METHYL-METHACRYLATE - INHALATION DEVELOPMENTAL TOXICITY STUDY IN RATS

Methyl methacrylate (99.9% pure) was administered by vapor inhalation exposure to five groups (27 rats/group) of presumed pregnant rats (Crl :CD) at concentrations of 0 (control), 99, 304, 1,178, and 2,028 ppm f or 6 hr/day on days 6-15 of gestation (G). Maternal body weight, feed consumption, and clinical signs were recorded throughout gestation. Da ms were euthanized on day 20 G. Each uterus was weighed and corpora lu tea, implantation sites and resorptions were counted. The number of fe tuses per litter were counted and their location within the uterus rec orded. All fetuses were weighed, sexed and examined for external and s keletal alterations. One half of the fetuses from each litter were exa mined for visceral alterations. No treatment-related deaths were noted at any concentration tested. Treatment-related effects on maternal bo dy weight and feed consumption were noted at all exposure levels. The decreases in maternal body weight at 99 and 304 ppm were minimal and t ransient since they returned to control values by the next weighing pe riod. When exposure was discontinued, body weight gain and feed consum ption in all exposure groups returned to control values. There were no treatment-related changes in the number of litters produced or in the mean number per litter of corpora lutea, implantations, resorptions, live or dead fetuses, or sex ratio. Fetal body weights were similar be tween the control and treated groups. There were no treatment-related increases in the type or incidence of external, visceral, or skeletal malformations, developmental variations, or variations indicative of r etarded development. Exposure to methyl methacrylate concentrations up to 2,028 ppm resulted in no embryo or fetal toxicity or malformations even at exposure levels that resulted in maternal toxicity. (C) 1993 Wiley-Liss, Inc.