodology known as the TD50 approach,
which calculates the chronic dose rate that results in tumours in half of the animals at the end of lifetime study.
Mathematical models are used in probabilistic risk assessment to derive a dose-response
relationship and extrapolate the animal data to low doses. Often, several models will fit
the experimental animal data quite well and have at least some plausible basis in biology. The models nonetheless may yield low-dose risk estimates that vary enormously (by
factors of hundreds or thousands) for the same substance using the same data set.32
Judgement calls are necessary to complete a probabilistic dose-response evaluation on
a particular substance that is found to cause adverse effects in animal studies. Important
judgements include: (1) which set of animal data to use in the modelling process; (2)
which adverse effects in the animal to count (e.g., benign and/or malignant tumours); (3)
how to extrapolate the findings in animal studies (or occupational epidemiology) at high
doses to the low doses commonly encountered by humans in daily life; and, (4) how to
scale the doses between species, adjust for different routes of exposure (e.g., ingestion
in animals versus inhalation in humans), and account for variable durations or patterns
of exposure. None of these judgements can currently be resolved solely on the basis of
science. In the USA, quasi-policy judgements are made in the face of uncertainty pur-
32 Sielken, R.L., Jr. 1987. The capabilities, sensitivity, pitfalls, and future of quantitative risk assessment.
Environmental Health Risks: Assessment and Management. R. S. McColl, ed. University of Waterloo Press,
Waterloo, ON.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
45
suant to published guidelines,33 while other countries, the United Kingdom for example,
rely on the judgement of expert scientists.34
Various efforts are being taken to address the limitations of traditional probabilistic risk
assessment models. Concern that common models for low-dose extrapolation do not
adequately account for biological factors, including DNA repair and physiological adaptation, has spurred efforts to develop biologically based models for risk assessment. This
includes physiologically-based pharmacokinetic (PBPK) models and biologically based
models of dose-response.35 Use of these models, especially for metals for which organisms have known adaptive mechanisms, will be helpful in producing more realistic risk
estimates when sufficient data are available. Other new approaches, such as the margin
of exposure approach utilized by Health Canada (see Box 15), reduce reliance on the
most controversial and conservative assumptions in probabilistic risk assessment.
Ecotoxicology Dose-Response
The goal of dose-response evaluation for ecotoxic effects is to identify the predicted noeffect concentration (PNEC) for a substance in a particular environmental medium, often
water. The PNEC is based on the response threshold concept. Under various schemes
and depending on available data, adjustment factors are used to account for uncertainty
in extrapolating from acute to chronic tests, from a few indicator species to an ecosystem,
across taxonomic groups, and when data are sparse. Factors are applied to either a no
observed effect concentration (NOEC) from the sensitive species or to the concentration
of the substance lethal to 50 percent of the test organisms (LC50). As would be expected, larger adjustment factors are used with LC50 data than with NOEC data.
For example, in the Draft Technical Guidance on Environmental Risk Assessment of
Existing Substances,36 the European Commission (EC) draws distinctions between substances with data from long-term studies and those without, and those from more trophic levels rather than fewer (see Box 16). Other schemes use similar protocols,
decreasing the size of assessment factors as the quantity and relevance of the available
toxicity data increase.
33 See, for example, US EPA. 1996. Proposed Guidelines for Carcinogen Risk Assessment, 61 Fed. Reg. 17960(April
23, 1996).
34 Committee on Carcinogenicity of Chemicals in Food, Consumer Products, and the Environment.
1991.Guidance for the Evaluation of Chemicals for Carcinogenicity. UK Department of Health, London.
35 See, for example, Andersen, M.E., H.J. Clewell III, M.L. Gargas, F.A. Smith, and R.H. Reitz. 1987.
Physiologically-based pharmacokinetics and the risk assessment process for methylene chloride. Toxicology
and Applied Pharmacology. 87: 185-205; Conolly, R.B., and M.E. Andersen. 1991. Biologically-based
pharmacodynamic models: tools for toxicological research and risk assessment. Annual Review of
Pharmacology and Toxicology. 31: 503-523.
36 EC, Draft Technical Guidance on Environmental Risk Assessment of Existing Substances in the Context of
Commission Regulation 1488/94 in accordance with Council Regulation (EEC) No. 793/93 on the Evaluation
and Control of Existing Substances.
Risk Assessment and Risk Management of Non-Ferrous Metals
46
Box 15: The Canadian Approach
The approach developed by Health Canada to quantify carcinogen risk is an
example of a relatively new approach that may help to produce more reliable
and useful risk estimates. This approach first calculates the carcinogenic
potency of a substance expressed as the concentration or dose that induces a
5 percent increase in tumours considered to be associated with exposure. This
potency value is calculated directly from the dose-response curve rather than
from an upper confidence limit, given the stability of the data in the experimental range and the desirability of avoiding unduly conservative assumptions. The
potency estimates are generally limited to epidemiological or bioassay results
in which there has been observed a statistically significant increase in incidence
and a dose-response relationship. The quantitative estimate of carcinogenic
potency for a substance is then compared to the estimated daily intake in the
general population or to concentrations in specific relevant environmental
media. Among other benefits, such as reduced reliance on contentious and
conservative assumptions, this approach has the advantage for metal risk
assessment of taking into account background levels of metals in the environment due to natural and other causes.
Meek, M.E., R. Newhook, R.G. Liteplo, & V.C. Armstrong. 1994. Approach to assessment of risk to
human health for priority substances under the Canadian Environmental Protection Act. Environ.
Carcino. & Ecotox. Revs. C12(2): 105-134; Health Canada. 1994. Human Health Risk Assessment for
Priority Substances. Ottawa, ON.
When extensive data are available, an additional method has been proposed for setting
permissible environmental exposure levels. This method sets the protection level to protect 95 percent of the species in the ecosystem. Effects on endangered or essential
species are considered separately. However, rarely are sufficient data available to use
this method.
With essential metals, the predicted no effect concentration (PNEC) value may fall below
the concentration required in the environment to supply the essential trace elements
needed for normal functioning of enzyme systems or particular physiological functions,
such as moulting in birds which requires zinc. Estimates of NOEC and the concentration required for essentiality will vary between species and between ecosystems. Site
specific-risk assessment may, therefore, be necessary to guide appropriate risk management. Examples of attempts to quantify both toxic and essential concentrations for cop-
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
47
per and zinc, and to derive guidance values for environmental protection, can be found
in recent WHO Environmental Health Criteria documents37,38.
Exposure Assessment
The next step in risk assessment is exposure assessment, which quantifies the exposure
to the agent of interest by humans or the environment. Exposure assessment is in many
cases the most difficult and uncertain step in risk assessment, particularly for ecotoxicity risk assessment. Exposure of humans or other organisms to metals can occur through
different routes, including inhalation, dermal absorption and ingestion in food or water.39
In some situations, a source of metal contaminants will result in exposure through more
than one exposure pathway, although multiple pathways are not always considered in
risk assessments. The EC not only requests exposure assessments for direct exposure of
workers and consumers, but also for reasonably foreseeable indirect pathways.40
Environmental exposure to metals can occur through accidental release as well as emissions during manufacture, use or disposal of metals and metal-containing products, in
addition to natural sources of a metal in the environment.
Box 16: Ecotoxicity Adjustment Factors
The EC’s Draft Technical Guidance on Environmental Risk Assessment of Existing
Substances recommends the following assessment factors in calculating a PNEC
depending on the types of ecotoxicity data available:
•
•
•
•
•
1,000 applied to the lowest acute LC50 from fish, Daphnia, or algae;
100 if using a long-term NOEC from fish or Daphnia;
50 applied to the lower NOEC if both fish and Daphnia have been
tested;
10 applied to the lowest NOEC when fish, Daphnia, and algae have
been tested; or
1 applied to field studies (evaluated on a case-by-case basis).
37 WHO. 1997 (in press) Environmental Health Criteria for Copper. Geneva, Switzerland.
38 WHO. 1997 (in press) Environmental Health Criteria for Zinc. Geneva, Switzerland.
39 McKone, T.E. 1991. Human exposure to chemicals from multiple media and through multiple pathways:
research overview and comments. Risk Analysis. 11: 5-11.
40 Commission Regulation 1488/94 Annex I, Part B.
Risk Assessment and Risk Management of Non-Ferrous Metals
48
Regional or local exposure assessment is often performed to support two different types
of risk estimates: population risk (or incidence) and maximum individual risk.
Population risk is the traditional public health measure that estimates the number of
cases of disease in the exposed population attributable to a specific source or contaminant. The person at maximum individual risk (MIR) is the individual who suffers the
largest incremental risk due to a particular source or contaminant.
Since little is known about which people (or organisms in ecological risk assessment)
are the most sensitive to particular hazards, risk assessments usually assume that the
person at MIR is the maximally exposed individual (MEI). The MEI is the person,
whether hypothetical or real, predicted to receive the greatest lifetime exposure from a
particular source. For example, the MEI may be the resident living closest to a factory
which emits a pollutant or, in the case of ground water contamination, the resident
whose well for drinking water is next to a waste disposal site which may be leaking one
or more toxic substances.
Human and environmental exposures are usually calculated on the basis of predictive
models and assumptions, rather than direct measurements. For example, in estimating
exposures to a population surrounding a manufacturing facility, a mathematical dispersion model might estimate the air concentration of a pollutant 200 metres from the
source, considered to be the fence line of the factory and assumed to be the residence of
the MEI. In addition, in some risk assessments it is assumed that the MEI is outdoors
breathing air at this predicted concentration 24 hours a day for 70 years, even though no
one spends his or her entire life standing at the fence line of a factory.41 In cases involving clean-up of contaminated soils, the MEI is often assumed to be a child that eats the
contaminated soil on almost a daily basis for many years, when in many cases no children even play at or near the contaminated site.42 While the MEI calculation is designed
to be a worst-case estimate of true lifetime exposure, it often includes so many conservative assumptions that it is not representative of the exposures to any real-life person.
The population risk estimate, though arguably the most relevant to sound public policy,
is more difficult to calculate than the MIR because the assessor needs to know how many
people are exposed to the contaminant, at what levels, and for what periods of time.
Another complication is that not all people are equally susceptible to a particular toxic
substance, and therefore the level of exposure of susceptible sub-populations will often
41 Hawkins, N.C. 1991. Conservatism in maximally exposed individual (mei) predictive exposure assessments: A
first-cut analysis. Regulatory Toxicology and Pharmacology. 14: 107-116
42 For an example, see Breyer, S. 1993. Breaking the Vicious Circle: Toward Effective Risk Regulation. Harvard
University Press, Cambridge, MA.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
49
be of interest. This type of data is often not available, although in recent years greater
attention has been given to identifying and evaluating exposures to susceptible sub-populations, such as children.
Detailed measurements of a pollutant are often preferred to modelled estimates, but
monitoring is expensive and cumbersome. Exposure assessment for metals has an
advantage over organic chemicals in this respect in that better methods are available to
measure the levels of metals in the environment as well as in plant and animal tissues.
Since direct measurements generally are considered more reliable than the output of
predictive models, monitoring data should be preferred for exposure assessment. It is
critical, however, that the measurements be specific to the species of the metal under
consideration when species-specific data are available. Because measurements of total
metals are misleading, the generation and use of exposure data for the particular metal
compounds or species that may present a risk should be encouraged. A promising development for ecological exposure assessment of metals is the development and validation
of models to predict metal concentrations in aquatic species based on measurements of
free metal ions.43 This research illustrates clearly the utility of free ion measurements
over measures of total metal concentration.
In the absence of hard data, the exposure assessment process proceeds with common
“default” assumptions. For example, if a pollutant is found in drinking water, the US EPA
recommends that risk assessors assume that people consume two litres of water per day;
another frequent assumption is that everyone breathes 20 m3/day of air.44 In the absence
of pharmacokinetic data, exposure assessment frequently assumes 100 percent absorption of a substance ingested in food or water. Additional assumptions sometimes used
include that it is appropriate to average intermittent exposures over a lifetime, and that
current levels of a contaminant in the environment will remain unchanged for 70 years.
Food intake is generally derived from market basket surveys or national consumption
surveys which gauge the amount of all types of groceries purchased or consumed.
Exposure assessment must also make assumptions about the heterogeneity of the population, including differences between the sexes, adults, children and the elderly, different ethnic and socioeconomic groups, and different levels of activity.
Exposure assessment for ecological effects focuses on estimating the predicted environmental concentration (PEC). For example, estimation of the PEC for water requires
understanding of point source and non-point source releases of the substance, biodegradation of the material in the aquatic environment, and physical-chemical properties of
the material and the effect they have on the ultimate concentration of the substance in
43 Hare, L., and A. Tessier. 1996. Predicting animal cadmium concentrations in lakes. Nature. 380: 430-432.
44 US EPA. 1989. Exposure Factors Handbook (EPA/600/8-89/043).
Risk Assessment and Risk Management of Non-Ferrous Metals
50
water.45 For many substances, especially metals, reliable and high quality monitoring
data often are available and should be used in preference to estimation. Further, the
metal species should be identified to aid in dose-response evaluation of the appropriate
substance and because often only a fraction of the metal present is bioavailable due to
deactivating reactions with complexing agents.
Non-ferrous metals provide several unique challenges for exposure assessment. One
key factor is the dynamic nature of metal speciation. The form of a metal may depend
on the environmental matrix of concern. This means that site-specific factors may
strongly influence the bioavailability of the metal compound. Bioavailability refers to the
availability of a contaminant in some medium to be absorbed into biological systems.
Many factors affect the bioavailability of a metal, including dose, route of exposure, oxidation state, chemical and physical form, dietary matrix, interaction with other trace elements, and the nutritional and physiological state of the exposed individual.
Box 17: Bioavailability and Metals Speciation
Total metal concentration in an environmental medium is an unreliable guide to
hazard identification, as different species of a given metal can have substantially
different bioavailability. For example, metals usually exist in different forms in soil
with dramatically different bioavailability. A standard exposure assessment
assumes that the total content of a metal is bioavailable and able to be absorbed.
Evidence indicates, however, that most of the metals in soil are in a highly insoluble form and are not absorbed upon ingestion of soil.* A scientifically complete
exposure assessment should take into account any available data on differences
in bioavailability of different forms of metals.
*Thornton, Iain. 1996. Metals in the Global Environment: Facts and Misconceptions. International Council on
Metals and the Environment. Ottawa, Canada.
Local conditions, such as soil pH and the activity of bioconcentrating organisms, can also
significantly affect bioavailability and exposure potential. Thus, it is not just the identity of the metal species that is important, but also the environmental conditions in which
the metal species are present. Clearly, exposure assessment for non-ferrous metals presents some complex issues which challenge standard default assumptions and emphasize the need for site-specific information.
45 Risk Assessment of Existing Substances. 1993. Guidance Produced by a UK Government/Industry Working
Group, Chemical Industries Association, London.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
51
Box 18: Importance of Site-Specific Factors
Bioavailability and exposure to metals depend not only on the chemical and physical form in which the metal is present, but also on site-specific factors in the local
environment. For example, soil acidity is an important determining factor in the
bioavailability of metals in soil. The bioavailability of ions for metals such as zinc,
lead and cadmium is greatest under acidic conditions, while increasing pH
reduces bioavailability. The organisms present in soils also affect metal solubility, transport and bioavailability. Soil type, such as clay and sand content, affects
the migration of metals through soils, and therefore also the potential for exposure
through groundwater and other pathways. The dispersion of metals in surface
waters depends on the properties of the water body, such as flow rate. Exposure
to metals in the atmosphere is also affected by local conditions such as precipitation and wind. These site-specific factors emphasize the importance of context
in metal risk assessment.
Exposure assessment is yet another potential source of uncertainty in the risk assessment process, sometimes leading to large overestimates of exposure, as in the MEI, or
underestimates, as in the case of unevaluated exposure pathways. Bioavailability and
speciation are critical issues in metal exposure analysis, as exposure estimates based on
total metal levels in the environment will generally be misleading. Good exposure
assessment should explicitly quantify population variability in exposure. In addition,
assumptions should be clearly stated to permit informed evaluation of the findings.
Additionally, risk assessments for essential metals also require the determination of
whether organisms are living under deficiency conditions, and whether the particular
trace metal is rate limiting to growth. Such an assessment will be highly site-specific.
There is little published information in this difficult area and further fundamental
research will be needed to resolve outstanding questions.
In natural environmental communities, concentrations of metals are derived from the
underlying soil or surrounding water (the “background” level or the geochemical baseline). In some areas, human activity either ancient or modern, has led to an “ambient”
level which is higher than background. Biological communities have frequently adapted to ambient concentrations. Exposure and effects assessment must, therefore, discriminate between natural and anthropogenic metal concentrations and take into
account historical exposure of biological communities.
Risk Assessment and Risk Management of Non-Ferrous Metals
52
Risk Characterization
Risk characterization is the final stage of risk assessment which summarizes the information from hazard identification, dose-response evaluation and exposure assessment
into an overall conclusion on risk that is in a form useful for decision makers, legislators,
the media and members of the public.46 The result of a risk characterization is a qualitative or quantitative description of the potential hazards due to a particular exposure.
As such, risk characterization applies the available data on the inherent toxic properties
of an agent to local exposure conditions to present an overall conclusion on risk.
Because risk characterization is based in significant part on a specific exposure scenario
or scenarios, risk characterization is highly context-specific and cannot be automatically applied from one context or location to another.47
In environmental risk characterization, factors such as speciation, bioavailability, community structure, physical conditions (soil type, rainfall, seasonal weather, agricultural
practice) and biological variability affect both the exposure of organisms and the toxic
effects of metals. In addition, a sufficient concentration of essential metals is required in
the environment to avoid deficiency in organisms. This means that a generalized risk
estimate may not be appropriate to direct risk management. Currently, habitat-specific
approaches to environmental risk assessment need to consider information such as
background concentrations and biological community type. This offers scope for more
detailed and realistic estimation of risk factors for individual organisms and communities.
Quantitative risk characterization conveys a numerical estimate of the magnitude of the
risk that a substance poses to humans or the environment. This risk may be expressed
as individual risk (i.e., the probability that the substance will cause an adverse health
effect in any given organism) or population risk (i.e., an estimate of the number of organisms in a population which may be expected to be affected). Qualitative risk characterization describes in narrative form the adverse effect or effects associated with exposure
to an agent along with some measure of the evidence for the association.
The quantification of risk differs depending on whether, for example, the safety factor
approach or probabilistic risk assessment is used. The results of a probabilistic risk
assessment are estimates of the increased risk of mortality or disease, above background
rates, from a specific exposure. Any single risk estimate is dependent on many choices,
46 Gray, G.M., and J.D. Graham. 1991. Risk assessment and clean air policy. Journal of Policy Analysis and
Management. 10: 286-295.
47 This point was recently recognized by the Intergovernmental Forum on Chemical Safety, which in evaluating
the internationalization of national risk assessments observed that “Risk characterization, by definition, is a
quantitative process related to local exposure; national risk characterizations are not universally applicable.”
Intergovernmental Forum on Chemical Safety, Programme Area A: Expanding and Accelerating International
Assessment of Chemical Risks at 3 (ISG/95.3).
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
53
assumptions and judgements that are made in the calculation. Risk characterization for
the safety factor approach often relies on construction of a hazard ratio. This is the ratio
of the predicted exposure to the estimate of a safe dose, for example the RfD or TI. For
ecological risk assessment, the predicted environmental concentration/predicted noeffect concentration (PEC/PNEC) ratio is constructed in the same way. When these
ratios are well below one, it is generally assumed that the exposure is safe. Ratios near
one are often of concern and those well above one are considered a problem.
Interpretation of ratios near one is fraught with uncertainty because the safety factor
approach does not generate a best estimate of the population threshold but instead an
estimate from a consistent method. For this reason it is not clear at what dose adverse
effects might be expected.
It is primarily the way in which numerical estimates of risk are characterized and communicated that has led to much emphasis on improving the risk characterization
process. Although many risk characterization guidelines stress the need to address
uncertainty and ranges in risk estimates and to emphasize the conservative nature of
standard risk estimates, this guidance is not always fully implemented in practice.
Instead, procedures designed to generate upper bounds on the risk are often treated as
generating best estimates, and the uncertainty in risk assessment is frequently inadequately acknowledged.48 Risk estimates have often been presented as a single-point estimate rather than more appropriately expressed as a range, although many regulatory
agencies now give increased emphasis to presenting a range rather than a point estimate
of risk. Another problem is that the important roles of choice of data and extrapolation
model are sometimes not made clear, even though other plausible data or model choices may yield very different risk estimates.
Complete characterization of risk is very important to good risk management and risk
communication. Full characterization can help distinguish between exposures that are
likely to be associated with hazardous effects and those that are not. This could be
important information to make risk comparisons or to set priorities for resource allocation. In addition, characterizing risk more fully will help educate policy makers, legislators, the media and the public about what is known, and what is not known, about
health and environmental hazards.
General Principles of Sound Risk Assessment
Because all materials and activities have the potential to create risk in some contexts, it
is important to use risk assessment to distinguish the truly dangerous situations from
those which pose little risk. It is scientific information — on potential human health
48 Gray, G.M., and J.D. Graham. 1991. Risk assessment and clean air policy. Journal of Policy Analysis and
Management. 10: 286-295.
Risk Assessment and Risk Management of Non-Ferrous Metals
54
effects, potential environmental damage, and sources and types of exposure — that
allows risks to be distinguished. The following characteristics typify a sound and useful
risk assessment.
Box 19: Principles of Sound Risk Assessment
The seven principles of sound risk assessment reviewed in the following
text are:
1.
2.
3.
4.
5.
6.
7.
Evaluation of all relevant scientific information, including both positive and
negative studies.
Use of a weight-of-the-evidence approach.
Explicit identification of assumptions and uncertainties.
Evaluation of alternative assumptions.
Presentation of risk as a range rather than a point estimate.
Use of an iterative risk assessment process that progresses from bounding
or screening analyses to numerical distributions of risk.
Summarize results in a concise yet accurate report.
1. Evaluation of All Relevant Scientific Information, Including Both Positive and
Negative Studies. Risk assessment utilizes information from epidemiology, toxicology,
occupational medicine, industrial hygiene, exposure assessment, ecotoxicology and
many other disciplines to characterize the potential dangers of exposure to hazardous
materials. In order to characterize risk fully, it is necessary that all scientific information be evaluated and that the results of the risk assessment be measured against relevant criteria such as good laboratory practice standards. For metals, it is particularly
important that the data used be relevant to the specific metal species or compound being
assessed, which can happen only if such data are both available and considered.
Assembling all relevant scientific information is a prerequisite to good risk assessment.
This may include model estimates, the results of a literature search, and toxicological,
epidemiological, industrial hygiene, and environmental monitoring data. A risk assessment will be incomplete and prone to misleading results if it only considers some of the
available relevant data. The most useful risk assessments are therefore not limited to
positive studies showing an adverse effect from the substance in question, but also give
appropriate weight to negative studies that show no association between the substance
and adverse health effects. In such assessments, the entire data set for the substance is
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
55
considered to permit an informed and scientifically credible judgement of the weight-ofevidence for a harmful effect and to aid in understanding of the dose-response relationship.
The data may be compared, for instance, to evaluate whether animal-based risk estimates are consistent with epidemiological findings, or whether specific species in an
ecosystem may be particularly sensitive to an agent. Evaluation of the quality of available studies is also key. Of course, well-designed studies are preferred over those of
questionable relevance. Many older experiments were conducted before the standards
of good laboratory practice (GLP) were established and may not be as reliable as more
recent studies. Established guidelines for good epidemiological practice should also be
consulted to evaluate the quality of epidemiological data. Even studies that comply with
GLP can differ greatly in the quality of the study design and implementation. For risk
assessment to be based on a sound scientific foundation, it must use the most relevant
and best scientific information in a straightforward, unbiased manner.
2. Use of a Weight-of-the-Evidence Approach. Once all the relevant data have been
collected, including both positive and negative studies, the data are best reviewed and
considered using a weight-of-the-evidence approach. A weight-of-the-evidence approach
considers both animal and human data, the number and consistency of studies that produce a positive or negative result, the quality of the studies, the relevance of particular
disease mechanisms and routes of exposure in animal studies for humans, the uncertainties and limitations of particular studies, and any other data that may provide relevant information on whether a particular agent is likely to be a human or environmental
hazard and the magnitude of any such hazard.
There are no clear and simple rules for applying a weight-of-the-evidence approach, but
rather the analysis for any given agent must be based on sound scientific judgement that
considers all relevant data. Some risk assessments give undue emphasis to positive
results and give much less consideration to mechanistic data and negative test results,
and hence are not truly based on the weight of the evidence. In weighing the available
data, the absolute number of positive versus negative studies will rarely be a reliable
indicator of hazard. The quality of the data must be considered as well. Evaluation of
the relevance of a particular laboratory study or technique to the real-world situation
under consideration is also necessary. This approach relies on the judgement of scientists, medical experts, industrial hygienists and engineers to synthesize current information and new information as it becomes available.
3. Explicit Identification of Assumptions and Uncertainties. Rarely are data available to allow a complete assessment of risk. Instead, default assumptions are used when
data are lacking or theory is ambiguous. For example, in the absence of evidence to the
contrary, current carcinogen hazard identification practices assume that an animal car-
Risk Assessment and Risk Management of Non-Ferrous Metals
56
cinogen also has the potential to be a human carcinogen.49 It is usually assumed that a
compound which is carcinogenic at high doses, in either occupational studies or in animal tests, will also be carcinogenic at low doses. Some exposure assessments assume
that the MEI for an industrial facility spends his or her entire 70-year life span outdoors
at the fence line of the factory. Some of the assumptions used in risk assessment are generally accepted while others are matters of a great deal of contention.50
The most useful risk assessments explicitly identify and discuss the assumptions used as
well as their degree of scientific plausibility. Ideally, the rationale for a particular
assumption (as well as the degree of scientific consensus about its appropriateness) is
discussed. If there is no scientific agreement, credible alternative theories and assumptions are evaluated and presented. It is also helpful when pending or potential research
which could help refine or clarify the risk assessment is identified.
In addition to identifying the assumptions used, a meaningful risk assessment also
attempts to estimate and make explicit the uncertainties in the risk assessment. Because
of the unavoidable use of assumptions and models in risk assessment, risk estimates are
usually highly uncertain. Moreover, the exact relevance of animal tests to human risk
and the predictive value of epidemiology from high workplace exposure levels to environmental exposures raise additional uncertainties. The real-world representativeness
of uncertainty factors or mathematical models for high- to low-dose extrapolation in
dose-response evaluation is necessarily uncertain. Additionally, the quality of available
data may be limited. Methods of exposure assessment, especially when exposure may
be from many pathways, are generally rudimentary. All of these factors contribute to the
great uncertainty in estimates of risk.
In the past, uncertainty in risk assessment has led to the principle of conservatism. In
the face of uncertainty about the best estimate of an input to risk assessment, an “upper
bound” value was often used. More and more, however, it is recognized that conservative risk assessment distorts decision making because it does not provide the decision
maker with an accurate representation of the range of plausible risk estimates for a
given activity or substance. It is critical that uncertainty be acknowledged, characterized
and described quantitatively both to provide meaningful information to the decision
maker and to guide scientific research. Current and future scientific research will help
reduce the uncertainties in many aspects of risk assessment, but substantial uncertain-
49 Risk Assessment Forum, US EPA. 1991. Alpha2-Globulin: Association with Chemically Induced Renal Toxicity
and Neoplasia in the Male Rat, EPA/625/3-91/019F discusses a situation in which chemically induced tumours
in animals are not believed to indicate human risk.
50 Rosenthal, A., G.M. Gray, and J.D. Graham. 1992. Legislating acceptable risk from exposure to toxic chemicals. Ecology Law Quarterly. 19: 269-362.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
57
ties will remain in risk assessment for the foreseeable future.51 Explicit identification of
these uncertainties in a risk assessment helps to ensure that the analysis is properly
understood and used.
Box 20: Bioaccumulation of Metals
Animals and plants actively regulate the uptake of metals from their environment.
For essential metals, biochemical and behavioural mechanisms combine to facilitate uptake when the metal is needed. Organisms may also take up non-essential metals and store them away from sensitive cellular processes to reduce their
toxicity. An extreme example is for cadmium and zinc in isopods where levels of
up to 5000 mg/kg can be accumulated in the gut. Resistant plants may also hold
metals externally in nodules in root or cell walls and algae commonly adsorb metals to their external surface*. For organic substances, accumulation potential can
be estimated either from simple accumulation tests or from physico-chemical
properties, principally octanol-water partition coefficients, which correlate with
accumulation in tissues (for example see the European Union Risk Assessment of
Existing Substances: Technical Guidance Manual). However, for the reasons outlined above, this general approach cannot be applied to inorganic forms of metals, though it may apply to organometallic complexes. The wide variety of
mechanisms by which organisms handle essential and non-essential metals
means that bioaccumulation has to be assessed individually for both the metal
involved and the type of organism exposed.
*WHO. 1992. Environmental Health Criteria No.135 Cadmium - Environmental Aspects. Geneva, Switzerland.
*WHO. 1989. Environmental Health Criteria No. 85 Lead - Environmental Aspects. Geneva, Switzerland.
4. Evaluation of Alternative Assumptions. As discussed above, the choice of assumptions and analytic inferences have appreciable influence on estimates of risk. The most
useful risk assessments evaluate and report the effect of alternative assumptions and
inferences on estimates of risk. Some of these assumptions are made according to “science policy” guidelines derived by some agency, others fall into the realm of judgement
when risk assessors make one choice from many plausible alternatives. Examples of the
assumptions and choices in risk assessment include the choice of the animal data set for
modelling human risk, the choice of a dose-response model from many plausible alter-
51 See Rosenthal, A., G.M. Gray, and J.D. Graham. 1992. Legislating acceptable risk from exposure to toxic chemicals. Ecology Law Quarterly 19: 269-362 for a discussion of many of the sources of uncertainty in current risk
assessment.
Risk Assessment and Risk Management of Non-Ferrous Metals
58
natives, the choice of endpoint on which to base an RfD, the choice of which adjustment
factors to apply in deriving a PNEC, and the choice of the particular model parameter for
risk estimation. All of these choices have some effect on the final estimate of risk.
Alternatives for some assumptions might substantially change the estimate of risk, while
plausible options for others would have little effect.
Thorough risk characterization involves justification of the assumptions and choices
made in an assessment and discussion of the impact of alternative inferences on the estimate of risk. It is helpful when other plausible estimates of risk, developed using alternative assumptions, models or data, are presented. If possible, identification of the risk
estimate or estimates with the greatest scientific support also provides useful information. This fosters better understanding of a risk assessment by all users of a risk assessment, and more scientifically defensible decisions.
5. Presentation of Risk as a Range Rather Than as a Point Estimate. A potential
problem with risk assessment is that many decision makers and other users of risk
assessments may give too much credence to a single point estimate of risk and underappreciate the uncertainties that accompany the point estimate.52 It is desirable instead
to present the range of possible risk values, especially when there is no solid basis for
concluding that any one point estimate in the range is more likely than any other. One
way to address this problem is to present a central tendency of risk accompanied by
upper and lower bound risk estimates.53 Also, statistical methods are available and are
increasingly being used to provide a range of risk estimates. For example, a method
known as Monte Carlo analysis uses a range of data rather than a point estimate as
inputs for each parameter in the risk assessment and then uses a large number of iterations to generate a probability distribution for the risk estimate. Other approaches are
also being evaluated (Box 21).
6. Use of an Iterative Risk Assessment Process That Progresses from Bounding or
Screening Analyses to Numerical Distributions of Risk. A key characteristic of useful
risk assessments is that the analysis fits the intended use. Analysis can be costly and time
consuming. The risk assessment process, therefore, is most effective as an iterative
undertaking that progresses from quick and simple bounding calculations to more complex numerical distributions of risk only as the needs (and the stakes) of the decisions
increase.
52 Gray, G.M., and J.D. Graham. 1991. Risk assessment and clean air policy. Journal of Policy Analysis and
Management. 10: 286-295.
53 US EPA. 1986. Guidelines for Carcinogen Risk Assessment. (51 Fed. Reg. 33992); Gray, G.M., and J.D. Graham.
1991. Risk assessment and clean air policy. Journal of Policy Analysis and Management. 10: 286-295.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
59
The use of a risk assessment should influence the conduct of the analysis. In the risk
assessment framework described in Chapter 3 (Figure 2), the dashed line connecting
risk management and risk characterization is intended to highlight the fact that the level
of complexity of risk characterization should depend on the needs of the risk manager.
Frequently, bounding or default risk assessment procedures may be used to confirm that
a particular exposure situation is not a problem. However, if these screening calculations indicate a potential problem or the societal stakes in a decision are large, more
complete risk characterization will be necessary.54 Many current risk assessment
methodologies for ecotoxic effects also explicitly utilize this iterative approach.55
7. Results Summaries in a Concise Yet Accurate Report. Risk assessment is a complex process that relies on scientific information, mathematical models and expert
judgement. It is therefore important that the results of this process be reported in a way
that is concise and useful yet accurately portrays the uncertainties, assumptions and scientific knowledge that underlie the assessment.
Box 21: The Distributional Approach to Risk Analysis
One proposed method for more complete risk characterization is the distributional approach, which uses subjective expert judgement to assess the likelihood of
alternative estimates of risk. This method can capture the range of scientific evidence and opinion on the key biological uncertainties. The distributional
approach uses explicit expert judgement to analyse and quantify the plausibility
of alternative models and interpretations of available data. The result is a distribution of risk estimates, each weighted by the expert-assessed probability of the
plausibility of the estimate. This distribution can be contrasted with the single
estimate of risk developed through default procedures.
Gray, G.M., J.T. Cohen and J.D. Graham. 1993. The challenge of risk characterization: Current practice
and future directions. Environmental Health Perspectives Supplements 101: 203-208.; Evans, J.S., J.D.
Graham, G.M. Gray, and R.L. Sielken Jr. 1994. A distributional approach to characterizing low-dose cancer risk. Risk Analysis 14: 25-34.
54 National Research Council. 1994. Science and Judgement in Risk Assessment. National Academy Press,
Washington, DC.
55 For example, see Commission Regulation 1488/94 Laying Down the Principles for Assessment of Risks to Man
and the Environment of Existing Substances in Accordance with Council Directive 67/548/EEC; Zeeman, M.,
and J. Gilford. 1993. Ecological Hazard Evaluation and Risk Assessment Under EPA’s Toxic Substances Control
Act (TSCA): An Introduction in Environmental Toxicology and Risk Assessment. W.G. Landis, J.S. Hughes, and
M.S. Lewis, eds. American Society for Testing and Materials, Philadelphia, PA.
Risk Assessment and Risk Management of Non-Ferrous Metals
60
Risk assessments are used in many ways. They are used to assist in risk management
decisions such as how much a hazardous waste site should be cleaned up or what precautions are necessary to handle a dangerous material safely. The results of risk assessments are also communicated to legislators, policy makers, the media and the general
public. Because risk management is itself a process which requires input from many different disciplines (i.e., economics, engineering, political science, epidemiology, toxicology, occupational medicine, industrial hygiene) and requires judgement, more complete
characterization of risk is necessary. Factors such as scientific uncertainty, assumptions
used in exposure assessment, or level of population risk may be very important to a decision maker who relies on a risk assessment. It is therefore crucial that the results of a
risk assessment be communicated in a way that is clear, accurate and scientifically
defensible.
Conclusion
Risk assessment provides a method for organizing scientific information to aid in understanding potential human and environmental hazards. It is helpful when risk assessment can be quantitative, allowing understanding of the potential magnitude of risk or
the exposure levels which may lead to harm. However, it is important to emphasize that
risk assessment should not simply be an algorithm for producing regulatory numbers,
but rather should be a flexible process for providing insight into potential health and
environmental effects. Flexibility means that the level of sophistication of an analysis
should be tied to the needs of a risk management decision. It means that the risk assessment process should not be regimented but instead consider evidence and information
on a substance-by-substance basis. It means that the process must be able to respond to
new scientific information. It means that risk assessment must effectively organize and
communicate essential information to decision makers and to the public.
Risk assessment of non-ferrous metals presents many special challenges. Metals must
be assessed according to the species or compound under consideration to the extent that
available data permit. The essentiality of many metals for life puts logical lower bounds
on safe intake levels and reminds us that some dose of these metals is desirable. Metals
have also been found to have different effects through different routes of exposure in different biological species. Risk assessment should give the greatest weight to data for relevant routes of exposure. Exposure assessment of metals should also be specific for
each physico-chemical form when the necessary data are available. Differences in
bioavailability — due to solubility, the formation of complexes, or adsorption to soils or
sediments — must be considered. Local differences in the environment, such as soil pH
and the activity of bioconcentrating organisms, can also significantly affect metal risks.
Finally, the natural background levels of these elements must be kept in mind when estimating risk.
Chapter 4 - Towards Sound Risk Assessment of Non-Ferrous Metals
61
It is clear that effective risk characterization must adequately address uncertainties,
assumptions, alternative choices of analysis and the full range of plausible risk estimates. Risk managers, public policy decision makers and, insofar as possible, the public, must be made aware of the strengths and limitations of a risk assessment to allow
informed evaluation and use of a risk assessment.
Risk Assessment and Risk Management of Non-Ferrous Metals
62
CHAPTER 5
Balancing the Risks, Benefits and
Costs of Non-Ferrous Metals
Risks are only one side of the equation in evaluating non-ferrous
metals. The benefits of non-ferrous metals must also be considered,
as well as the costs of replacing or limiting specific uses of metals.
This chapter summarizes key issues that must be evaluated in
weighing the risks, benefits and costs associated with non-ferrous
metals. A common factor in evaluating these three parameters is
that they are all highly context-specific and depend on the specific
metal type and application at issue. Reasonable decision making
therefore requires the balancing of the risks, benefits and costs
associated with specific uses of non-ferrous metals.
T
he identification and assessment of risks, as discussed in the previous two
chapters, provide necessary but insufficient information for making sound risk
management decisions for non-ferrous metals. Also critical to the policy-making
process are the benefits of the various applications of non-ferrous metals and the societal
costs of reducing the risks from non-ferrous metals. Individuals and organizations
generally make decisions by balancing the actual or potential risks, benefits and costs of
alternative courses of action. Benjamin Franklin referred to this weighing of pros and
cons as the “moral or prudential algebra” of decision making.56 In the same way,
industry, governments and society as a whole must balance risks, benefits and costs in
developing sound, responsible policies for the safe and productive use of non-ferrous
metals. This balancing of risks, benefits and costs cannot be done in the abstract or for
metals in general, but must look at the specific context of each metal application, and the
particular risks, benefits and costs associated with each application and its alternatives.
The risks of a metal application, as discussed in the previous two chapters, are the
potential created by a specific metal use to cause harm to public health or the
environment. The benefits of a specific metal application are the economic, social and
aesthetic value provided to society by that use of metal. Finally, costs refer to what
56 Quoted in E.M. Gramlich. 1981. Benefit-Cost Analysis of Government Programs. Prentice-Hall, Englewood
Cliffs, NJ.
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
63
society has to give up to reduce the risks of a particular metal application. The goal of
society should be to maximize benefits while minimizing risks and costs, including the
transaction costs of the regulatory or risk management apparatus through which the
goal is sought. Because this goal involves many tradeoffs and choices, it necessarily
involves the balancing of risks, benefits and costs. Only by fully exploring the benefits,
risks and costs of particular metal applications in the specific contexts in which they
occur can the optimal balance for the various potential uses of non-ferrous metals be
identified.
Box 22: Example of Metal Toxicity from Industrial Source
An example of acute metal toxicity from an industrial source of metals is the
occurrence of numerous cases of itai-itai (ouch-ouch) disease in the Toyama prefecture in Japan after World War II. This outbreak of itai-itai disease, which
adversely affects bones, kidneys and other organs, was found to be primarily
associated with excessive ingestion of cadmium in food and drinking water, possibly modified by other factors such as living conditions, exposure to sun and
nutrition. The risk was identified, remedial and preventive measures were taken,
and consequently this painful disease is now very rare.
Tsuchiya, K. 1992. Health effects of cadmium with special reference to studies in Japan, in Cadmium in
the Human Environment: Toxicity and Carcinogenicity, Nordberg, G.F., et al., eds. IARC Scientific Publication
No. 118.
Risks
The application of hazard identification and risk assessment to non-ferrous metals was
discussed in the two previous chapters. The key point emphasized here is that the
potential risks from real-world applications of non-ferrous metals are highly contextspecific. Risk depends on factors such as the type and species of the metal, the intended
use of the metal, the potential for exposure, the dose that is actually delivered, and the
potency and toxicity of the specific metal substance in question to the human or
environmental receptor of concern. Both in nature and as used by humans, most metals
(with certain exceptions) are not in a form that can be easily dispersed, and thus do not
result in significant environmental or human exposure, a critical determinant of risk.
Nevertheless, in some contexts, environmental releases of non-ferrous metals can occur
from natural causes such as weathering of rock and soil, or from human activity such as
the combustion of metal-containing fossil fuels (i.e., coal and oil), a variety of industrial
Risk Assessment and Risk Management of Non-Ferrous Metals
64
processes including the production and processing of non-ferrous metals, and the use or
disposal of metal-containing products. In some cases, those natural, industrial or
consumer sources of released metals can result in a significant or unreasonable risk to
human health or the environment.
Toxicity from industrial production of non-ferrous metals is often perceived as a primary
source of human exposure. Such exposures are dramatized by high-profile incidents
involving acute exposures with clearly manifested health or environmental impacts. An
example is the outbreak of itai-itai disease in Japan after World War II caused by high
cadmium exposures (Box 22). Most metal exposures of concern from industrial
processes, however, involve lower, chronic exposures that are usually more difficult to
evaluate for their impact on public health and the environment.
Toxicity can also result from the use of specific metal products. Such toxicity usually, but
not always, results from products that are dispersed into the environment. Such
dispersion can result from processes such as flaking, disintegration from wear and tear,
leaching, combustion or other processes that cause the metal to be dispersed into the air,
water or other media. An example is the flaking and peeling of lead-based paint,
resulting in lead dust particles that can result in human exposure through ingestion and
inhalation (Box 23).
Box 23: Example of Toxicity from a Metal Product
An example of a metal-containing product that has resulted in unacceptable societal risks is lead-based interior paints. Although intact lead-based paint does not
result in significant human exposure, flaking and peeling paint creates the potential for childhood lead poisoning. Children are particularly susceptible to exposure
through the ingestion of paint chips and inhalation of lead-containing dust particles resulting from deteriorated lead paint. In many industrialized countries, deteriorated lead-based paint is now believed to be the most significant source of lead
exposure for children. High exposures to lead have been associated with
impaired neurobehavioural functioning and other health effects. Because of the
potential for such exposure, the use of lead in interior paints has been banned or
restricted in most industrialized countries.
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
65
Finally, exposure to non-ferrous metals can result from natural sources of the metals,
which are ubiquitous in the Earth’s crust, soils, air and waters. Major uncertainties exist
about the relative contributions of natural and anthropogenic sources of metals in the
environment. For example, while airborne metals are often assumed to result from
human activities, naturally occurring metals are present and are transported in the
atmosphere as a result of windblown dust, sea spray, volcanic activity, forest fires and
other processes. Significant data gaps and uncertainties remain about the relative
contribution of natural and anthropogenic sources of non-ferrous metals in various
environmental media.
Box 24: Natural Sources of Metals in the Atmosphere
There is substantial uncertainty about the relative contributions of natural and
anthropogenic sources of metals found in the atmosphere and deposited on land
and in water. A recent review found large variations in the published literature
about the contribution of natural sources to atmospheric mercury levels. Five
published studies differed by almost three orders of magnitude in estimating natural sources of mercury to the atmosphere. The review concluded that “ample evidence exists in the literature to indicate that geological sources and pathways of
Hg [mercury] are significant in any remote landscape and should not be assumed
to be negligible.”
Rasmussen, P.E. 1994. Current methods of estimating atmospheric mercury fluxes in remote areas.
Environmental Science and Technology. 28: 2233-2241.
Life Cycle Analysis
Examples of unreasonable risk such as those noted above are the exception rather than
the norm for metal uses today, and are typified by substantial acute or chronic exposures
to bioavailable forms of metal. The potential for these types of exposure is a critical
factor in determining risks from non-ferrous metals. Life cycle analysis is the process of
evaluating the potential environmental impacts associated with a product from “cradle
to grave” and evaluating opportunities to reduce those impacts. For non-ferrous metals
that are recycled, life cycle analysis could be described as “cradle-to-cradle”
management. There are several stages in the life cycle of a typical use of metals that
have the potential for human or environmental exposures, and therefore are most
relevant for risk management consideration.
The first stage of the product life cycle of relevance to risk management is the production
process, including both the primary production of the raw metal and the fabrication of
Risk Assessment and Risk Management of Non-Ferrous Metals
66
the finished metal product. Such production involves the potential for environmental
release and human exposure to metals via air emissions, dust and fugitive emissions,
wastewater discharges, solid and hazardous waste production, and occupational
exposures. These potential exposures could affect workers in the facility and the
surrounding communities and environment. Exposures from production processes have
been dramatically reduced over the past 25 years through the use of new process
equipment such as closed system processing units, better work practices, improved
industrial hygiene, “end-of-pipe” controls on discharges, and more strictly controlled
waste-handling procedures. Nevertheless, because the production process often
involves the potential for the highest exposures, this step of the metal’s life cycle remains
a major focus of risk management activities for non-ferrous metals.
The second stage of potential exposure is during product use. Most metal products used
by consumers are stable and intact, with little or no metal dispersion or exposure. The
potential for risk from the use of metal products arises from specific uses or types of
metal-containing products that have the potential for significant human or
environmental exposure to metals in a bioavailable form. For example, the use of lead
solder in contact with certain foods or waters has been found to result in leaching of the
metal into food or water, creating the potential for human exposure. In contrast, nonferrous metals contained in many consumer products are immobile or embedded in an
insoluble matrix that minimizes the potential for significant leaching or consumer
exposure. The potential risks from each metal-containing product therefore depend on
the specific use, composition and form of the individual product, as well as the potential
for environmental dispersion of the metal in the product.
Box 25: The Relationship Between Release and Risk
While the potential for environmental release of non-ferrous metals is one critical
factor for determining the existence and magnitude of health risks from metal-containing products, it should be emphasized that not all releases of metals into the
environment are necessarily dangerous. Many releases are too small to present
or contribute to a significant risk to human health or the environment, and some
“releases” into the environment are beneficial, such as the use of zinc fertilizers
in gardens. Conversely, a few uses of metals in products can also present risks
without environmental release, such as the contact dermatitis that may result in
sensitized individuals from skin contact with some products containing metals
such as cobalt or nickel.
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
67
The third relevant stage of the product life cycle for risk management is disposal. Like
the other stages of the product life cycle, the potential for risk at the disposal stage
depends largely on the extent to which the metal will be released into the environment
and results in significant adverse exposure to receptor organisms. Recycling reduces the
amount of metal-containing waste that needs to be disposed, thereby reducing the
potential for exposure at the disposal stage. For metal that is disposed, more stringent
regulatory requirements for industrial and municipal waste disposal in recent years have
substantially reduced the potential for runoff and leaching of metals from disposal sites.
Moreover, most elemental metals and metal compounds are stable, and therefore do not
present a significant risk of environmental release when properly disposed. Thus,
compliance with appropriate disposal methods is key for minimizing risks at the disposal
stage of the product life cycle. The incineration of wastes has the potential to emit
metals contained in the waste stream, but proper emission control technology will
capture almost all such metal emissions. The captured metals must again be properly
managed to avoid damaging releases to the environment.
Box 26: Facility Decommissioning
In addition to proper disposal of metal-containing products and wastes, sound
environmental practices also require appropriate closing and decommissioning of
facilities that are no longer in use. Many years ago, the common practice in industry may have been to simply abandon closed facilities, which may have presented
risks to nearby residents and future users of the property. Today, increasingly
sophisticated practices have been developed for environmentally responsible
closing and decommissioning of facilities, including restoration actions and due
diligence audits to assess any remaining environmental risks at the facility.
Facilities that do not follow such practices, however, can produce residual risks to
surrounding areas following shut-down.
In summary, the risks associated with the use of metal products are context-specific, and
should be evaluated for each individual use of metal throughout the product life cycle.
The potential for environmental dispersion is important in understanding the potential
for risks to human health or the environment, but is not, in itself, determinative. Most
properly managed uses of metals proceed through their product life cycle without
damaging release of metals into the environment. Where there is the potential for such
release of metals into the environment, the environmental and health risks from those
particular metal uses should be evaluated to determine whether such risks are
acceptable.
Risk Assessment and Risk Management of Non-Ferrous Metals
68
Acceptable Risk
The acceptability of any particular risk cannot be determined by any simple parameter
-6
or rule. Individual lifetime risks of one in one million (1 x 10 ) or smaller are often
described as de minimis and are usually considered to be acceptable. An individual
-3
lifetime risk of one in one thousand (1 x 10 ) or higher is usually considered to be
unacceptable. But the acceptability of a risk between these two poles will usually depend
on a number of other factors. Research on public perception of risk indicates that
acceptability will often depend on factors such as whether or not the risk is voluntary,
57
controllable, inequitable or dreaded. The number of people at risk, and therefore the
expected incidence of the health effect in the population, is also an important factor in
58
determining the acceptability of levels of individual risk.
Finally, the benefits associated with a particular risk, and the costs of reducing that risk,
59
are often a critical factor in determining the acceptability of the risk. For example, even
though automobile accidents are one of the largest causes of death and injury in
industrial societies, most people find such risks acceptable (as evidenced by their
continued use of automobiles) because of the benefits they obtain from automobile use.
Of course, even if a risk is acceptable, additional risk reduction should be pursued if it
can be achieved at reasonable cost and without sacrificing the benefits of the activity.
Thus, the initial acceptability of a risk, and the reasonableness of further risk reductions,
will often depend on the costs and lost benefits associated with a potential risk reduction
option. Benefits and costs are discussed in the next two sections.
Benefits
The other side of the ledger to risks is the benefits of non-ferrous metals. If non-ferrous
metals did not produce any societal benefits, the simplest risk management strategy
might be to simply restrict all uses of non-ferrous metals that present non-negligible
health risks. Of course, non-ferrous metals do provide important benefits to society, as
demonstrated by the multitude of diverse applications of these materials. A more
balanced approach, that considers both the risks and benefits of particular uses of nonferrous metals, is therefore necessary.
The benefits of non-ferrous metals are largely demonstrated by the multitude of uses of
these materials, summarized in Chapter 2. These many applications provide social
benefits through the direct use of metals to fulfil human needs and aspirations, such as
shelter, warmth, food supply, communication, transportation, security, leisure, aesthetic
57 Slovic, P. 1987. Perception of risk. Science. 236: 280-285.
58 Travers, C.C., et al. 1987. Cancer risk management. Environmental Science and Technology. 21: 415-420.
59 Alhakami, A.S. and P. Slovic. 1994. A psychological study of the inverse relationship between perceived risk
and perceived benefit. Risk Analysis. 14: 1085-1096.
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
69
appreciation, information supply and many others. Indeed, it is difficult to envision a
human need or activity that in some way does not involve non-ferrous metals. In
addition to these direct benefits of metals, non-ferrous metals contribute additional
benefits to society as a critical component of the manufacturing, telecommunications,
computer and transportation infrastructure that is used to provide many other goods and
services to the public. It is not coincidental that the richest, healthiest countries in the
world also consume the most metals. Capital investment — not just in machinery and
transport, but also in schools and hospitals — is a driver of future growth and material
well-being, and is a highly metals-intensive undertaking.
An important consideration in evaluating the benefits of any particular use of metals is
the relative availability of suitable substitute materials. There are some uses of metals
that are being phased out because of the availability of cheaper, less toxic, or better
performing substitutes. For example, optic fibres are now replacing copper for many
uses in electrical signal transmission because of lower cost and other desirable
properties. Similarly, high octane gasoline components have replaced lead in gasoline
in many areas of the world for anti-knock protection because of health and
environmental concerns from the use of leaded gasoline (it might be noted, however,
that the removal of tetraethyl lead from gasoline did increase risks associated with
increase in the aromatics content of gasoline). On the other hand, there are many uses
of non-ferrous metals that are indispensable and for which no suitable substitutes exist.
There are still more uses where the many desirable attributes of metals provide
important advantages over available substitutes. In addition, new technologies, products
and processes are continually being developed which — after consideration of all
relevant performance, cost and environmental factors — incorporate metals as the most
suitable material for the new applications.
The competitive advantage, and therefore benefits, of any particular use of non-ferrous
metals is in dynamic flux, changing and evolving over time. Certain uses of metals that
provided major social benefits in past years may have their benefits diminished as new
substitutes become available, and therefore will be gradually phased out. As both
modern history and future projections confirm, however, new uses of metals arise to take
their place. The end result of these dynamic processes has been a continuous increase
in the overall use of non-ferrous metals, with a corresponding increase in societal
benefits.
In considering the benefits of any particular use of non-ferrous metals, the specific
context and circumstances of that use are critical for determining net benefits to society.
As demonstrated by the example in Box 27, the reasonableness or acceptability of risks
depends on the nature and context of the risk-creating activity, and the benefits
associated with the activity.
Risk Assessment and Risk Management of Non-Ferrous Metals
70
Box 27: The Importance of Context
The importance of context in considering risks and benefits is illustrated by an
example involving two uses of mercury that present similar risks but very different
benefits. A recall was recently announced in the USA for necklaces containing
small glass vials of mercury, because of the risk that the vials would break and
result in human exposure to mercury.* Even though the risks involved may be very
small, the minimal societal benefits of using mercury vials in jewellery were
judged not to justify those risks. In contrast, the use of mercury in thermometers
may present similar risks (i.e., the potential for some mercury exposure as a result
of infrequent breakage), but there has been no recall of mercury-containing thermometers given the important medical and other benefits provided by this use of
mercury.
Product Safety & Liability Reporter (BNA) (Dec. 9, 1994) “Product Recalls: Necklaces Poses Health Risk”.
•
Costs
The third major input to sound risk management decisions, which unlike risks and
benefits has not been discussed in previous chapters, is the cost of reducing risks.
Attempts to reduce risks usually impose direct and indirect costs on the affected industry,
consumers and society in general. These costs accordingly can potentially be evaluated
from many different perspectives — including that of the regulated industry, consumers
or society at large. While overall societal costs are usually the appropriate metric to
evaluate the costs of regulation, the distribution of those costs within different sectors of
society may also be a relevant factor to consider. It also bears emphasizing that the
evaluation of regulatory costs, like the assessment of health and environmental risks,
often involves incomplete information and uncertainties that must be addressed by
assumptions and models. As with risk assessment assumptions and models, these
economic assumptions and models can be controversial and subject to differing views.
Sensitivity analysis is often a useful tool to evaluate how critical a specific assumption is
to the final result.
The most important societal costs are those that result in the unavailability of certain
materials or increase in cost or quality of goods to consumers. These costs are generally
the mirror image of the benefits discussed in the previous section, and therefore risk
management will be most successful when it controls risks while to the maximum extent
possible retaining the benefits of metal uses and thus avoiding the societal costs
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
71
associated with reducing those benefits. In addition to the costs of lost benefits, other
relevant cost considerations for evaluating risk management options include the costs of
promulgating and complying with regulations, the adverse effects on an industrial
sector’s competitiveness, potential structural changes in economies and markets
resulting in job transfers or even unemployment, and increased use of substitutes for the
regulated products which may themselves present other risks.
In many cases, the costs of reducing risks will be justified by the resulting improvements
in environmental quality, worker health and public health. In other cases, the costs
imposed on society may be disproportional to the health and environmental benefits
achieved by a particular control option. Finally, there may be other ways to achieve
equivalent risk reductions at a much lower overall cost. Under any of these scenarios,
the estimation and consideration of the cost impacts of a particular course of action is
essential to ensure prudent decision making.
Box 28: Cost Analysis — Three Basic Questions
The evaluation of the costs of possible risk reduction measures involves a series
of questions, including:
1.
2.
3.
What is the cost of implementing and administering the regulations?
What is the implied cost of substitution?
What are the macroeconomic costs involved?
The appropriateness of the proposed measures will depend significantly on the
evaluation of these three questions.
1. What Is the Cost of Implementing and Administering the Regulations? The
implementation of any regulation involves two types of direct costs: administrative costs
and compliance costs. Administrative costs are the costs for a government agency or
other authority to collect relevant data, draft a proposed regulation, provide for public
and expert comment, promulgate a final regulation, and monitor and enforce the
regulation. These costs are mostly borne by the government agency promulgating the
regulation, and ultimately taxpayers. Although these administrative costs are
substantial, they represent a relatively small percentage of the total costs of most risk
reduction regulations.
Risk Assessment and Risk Management of Non-Ferrous Metals
72
Regulated entities incur compliance costs in order to undertake the actions necessary to
participate in the rule-making process and to comply with the regulations. These
compliance costs can take many different forms, including the costs of pollution control
equipment, the modification of production or distribution processes, changes in plant
architecture and layout, the substitution of more costly alternatives, increased
occupational exposure monitoring and controls, and the training, research, monitoring,
testing and reporting necessary to meet the ancillary requirements of many regulations.
Because these compliance costs are mostly incurred by private businesses, they are not
part of governmental budgets. These costs are therefore not always apparent to the
public, even though the costs are ultimately paid for by consumers in the form of
increased prices and reduced availability of consumer products. In recent years, the
public has nevertheless made clear with actions and words that it is prepared to incur
significant costs that are necessary to ensure safe jobs and products, and a clean
environment. There are limits to how much the public is willing to pay, however, and
therefore the costs of proposed actions need to be carefully calculated and considered.
2. What is the Implied Cost of Substitution? Regulations that directly or indirectly
limit the production, distribution or use of a substance or product can lead to substitution
by other products to fulfil the same function or consumer need. Substitution is a wellknown phenomenon for economists, who generally evaluate the substitutability of two
products based on their relative prices. Like relative pricing, regulation can also trigger
substitution, either by banning or phasing out a substance (which automatically results
in transfer to substitutes), or by increasing the costs associated with one substance
through increased regulatory burdens, which adversely affects the product’s
competitiveness relative to less regulated substitutes.
The potential of regulation to promote substitution can impose two types of costs on
society. First, from a strictly economic standpoint, recourse to substitution raises the
costs of the function fulfilled by the initial product. If a product occupies a particular
segment of an open market prior to regulation, it very likely offers certain price and
performance advantages that make it the best value compared with its competitors. The
transfer to the substitute forced by regulation will therefore lead, in the short term at
least, to lower performance, higher cost, or both, compared with the market’s previous
balance. For some metal uses, it may be difficult to find a suitable substitute material
because of the unique properties of metals. When no suitable substitute is available, the
costs of restricting or increasing the cost of a metal use will result in greater societal
costs as some product uses will be foregone completely.
The second potential cost of regulation-induced substitution is that the substitute
product may impose its own risks on society, which may reduce or even outweigh the
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
73
60
risk reduction benefits from the regulation. Many substances that are later determined
to be unreasonably dangerous were initially justified for their capability to reduce other
risks. For example, asbestos was at one point required by regulations aimed at
minimizing fire hazard, PCBs replaced other substances more prone to fire in electrical
transformers, and CFCs replaced dangerous ammonia in refrigeration. In retrospect, we
now know that these products presented their own risks that may have been greater than
the products that they were intended to replace.
Box 29: Risk-Risk Tradeoffs
Risk-risk tradeoffs are common to many regulatory programs, although the importance of such tradeoffs has generally been underappreciated until recently. An
example is the occupational and transportation risks associated with hazardous
waste site remediation. A case study of a Superfund cleanup site at a copper
smelter in the USA found that the increased fatalities and injuries incurred by
workers involved in cleaning up and transporting the hazardous wastes at the site
would approach, and in some scenarios surpass, the predicted health benefits of
cleaning up the site. The more stringent the clean-up, the greater the risks to
workers involved in the clean-up. This type of indirect risk demonstrates the
importance of considering risk-risk tradeoffs in regulatory programs, which can
significantly alter the risk-benefit balance for many proposed options.
Mar, T., F. Frost and K. Tollestrup. 1993. Physical injury risk versus risk from hazardous waste remediation: A case history. Regulatory Toxicology & Pharmacology, 17 130-135; Hoskin, A.F., J.P. Leigh and T.W.
Planek. 1994. Estimated risk of occupational facilities associated with hazardous waste site remediation.
Risk Analysis, 14: 1011-1017.
Before a risk management approach is adopted, therefore, it is important to look at the
net risk of the proposed action, including the risk reductions from the regulated material
and the increased risks from greater use of substitute materials. These increased risks
from substitutes are frequently given inadequate consideration in regulatory
proceedings, resulting in an unexamined cost being imposed on society.
3. What Are the Macroeconomic Costs Involved? In addition to the impacts on
specific products, regulation can have macroeconomic impacts, including effects on a
country’s productivity, unemployment and international competitiveness. While the
60 Graham, J.D. and J.B. Wiener. 1995. Risk vs. Risk: Tradeoffs in Protecting Health and the Environment. Harvard
University Press, Cambridge, MA.
Risk Assessment and Risk Management of Non-Ferrous Metals
74
magnitude and long-term consequences of these impacts have been debated for many
years, there is no question that regulation has the potential to create at least short-term
61
economic disruption and dislocation. Markets do not immediately adjust to major
industry changes, investments in plants and machines are not interchangeable, and
workers with many years of experience in one industry cannot be absorbed into other
industries overnight.
Box 30: Indirect Health Consequences
Large regulatory costs can have negative indirect health impacts due to factors
such as the negative income effect and the pathologies associated with unemployment. These indirect impacts are generally difficult to calculate, and may not
be significant for regulatory programs that achieve significant direct health benefits at reasonable cost. For more expensive regulatory programs that achieve
minimal direct health benefits, however, the indirect negative health impacts of the
expenditures may result in net health benefits that are negligible or even negative.
For example, one recent analysis estimated that, under one set of assumptions,
each $7.5 million spent on regulatory programs results in one additional fatality
due to the negative income effect. Another study estimated that for every 1 percent increase in the national unemployment rate in the USA, the following increases occur:
•
•
•
•
•
•
•
36,887 deaths
20,240 cardiovascular failures
495 deaths from cirrhosis of the liver related to alcoholism
920 suicides
648 additional homicides
4,227 additional admissions to mental hospitals
3,340 additional admissions to state prisons
Keeney, R.L. 1990. Mortality risks induced by economic expenditures. Risk Analysis, 10: 147-159; M.
Tabor. 1982. The stress of job loss. Occupational Health & Safety, June: 20-26.
61 Stewart, R.B. 1993. Environmental regulation and international competitiveness. Yale Law Journal. 102: 20392106.
Chapter 5 - Balancing the Risks, Benefits and Costs of Non-Ferrous Metals
75
The macroeconomic impact of these disruptions can adversely affect both the economy
and public health. Unemployment, for example, is associated with huge social, health
and financial costs, not to mention its psychological and morale costs (Box 30). The
increased cost of certain products caused by regulatory requirements also leads to what
economists call a negative income effect for the consumer. As family or community
income decreases, so too do health and life expectancy. When national income falls,
there is often a significant increase in morbidity and even in the mortality rate. Less
money means less investment in public health, highways, education and other valuable
infrastructure. The health benefits of economic growth and investment, which usually
involve use of metals, therefore provides a further reason for carefully considering the
benefits of specific metal uses in risk management decisions.
The non-ferrous metals industry is a major industrial sector and source of employment
and income in many nations. For a country such as France, for example, the non-ferrous
metals sector consists of 200 companies of various sizes, employing 32,000 people and
worth 22,200 million francs (US$4,000 million) in exports to the country. It has been
estimated that every job in a basic industry generates on average approximately three
additional jobs in downstream industries. Incurring unnecessary or excessive costs in
the risk management of non-ferrous metals therefore has the potential to cause large
adverse economic and public health impacts. In addition, such costs can reduce the
competitiveness of a domestic industry in the international marketplace, resulting in a
loss of international competitiveness and jobs. As commodity products, non-ferrous
metals are particularly sensitive to this type of effect.
Conclusion
Like all materials, non-ferrous metals can present risks to public health and the
environment. The existence and severity of those risks depend on the specific substance
and circumstances of use. Each metal application presents a unique profile of risks,
benefits and costs that must be weighed in the context of the individual application.
Some potential uses of metals may result in risks that most would agree are
unreasonable or unacceptable, while other uses of metals present no significant risks.
Still other uses present some risks that may or may not be acceptable depending on the
associated benefits and costs and varying perceptions of acceptable risk. A coherent and
non-arbitrary risk management strategy must be based on an accurate understanding of
the real-world risks, benefits and costs of the substance or activity under consideration.
The identification and characterization of the risks, benefits and costs associated with
the various uses of non-ferrous metals, and the contexts in which such risks and benefits
may arise, is thus a prerequisite to effective and rational risk management of nonferrous metals.
Risk Assessment and Risk Management of Non-Ferrous Metals
76
CHAPTER 6
Risk Management
of Non-Ferrous Metals
Risk management seeks to minimize risks and costs while
maximizing the benefits associated with a substance. This chapter
begins by describing a framework for risk management, and then
identifying a series of risk management approaches that have been
undertaken in the past and which have cumulatively achieved
major reductions in the risks presented by non-ferrous metals.
These risk management strategies have resulted from a
combination of industry initiatives, government regulation,
scientific and technological advances, and increased public
expectations and corporate accountability. The final part of the
chapter addresses some principles to guide risk management in the
future in order to achieve additional risk reduction at acceptable
cost to society. Risk management in the future will require a more
flexible and cooperative approach between governments, industry
and other interested parties that effectively utilizes the expertise and
resources of each.
T
he decision-making process by which risks are controlled or regulated is called
risk management. While the term “risk management” refers only to risk, it
actually involves the management of risks, costs and benefits, as described in the
previous chapter. Risks and benefits often go hand-in-hand, and it is not possible to
manage one effectively without considering and managing the other. A hierarchy of
increasingly restrictive options is usually available to control risks, but the key to
effective risk management is to choose the strategy that best reduces “unacceptable” or
“unreasonable” risks at the least cost, including minimizing the loss of benefits.
Environmental risk management, which focuses on risks to health and the environment,
is performed by governments in establishing regulatory requirements, by businesses in
establishing corporate environmental policies and practices, and by consumers in
making personal choices about products and activities. In each case, the objective is to
achieve the optimal trade-off between maximizing benefits and minimizing risks and
costs.
Chapter 6 - Risk Management of Non-Ferrous Metals
77
This chapter addresses the strategies, challenges and opportunities for risk management
of non-ferrous metals. The chapter begins by discussing a framework for risk
management decisions. It then reviews a series of past and current risk management
practices for non-ferrous metals, including those mandated by government regulation
and those undertaken voluntarily by industry. This section not only describes the
progress that has been made to date in risk management of non-ferrous metals, but also
identifies possible risk management approaches that can be used to achieve even greater
progress in the future. The final section of the chapter presents some key principles that
can guide sound risk management of non-ferrous metals in the future, including: (i) the
increasing importance of, and opportunities for, industry-government cooperation; (ii)
the need to set priorities; (iii) the importance of matching appropriate solutions to
particular risks; (iv) the value of innovative new approaches; and, (v) the need to agree
on reasonable stopping points for risk management.
Risk Management Framework
As discussed in Chapter 3, a four-step coordinated framework for risk assessment —
consisting of hazard identification, dose-response evaluation, exposure assessment and
risk characterization — is widely used to structure risk assessment decision making. No
similar, broadly accepted framework for risk management exists, although several
governmental and non-governmental bodies have focused on developing such a
framework in recent years (Box 31).
Box 31: Recently Proposed Risk Management Frameworks
For example, the US Commission on Risk Assessment and Risk Management,
established by the 1990 Clean Air Act Amendments, has recently proposed an
integrated risk management framework consisting of six steps: (i) identify the
problem and its context; (ii) assess risks; (iii) identify options; (iv) decide control
measures; (v) implement selected actions; and, (vi) evaluate outcomes. A similar
approach has been recommended in a guidance document prepared by a UK government/industry working group on risk-benefit analysis of existing substances.
Commission on Risk Assessment and Risk Management, Risk Assessment and Risk Management in
Regulatory Decision-Making (June 13, 1996) (Draft Report); Risk-Benefit Analysis of Existing Substances,
Guidance produced by a UK Government/Industry Working Group (Feb. 1995).
Risk Assessment and Risk Management of Non-Ferrous Metals
78
Despite the lack of any formal risk management framework, there is a general
consensus on the broad steps that are essential for rational risk management. A critical
first step in risk management is information gathering, as the quality of the risk
management output will often depend on the quality of the information input.
Assessment of risks is obviously a central input for risk management. Before
quantitative risk assessment is possible, it is first necessary to identify the specific
products or materials that need to be evaluated. Next, the potential hazards of the
product must be identified, followed by an analysis of the likelihood, magnitude and
distribution of the risks that may be presented in specific real-world contexts. In each of
these risk assessment steps, described in greater detail in Chapters 3 and 4, it is
important to identify the uncertainties and assumptions involved. A final step in
characterizing risks is to identify the specific stages in the manufacture, storage,
distribution, use or disposal of the product that produce the risks which may need to be
managed. This life cycle risk analysis of products was discussed in Chapter 5.
As also discussed in Chapter 5, risk information is not the only information that is
required for risk management decisions. It is also important to identify the benefits of
the product or material to users, producers and society as a whole. This should include
an assessment of any risks, drawbacks and advantages that would result from the
increased use of substitute products or materials. Such an analysis will provide the
information needed to evaluate the net advantages and drawbacks of any proposed risk
reduction strategy.
Once the risks and benefits of the product have been identified, the next step is to identify
potential risk reduction options. In so doing, it is appropriate to take account of any
existing risk reduction measures. It is also relevant to consider the administrative, legal
and other methods by which any proposed risk reduction strategy could be implemented.
A list of some risk reduction strategies that have been used in the past, many of which
are also applicable for the future, is presented in the next section of this chapter.
Finally, once the risks and benefits have been characterized and the potential risk
reduction strategies identified, the most appropriate risk reduction strategy can be
selected. This is done by evaluating the list of potential risk reduction strategies and
their implementation methods against their effectiveness, practicality, costs,
monitorability, and costs and other impacts. Such decision making inevitably involves
weighing the relevant risks, benefits and costs that are affected by any potential risk
reduction strategy. As discussed in Box 32, this weighing of risks, costs and benefits can
be qualitative or quantitative, depending on the available information, the applicable
legal authority and the stakes involved. Some principles to guide this final step in risk
management are provided in the final section of this chapter.
Chapter 6 - Risk Management of Non-Ferrous Metals
79
Box 32: Quantitative vs. Qualitative Weighing
The identification and weighing of the risks, costs and benefits associated with
specific risk reduction options can be carried out with varying levels of detail and
precision, ranging from the completely qualitative to the fully quantitative. The
extent of quantification will depend on factors such as the quality and amount of
information available, the anticipated balance between risks and benefits, the
applicable legal authority, and the importance of the final decision. Three general types of risk-benefit weighing can be distinguished, although there are a range
of variants of the three basic approaches described below:
• Qualitative Risk-Benefit Analysis - Appropriate where available data are very
limited, and/or the risk is obviously acceptable or unacceptable. Involves a
descriptive but systematic listing of risks and benefits to ensure that the proposed
action will do more good than harm.
• Semi-Quantitative Risk-Benefit Analysis - Appropriate where some of the costs
and benefits can be quantified, but some inputs are unable to be quantified or
quantitatively compared. Involves systematic listing and comparison of quantified
and non-quantified costs and benefits of the proposed action.
• Cost-Benefit Analysis - Appropriate where both risk and benefits can be quantified and valued in a comparable metric. This involves quantitative assessment
of risks as probabilities of harm that can be costed by application of the appropriate value of life estimates, and quantification of the cost of reduced consumer
and producer benefits. Because of time and effort of such a complete analysis,
this approach will usually be necessary where decision is not obvious and/or the
outcome is of significant importance.
Risk Management Strategies
Risk management of non-ferrous metals has continuously improved over time through
the combined effect of several factors. One of the most important driving forces for
better risk management has been governmental regulation. Although such regulation
has not always been as cost-effective and efficient as it could and should be, it has been
a primary driving force for major reductions in exposures and risks from non-ferrous
metals. Not all progress can be attributed to governmental regulation, however. Greater
Risk Assessment and Risk Management of Non-Ferrous Metals
80
scientific understanding of the health effects of non-ferrous metals, and improvements
in pollution control technology, have also made important contributions to risk
reduction.
Industry initiatives have also played a key role in past and present risk management of
non-ferrous metals. Various influences have created the incentives and will for industry
to take a number of important voluntary actions to reduce risks. Some of those nonregulatory forces for risk reduction include pressures from the public, consumers and
downstream customers, insurance requirements, tax incentives, workers’ compensation
and product liability prevention. Major changes in corporate culture have also been
influential. Industry has responded to the increased environmental expectations of
employees, customers and surrounding communities by internalizing the need for
greater environmental stewardship and accountability. Sound environmental practices
are now viewed as good business as well as good policy. Some of the specific strategies
that have been used for the risk management of non-ferrous metals are listed in Box 33
and reviewed in the following sections.
Box 33: List of Risk Management Strategies
The risk management strategies that have been applied to non-ferrous metals and
are discussed in the following text include the following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
health research
joint industry-government environmental projects
pollution control technologies
phase-out of high-risk uses
voluntary programs
worker health and safety programs
risk communication
pollution monitoring and remediation
recycling
environmental management systems
product stewardship
technology transfer
“green design”
Chapter 6 - Risk Management of Non-Ferrous Metals
81
Health Research
It is obviously not possible to manage effectively risks whose existence is unknown, and
thus the identification and characterization of health risks from non-ferrous metals is an
essential prerequisite to effective risk management. One of the most important
contributions to risk management has been the substantial progress over the past few
decades in the scientific understanding of the potential health risks associated with nonferrous metals. This progress has resulted from extensive research sponsored or
conducted by industry, government, universities and independent research institutes.
Box 34: The Belgian Cadmibel Study
A prominent example of industry-government cooperation is the Belgian
“Cadmibel” study, co- sponsored by industry and the Belgian government, which
investigated the potential health effects of population exposure to environmental
pollutants such as cadmium. This study, undertaken in the late 1980s, involved
detailed evaluations of heavy metal exposure and associated health effects in a
cross-section of the Belgian population. The study found that historical emissions
from smelters had resulted in elevated cadmium exposures in some parts of the
general population, although such exposures had declined substantially over
time. The increased cadmium exposures in subgroups of the general population
appeared to be associated with subtle alterations in kidney physiology of uncertain medical significance. This finding triggered joint industry-government followup studies and remediation efforts. The “PheeCad” study was initiated in 1991 to
conduct follow-up evaluations of a select sub-cohort of the Cadmibel study to
determine whether the observed slight changes in renal function have medical
significance and to further document the evolution in heavy metal exposure levels.
The substantial contribution of the non-ferrous metals industry to scientific research on
potential health effects associated with metals exposure is coordinated largely through
several commodity-based research organizations established to fund and sponsor
research. Examples include the International Lead Zinc Research Organization (ILZRO)
for lead and zinc, the Nickel Producers Environmental Research Association (NiPERA)
for nickel, and the International Copper Association (ICA) for copper. The scientific
studies sponsored by such institutes are generally undertaken by independent, qualified
scientists and published in peer-reviewed scientific journals. With increasing frequency,
industry has collaborated with other stakeholders — such as governments, labour unions
and academics — to establish research priorities and evaluate findings. For example,
Risk Assessment and Risk Management of Non-Ferrous Metals
82
many companies have established joint management-labour occupational health
committees, or other mechanisms to solicit labour input, identify research priorities and
oversee research programs.
In addition to studies on the potential health effects of metal exposure to workers and the
general population, research has also led to new methods and biomarkers to monitor
exposure and effects, and more effective regulation and other measures to ensure the
safe use of non-ferrous metals. For example, in the mid-1980s considerable concern
arose about the use of cobalt in the hard metal industry, which had been linked in
scientific papers with interstitial lung fibrosis, the so-called “hard metal disease.”
Scientific research sponsored by industry demonstrated that there was a clear difference
between the toxicological properties of pure cobalt powder and the alloy of this powder
with the other components of the hard metal. This finding made it possible for
governments and industry to take appropriate regulatory and protective measures for
workers and users.
Joint Industry-Government Environmental Projects
In addition to the joint industry- government health research studies such as the Belgian
Cadmibel study, a variety of other industry-government cooperative projects has played
an increasingly important role in the management of risks from non-ferrous metals. An
example is the Canadian Mine Environment Neutral Drainage (MEND) program, a
cooperative research program sponsored, financed and administered by a partnership of
the Canadian mining industry, the Canadian federal government and the governments of
several Canadian provinces. The objectives of the MEND program include establishing
techniques “that will enable the operation and closure of acid-generating tailings and
waste rock disposal areas in a predictable, timely, affordable, and environmentally
acceptable manner.” The program was intended to spend approximately Cdn$18 million
over seven years on research and technology development directed towards improved
environmental practices in the mining industry.
Another recent industry-government undertaking is the Environmental Protection
Working Group on Mining and Metallurgy established by the International Council on
Metals and the Environment (ICME) and the United Nations Environment Programme
(UNEP). The purpose of the UNEP/ICME working group is to “collect and disseminate
information on economic and environmentally appropriate technologies and
environmental management systems relevant to mining and metallurgy.” The Working
Group’s action plan includes: (i) publishing case studies that reflect environmental
improvements made by industry; (ii) identifying training materials which encourage and
enhance employee involvement in environmental management; and, (iii) establishing
an extended network of experts within industry and academic institutions who are
available to support UNEP and ICME technology transfer workshops and seminars.
Chapter 6 - Risk Management of Non-Ferrous Metals
83
Pollution Control Technologies
Discharges and emissions into the environment, as well as worker exposures within
plants, have been dramatically reduced in recent years through the implementation of
state-of-the-art process changes and pollution control equipment in primary and
secondary non-ferrous metal facilities and in metal-using industries. For example, lead
emissions from US primary and secondary smelters were reduced by 91 percent from
62
1970 to 1993.
Data collected under the Canadian ARET (Accelerated Reduction
Elimination of Toxics) program by Environment Canada from 13 Canadian mining and
metallurgical companies, representing over 80 percent of base metal production in
Canada, indicate that total releases to the air and water will decrease in the period from
1988 to 2000 by 85 percent for cadmium, 70 percent for lead, 85 percent for zinc and 60
percent for nickel. Emission levels in 1988 were, in turn, substantially lower than 20
years earlier.
Box 35: Emissions Reduction Case Studies
While new facilities have been designed from the ground up to minimize pollution
and waste, the upgrading of existing facilities has resulted in some of the most
dramatic progress in reducing pollution. A good case study is a zinc refinery on
the Derwent River in Tasmania, Australia, which, over 70 years of operation, had
contaminated the local river resulting in zinc and cadmium levels in fish that
exceeded applicable health standards. Beginning in 1972, environmental
improvement projects at this facility have reduced metal discharges by 99 percent.
These improvements have brought water quality in the river into compliance with
drinking water standards, and fish from the river are now edible. The Inco smelter
in Sudbury, Canada is another example. Once the largest source of sulphur dioxide emissions in North America, the facility has undergone extensive modifications. The $530 million project enabled the capture of an additional 60 percent of
remaining sulphur dioxide emissions, resulting in overall 90 percent emissions
containment. In addition to reducing sulphur dioxide emissions, the process
changes reduced other emissions and reduced energy consumption by two-thirds.
A final example is cadmium production in Belgium, where cadmium is now produced with nearly zero emissions to air and water. Through changes in production
processes, consolidation of all cadmium production processes at one site, and
development of improved engineering designs, total emissions have been
reduced by a factor of more than 10,000 over the past 40 years.
62 US EPA. 1994. National Air Quality and Emissions Trends Report, 1993 (EPA 454/R-94-026).
Risk Assessment and Risk Management of Non-Ferrous Metals
84
The major reductions in pollution have resulted primarily from installation of new
emission control equipment such as scrubbers, fabric filters and electrostatic
precipitators, the use of closed continuous process units that virtually eliminate release
of gases and contaminants, the recovery of metals from waste streams, and the recycling
of wastewater. Systems for fugitive dust control have been installed at many facilities to
reduce metal releases during the storage, processing or transport of metal concentrate.
Production facilities have also implemented new processing equipment that has reduced
waste generation by processing raw materials more efficiently and by recycling waste
streams back into the production process.
Phase-Out of High-Risk Uses
Certain historical uses of non-ferrous metals have been responsible for a
disproportionately high percentage of total human exposure, whereas other uses of nonferrous metals have resulted in little or no human exposure. High-exposure, high-risk
uses of non-ferrous metals have in many instances been phased out in many countries.
The list includes lead solder in food cans and lead-based residential paint. In some
countries, current non-occupational metal exposures appear to be due almost entirely to
residual contamination from past uses and activities rather than from existing metal
applications.
While government regulation has played a central role in the phase-out of some highrisk uses of non-ferrous metals, metal producers have actively supported restrictions on
specific product applications that were found to present unacceptable risks. For
example, the US lead industry supported the phase-out of leaded paint (Box 36).
Similarly, the nickel industry has cooperated with European regulators to eliminate
nickel from certain applications in jewellery to avoid nickel-related dermatitis. Nonferrous metal producers and their trade associations continue to support appropriate
legislation for abating and restricting the uses of non-ferrous metals that result in
unreasonable health risks. In some cases, high-risk uses of non-ferrous metals have
been voluntarily phased out without the need for regulation, such as the use in the USA
of lead solder in food cans.
Voluntary Programs
Voluntary standards established by non-governmental organizations have also
contributed to risk management of non-ferrous metals by supplementing governmental
regulations. For example, voluntary performance-based standards for the leaching of
lead from ceramics and brass have been established by standard-setting organizations
such as the International Standards Organization (ISO) and the American National
Standards Institute (ANSI).
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85
Box 36: The Leaded Paint Example
The Lead Industries Association in the USA actively supported the Lead Based
Paint Poisoning Act of 1971, which restricted the use of lead-based paint.
Senator Edward Kennedy, who was at that time Chairman of the Senate
Subcommittee that sponsored the legislation, recognized the industry’s cooperation and responsibility with the following statement:
“The Lead Industries Association deserves great credit for the help it has
provided to Congress in this area. Many times, industry associations have
not been as cooperative in matters affecting their own industry, have not
been nearly as positive or constructive as your industry has been; and I
appreciate it.”
Lead Based Paint Poisoning Amendments of 1972, Hearings before the Senate Subcomm. on Health, Comm.
on Labor and Public Welfare, 92nd Cong., 2d Sess. 102 (1972).
Other types of voluntary programs include cooperative industry-government efforts such
as the Canadian ARET program. ARET is a consensus-oriented group, composed of
representatives of industry, health and academic associations, and the federal and
provincial governments of Canada. Its goal is the accelerated reduction or elimination
of selected toxic substance emissions. The premise of the ARET program is that
voluntary action on the part of industry will result in reductions of toxic substances more
quickly and effectively than traditional regulatory approaches. ARET has established
science-based criteria to identify candidate substances for voluntary reductions of 50 to
90 percent of emissions, and has developed a prioritized list of candidate toxic
substances for action based on the work of a multi-stakeholder technical subcommittee.
Non-ferrous metal producers are active participants in the ARET program, and through
such participation, are achieving significant voluntary reductions in discharges of nonferrous metals.
Non-ferrous metal producers and their customers participate in similar voluntary
programs in other countries, such as the “33/50 Project” in the USA, which was initiated
by the US EPA in 1990 in connection with its Toxics Release Inventory (TRI) program.
The goal of the 33/50 Project was to encourage industry to voluntarily achieve a 33
percent reduction in releases and transfers of 17 TRI chemicals (including non-ferrous
metals such as cadmium, chromium, lead, nickel and their compounds) by 1992 and a
50 percent reduction by 1995. The percentage reductions are measured against the 1988
Risk Assessment and Risk Management of Non-Ferrous Metals
86
baseline. By the 1993 reporting year, a 46 percent reduction in releases and transfers of
these 17 chemicals had already been achieved by TRI reporting companies, and the 50
percent target was expected to be reached a year ahead of schedule. Moreover, the
companies participating in the 33/50 Project (including non-ferrous metals producers
63
and users) had already achieved a 57 percent reduction by 1993.
An example that has been less successful is the “North Sea Emission Reduction
Programme” in Europe. Unlike the Canadian and US programs, the objectives and
approaches of the European program were unilaterally declared by the participating
governments without any consultation with industry. This may have contributed to the
limited results of the European program, which achieved less efficient and lower
pollution reductions than the more cooperative US and Canadian programs.
Worker Health and Safety Programs
At the same time that major reductions have been made in environmental releases from
non-ferrous metal production facilities, major progress has also been made in reducing
occupational exposures to workers at those same facilities. These reductions in
occupational exposures are likewise attributable to a combination of factors, including
voluntary initiatives undertaken by industry, occupational health and safety regulation
by government, increased awareness by workers and employers of potential workplace
hazards through right to know and similar programs, changes in corporate citizenship
and community expectations and awareness, and increased priority given to health and
safety issues in collective bargaining agreements between labour and management.
The methods that have been used to reduce occupational exposures include engineering
controls, process equipment changes, such as the increased use of closed systems, better
administrative controls, industrial hygiene improvements and, where appropriate,
personal protective equipment. Medical surveillance programs instituted at non-ferrous
metal production facilities play a key role in ensuring that worker exposures remain at
acceptable levels. Medical removal programs in use in some countries provide a
safeguard for workers who may experience unusually high exposures, although the need
to resort to such measures has greatly diminished in recent years as a result of the
overall reduction in occupational exposure levels. Worker training has also had an
instrumental role in controlling occupational exposures by increasing worker awareness
and involvement, and promoting safe and healthful work practices and risk avoidance
measures by workers.
Other types of industrial hygiene programs have also been important. For example,
research has shown that the families of workers can be at risk as a result of contaminants
63 See US EPA, 1993 Toxics Release Inventory Public Data Release 262 (1995).
Chapter 6 - Risk Management of Non-Ferrous Metals
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carried home on work clothes. To protect against such exposure, workers in some
facilities are provided with, and required to use, locker and shower facilities, and to
leave work clothes to be laundered at the workplace. As a further inducement for
protective work practices, some companies have made health and safety part of a
worker’s performance assessment. At many facilities, workers play a major role in
designing and overseeing worker health and safety programs through joint labourmanagement health and safety committees or other mechanisms for labourmanagement consultation on health and safety issues.
Risk Communication
Risk communication can be a remarkably effective addition to risk management
programs. Current concepts of risk communication are based on scientific principles
64
established over the past 20 years by a number of academically based researchers. The
goal of risk communication is to provide the public and workers with information they
need to use products safely, adopt risk avoidance strategies and make informed risk
decisions. For example, risk communication programs required by governments
include the Emergency Planning and Community Right to Know Act in the USA and the
“Seveso Directive” in the European Union, which both require industrial facilities to
65
provide information on releases of hazardous substances to surrounding communities.
Risk communication will be effective only to the extent that it takes account of public
perceptions of risks. For many people, risk is a function of the hazard of a substance plus
66
the level of outrage that it engenders. In other words, it is an issue of acceptability. This
is different from the purely scientific definition of risk as a function of exposure and
toxicity. These disparate perspectives of risk lead to confusion when the different
approaches are not taken into account in communicating risk within the workplace and
to the general public. All too often, a classical scientific approach is used, which consists
of disclosure of exposure and toxicity data and measures of risk such as “one in a
million.” This often results in increased outrage and greater risk concerns among those
to whom the communication is addressed.
Risk communication science suggests, instead, that the communications acknowledge
concerns and work to address them, as well as providing appropriate data on the hazard
and opportunities for purposeful exchanges of information between the respective
parties. One of the essential factors that influence the outcome is credibility. Credibility
components include: acknowledgement, caring, empathy, honesty, openness,
64 National Research Council. 1989. Improving Risk Communication. National Academy Press, Washington, DC.
65 See Baram, M.S., and D.G. Partan. 1990. Corporate Disclosure of Environmental Risks: US and European Law.
Butterworth, Salem, NH.
66 Slovic, P. 1987. Perception of risk. Science. 236: 280-285; Sandman, P.M. 1986. Explaining Environmental Risk:
Some Notes on Environmental Risk Communication. US EPA, Washington, DC.
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88
competence and commitment. This approach to risk communication is a learned skill;
it is essential to the effective communication of risk to concerned parties.
Risk communication, therefore, is best approached in two ways: from the traditional
scientific perspective of communicating risks in terms of exposure and toxicity; and,
from the social science perspective of dealing with real and/or perceived risk. The
former is generally addressed through the traditional risk communication tools
discussed above of product labels, material safety data sheets, audio-visual materials and
pamphlets. The latter is accomplished through the effective interchange of information
using credible sources and instruments such as community panels, and public education
and information exchange opportunities. In both cases, training of the persons
responsible for the preparation and delivery of the risk communication program and
process is essential. While these different types of risk communication are not intended
to supplant direct risk reduction efforts, they do have an important role in the safe
management of risks from non-ferrous metals and their compounds.
Box 37: Product Labels
Product labels, when used appropriately, can be a very effective risk communication tool. Labels can warn workers and consumers of potential risks, and provide
safe use instructions. When hazard warning labels are overused, however, they
can result in reduced effectiveness for all such labels, including those for products
with serious potential risks. Research indicates that when there are too many
warning labels, people experience “information overload” and begin ignoring
warnings. It is therefore important to reserve the use of product warning labels
for products that present real potential health and safety risks. In both the USA
and Europe, labelling requirements are based on hazard identification rather than
risk assessment based on real-life uses. This results in overlabelling of some
materials that likely present negligible risks in most or all anticipated uses.
Pollution Monitoring and Remediation
The effectiveness of pollution control efforts directed at non-ferrous metal production
facilities can be evaluated through monitoring programs that assess exposures to the
surrounding population and environment. For example, US primary and secondary lead
smelters commonly obtain and report blood lead levels of children living near the
smelters in accordance with protocols established jointly with the US EPA and the
Centers for Disease Control. In addition to ensuring that exposures from current
production of metals are properly controlled, the industry has participated in monitoring
and remediating exposures from past uses of non-ferrous metals. In Belgium, for
Chapter 6 - Risk Management of Non-Ferrous Metals
89
example, a variety of government-industry supported actions have been implemented to
reduce the potential exposure of the general population due to historical soil
contamination with metals. In addition to neighbourhood screening programs, these
cooperative actions have included hook-up of residences to public water utilities,
general informational campaigns and revegetation programs.
Remediation efforts to clean up contamination from past uses of non-ferrous metals that
present a significant risk to human health or the environment are also under way in
other countries. While legitimate concerns have been raised about the substantive and
procedural requirements and costs of some governmental remediation programs such as
the US Superfund program, remediation of past contamination can be a necessary risk
management strategy in appropriate circumstances. Prevention is, however, more
effective than remediation. The major progress that has been, and continues to be, made
in controlling current pollution and wastes will therefore ensure that similar
remediation efforts will not be necessary in the future.
Recycling
Another important element of risk management of non-ferrous metals is recycling.
Recycling reduces the quantity of metal-containing waste, while also reducing the need
to extract new metal, both of which result in reduced potential for exposure and
therefore risk. On the benefit side of the risk-benefit balance, recycling vastly increases
the benefits associated with a given unit of metal that is reused repeatedly in a variety of
uses.
Because of their intrinsic value, non-ferrous metals — especially copper, lead and their
alloys — have traditionally been recycled as a result of competitive market forces. It has
generally not been necessary for governments to take special measures to create
markets for these materials. It is also true, however, that various industry and
government actions have helped to increase recycling rates. Because recycling of some
metal products depends on widespread citizen participation, incentives that encourage
recycling are more effective than largely unenforceable regulations that mandate
recycling. Examples of the types of programs that have been used to encourage
recycling include manufacturer “take back” programs in which manufacturers and
suppliers take back used metal-containing products, deposit-refund schemes that
require consumers to pay a deposit that is refunded when they return the metalcontaining product at the end of its use, and promotional campaigns to encourage
consumers to recycle. Perhaps the greatest success in encouraging recycling has been
with lead-acid batteries, where recycling rates are well over 90 percent in several
countries.
Risk Assessment and Risk Management of Non-Ferrous Metals
90
Box 38: Industry-Sponsored Recycling Program
An example of an effective industry-sponsored recycling program is the battery
recycling program organized by the Portable Rechargeable Battery Association in
the USA. Under this program, arrangements have been made to give commercial
entities and consumers a readily available means to collect and send used nickel-cadmium batteries to a pyrometallurgical facility for the recovery of nickel and
cadmium. By making recycling more convenient for both sellers and buyers of
these batteries, this program helps to increase battery recycling without imposing
unduly costly mandatory requirements.
While recycling is an important risk management strategy for non-ferrous metals,
regulatory requirements sometimes have the unintended effect of creating obstacles to
recycling. This has been true, for example, of certain elements of the hazardous waste
regulatory program in the USA. Recent amendments to the Basel Convention on the
Control of Transboundary Movements of Hazardous Wastes and Their Disposal may have
a similar effect internationally. Thus, in designing regulatory programs, care should be
taken to avoid creating obstacles to recycling that may be environmentally
counterproductive as well as economically harmful. Conversely, a soundly conceived
regulatory program may facilitate the recycling of non-ferrous metals. An example in
the case of nickel-cadmium batteries is the so-called “Universe Waste Rule” promulgated
by the US EPA in 1995, which includes incentives for recycling in the form of reduced
regulatory burdens without jeopardizing health and environmental protection.
Environmental Management Systems
Many companies have now integrated growing corporate awareness and accountability
on environmental issues into comprehensive environmental management systems.
These systems ensure that environmental concerns are considered and addressed at
every level of corporate planning and operations. While each company’s environmental
program is tailored to its own operations, needs and management structure, some of the
elements that are often included in environmental management systems are: an
environmental management staff, corporate-wide environmental policies and standards,
employee training programs, increased environmental reporting to the public, and
environmental auditing. Most corporations have assigned a high-ranking executive,
often at the corporate vice-president level, to be responsible for the company’s
environmental affairs.
In addition to improving the monitoring, prevention and management of environmental
and health risks in the day-to-day operations of the company, a comprehensive
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91
environmental management system helps to instill an increased environmental
awareness and ethic throughout the company. The existence of such programs sends a
clear message from management that sound environmental performance and a strong
commitment to continuous environmental improvement is important to the long-term
reputation and success of the company and should not be sacrificed for short-term gains.
The development of voluntary international standards for corporate environmental
management programs, such as the ISO 14000 series of standards, will further
encourage the implementation of environmental management programs. Governmental
actions — such as appropriate enforcement actions, recognition of a self-audit or selfevaluative privilege, or other means — can provide additional incentives for corporate
risk management programs by providing assurance to companies that they will not be
penalized as a result of voluntary steps they take to improve their environmental
performance.
Product Stewardship
One of the more recent additions to the risk management toolbox is “cradle-to-grave”
product stewardship, which has received growing emphasis in the non-ferrous metals
industry in recent years. Metal producers have instituted product stewardship programs
to advise and assist downstream users and consumers on the safe use, disposal and
recycling of non-ferrous metals. Publications on safe use of products have been
produced and distributed to customers and their employees. Labour unions and trade
associations are often helpful in these efforts. Another aspect of product stewardship is
insisting that contractors follow best environmental practices.
Because non-ferrous metals are commodities that are sold and brokered on international
markets, it is impossible for an individual producer to track the use of all the metal it
produces. In addition, some product manufacturers that purchase metals for fabrication
purposes are reluctant to disclose to the metal producer the intended use of the metal
because of fears that the producer will pass on the information to other customers to
increase sales. Because of these limitations on company-specific product stewardship
efforts, the industry has put increasing emphasis on product stewardship campaigns
coordinated through commodity-based and industry-wide trade associations. For
example, the Nickel Development Institute (NiDI) and the Nickel Producers
Environmental Research Association (NiPERA) have published and distributed to nickel
producers and users a comprehensive Health Guide entitled Safe Use of Nickel in the
Workplace. NiDI and NiPERA also have sponsored Nickel Users Environmental
Conferences in Europe and the USA. These product stewardship efforts by non-ferrous
metal producers have been complemented by product stewardship efforts of specific
user groups such as the Battery Council International, the Portable Rechargeable Battery
Association, the European Federation of Capsule Manufacturers, and others.
Risk Assessment and Risk Management of Non-Ferrous Metals
92
Box 39: ICME and Product Stewardship
To further enhance its product stewardship activities, the non-ferrous metals
industry has formed the industry-wide International Council on Metals and the
Environment to promote sound environmental policies and practices for non-ferrous metals. ICME, representing 29 primary metal-producing companies from 15
different countries, adopted the following product stewardship principles:
• Develop or promote metal products, systems and technologies that minimize
the risk of accidental or harmful discharges into the environment.
• Advance the understanding of the properties of metals and their effects on
human health and the environment.
• Inform employees, customers and other relevant parties concerning metalrelated health or environmental hazards and recommend risk management
measures.
• Conduct or support research and promote the application of new technologies
to further the safe use of metals.
• Encourage product design and uses that promote the recyclability and the
recycling of metal products.
• Work with government agencies, downstream users and others in the
development of sound, scientifically based legislation, regulations and product
standards that protect and benefit employees, the community and product
standards that protect and benefit employees, the community and the
environment.
Technology Transfer
One of the distinguishing features of the non-ferrous metals industry is the openness by
which environmental management technologies and ideas are shared. Because nonferrous metals are commodity products that often cannot be identified by brand name or
distinguishing characteristics, environmental mismanagement or improper use of a
metal by one company has the potential to tarnish the reputation and economic wellbeing of the entire industry. It is perhaps for this reason that the industry has been so
willing to share environmental expertise between producers and with downstream
Chapter 6 - Risk Management of Non-Ferrous Metals
93
customers. One of the most important mechanisms for this technology transfer is the
numerous industry-sponsored workshops and seminars in which technical information
on best environmental practices is shared. For example, ICME has sponsored seminars
in various countries on environmental practices in the industry in which companies
share information on the development and operation of environmental management
systems with other companies and other interested stakeholders. In August 1994, for
instance, ICME co-sponsored with the Kazakh government a seminar in Kazakhstan on
environmental management of non-ferrous metals that featured speakers from industry
67
and government organizations from both developed and developing nations. Similarly,
one of the principal purposes of the recently established UNEP/ICME Environmental
Working Group on Mining and Metallurgy is to sponsor technology transfer workshops
and seminars.
Technology transfer of environmental expertise has not only played an important role
within industrialized countries, but has also been instrumental in the transfer of sound
environmental practices from industrial countries to less developed nations.
Multinational mining companies have applied corporate-wide environmental policies
and best environmental practices to their operations worldwide, even in countries that
have not yet developed their own environmental regulations. This voluntary industry
self-regulation has permitted the transfer of environmental programs to domestic
companies in developing countries, and has laid the groundwork for the establishment
68
of governmental regulations that apply to all companies operating in those countries.
“Green Design”
Many new applications of non-ferrous metals are being developed based on their
numerous unique properties and characteristics. In developing such products, the
industry has recognized the need for risk analyses of new products to ensure that they
are environmentally sustainable. The term “green design” has been coined to describe
efforts to design new products with good environmental performance and to improve the
69
environmental performance of existing products. The non-ferrous metals industry has
devoted considerable resources to the development of environmentally sustainable
products in recent years, through the combined efforts of internal company product
development teams, commodity-based research organizations, trade association product
development committees, and industry-government cooperative undertakings such as
the UNEP/ICME Environmental Protection Working Group on Mining and Metallurgy.
67 ICME. 1994. Seminar on Environmental Management for the Non-Ferrous Metal Mining and Metallurgical
Industries. Almaty, Republic of Kazakhstan.
68 See, for example, O’Brien, J. 1994. Undoing a Myth: Chile’s Debt to Copper and Mining. International Council
on Metals and the Environment, Ottawa, ON.
69 US Office of Technology Assessment. 1992. Green Products by Design. Washington, DC.
Risk Assessment and Risk Management of Non-Ferrous Metals
94
These green design efforts are paying off in commercially promising products that are
safe for the environment. A key example for non-ferrous metals is the design of products
to facilitate recycling. Products can be designed and manufactured in ways that make it
70
easier to recover and isolate their metal constituents. Another example of green design
is the development of a coating that would permit the safe use of corrosion-proof lead
roofs while achieving effectively zero metal runoff.
Future Risk Management of
Non-Ferrous Metals
The risk management of non-ferrous metals — through the combination of voluntary
industry initiatives, government regulation, and scientific and technology progress —
has made enormous strides in reducing exposures and risks from non-ferrous metals.
Considerable progress has been made in phasing out or controlling the metal uses which
present the most obvious and severe risks to human health and the environment, and
implementation of the most obvious pollution control strategies is, for the most part, now
complete. Indeed, one consequence of the improvement in risk management practices
is that, in many cases, it is existing contamination from past uses, rather than present
uses of metals, that presents risks to human health or the environment.
The remaining risks in industrialized countries will be much more difficult and
expensive to eliminate, given the law of diminishing returns in which each successive
unit of risk reduction typically becomes progressively more difficult and expensive to
achieve. The trade-offs inherent in risk management will become much more apparent
and pressing, while competing demands for scarce societal resources will become more
intense as the remaining risks become smaller, more diffuse and less manageable. The
relationship between wealth and health will come to the forefront as industry and
government confront smaller and smaller risks, with increasing recognition that
excessive risk reduction not only harms the economy, but also undermines human
health because of the positive association between health and wealth, employment and
71
other indicators of economic prosperity. As risks become smaller and more diffuse, the
importance of risk-risk tradeoffs and the risks of substitute products also become more
significant. In addition, the focus of risk management in the future will increasingly be
on a broader range of human and environmental effects, including more subtle low-dose
effects that will often be difficult to identify and control. Issues such as causation and the
definition of an “adverse effect” will have to be resolved in attempting to manage such
low-dose exposures.
70 Henstock, M.E. 1988. Design for Recyclability. Institute of Metals, London, UK.
71 Wildavsky, A. 1991. Searching for Safety; Keeney, R.L. 1990. Mortality risks induced by economic
expenditures. Risk Analysis. 10: 147-158.
Chapter 6 - Risk Management of Non-Ferrous Metals
95
Despite these challenges, valuable lessons have been learned from past efforts at risk
management that can help guide future programs. Identification of risk management
approaches that have worked or not worked, as well as how things could have been done
more efficiently or quickly, can now be evaluated from real-life examples. Drawing from
this past experience, and considering the challenges that lie ahead, it is possible to
identify some principles that will be important for effective risk management in the
future:
Industry-Government Cooperation
One of the clearest lessons from the past is that cooperation and consultation between
industry, governments and other stakeholders is much more effective than
confrontation. While industry, governments and non-governmental organizations will
continue to have different views and interests on many environmental issues, a
cooperative approach that attempts to find common ground is likely to produce a better
outcome, both procedurally and substantively, than an adversarial approach in which
conflicting positions become hardened and fragmented. Examples such as the Canadian
ARET program and the US 33/50 program demonstrate that cooperative efforts can result
in greater risk reductions at less cost and in less time — an outcome that all sides can
support and to which they can be committed. Cooperative processes can also break
down the misunderstanding, mistrust and stereotypes that have developed on
environmental matters.
Industry has much that it can bring to the table, including important information that
government needs for effective regulation. Industry has the first-hand knowledge to
accurately identify both the opportunities and costs of reducing risks. Industry has the
expertise and knowledge to achieve given risk reduction goals in the most efficient and
cost-effective manner possible. Industry also has the resources and the wherewithal to
collect data on exposures and health effects in their facilities that are essential for
informed risk management.
There are many different ways that industry, government and other stakeholders can
cooperate. One of the most important, and easiest, types of cooperation is to identify and
agree jointly on research priorities. The use of multi-stakeholder advisory groups, while
often time consuming, has proven to be effective in reaching consensus on many issues.
Other types of consultation between industry and government scientists, risk managers
and decision makers are also worth pursuing. The most important prerequisite to the
success of such cooperative efforts is a commitment to mutual respect. Although some
retain the outdated stereotype of industry as uncaring on environmental matters,
industry has proven with both words and deeds that it is prepared to be a positive and
responsible participant in sound risk management.
Risk Assessment and Risk Management of Non-Ferrous Metals
96
Setting Priorities
When the modern environmental era began 25 to 30 years ago, the popular conception
of environmental problems was very different than it is today. Back then, environmental
problems were seen as a function of a few bad substances that needed to be eliminated,
whereas all other substances were safe. Today, we know that this view is overly
simplistic — that both safety and risk are relative rather than absolute concepts, and that
all substances can be toxic in some contexts and at some dose. The goal of risk
management should therefore be to identify and control the greatest risks that can be
reduced at the least cost and disruption to society. The US EPA has recently adopted a
risk-based approach to identify priorities for risk reduction and risk management (Box
40). A similar recognition of the need to establish priorities is exemplified by an
extensive EC program called the “Existing Substances Programme,” which seeks to
establish priorities for action based on risk, although the protocols for this program
require further refinement.
Box 40: A Risk-Based Priority-Setting Approach
The US EPA has adopted a risk-based priority-setting approach based on the following recommendation from its Science Advisory Board:
“The nation cannot do everything at once. In national efforts to protect the
environment, the most obvious steps have been taken to reduce the most
obvious risks. Now environmental priorities must be set. ... EPA programs
should be shaped and guided by the principle of relative risk reduction, and
all available risk data and the most advanced risk assessment and comparison methodologies should be incorporated explicitly into the Agency’s decision-making process.”
US EPA. 1990. Reducing Risk: Setting Priorities and Strategies for Environmental Protection (SAB-EC-90021) (emphasis in original).
Matching Risks with Solutions
Effective risk management involves a trade-off between maximizing risk reduction and
minimizing associated costs and benefit reductions. Once the presence of a significant
risk has been identified, a hierarchy of responses is available. One extreme is to take no
action, which leaves the risks and benefits unchanged and imposes no new costs. The
other extreme is an outright ban on the risk-creating product or activity. This eliminates
the risks associated with production or use of the product. But it may also create
“substitution risks,” force society to forfeit many of the benefits associated with use of the
product, and impose large costs on producers and consumers. Except in rare
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97
circumstances, neither of these extreme responses represents a sound approach to risk
management.
An example of the risk management hierarchy of responses is provided by the US Toxic
Substances Control Act (TSCA). TSCA expressly provides for a hierarchy of risk
management responses that the EPA can take to regulate substances that present an
“unreasonable risk.” These range from labelling as the least stringent option to a total
ban on the most dangerous substances. EPA is instructed to adopt the least burdensome
option for achieving an acceptable level of risk.
While the simplicity of a product ban may have a superficial appeal to some, bans almost
inevitably do more harm than good. As regulation gets progressively more stringent, the
marginal costs of an additional unit of risk reduction increase at an exponential rate. At
some point, usually long before absolute prohibition, the costs of further risk reduction
begin to outweigh significantly the health benefits. At that point, resources would be
more effectively utilized addressing other sources of risk. Even in the rare cases where
an absolute prohibition may be justified, it is preferable to impose a performance
standard that may as a practical matter prohibit a current use, but which leaves the door
open to future product improvements that may be able to meet acceptable standards.
Product bans should therefore be a last resort for the most severe risks, and even then
the ban should be as narrowly focused as possible.
Innovative New Approaches
Innovative new approaches to environmental risk management will be needed to meet
the environmental challenges of the future. Many of the historical approaches to risk
management, while they may have sufficed to deal with the gross insults of the past, are
too crude and inefficient to deal with remaining risks. A prime example is command and
control regulation involving the establishment of end-of-pipe limits on emissions or
discharges that industry must meet. While this approach has helped achieve dramatic
reductions in pollution discharges, its effectiveness for achieving further reductions is
limited. Government usually does not have the expertise and knowledge to mandate the
most cost-effective controls on discharges. Command-and-control standards also fail to
take account of substantial variations in the costs and benefits of reducing discharges,
and fail to provide an incentive for companies to innovate and go beyond regulatory
standards. Command-and-control regulation establishes an adversarial relationship
between industry and government, often resulting in confrontation, litigation and
disincentives to cooperate through the sharing of information and ideas. There is broad
consensus that the command-and-control regulation of the past has achieved important
environmental benefits, but at a cost that could have been much lower. As two
prominent US commentators summarized the situation, “[t]he present regulatory system
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98
wastes tens of billions of dollars every year, misdirects resources, stifles innovation, and
72
spawns massive and often counterproductive litigation.”
A more flexible approach that has proven effective for some types of environmental
problems is the use of economic instruments such as tradeable emission discharge
permits, emission taxes, or creation of other forms of property rights, such as
development rights. So far, these approaches have found no applicability to risks
presented by metals, in part because they treat each unit of the substance as equivalent,
without regard to differences in environmental release, human exposure and uptake
potential from various uses which typically are present with metals. To date, market
incentives have been found to be most appropriate for problems such as
chlorofluorocarbons, sulphur dioxide and greenhouse gases associated with global
warming that have a global or regional effect and where localized concentrations are not
particularly important. Pollution taxes or marketable permits, however, seem to make
little sense for substances like non-ferrous metals where the risks, if any, from present
73
uses are presented primarily by localized pollutant concentrations.
More innovative and custom-tailored approaches will be necessary to manage effectively
the risks from current and future uses of non-ferrous metals. Government regulators are
increasingly recognizing the importance of setting regulatory goals supported by
appropriate risk assessments, leaving industry as much flexibility as possible to find the
most cost-effective ways to meet those goals. In addition, the increased application of
non-regulatory risk management tools such as product stewardship and green design
should be pursued as part of an industry-government cooperative approach to risk
management.
Reasonable “Stopping Points”
The pursuit of zero risk is wasteful, counter-productive and futile. As regulators from
the US Department of Health and Human Services stated at a recent workshop on risk
assessment of essential metals, it is “important to stress that all risks are relative — there
74
is no such thing as zero risk.” A goal of zero risk would be particularly inappropriate
for non-ferrous metals, which are naturally occurring and in many cases are essential
nutrients, and have unquestioned broad utility in the modern world. Spending scarce
resources trying to root out the last residues of risk from one or another substance
72 Ackerman, B.A. and R.B. Stewart. 1985. Reforming environmental law. Stanford Law Review. 37: 1333-1365.
73 See for example, Stewart, R. 1988. Controlling environmental risks through economic incentives. Columbia
Journal of Environmental Law 13: 153; Stavins, R. 1990. Innovative Policies for Sustainable Development in the
1990’s: Economic Incentives for Environmental Protection. Resources for the Future Discussion Paper QE 9011.
74 Johnson, B.L. and A. Ademoyero. 1994. A public health perspective on risk assessment of essential elements.
Risk Assessment of Essential Elements. Mertz, W., C.O. Abernathy, and S.S. Olin, eds. International Life Sciences
Institute Press, Washington, DC.
Chapter 6 - Risk Management of Non-Ferrous Metals
99
necessarily takes resources away from other risks and problems that are insufficiently
controlled. In this sense, over-regulation of some risks results in under-regulation of
75
many other risks, in what has been called “the dilemma of toxic substance regulation.”
Moreover, since every substance presents risks in some contexts, it is impossible to
eliminate all risk, and any substitute product will present its own risks. Because of these
factors, the wasteful pursuit of zero risk fails to meet the first principle of sound risk
76
management of doing “more good than harm.”
Much of the controversy that exists today on environmental issues can be traced to the
lack of a consensus on the levels of risk that are acceptable to society. It is ultimately
government’s role to decide acceptable risk, with input from the public and stakeholders.
Without agreement on a consistent and systematic approach that can be applied evenhandedly, environmental regulation is often arbitrary and capricious, with specific risks
singled out for unfair treatment. The failure to apply consistent standards is
demonstrated by recent surveys of US regulations showing that the values that
regulatory agencies explicitly or implicitly assign to saving a statistical life range wildly
77
from under $100,000 to over $5 trillion. Such grossly disparate treatment of health and
safety risks is not rational, efficient or fair. As the US EPA’s Science Advisory Board has
pointed out, sound risk management requires consistent standards that are based on
realistic assessments of the risks and benefits associated with specific uses:
“One system that can help foster the evolution of an integrated and targeted national environmental policy is the concept of environmental
risk. Each environmental problem poses some possibility of harm to
human health, the ecology, the economic system, or the quality of
human life. That is, each problem poses some environmental risk....
The concept of environmental risk, together with its related terminology and analytical methodologies, helps people discuss disparate environmental problems with a common language. It allows many
environmental problems to be measured and compared in common
terms, and it allows different risk reduction options to be evaluated
from a common basis. Thus the concept of environmental risk can help
the nation develop environmental policies in a consistent and systematic way.”78
75 Mendeloff, J.H. 1988. The Dilemma of Toxic Substance Regulation. MIT Press, Cambridge, MA.
76 Warren, E.W. and G.E. Marchant. 1993. “More good than harm”: A first principle for environmental agencies
and reviewing courts. Ecology Law Quarterly. 20: 379-439.
77 US Office of Management and Budget. 1992. Regulatory Program of the United States Government. Washington,
DC.
78 US EPA. 1990. Reducing risk: Setting priorities and strategies for environmental protection (SAB- EC-90-021).
Risk Assessment and Risk Management of Non-Ferrous Metals
100
Conclusion
Significant progress has been achieved in managing the risks from non-ferrous metals,
but further progress will require more innovative and effective approaches that reduce
significant risks without unduly sacrificing the important societal benefits provided by
non-ferrous metals. An essential prerequisite to sound risk management is scientifically
credible risk assessment, which in turn requires reliable scientific research and data.
Risk information must then be combined with cost and benefits assessments to establish
reasonable goals and effective means to achieve those goals. The extensive historical
record that is now available of risk assessment and risk management approaches for
non-ferrous metals provides useful guidance on the types of approaches that will and
will not work in the future. A more cooperative and flexible approach that combines the
expertise and capabilities of governments, industry and other interested parties is likely
to be much more successful than the adversarial, “zero sum” strategies that have been
relied on too often in the past. Perhaps the most important lesson that can be learned
from the past is that risk assessment and risk management of non-ferrous metals must
take account of the special properties of non-ferrous metals as a group, and the unique
risk and benefit profile presented by each specific species and application of non-ferrous
metals.
Chapter 6 - Risk Management of Non-Ferrous Metals
101
CHAPTER 7
Acronyms and Abbreviations
ACGIH
ADI
ANSI
ARET
DNA
EC
EU
FDA
GLP
GRAS
IARC
ICA
ICME
ILZRO
ISO
kg
LC50
LO(A)EL
MEI
mg
MIR
MTD
NiPERA
NO(A)EL
NOEC
NTP
OECD
PBPK
PEC
PNEC
redox
RDA
RfD
SMR
TI
American Conference of Governmental Industrial Hygienists
Acceptable Daily Intake
American National Standards Institute
Accelerated Reduction/Elimination of Toxics
Deoxyribonucleic Acid
European Commission
European Union
Food and Drug Administration
Good Laboratory Practice
Generally Recognized As Safe
International Agency for Research on Cancer
International Copper Association
International Council on Metals and the Environment
International Lead Zinc Research Organization
International Standards Organization
Kilogram
Lethal Concentration for 50 Percent of Subjects
Lowest Observed (Adverse) Effect Level
Maximally Exposed Individual
Milligram
Maximum Individual Risk
Maximum Tolerated Dose
Nickel Producers Environmental Research Association
No Observed (Adverse) Effect Level
No Observed Effect Concentration
National Toxicology Program
Organization for Economic Cooperation and Development
Physiologically-Based Pharmacokinetic
Predicted Environmental Concentration
Predicted No Effect Concentration
Oxidation/Reduction
Recommended Daily Allowance
Reference Dose
Standardized Mortality Ratio
Tolerable Intake
Chapter 7 - Acronyms and Abreviations
103
UCL
UNEP
US EPA
WHO
Upper Confidence Limit
United Nations Environment Programme
US Environmental Protection Agency
World Health Organization
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CHAPTER 8
Glossary
Absorption - The process of active or passive transport of a substance across a biological
barrier into an organism: in the case of mammal or human beings, this is usually
through the lungs, gastrointestinal tract or skin.
Adsorption - Enrichment of one or more components on a surface of a solid or in an
interfacial layer.
Acceptable Daily Intake - The maximum dose of a substance that can be consumed
daily without causing adverse effects over a lifetime.
Acute - Severe, often dangerous, condition in which relatively rapid changes are
occurring.
Alloy - A metallic material consisting of two or more elements, homogeneous to outward
appearance, and so combined that they cannot be readily separated by physical
means, and having different properties than its individual components.
Anthropogenic - Resulting from human activities.
Benign Tumour - A tumour confined to the location in which it arose (i.e., nonmalignant).
Benchmark Dose - A statistical estimate of the dose producing a predetermined level of
altered response above the control level.
Bias - A systematic error in an epidemiological or other type of study which tends to
overestimate, or underestimate, the hazard.
Bioassay - A study that uses animals to measure an effect (e.g., toxicity) or a
phenomenon (e.g., bioaccumulation).
Bioavailability - The extent to which a substance can be absorbed by an organism and
the rate at which this occurs.
Chapter 8 - Glossary
105
Biomarker - Indicator signalling an event or condition in a biological system or sample
and giving a measure of exposure, effect or susceptability.
Carcinogenic - Capable of causing cancer.
Chronic - Having a persistent, recurring or long-term nature.
Compound - A chemical substance of two or more elements chemically united in fixed
proportions.
Concentrate - The product of the treatment of ore by which differences in physical and
surface properties of the components are used to separate valuable minerals (as a
concentrate) from unwanted minerals (gangue).
Confounding Factor - The distortion of the apparent effect of an exposure on risk
brought about by the association of other factors which can influence the outcome.
De minimis - A level of risk below which there is no reason for concern or attention.
Dermatitis - Inflammation of the skin from any cause.
Desorption - The release of an adsorbed component from a surface.
Dose - Total amount of a substance administered to, taken or absorbed by an organism.
Dose-Response - A quantitative relationship between the dose of an agent and the
incidence of a defined biological effect in an exposed population.
Ecosystem - Grouping of organisms (micro-organisms, plants and animals) interacting
together, with and through their chemical environments, to form a functional entity.
Ecotoxicity - The toxic effects of chemical and physical agents on populations and
communities of organisms within a defined ecosystem.
Element - Matter that cannot be further decomposed into simpler substances by
chemical means.
Emissions - Releases of a substance from a source, including discharges into the wider
environment.
Enzyme - A protein acting as a catalyst in a specific biochemical reaction.
Risk Assessment and Risk Management of Non-Ferrous Metals
106
Epidemiology - The study of the distribution and determinants of diseases and injuries
in human populations.
Exposure Assessment - Process of measuring or estimating concentration (or intensity),
duration and frequency of exposures to an agent present in the environment.
Extrapolation - The process of using observed values in estimating unknown values
outside the range of observation.
Ferrous Metal - A metal or alloy containing a significant amount of iron.
Genotoxic - The property of a substance to interact with and alter the genetic material
of a cell.
Grade - A measure of the concentration of a metal in a mixture such as an ore or
concentrate.
Hazard - Set of inherent properties of a substance that makes it capable of causing
adverse effects to organisms or the environment.
Hazard Identification - Identification of the adverse effects which a substance has an
inherent capacity to cause.
Ion - An atom or molecule that has acquired an electrical charge by the gain or loss of
one or more electrons.
Labile - Unstable; liable to displacement or change especially if an atom or group is
easily replaced by other atoms or groups.
LC50 - The concentration that is lethal to 50 percent of the organisms to which it is
administered within a specified period; specific to a species.
Leach - The movement of liquid through or the dissolution of a substance from soil or
other media.
Life Cycle Analysis - A process to evaluate the environmental burdens associated with
a product, process or activity by identifying and quantifying energy and materials used
and wastes released to the environment from extraction and processing of raw
materials; through manufacturing, transportation, distribution, use, re-use and
maintenance, to recycling and final disposal.
Chapter 8 - Glossary
107
Lowest Observed (Adverse) Effect Level (LO[A]EL) - The lowest dose at which a
statistically or biologically significant (adverse) effect is detected in a population.
Malignant Tumour - A tumour that is capable of spreading to other tissues.
Malleability - The ability of a material to undergo shaping or mechanical working
without rupture.
Maximum Tolerated Dose - The maximum dose in a study that does not produce
mortality or effect that would be expected to shorten the organism’s natural life span.
Methylation - The introduction of a methyl group (CH3) into a molecule or compound.
Milling - The process in which mined ore is crushed and ground for the separation from
the waste rock and concentration of the valuable minerals.
Mineral Exploration - The process of searching for mineral deposits that are potentially
suitable for mining.
Morbidity - Any departure, subjective or objective, from the state of well-being: in this
sense, sickness, illness and morbid condition are similarly defined and synonymous.
Mortality Rate - The relative incidence of death in a population.
Neurotoxicity - An adverse change in the structure or function of the nervous system
after exposure to a chemical agent.
No Observed (Adverse) Effect Level (NO[A]EL) - The highest dose at which no
statistically or biologically significant (adverse) effect is detected in a population.
Non-Ferrous Metal - A metal or alloy that does not contain a significant amount of iron.
Ore - Naturally occurring rock with a metal content that could be profitably extracted.
Ore Body - A deposit of ore.
Organism - Any living organism (e.g., animal, plant, bacterium, including humans).
Organometallic Compound - A compound that contains one or more metal atoms
combined with one or more carbon atoms.
Pathological - Abnormal or diseased.
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108
pH - A logarithm of the reciprocal of the hydrogen ion concentration in a solution giving
a measure of the acidity or alkalinity of a solution.
Pharmacokinetic - The process whereby substances are taken up by the body, the
biotransformations they undergo, the distribution of these and their metabolites in the
tissues and their elimination from the body.
Physiologically - Based Pharmacokinetic Model - Dose-response model based on the
biological mechanism by which an agent causes an adverse effect.
Pollutant - Any undesirable matter in an environmental medium.
Poly-Metallic Mineralized Deposits - Naturally occurring concentrations of a
combination of metal-bearing minerals (e.g., sphalerite [zinc mineral], galena [lead
mineral] and chalcopyrite [copper mineral]).
Precious Metals - A category of metals that includes gold, silver and platinum that are
extracted and used for their own intrinsic value.
Primary Metal - Metal recovered through the process of mining and extraction from
ores, rather than via recycling of scrap materials.
Product Stewardship - The process that an organization undertakes to ensure that its
products are produced, consumed, recycled and disposed of with due care for human
health and the environment.
Protein - Any of a group of organic compounds composed of one or more chains of
amino acids and forming an essential part of all living organisms.
Reference Dose (RfD) - For human populations (including sensitive subgroups), an
estimate (spanning perhaps an order of magnitude) of a daily exposure that is likely
to be without an appreciable risk of deleterious effects during a lifetime.
Reproductive Toxin - A substance or preparation that produces harmful effects and/or
impairment of the male and female reproductive function or capacity.
Risk - The probability that a harmful event, arising from exposure to a chemical or
physical agent, may occur under specific conditions.
Risk Assessment - The determination of the relationship between the predicted
exposure/concentration and adverse effects in four major steps: hazard identification,
dose-response assessment, exposure assessment and risk characterization.
Chapter 8 - Glossary
109
Risk Characterization - The estimation of the incidence and severity of the adverse
effects likely to occur in an environmental compartment due to an actual or predicted
exposure to a substance (i.e., integration of hazard identification, dose-response
evaluation and exposure assessment).
Risk Management - The decision-making process involving considerations of political,
social, economic and engineering factors combined with risk assessment information
to develop, analyse and compare options and to select between them.
Safety Factor - A number used to account for uncertainties in estimating a safe level of
exposure.
Secondary Metal - Metal produced from recycled scrap metals and related materials.
Smelting - A set of chemical processes (sometimes including sintering, roasting and
converting) whereby high temperatures are employed to achieve molten phases of
metal, sulphides and/or oxides, and unwanted elements are preferentially distributed
into the oxide phase.
Speciation - The process by which the different chemical forms or species of an element
is determined.
Species - A specific form of a chemical.
Standardized Mortality Ratio - Ratio of the number of events observed in the study
group or population to the number of deaths expected if the study population had the
same mortality rates as the standard population.
Systemic - Referring to the whole body; affecting all body systems and organs; not
localized to one spot or area.
Teratogenic - Capable of causing structural malformations or defects in offspring.
Threshold - The dose of a toxicant below which no adverse effect is expected.
Trophic Level - A segment of the food chain in which all organisms obtain food and
energy in the same manner, e.g., photosynthesis.
Tolerable Intake (TI) - Regulatory value of the acceptable intake of a substance per unit
of time (eg. daily).
Risk Assessment and Risk Management of Non-Ferrous Metals
110
Toxicology - The scientific discipline that identifies poisonous or toxic properties of a
substance using controlled studies in organisms, isolated tissues, cells or cellular
components.
Weight-of-the-Evidence - Extent to which the available data support the hypothesis
that a substance causes a defined effect.
Chapter 8 - Glossary
111
CHAPTER 9
Further Reading
Breyer, S. 1993. Breaking the Vicious Circle: Toward Effective Risk Regulation. Harvard
University Press, Cambridge, MA.
Chapman, P.M. 1996. Hazard Identification, Hazard Classification and Risk Assessment
for Metals and Metal Compounds in the Aquatic Environment. International Council on
Metals and the Environment, Ottawa, ON.
Crowson, P. 1992. The Infinitely Finite. International Council on Metals and the
Environment, Ottawa, ON.
Fairbrother, A. 1997. Hazard Classification of Elements and Derivative Inorganic
Substances in Terrestrial Systems with Special Emphasis on Metals and Metalloids.
International Council on Metals and the Environment, Ottawa, ON.
Glickman, T.G., and M. Gough. 1990.
Washington, DC.
Readings in Risk. Resources for the Future,
Henstock, Michael E. 1996. The Recycling of Non-Ferrous Metals. International Council
on Metals and the Environment, Ottawa, ON.
International Council on Metals and the Environment. 1997. Report of the International
Workshop on Risk Assessment of Metals and their Inorganic Compounds, Angers,
France, November 13-15, 1996. International Council on Metals and the Environment,
Ottawa, ON.
International Council on Metals and the Environment. 1994. A Guide to Neurotoxicity:
International Regulation and Testing Strategies. Ottawa, ON.
Institute for Life Sciences International. 1994. Risk Assessment of Essential Elements
(1994). W. Mertz, C. Abernathy and S. Olin, eds. ILSI Press, Washington, DC.
Landis, W.G., J.S. Hughes, and M.S. Lewis, eds. 1993. Environmental Toxicology and Risk
Assessment. American Society for Testing and Materials, Philadelphia, PA.
Chapter 9 - Further Reading
113
McDivitt, J.F., and G. Manners. 1974. Minerals and Men. John Hopkins University Press,
Baltimore, MD.
Merian, E. ( ed). 1991. Metals and Their Compounds in the Environment: Occurrence,
Analysis, and Biological Relevance. Weinheim, New York, NY.
National Research Council. 1994. Science and Judgment in Risk Assessment. National
Academy Press, Washington, DC.
National Research Council. 1989. Improving Risk Communication. National Academy
Press, Washington, DC.
National Research Council. 1983. Risk Assessment in the Federal Government: Managing
the Process. National Academy Press, Washington, DC.
O’Brien, J. 1994. Undoing a Myth: Chile’s Debt to Copper and Mining. International
Council on Metals and the Environment, Ottawa, ON.
Ottoboni, M. Alice. 1991. The Dose Makes the Poison. Second Edition. Van Nostrand
Reinhold, New York, NY.
Parametrix, Inc. 1995. Persistence, Bioaccumulation and Toxicity of Metals and Metal
Compounds. International Council on Metals and the Environment, Ottawa, ON.
Rasmussen, P.E. 1996. Heavy Metals in the Environment: A Geoscience Perspective.
International Council on Metals and the Environment, Ottawa, ON.
Rosenthal, A., G.M. Gray, and J.D. Graham. 1992. Legislating acceptable risk from
exposure to toxic chemicals. Ecology Law Quarterly. 19: 269-362.
Rothman, K.J. 1986. Modern Epidemiology. Little, Brown & Co., Boston, MA.
Strauss, S.D. 1986. Trouble in the Third Kingdom. Mining Journal Books, London, UK.
Thornton, I. 1995. Metals in the Global Environment: Facts and Misconceptions.
International Council on Metals and the Environment, Ottawa, ON.
US Department of the Interior. 1985. Mineral Facts and Problems. Government Printing
Office, Washington, DC.
Risk Assessment and Risk Management of Non-Ferrous Metals
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