In one study, degenerative changes in the liver were observed in dogs chronically orally exposed to parathion. EPA has not established an RfC for parathion. A reduced number of offspring and decreased fetal weight have been reported in rats exposed to parathion by injection, but no malformations were observed. High postnatal mortality was also observed in an animal study. EPA has classified parathion as a Group C possible human carcinogen.
Pure parathion is a pale yellow liquid, while the technical grades are brown.
Parathion is practically insoluble in water. U.S. Department of Health and Human Services. National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993. World Health Organization, Lyon. The Merck Index.