Acute dermal toxicities of various organophosphate insecticides in mice

Dermal LD50 values for five organophosphate insecticides were determined in mice by application of solutions to hind feet. Values were simultaneously generated for the ED50 (milligrams per kilogram) for both cholinesterase and acetylcholinesterase. Lethality was greatest with mevinphos, followed by parathion, methyl parathion, diazinon, and azinphosmethyl. LD50 values were higher than reported values for mice treated on shaved back skin. Cholinesterase ED50 values roughly agreed with LD50 values for mevinphos, parathion, methyl parathion, and azinphos-methyl, but diazinon appeared much more inhibitory of blood than neuronal cholinesterase. Red blood cell and plasma cholinesterase activities were equally sensitive for all but mevinphos and diazinon.