Phenthoate toxicity: cumulative effects in rats.

This study was designed to provide information on the cumulative effects of phenthoate, an organophosphorus insecticide. Male rats were given the test compound orally 6 days/week for a minimum of 10 weeks and until the cumulative LD50 (CLD50) remained constant for 3 consecutive weeks. The oral LD50 value for phenthoate in rats was highest (116 mg/kg) in groundnut oil followed by dimethylsulfoxide (DMSO) and alcohol. The animals with lesser weight were more susceptible than the heavier animals. Rats receiving 2.5 to 10 mg/kg phenthoate for 13 weeks showed varying decreases in weights of liver, heart, spleen, brain, testes and adrenals. At 40 mg/kg, none of the animals survived. The CDL50 for 13 weeks was 12 mg/kg with a cumulative toxicity factor of 6.3. The compound has been rated as a moderately hazardous one.