Permethrin transfer from treated cloth to the skin surface: potential for exposure in humans.

Permethrin is an agricultural insecticide of great interest to the military because of its repellency toward disease-bearing insects when impregnated into uniforms. However, migration of the substance from clothing to the skin surface is of toxicological importance. To quantitate leaching from treated clothing, studies were performed in which swatches of fabric impregnated with 14C-labeled permethrin were applied to the backs of rabbits for 1 wk. Permethrin migration was quantitated by measuring the fate of the 14C label. Conditions that could affect leaching and/or absorption were also evaluated, that is, varying environments, the presence of sweat, different fabric types, and the effects of prelaundering. Results showed that fabric treated with permethrin at a rate of 0.125 mg/cm2 lost the substance to the skin surface at an average rate of 0.49%/d. At the end of the 7-d exposures in rabbits, about 3.2% of the available permethrin had reached the skin, 2% having been recovered from excreta (absorbed) and 1.2% remaining on the skin surface. Prelaundering the treated fabric had little effect on migration rate, nor did the other variables tested. Exposure dose to humans from wearing permethrin-treated (0.125 mg/cm2) military clothing is predicted to be 6 x 10(-4) mg/kg/d.