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MSU Faculty Authors

Author

William L. Giles Distinguished Professor
Director, Center for Environmental Health Sciences
Diplomate, American Board of Toxicology
Fellow, Academy of Toxicological Sciences

Education
  • B.S. - University of San Francisco
  • Ph.D. - Mississippi State University

Special Interests
  • Research - Mechanism of action and biotransfomation of neurotoxicants; neurochemical and behavioral effects of anticholinesterase insecticides; metabolism of insectidices and other xenobiotics; pesticide exposure assessment; developmental neurotoxicity; assessment of the effects of mixtures of toxicants
  • Teaching - Environmental Toxicology; Mechanisms of Toxicant Action; Current Topics and Controversies in Toxicology; Risk Assessment of Pesticides

Primary Area of Expertise
  • Toxicology
  • Biochemical Toxicology
  • Environmental Toxicology
  • Neurotoxicology

Effects of Chronic Exposures to Pesticides on Animal Systems

Chambers, Janice E.
Publisher: Raven Press
1982
ISBN: 0890047561
Collaborators: James D. Yarbrough

The idea for this volume arose from the need to organize a compilation of some of the major effects resulting from chronic exposures to pesticides. The acute effects of pesticides, i.e., the mechanisms by which they kill as well as other short-term effects resulting from single exposures, have been well studied. Many of these mechanisms and effects have been precisely defined and, in some cases, structure-activity relationships have been elucidated. Except for unpredictable accidents, however, non-target populations will not encounter pesticides at levels resulting in acute toxicity. Realistically, any danger of pesticides to non-target organisms will result from long-term, indirect toxic effects of these chemicals.

What is the fate of a pesticide encountered in chronic exposures? If the pesticide is lipophilic, as many are, it can be sequestered in fat, yielding a dramatic biomagnification; these chemicals could remain trapped until the fat stores are utilized. If the chemical is metabolized to polar, nontoxic metabolites that are readily excreted, the probability of deleterious effects will be minimized. However, if the chemical is metabolized to reactive intermediates or toxic metabolites, it may pose a serious threat. Because of the potential of these metabolites to form adducts with genetic material and/or react with other critical macromolecules, pesticides could cause alterations in an individual's normal physiology, biochemistry, or behavior, or in the genetic material that an individual could pass on to future generations.

This volume covers chronic pesticide effects from the subcellular to the organismic level. Initially there is a discussion on the microsomal mixed-function oxidase system describing the characteristics and specificity demonstrated by this group of enzymes and the aspects of the system's inhibition and induction by xenobiotics.

Next is discussion of the liver and kidney, two organs critical in the concentration and the clearance of pesticides. Chronic damage in these organs would result in far-reaching effects on homeostasis and limit the animal's functional capacity to survive in any environmental circumstance.

Discussion follows on the delayed neurotoxicity phenomenon resulting from exposures to some organophosphorus compounds. Different from the acute neurotoxic mechanism mediated through acetylcholinesterase inhibition, delayed neurotoxicity phenomena involve progressive loss of nervous function with resultant long-term paralysis. The reproductive system also can be affected by pesticides. There is discussion of the estrogenic effects of selected organochlorine pesticides known to bind to estrogen receptors and which exert the same effects within the nucleus as does endogenous estrogen.

The following chapters discuss the three generalized chronic toxicity phenomena: carcinogenicity, mutagenicity, and teratogenicity. One chapter focuses on carcinogenicity caused by pesticides and the types of cancers that some pesticides have produced in the laboratory. Included is a list of pesticides that are not carcinogenic. Another chapter discusses pesticide-related mutagenicity and tertogenicity.

Pesticide-altered behavior is considered next. Even if morphological and physiological parameters appear normal, there could be subtle cellular or biochemical alterations that could alter the behavior of individuals.

The final chapter deals with pesticide interactions and the development of tolerance. To presume that populations will be exposed to single pesticides only is unrealistic. The predicted toxic hazard may be reduced or exaggerated during simultaneous exposure to two or more chemical agents. With continued exposure, populations may develop a tolerance of the toxic effects of pesticides.

The editors hope that this volume will prove useful in understanding the chronic effects of pesticides on non-target organisms. This volume will be of interest to environmental toxicologiests and all those working in the disciplines of toxicology, pharmacology, physiology, or environmental risk assessment who have an interest in pesticide effects on non-target organisms and/or the effects of chronic exposures of xenobiotics in animals.