Teratogenic evaluation of 1,4-dichlorobutene-2 in the rat following inhalation exposure

The teratogenic potential of 1,4-dichlorobutene-2 (1,4-DCB) was evaluated in the rat. From inhalation toxicity studies, particularly ongoing lifetime studies, exposure levels of 0, 0.5, and 5.0 ppm were selected. Rats were exposed for 6 hr per day on Days 6 through 15 of gestation (sperm-positive vaginal smear considered Day 1). Female rats were killed 1 day prior to natural delivery and fetuses were examined for external development, structure and integrity of internal tissues and organs, and skeletal development. The only clinical sign of toxicity observed among rats exposed to 1,4-DCB, was a significantly-reduced rate of weight gain seen at the 5.0-ppm level. 1,4-DCB exposure did not change either the number of pregnant rats or the number of implantation sites, resorption sites, and fetuses per female. Treatment did not affect embryonal development as measured by fetal weight and crown-rump length, or by gross external, visceral, and skeletal examination of the fetuses. Under the test conditions of this study, 1,4-DCB was neither embryotoxic nor teratogenic.