The evaluation of a new synthetic pyrethroid pesticide (permethrin) for neurotoxicity.

A new synthetic pyrethroid, permethrin, has recently been granted a registration by the United States Environmental Protection Agency. Permethrin and a large number of other chemicals of its type are expected to receive widespread use in the environment in the near future. Since the mechanism by which these compounds exert their toxic effect in insects (and at higher doses in mammals) is by disruption of the normal function of nervous tissue, a detailed morphologic evaluation of the nervous system was performed on rats from two long-term feeding studies conducted on permethrin. In this evaluation, examination of central and peripheral nervous plus examination of extensive morphometric data and teased myelinated fibers of distal sural and tibial nerves and of the maxillary division of cranial nerve V did not reveal any changes which could be attributed to the feeding of the pesticide.