Current status of tests of carbaryl for reproductive and teratogenic effect

Abstract

A 3-generation rat reproduction study with technical carbaryl (1-naphthyl methylcarbamate) added to the diet to provide daily doses up to 10 mg/kg resulted in no statistically significant, dose-related effect upon fertility, gestation, viability of pups or lactation. A rat teratogenic study with carbaryl added to the diet to provide daily doses up to 500 mg/kg resulted in no increase in teratogenic anomalies and no effect on fertility or gestation. Only at the highest dose was weight gain reduced; many pups in this group died before weaning from carbaryl-fed mothers. A rat reproduction study included groups receiving carbaryl in the diet at daily doses up to 200 mg/kg, while other groups concurrently received carbaryl by po intubation of doses up to 100 mg/kg/day. A dose of 100 mg/kg/day given by intubation before mating resulted in mortality, signs of cholinesterase inhibition and reduced fertility. None of these effects were seen in groups dosed in the diet. Reduction in growth at 100 mg/kg/day given by intubation was equivalent to that of 200 mg/kg/day given in the diet. Guidelines for an acceptable experimental design of studies to evaluate human risks are discussed in relation to published articles and unpublished reports on the effect of carbaryl on animal reproduction or teratology. Only 1 study other than the 3 reported here conformed to all the guidelines; in this study it was reported that no reproductive effects occurred in rats given 2000 ppm in the diet.