Diphenyl ether herblcldes, includlng nitrofen, have been identified as mammalian teratogens and cause perinatal mortality. American kestrel (Falco sparverius) nestlings were orally dosed for 10 days w1th 5 ul/g of corn oil (controls) or one of the diphenyl ether herbicides (nitrofen, bifenox, or oxyfluorofen). At 500 mg/kg, nitrofen resulted in complete mortality, bifenox in high (66%) mortality, and oxyfluorofen in no mortality. Nitrofen, at 250 mg/kg, reduced nestling growth, as reflected by decreased body weight and bone length. Bifenox at 250 mg/kg had less effect on growth than nitrofen but crown rump, humerus, radiusulna and femur lengths were significantly less than controls. Liver welght (percent of body welght) increased with 50 mg/kg nitrofen. Other manifestations of hepatotoxicity following nitrofen ingestion included increased hepatic GSH peroxidase activity with 0 mg/kg nitrofen, and increased plasma enzyme activities for ALT, AST. and LDHL with 250 mg/kg. Blfenox lngestion (50 mg/kg) resulted in increased hepatlc GSH peroxidase activity. Nitrofen exposure increased total plasma thyroxlne (T4) concentratlon. These findings suggest that altricial nestllng kestrels are more sensitive to diphenyl ether herbicides than precocial young or adult birds.
Additional publication details
Developmental toxicity of diphenyl ether herbicides in birds