Acute toxicity of pesticides.

Abstract LD50 values have been determined for 98 pesticides and 2 metabolites of DDT administered in a single dose by the oral or dermal route to Sherman strain adult rats. Most compounds tested by the oral route were more toxic to female than to male rats, but 9 of 85 compounds (aldrin, chlordane, heptachlor, Abate, Imidan, methyl parathion, ronnel, schradan, and metepa) tested in both sexes were markedly more toxic in male rats. Although the pesticides were generally more toxic by the oral than by the dermal route, 5 compounds (fenitrothion, Merphos, mevinphos, Isolan, and Omite) were more toxic by the dermal route. LD50 values for rats treated by the dermal route with parathion or dichlorvos and restrained so as to prevent the possibility of oral or respiratory exposure were not significantly different from those values in rats treated according to the procedure used routinely in this laboratory. In screening tests for the production of paralytic effect in chicken hens 3 of 9 carbamate and 22 of 30 organic phosphorus pesticides tested caused paralysis. The onset of paralysis was delayed at least 3 days in chickens treated with Dursban and Merphos and at least 14 days in chickens treated with DEF. Chickens treated with the other 22 pesticides that produced paralysis showed this effect within 24 hours.