Oral Toxicity of Mirex in Adult and Suckling Rats

Abstract

The oral toxicity of mirex and its effect on reproduction was studied in rats. The one-dose oral lethal dose for 50% survival of the group (LD₅₀) in females was 365 mg/kg/day; the 90-dose oral LD50 was 6 mg/kglday. The chronicity factor was 60.8. Females fed 25 ppm mirex had fewer offspring born alive, significantly fewer offspring survived to weaning, and many pups developed cataracts. Females fed 5 ppm produced normal litters. Offspring born to mothers fed 25 ppm mirex and nursed by nontreated foster mothers had a low incidence of cataracts and a normal survival rate to weaning. Gas chromato-graphic analysis of milk and fetuses showed excretion of mirex in the milk and passage through the placental barrier. Livers of male and female rats fed 25 ppm mirex weighed significantly more than controls. Proliferation of smooth endoplasmic reticulum and osmiophilic dense bodies were observed in these livers with the electron microscope.