Embryo- and Fetotoxicity of Inhaled Methyl Ethyl Ketone in Rats

Pregnant Sprague-Dawley rats inhaled 0, 400, 1000, or 3000 ppm methyl ethyl ketone (MEK) for 7 hr/day on Days 6 through 15 of gestation. Maternal toxicity, as evidenced by decreased weight gain and increased water consumption, was observed among rats exposed to 3000 ppm MEK. Slight fetotoxicity was observed among litters of rats exposed to 3000 ppm MEK as evidenced by an increased incidence of two minor skeletal variants. The results of this study duplicate the increased incidence of skeletal variants observed in an earlier study by B. A. Schwetz, B. K. J. Leong, and P. J. Gehring (1974, Toxicol. Appl. Pharmacol. 28, 452–464), and do not indicate that inhaled MEK causes either an embryotoxic or teratogenic response in rats at exposure levels up to 3000 ppm.