The chronic toxicity of p-nitrophenyl diethyl thiophosphate (E. 605): A long-term feeding experiment with rats

Abstract

1. The results of feeding albino rats on diets containing 100, 75, 50, 20 and 10 parts per million of the insecticide p-nitrophenyl diethyl thiophosphate (E. 605, Parathion) are described. The feeding of 50, 20 and 10 p.p.m. was continued for a year.2. At 100 and 75 p.p.m. most of the rats died in the first few weeks. At 50 p.p.m. a few deaths resulted from poisoning, and symptoms were seen on and off throughout the year. At 20 and at 10 p.p.m. no evidence of poisoning was found.3. Histological examination of animals dying with symptoms showed the lesions of the exocrine glands and the hypoplasia of spleen and thymus that have been reported in acute poisoning by E.605. No other lesions attributable to chronic poisoning were found.4. Breeding experiments were done with animals from all groups. The second generation of rats fed at 10 p.p.m. produced many dead in their litters. No explanation has been found for this observation.