Developmental toxicity study of chlorpyrifos in rats

Chlorpyrifos (O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)-phosphorothioate) was evaluated for potential developmental toxicity. Groups of 30 bred female Fischer 344 rats were given 0, 5, 15, and 25 mg/kg per day by gavage on gestation days 6-15; the fetuses were evaluated on gestation day 21. Clinical signs of toxicity attributed to chlorpyrifos were, noted in dams receiving 15 and 25 mg/kg per day. Maternal effects in these groups also included depressed body weight and acetylcholinesterase activity. Fetal weight and viability were decreased, and fetal death and early resorption were increased at the 25 mg/kg per day maternal dose. Visceral, skeletal, and external variations were also increased in this group. Chlorpyrifos showed fetotoxic and teratogenic effects at a maternal dose of 25 mg/kg per day, a dose, that also produced maternal toxicity. (C) 2002 Elsevier Science Inc. All rights reserved.