Chloroprene, 2-chloro-1,3-butadiene, is a colorless liquid with a pungent ethereal odor that is primarily used as an intermediate in the manufacture of neoprene rubber, and has been used as such since about 1930. This study addressed the potential for chloroprene to cause developmental toxicity in New Zealand white rabbits following gestational exposure to 0, 10, 40, or 175 ppm chloroprene vapors, 6 hours per day, 7 days per week. Each treatment group consisted of approximately 15 artificially inseminated females exposed on 6 through 28 days of gestation. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice on 29 dg. Implants were enumerated and their status recorded and live fetuses were examined for gross, visceral, skeletal, and soft-tissue craniofacial defects.
There were no overt signs of maternal toxicity and the change in maternal body weight over the course of the study was not affected. Exposure of pregnant rabbits to chloroprene vapors on 6-28 dg had no effect on the number of implantations, the mean percent of live pups per litter, or on the incidence of resorptions per litter. Fetal body, kidney, and liver weights (as means of litter means) were not affected by gestational exposure to chloroprene, nor was the fetal sex ratio affected. The incidence of fetal malformations was not increased by exposure to chloroprene. There were no significant alterations in the incidence of total fetal variations or reduced ossifications among exposed groups. Results of this study indicate that gestational exposure of New Zealand white rabbits to 10, 40, or 175 ppm chloroprene did not result in observable toxicity to either the dam or the offspring. The highest exposure group, 175 ppm, was the no observable adverse effect level for rabbits in the study with respect to both maternal and developmental toxicity.