NTP technical report on the toxicity studies of Ethylbenzene (Cas No. 100-41-4) in F344/N Rats and B6C3F1 Mice (Inhalation Studies).

Ethylbenzene is commonly used as a solvent and chemical intermediate and as an additive in some motor fuel formulations. Inhalation toxicology studies of ethylbenzene (99% pure) were conducted by exposing groups of F344/N rats and B6C3F1 mice of each sex to ethylbenzene vapor at chamber concentrations of 0, 100, 250, 500, 750, or 1000 ppm, 6 hours per day, 5 days per week for 13 weeks. No rats or mice died during the 13-week exposure. Body weight gains were slightly lower in the high dose groups of male and female rats, but the differences were not statistically significant. Absolute and relative kidney, liver, and lung weights were increased in the exposed rats, while weight increases occurred only in the livers of exposed mice. Chemically related histopathologic changes were not observed in any tissues of rats or mice. No changes were observed in the evaluation of sperm or vaginal cytology in rats or mice. Ethylbenzene was not mutagenic in Salmonella and did not induce chromosomal aberrations or sister chromatid exchanges in Chinese hamster ovary (CHO) cells in vitro, though it did induce trifluorothymidine resistance in mouse lymphoma cells at the highest concentration tested. Micronuclei assays in peripheral blood of mice were negative. Thus, there appears to be only minimal evidence of toxicity in F344/N rats and B6C3F1 mice exposed to ethylbenzene by inhalation at concentrations as high as to 1000 ppm for 13 weeks. Synonyms: EB, ethyl benzene, ethylbenzol, phenylethane. (NOTE: These studies were supported in part by funds from the Comprehensive Environmental Response, Compensation, and Liability Act trust fund (Superfund) by an interagency agreement with the Agency for Toxic Substances and Disease Registry, U.S. Public Health Service.)