Comparative penetration of insecticides in target and non-target species

Dermal penetration of 14C-labeled carbaryl, parathion, DDT, dieldrin and permethrin was compared in American roaches, tobacco hornworms, Japanese quail, grass frogs and mice. Insecticides were absorbed more quickly in mice (one exception) while entry into insects was generally slow. The half time penetration rates for carbaryl ranged from 6 min for frogs to 4600 min for roaches. Whereas permethrin penetrated easily into insects, other insecticides showed generally slower penetration into target organisms. Carbaryl tended to penetrate most rapidly in all species except roaches, while DDT and dieldrin tended to penetrate slowly in all organisms tested. Distribution of insecticides in the blood and liver of Japanese quail and grass frogs was surprisingly low. Insect species tended to show higher amounts in hemolymph than most other species. Excretion of radioactivity was relatively low in the frog in these experiments but was high in the quail for rapidly-metabolized compounds.