Effects of Atrazine on Fish, Amphibians, and Aquatic Reptiles: A Critical Review

Abstract

The herbicide atrazine is widely used in agriculture for the production of corn and other crops. Because of its physical and chemical properties, atrazine is found in small concentrations in surface waters—habitats for some species. A number of reports on the effects of atrazine on aquatic vertebrates, mostly amphibians, have been published, yet there is inconsistency in the effects reported, and inconsistency between studies in different laboratories. We have brought the results and conclusions of all of the relevant laboratory and field studies together in this critical review and assessed causality using procedures for the identification of causative agents of disease and ecoepidemiology derived from Koch's postulates and the Bradford–Hill guidelines. Based on a weight of evidence analysis of all of the data, the central theory that environmentally relevant concentrations of atrazine affect reproduction and/or reproductive development in fish, amphibians, and reptiles is not supported by the vast majority of observations. The same conclusions also hold for the supporting theories such as induction of aromatase, the enzyme that converts testosterone to estradiol. For other responses, such as immune function, stress endocrinology, parasitism, or population-level effects, there are no indications of effects or there is such a paucity of good data that definitive conclusions cannot be made.

Keywords:

• adverse effects
• amphibians
• atrazine
• fish
• endocrine
• reptiles

ACKNOWLEDGMENTS

This review was developed with a grant from Syngenta Crop Protection, Inc. The authors specifically thank the following individuals for their help in preparing this review: Dr. Norbert Kaminski of the Department of Pharmacology and Toxicology, Michigan State University, for his contributions to reviewing the immunotoxicity papers; the late Sir Richard Doll, Green College, Oxford, for his helpful discussions of the Bradford-Hill guidelines; Cathy Bens for advice on quality assurance and report data; Susanne Williamson for logistics, coordination, and meeting arrangements; and Robert Bruce of Ecorisk for his management support.