Pesticide Toxicology, Evaluating Safety and Risk

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Toxicology is the scientific study of the harmful effects of chemicals on living organisms: humans, animals, and plants. Toxicological testing evaluates whether short-term exposure to a pesticide will produce acute effects (e.g., eye and skin irritation, death) and whether long-term, continual exposure will cause chronic effects (e.g., impaired liver function, reproductive abnormalities, cancer).
Toxicological evaluations are conducted with experimental animals exposed to various levels of the pesticide for various lengths of time, from hours to years. Results often lead investigators to additional research on the interaction of the pesticide with biological systems. Understanding the biological mechanisms that underlie effects observed in animals allows toxi5 Pesticide and Animal Interaction cologists and risk assessors to predict the chances of harm to human populations exposed to the pesticide.
Consideration of exposure levels and effects produced at specific doses is essential in determining toxicity. Exposure, in and of itself, does not necessarily produce harmful effects; for instance, people who are exposed to low levels of pesticides in their food or drinking water, or through contact at the workplace, usually suffer no harm. But harm is to be expected when people are exposed, accidentally or otherwise, to much higher levels that have been shown to produce adverse health effects in laboratory animals.
The dose/response concept is familiar: High doses are likely to produce detectable injury, while low doses may produce little or no injury. For example, ingesting one or two sleeping tablets might have a beneficial effect, while consuming a bottle of them could be lethal. One glass of beer may not affect an adult, but the same amount could easily intoxicate a child. A little salt improves the taste of food, but a lot could cause serious health consequences—even death.

Fred Whitford
Tom Fuhremann
K.S. Rao
Gail Arce
James E. Klaunig
Purdue University Cooperative Extension Service