Acute and subacute toxicity of dimethoate

Abstract

Dimethoate is among the less toxic organic phosphate insecticides. The acute oral LD 50 for rats is of the order of 200 mg/kg for both sexes. The compound is not readily absorbed through skin and is not irritating to skin or eyes. There is no evidence that mixtures of dimethoate with various other organic phosphate compounds exhibit greater-than-additive acute toxicity for rats. Erythrocyte cholinesterase of rats and dogs is more susceptible to the inhibitory action of dimethoate than is plasma cholinesterase. In 90-day feeding, the minimally effective dietary level of dimethoate for inhibition of both plasma and erythrocyte cholinesterase of rats lies between 32 ppm and 50 ppm. In the case of dogs, erythrocyte cholinesterase activity is depressed slightly at 50 ppm but not at 2 ppm or 10 ppm, whereas plasma cholinesterase activity is not affected at 50 ppm. Feeding of relatively very high levels of dimethoate to rats and dogs for 90 days produces marked depression of cholinesterase activities, but no significant hematologic changes or anatomical pathology.