Subchronic Inhalation Toxicity of Ethylbenzene in Mice, Rats, and Rabbits

Mice, rats, and rabbits (five/sex/group) were exposed by inhalationto ethylbenzene (EB) vapors for 6 hr/day, 5 days/week for 4weeks (20 exposures). Rats and mice received 0, 99, 382, or782 ppm EB while rabbits received 0, 382, 782, or 1610 ppm.No changes were evident in mortality patterns, clinical chemistries,urinalyses, or treatment-related gross/microscopic (includingophthalmologic) lesions. Rats exhibited sporadic lacrimationand salivation, as well as significantly increased liver weightsat 382 and 782 ppm, and small increases in leukocyte countsat 782 ppm. Males at this exposure level also showed marginalelevations in platelet counts. In mice, females showed statisticallyincreased absolute and relative liver weights at 382 and 782ppm, while males had statistically increased relative liver-to-brainweight ratios only at 782 ppm. Female rabbits at the high exposurelevel of 1610 ppm gained weight more slowly than controls (notstatistically significant); males showed a similar transientdownward trend after 1 week, but showed no differences fromcontrols at study's end. A no observed adverse effect level(NOAEL) of 382 ppm appears appropriate for rats and mice witha lowest observed adverse effect level (LOAEL) of 782 ppm. ANOAEL of 782 ppm and LOAEL of 1610 ppm are appropriate for rabbits.