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Chapter 18
Environmental Hazards
and Human Health
Chapter Overview Questions
 What
types of hazards do people face?
 What types of disease (biological hazards)
threaten people in developing countries and
developed countries?
 What chemical hazards do people face?
 How can risks be estimated and recognized?
Core Case Study: The Global
HIV/AIDS Epidemic
 According
to the World Health Organization
(WHO), in 2005 about 42 million people
worldwide (1.1 million in the U.S.) were
infected with HIV.
 There is no vaccine for HIV – if you get
AIDS, you will eventually die from it.
 Drugs help some infected people live
longer, but only a tiny fraction can afford
them.
Core Case Study: The Global
HIV/AIDS Epidemic
 AIDS
has reduced the
life expectancy of subSaharan Africa from 62
to 47 years – 40 years
in the seven countries
most severely affected
by AIDS.
Projected age structure
of Botswana's population
in 2020.
Figure 18-2
Core Case Study: The Global
HIV/AIDS Epidemic
 The
virus itself is not deadly, but it cripples
the immune system, leaving the body
susceptible to infections such as Kaposi’s
sarcoma (above).
Figure 18-1
RISKS AND HAZARDS
 Risk
is a measure of the likelihood that you
will suffer harm from a hazard.
 We can suffer from:




Biological hazards: from more than 1,400
pathogens.
Chemical hazards: in air, water, soil, and food.
Physical hazards: such as fire, earthquake,
volcanic eruption…
Cultural hazards: such as smoking, poor diet,
unsafe sex, drugs, unsafe working conditions,
and poverty.
BIOLOGICAL HAZARDS:
DISEASE IN DEVELOPED AND
DEVELOPING COUNTRIES
 Diseases
not caused by living organisms
cannot spread from one person to another
(nontransmissible disease), while those
caused by living organisms such as bacteria
and viruses can spread from person to
person (transmissible or infectious)
Transmissible Disease
Zombies
Werewolves
Vampires
 Pathway
for infectious disease in humans.
Figure 18-4
Transmissible Disease
 WHO
estimates that
each year the
world’s seven
deadliest infections
kill 13.6 million
people – most of
them the poor in
developing
countries.
Figure 18-5
Case Study: Growing Germ
Resistance to Antibiotics
 Rapidly
producing infectious bacteria are
becoming genetically resistant to widely used
antibiotics due to:


Genetic resistance: Spread of bacteria around
the globe by humans, overuse of pesticides
which produce pesticide resistant insects that
carry bacteria.
Overuse of antibiotics: A 2000 study found that
half of the antibiotics used to treat humans were
prescribed unnecessarily.
Case Study: The Growing Global
Threat from Tuberculosis
 The
highly infectious tuberculosis (TB) kills
1.7 million people per year and could kill 25
million people 2020.
 Recent increases in TB are due to:


Lack of TB screening and control programs
especially in developing countries due to
expenses.
Genetic resistance to the most effective
antibiotics.
Viral Diseases
 Flu,
HIV, and hepatitis B viruses infect and
kill many more people each year then highly
publicized West Nile and SARS viruses.

The influenza virus is the biggest killer virus
worldwide.
• Pigs, chickens, ducks, and geese are the major
reservoirs of flu. As they move from one species to
another, they can mutate and exchange genetic
material with other viruses.
Viral Diseases
 HIV
is the second biggest killer virus
worldwide. Five major priorities to slow the
spread of the disease are:





Quickly reduce the number of new infections to
prevent further spread.
Concentrate on groups in a society that are likely
to spread the disease.
Provide free HIV testing and pressure people to
get tested.
Implement educational programs.
Provide free or low-cost drugs to slow disease
progress.
Case Study:
Malaria – Death by Mosquito
 Malaria
kills
about 2 million
people per year
and has
probably killed
more than all of
the wars ever
fought.
Figure 18-7
Female mosquito bites
infected human, ingesting
blood that contains
Plasmodium gametocytes
Merozoites enter
bloodstream and
develop into
gametocytes
causing malaria
and making
infected person a
new reservoir
Sporozoites
penetrate liver
and develop
into merozoites
Plasmodium
develop in
mosquito
Female mosquito injects
Plasmodium sporozoites
into human host.
Fig. 18-7, p. 423
Case Study:
Malaria – Death by Mosquito
 Economists
estimate that spending $2-3
billion on malaria treatment may save more
than 1 million lives per year.
Figure 18-6
Case Study:
Malaria – Death by Mosquito
 Spraying
insides of homes with low
concentrations of the pesticide DDT greatly
reduces the number of malaria cases.

Under international treaty enacted in 2002, DDT
is being phased out in developing countries.
Solutions
Infectious Diseases
Increase research on
tropical diseases and
vaccines
Reduce poverty
Decrease malnutrition
Improve drinking
water quality
Reduce unnecessary
use of antibiotics
Educate people to take all
of an antibiotic prescription
Reduce antibiotic use to
promote livestock growth
Careful hand washing by
all medical personnel
Immunize children against
major viral diseases
Oral rehydration for
diarrhea victims
Global campaign to
reduce HIV/AIDS
Fig. 18-8, p. 424
Ecological Medicine and
Infectious Diseases
 Mostly
because of human activities,
infectious diseases are moving at increasing
rates from one animal species to another
(including humans).
 Ecological (or conservation) medicine is
devoted to tracking down these connections
between wildlife and humans to determine
ways to slow and prevent disease spread.
CHEMICAL HAZARDS
A
toxic chemical can cause temporary or
permanent harm or death.



Mutagens are chemicals or forms of radiation
that cause or increase the frequency of mutations
in DNA.
Teratogens are chemicals that cause harm or
birth defects to a fetus or embryo.
Carcinogens are chemicals or types of radiation
that can cause or promote cancer.
CHEMICAL HAZARDS
A
hazardous chemical can harm humans or
other animals because it:





Is flammable
Is explosive
An irritant
Interferes with oxygen uptake
Induce allergic reactions.
Effects of Chemicals on the Immune,
Nervous, and Endocrine Systems
 Long-term
exposure to some chemicals at
low doses may disrupt the body’s:



Immune system: specialized cells and tissues
that protect the body against disease and harmful
substances.
Nervous system: brain, spinal cord, and
peripheral nerves.
Endocrine system: complex network of glands
that release minute amounts of hormones into
the bloodstream.
Effects of Chemicals on the Immune,
Nervous, and Endocrine Systems
 Molecules
of certain synthetic chemicals
have shapes similar to those of natural
hormones and can adversely affect the
endocrine system.
Figure 18-9
Normal Hormone Process
Hormone
Hormone Mimic
Estrogenlike
chemical
Hormone Blocker
Antiandrogen
chemical
Receptor
Cell
Fig. 18-9, p. 427
Case Study:
A Black Day in Bhopal, India
 The
world’s worst industrial accident
occurred in 1984 at a pesticide plant in
Bhopal, India.



An explosion at Union Carbide pesticide plant in
an underground storage tank released a large
quantity of highly toxic methyl isocyanate (MIC)
gas.
15,000-22,000 people died
Indian officials claim that simple upgrades could
have prevented the tragedy.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
 Factors
determining the harm caused by
exposure to a chemical include:





The amount of exposure (dose).
The frequency of exposure.
The person who is exposed.
The effectiveness of the body’s detoxification
systems.
One’s genetic makeup.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
 Typical
variations in
sensitivity to a
toxic chemical
within a
population,
mostly because
of genetic
variation.
Figure 18-10
Number of individuals affected
Very
sensitive
Majority of
population
Dose (hypothetical units)
Very
insensitive
Fig. 18-10, p. 430
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
 Estimating
human
exposure to
chemicals and their
effects is very
difficult because of
the many and often
poorly understood
variables involved.
Figure 18-11
Water pollutant
levels
Soil/dust levels
Air pollutant levels
Food pesticide levels
Nutritional health
Overall health
Mathematical
measurements
& modeling
?
Lifestyle
Predicted level of
toxicant in people
Personal habits
Metabolism
Accumulation
Excretion
Genetic
predisposition
Lung, intestine
& skin absorption rates
Fig. 18-11, p. 431
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
 Children
are more susceptible to the effects
of toxic substances because:



Children breathe more air, drink more water, and
eat more food per unit of body weight than
adults.
They are exposed to toxins when they put their
fingers or other objects in their mouths.
Children usually have less well-developed
immune systems and detoxification processes
than adults.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
 Under
existing laws, most chemicals are
considered innocent until proven guilty,
and estimating their toxicity is difficult,
uncertain, and expensive.

Federal and state governments do not regulate
about 99.5% of the commercially used chemicals
in the U.S.
Protecting Children from Toxic
Chemicals
 The
U.S. Environmental Protection Agency
proposed that regulators should assume
children have 10 times the exposure risk of
adults to cancer-causing chemicals.
 Some health scientists contend that
regulators should assume a risk 100 times
that of adults.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
 Some
scientists and health officials say that
preliminary but not conclusive evidence that
a chemical causes significant harm should
spur preventive action (precautionary
principle).
 Manufacturers contend that wide-spread
application of the precautionary principle
would make it too expensive to introduce
new chemicals and technologies.
How Would You Vote?
To conduct an instant in-class survey using a classroom response
system, access “JoinIn Clicker Content” from the PowerLecture main
menu for Living in the Environment.

Should we rely more on the precautionary principle
as a way to reduce the risks from chemicals and
technologies?


a. No. Assuming that every chemical or technology is a
serious health or environmental threat will lead to
wasteful over-regulation, high costs and hinder the
development of critically needed pesticides, plastics, and
other commercial products.
b. Yes. Preventing the commercialization of harmful
chemicals and technologies is better than dealing with the
high costs of medical treatments and environmental
damage.
RISK ANALYSIS
 Scientists
have
developed ways to
evaluate and compare
risks, decide how
much risk is
acceptable, and find
affordable ways to
reduce it.
Figure 18-12
Comparative Risk Analysis
Most Serious Ecological
and Health Problems
High-Risk Health Problems
• Indoor air pollution
• Outdoor air pollution
• Worker chemical exposure
• Pollutants in drinking water
• Pesticide residues on food
• Toxic chemicals in consumer products
High-Risk Ecological Problems
• Global climate change
• Stratospheric ozone depletion
• Wildlife habitat alteration & destruction
• Species extinction, loss of biodiversity
Medium-Risk Ecological Problems
• Acid deposition
• Pesticides
• Airborne toxic chemicals
• Toxic chemicals, nutrients, and sediment in
surface waters
Low-Risk Ecological Problems
• Oil spills
• Groundwater pollution
• Radioactive isotopes
• Acid runoff to surface waters
• Thermal pollution
Fig. 18-12, p. 433
RISK ANALYSIS
 Estimating
risks from using many
technologies is difficult due to unpredictability
of human behavior, chance, and sabotage.
 Reliability

of a system is multiplicative:
If a nuclear power plant is 95% reliable and
human reliability is 75%, then the overall
reliability is (0.95 X 0.75 = 0.71) 71%.
RISK ANALYSIS
 Annual
deaths in the U.S. from tobacco use
and other causes in 2003.
Figure 18-A
Cause of Death
Deaths
442,000
Tobacco use
101,500 (43,450 auto)
Accidents
85,000
Alcohol use
75,000 (16,000 from AIDS)
Infectious
diseases
Pollutants/
toxins
Suicides
Homicides
Illegal drug
use
55,000
30,600
20,622
17,000
Fig. 18-A, p. 435
RISK ANALYSIS

Number of deaths per year in the world from various
causes. Parentheses show deaths in terms of the
number of fully loaded 400-passenger jumbo jets
crashing every day of the year with no survivors.
Figure 18-13
Cause of death
Annual deaths
11 million (75)
Poverty/malnutrition/
disease cycle
5 million (34)
Tobacco
3.2 million (22)
Pneumonia and flu
Air pollution
3 million (21)
HIV/AIDS
3 million (21)
Malaria
Diarrhea
Tuberculosis
Car accidents
Work-related injury
& disease
Hepatitis B
Measles
2 million (14)
1.9 million (13)
1.7 million (12)
1.2 million (8)
1.1 million (8)
1 million (7)
800,000 (5)
Fig. 18-13, p. 435
Perceiving Risk
 Most
individuals evaluate the relative risk
they face based on:





Degree of control.
Fear of unknown.
Whether we voluntarily take the risk.
Whether risk is catastrophic.
Unfair distribution of risk.
 Sometimes
misleading information, denial,
and irrational fears can cloud judgment.
RISK
ANALYSIS
 Comparisons
of
risks people face
expressed in
terms of shorter
average life
span.
Figure 18-14
Hazard
Poverty
Born male
Smoking
Overweight (35%)
Unmarried
Overweight (15%)
Spouse smoking
Driving
Air pollution
Alcohol
Drug abuse
Flu
AIDS
Drowning
Pesticides
Fire
Natural radiation
Medical X rays
Oral contraceptives
Toxic waste
Flying
Hurricanes, tornadoes
Lifetime near nuclear plant
Shortens average life span in the U.S. by
7–10 years
7.5 years
6–10 years
6 years
5 years
2 years
1 year
7 months
5 months
5 months
4 months
4 months
3 months
1 month
1 month
1 month
8 days
5 days
5 days
4 days
1 day
1 day
10 hours
Fig. 18-14, p. 436
Becoming Better at Risk Analysis

We can carefully
evaluate or tune out of
the barrage of bad
news covered in the
media, compare risks,
and concentrate on
reducing personal risks
over which we have
some control.
Figure 18-3
Risk Assessment
Risk Management
Hazard identification
Comparative risk analysis
What is the hazard?
How does it compare with
other risks?
Risk reduction
Probability of risk
How likely is the
event?
How much should it be
reduced?
Risk reduction strategy
How will the risk be
reduced?
Consequences of risk
Financial commitment
What is the likely
damage?
How much money should
be spent?
Fig. 18-3, p. 419