Relative Developmental Toxicities of Inhaled Aliphatic Mononitriles in Rats

The developmental toxicities of eight aliphatic raononitrileswere studied in Sprague-Dawley rats after inhalation exposurefor 6 hr/day, during Days 6 to 20 of gestation. The range ofexposure concentrations for acetonitrile was 900 to 1800 ppm;for propionitrile and n-butyronitrile, 50 to 200 ppm; for isobutyronitrile,50 to 300 ppm; for acrylonitrile and methacryloni-trile, 12to 100 ppm; for allylnitrile 12 to 50 ppm; and for 2-chloroacrylonitrile,1 to 12 ppm. Embryolethality was observed after exposure to1800 ppm acetonitrile, 200 ppm propionitrile, 300 ppm isobutyronitrile;fetotoxicity was observed after exposure to 200 ppm propionitrile,n-butyronitrile, or isobutyronitrile, or to 25 ppm acrylonitrile,in the presence of overt signs of maternal toxicity. In theabsence of significant maternal toxicity, allylnitrile causedembryolethality, fetotoxicity, and clear teratogenicity at 50ppm, and n-butyronitrile and methacrylonitrile caused fetotoxicityat 200 ppm and 100 ppm, respectively. While maternal toxicitywas observed for 2-chloroacrylonitrile, it did not cause significantembryonal or fetal toxicity up to 12 ppm.