Toxicological studies with the insecticide tetrachlorvinphos

Acute and long‐term mammalian toxicity studies have been made with the organophosphorus insecticide tetrachlorvinphos. The acute oral LD50 values for technical material were greater than the maximum dose which could be administered to guinea‐pig and domestic fowl (5000 and 1500 mg/kg respectively). For formulations, the figures range from about 500 to >5000 mg/kg, those containing phenol having the lowest values. In 13‐week feeding studies, most changes occurred at dietary concentrations of 800 parts/million or greater with inhibition of plasma cholinesterase appearing to be the most sensitive indicator of exposure. 200 parts/million was considered to be without toxicological effect in rats and dogs after 3 months feeding. In a two‐year study in rats 125 parts/million produced no changes of toxicological significance.