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Environmental Toxicology
The study of the effects of manufactured chemicals, other anthropogenic
materials, and natural materials on living organisms.
Effects Studied by Environmental Toxicologists
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Lethality
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Also study: concentrations of chemicals found in the environment, how
Sublethal Effects:
they move about in the environment, are transformed in the
environment, and their ultimate fate in the environment.
Environmental Toxicology
... is a multidisciplinary field:
Must understand:
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Chemistry
Physical Factors
Biology
Ecology
Statistics… see document camera
Toxicology
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Stems from the study of poisons
Basic statement of toxicology written by Paracelsus (1449-1541):
History of Toxicology
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Prehistory: human experimentation with plants for medicinal and food
uses
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Poisons used for hunting and fishing
Also used in warfare and to murder people
History of Toxicology
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Early Greeks, Romans, Egyptians
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Egyptian papyrus 1500BC
Greeks - poisoning was state method of execution
History of Toxicology
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Chinese literature:
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Middle ages : Italians brought the art of poisoning to new heights:
Toffana
Catherine de Medici -earliest untrained experimental toxicologist
Catherine de Medici
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Noted: rapidity of onset of response
Effectiveness of compound (potency)
Degree of response of various parts of the body (specificity)
Complaints of the victim (clinical signs and symptoms)
Paracelsus: formulated many ideas that remain part of foundations of
toxicology today:
• Experimentation necessary in examining responses to chemicals
• Distinction should be made between therapeutic and toxic properties
of a chemical
• A given chemical will produce a given effect or group of effects
MJB Orfila (1787-1853)
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Attending physician to Louis the 17th
First book published on the harmful effects of chemicals on organisms
Personally observed effects of poisons on 1000s of dogs
Worked on treatment of poisons with antidotes
Devised methods for detecting poisons…forensic toxicology.
1800s - basic toxicology research on rodents, fish, insects
1920s - study of toxic effects on lab animals (as surrogates for
humans)
• 1940s and 1950s - concern about effects of wastes and chemicals on
non human organisms
• 1962 Rachel Carson wrote “Silent Spring”
• 1960s - impacts of industrial effluents on receiving streams
• 1970s - acceptance of fish tests as a valid parameter for creating
governmental regulations and guidelines on water pollution control
• 1980s - increasingly complex tests (sediment tox., biochemical tox.,
toxicity evaluation identification (TIE), multispecies tests, ecosystem
endpoints
Why does toxicology matter to you?
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70 new chemicals registered per hour, 70, 000 chemicals in everyday
use
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Everyone, even people in the most remote areas, are exposed to some
of these chemicals
Quantitation
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Basic questions:
1. How toxic is it?
2. At what dose does it become toxic?
Dose-Response Relationship: the mathematical relationship between the
chemical dose and the proportion of the test organisms responding to
a specific dose for a given exposure period
Dose-Response Graphs
• X - axis : dose (in mg/kg, for instance)
• Y- axis : the response
1. Frequency dose-response graph - generally a bell curve. Depicts the
distribution of minimal doses of drug that produce an effect.
• 2. Cumulative dose- response graph - cumulative sum of responses
from lower to higher doses
Population Sensitivity Variations
LD50