The teratogenic potential of ethylbenzene (100414) or 2- ethoxyethanol (110805) was studied in rats and rabbits. Female Wistar-rats and New-Zealand-white-rabbits were exposed to 100 or 1,000 parts per million (ppm) ethylbenzene vapor or 160, 202, 617, or 767ppm 2-ethoxyethanol vapor 7 hours daily 5 days per week for 3 weeks. The rats were mated and exposed daily through day 19 of gestation. The rabbits were artificially inseminated and exposed through day 18 or 24 of gestation for 2-ethoxyethanol or ethylbenzene, respectively. The dams were observed for signs of toxicity such as altered food consumption, body weight gain changes, and weight and histopathologic changes in selected tissues. At delivery, litters were examined for the presence of external, visceral, and skeletal malformations, and crown/rump lengths were measured. The numbers of living and dead fetuses, and resorptions were recorded. Ethylbenzene did not cause maternal toxicity or embryotoxicity in rabbits. The 1,000ppm dose caused increased weights of maternal livers, kidneys, and spleens, and increased body weight gain in rats. An increase in supernumerary ribs occurred in rat fetuses; however, this was not considered to be a teratogenic effect. 2-Ethoxyethanol at 617ppm in rabbits and 767ppm in rats caused decreased maternal food consumption, body weight loss, and mortality. Liver and kidney weights were elevated. Significant increases in embryo mortality occurred. The 160 or 202ppm doses caused fetal growth retardation, increased embryo mortality, and an increase in minor malformations. The authors conclude that ethylbenzene at 1,000ppm is toxic to pregnant rats, but probably not for pregnant rabbits. Higher doses might be teratogenic in rats. 2- Ethoxyethanol is a teratogen in both rabbits and rats. It should probably be regarded as presenting similar risks to humans.
Division of Biomedical And Behavioral Science, NIOSH, U.S. Department of Health, Education and Welfare, Cincinnati, Ohio