Developmental toxicities of methacrylic acid, ethyl methacrylate, n-butyl methacrylate, and allyl methacrylate in rats following inhalation exposure

The developmental toxicities of 4 methacrylates were studied in Sprague-Daw ley rats after inhalation exposure for 6 h/day, during days 6 to 20 of gest ation. The exposure concentrations were, for methacrylic acid, 0, 50, 100, 200, or 300 ppm; for ethyl methacrylate, 0, 600, 1200, 1800, or 2400 ppm; f or n-butyl methacrylate, 0, 100, 300, 600, or 1200 ppm; and for allyl metha crylate, 0, 12, 25, 50, or 100 ppm. No significant increases in embryo/feta l lethality or fetal malformations were observed after exposure to any of t hese methacrylates. Fetal toxicity evidenced by statistically significant d ecreases in fetal body weights was observed at exposure levels greater than or equal to 1200 ppm ethyl methacrylate, greater than or equal to 600 ppm n-butyl methacrylate, and at 100 ppm allyl methacrylate. Statistically sign ificant increases in the incidence of fetuses with skeletal variations and of fetuses with any variations were noted at 1200 ppm n-butyl methacrylate. These developmental effects were observed in the presence of overt signs o f maternal toxicity. While maternal toxicity was observed, methacrylic acid caused no evidence of developmental toxicity up to 300 ppm.