Environmental Toxicologyand Chemistry Principles of Toxicology
What is Toxicology? “Study of the toxic effects of xenobiotics in living organisms”
Antiquity Hunting and warfare
Ebers Papyrus (circa 1500 B.C.) Hippocrates (circa 400 B.C.) Antiquity
Dioscorides Socrates (470-399 B.C.) Antiquity
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
20th Century • Word War II and TCDD • Delaney Clause • Thalidomide and Love Canal cases
Clinical Forensic Molecular Food Toxicology Environmental Regulatory Plant Toxicology Veterinary Approaches to Study Toxicology
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.
What is Intoxication? “The process by which a toxic chemical causes an adverse effect in a living organism”
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”
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. Major Toxic Hazards
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/fdctoc.htm • FIFRA: http://www.epa.gov/pesticides/fifra.htm