Permethrin

Abstract

Evaluates the design and findings of over 250 studies concerned with the effects on human health and the environment posed by permethrin, a photostable synthetic pyrethroid insecticide marketed since 1977. Because of its strong repellent properties and effectiveness as a stomach and contact insecticide, permethrin is widely used in the protection of several agricultural crops, in the control of insects in households and on cattle, in aerial application for forest pest control, as a fog in mushroom houses, and as a wood preservative. Public health applications include the disinsection of aircraft, treatment of mosquito nets, and human lice control. In view of the uses of permethrin and its photostable properties, a section devoted to sources of human exposure concentrates on the large number of studies investigating residues in fruits, vegetables, dairy milk, and grains. Findings from laboratory studies, indicating that permethrin is highly toxic to certain beneficial insects and natural enemies of pests, are contrasted with field investigations demonstrating the transitory nature of most toxic and repellent effects on non-target species. The most extensive section reviews the findings of experimental studies conducted to assess toxicity. Paricular attention is given to differences in study design, dose, and mode of administration that can affect the validity of findings when extrapolated to humans. The final section draws upon a limited number of occupational and clinical studies to evaluate direct evidence of adverse effects on health. On the basis of this review, the book concludes that most toxic effects are transitory, that the likelihood of carcinogenic effects in humans is extremely low or non-existent, and that permethrin, when used as recommended, is not likely to present a hazard to the general public, exposed workers, or the environment