Environmental Toxicology
and Chemistry
Principles of Toxicology
What is Toxicology?
“Study of the toxic effects of
xenobiotics in living organisms”
History of Toxicology
Antiquity
• Hunting and warfare
Antiquity
• Ebers Papyrus (circa 1500 B.C.)
• Hippocrates (circa 400 B.C.)
Antiquity
• Dioscorides
• Socrates (470-399 B.C.)
Middle Ages
• Toffana
• The Borgias
• Catherine de Medici
Age of Enlightenment
“All
substances
are
poisons, there is none
which is not a poison. The
right dose differentiates a
poison from a remedy”
Paracelsus (1493-1541)
Main Contributions by Paracelsus
• Described the concept that “the dose
makes the poison”.
• Toxicity is related to chemical structure.
• Described the main clinical manifestations
of two common poisoning: arsenic and
mercury.
Age of Enlightenment
• Percival Pott
• Orfila
th
20
Century
• Word War II and TCDD
• Delaney Clause
• Thalidomide and Love
Canal cases
Approaches to Study Toxicology
•
•
•
•
Clinical
Forensic
Molecular
Food Toxicology
•
•
•
•
Environmental
Regulatory
Plant Toxicology
Veterinary
Main Areas of Toxicology
• Mechanistic
• Descriptive
• Regulatory
Major forces behind the development
of the field of Toxicology
• Steady increase in the production of synthetic
industrial chemicals, drugs, pharmaceuticals,
agricultural chemicals, etc.
• Increased in public awareness of the possible
adverse effects of many of these chemicals on
humans, animals and the environment.
• Mandatory testing and controls of chemicals used
in many fields.
• Litigation, especially related to occupational-related
illnesses and other sources of exposure.
Legislation and Toxicology
Food and Drug
Administration (FDA).
Federal Food, Drug and
Cosmetic Act.
Environmental Protection
Agency (EPA).
Federal Insecticide, Fungicide
and Rodenticide Act.
Clean Air Act.
Safe Drinking Water Act.
Toxic Substances Control Act.
Occupational Safety and
Health Act.
Occupational Safety and
Health Administration
(OSHA).
Consumer Product Safety
Commission (CPSC).
Consumer Product Safety Act.
Toxicity
What is Intoxication?
“The process by which a toxic
chemical causes an adverse effect
in a living organism”
Human Intoxication
Domestic Animals
• Approximately 42,000
poisonings reported in 1990:
– ⅓ due to insecticides,
herbicides, fungicides and
rodenticides.
– ¼ due to veterinary drugs.
– 12% due to toxic plants.
• Most poisonings were due
to pesticides.
Wildlife
• Animals that are not
domesticated.
• Known cases of bird
poisonings caused by:
– DDT.
– Organophosphorus
Pesticides.
• Fish kills are still very
common.
Environmental Toxicology
Branch of Toxicology that studies the
fate, behavior, properties, effects and
levels of toxicants in the environment and
their respective effects in living organisms.
Environmental Chemistry
“Study of sources, reactions, transport and
fate of chemicals in the air, water and soil
environments, as well as their effects on
human
health
and
the
natural
environment” (2)
Characteristics of the Molecule
(molecular weight, charge,
type of chemical bonds, etc)
Properties of the
Chemical
The Compound and its
Physico-chemical Properties
(solubility, vapor pressure,
partition coefficients, etc)
Properties of the
Environment
Environmental Processes
(transport, transformation, persistence,
bioaccumulation, etc)
Biological Effects
(lethality, reproductive effects, etc)
Hazard and Risk
• Hazard = potential to cause harm.
• Risk = probability that a hazard occurs.
Risk Assessment
“Systematic and scientific evaluation of the
potential for toxicity when humans or
wildlife are or will be exposed to hazardous
compounds or situations”
Major Toxic Hazards
• Polycyclic Aromatic
Hydrocarbons:
– Benzo(a)pyrene.
• Biotoxins
– Nicotine, aflatoxins, shellfish
poisons.
• Reactive Gases
– CO, O3, H2S, etc.
• Metals and metalloids
– Cadmium, lead, mercury,
chromium, arsenic, etc.
• Cholinesterase inhibitors
– Organophosphate pesticides,
carbamate insecticides.
• Halogenated hydrocarbons
– CCl4, chlordane,
chloroethylenes, DDT, HCB,
TCDD.
• Solvents, corrosives.
• Other chemicals
– Drugs, pharmaceuticals,
phenols, etc.
Conclusions
• Toxicology is a very diverse field that developed
throughout human history.
• Humans are exposed daily to chemicals at
home, at work, at school and even outdoors.
• Wildlife is also exposed to environmental
pollutants.
• Environmental Toxicology and Chemistry is a
branch of toxicology that studies the fate,
behavior and effects of xenobiotics in humans,
animals and the environment itself.
References
• 1-Crosby, D.G. Environmental Toxicology and Chemistry.
2000. Oxford University Press, New York.
• 2- Connell, D.W. Basic Concepts of Environmental
Chemistry. 1997. Lewis Publishers, New York.
• 3- Gallo, M.A. History and Scope of Toxicology. In:
Klaassen, C.D. (Ed), Casarett and Doull’s Toxicology,
The Basic Science of Poisons. Fifth edition, McGraw Hill,
1995, pp.3-11.
Additional Resources
• Federal Food, Drug and Cosmetic Act:
http://www.fda.gov/opacom/laws/fdcact/fdc
toc.htm
• FIFRA:
http://www.epa.gov/pesticides/fifra.htm