||Hazleton Labs., Inc., Falls Church, VA.; Phillips Petroleum Co., Odessa, TX.; Environmental Protection Agency, Washington, DC. Office of Toxic Substances.
Cyclohexane was tested for acute toxicity to rats (5/sex/group) exposed by inhalation to a nominal concentration of 32.88 mg/L. Exposure-related increased incidence of tremors, hyperactivity, rapid respiration, and prostration were noted in both sexes. Similar exposure of male mice (4/group) led to slight reduction in respiratory rate in 1 animal and increased rate in the other 3. No evidence of upper airway irritancy was seen. Washed and unwashed primary eye irritation studies were conducted in rabbits (6/group) exposed to cyclohexane. Conjunctival redness was noted at one hour, but cleared by 24 hours. A primary skin irritation test in rabbits (6/sex) showed no evidence of irritation; whether skin sites were abraded or intact was not reported. An acute oral toxicity study in rats (5/sex/group) exposed to a single dose of 5000 mg/kg cyclohexane showed only transitory clinical signs of depression, salivation, and soft feces. Rabbits (6/sex) dermally exposed to single applications of 2000 mg/kg cyclohexane showed no evidence of systemic toxicity, but slight transient erythema and edema were noted. Salmonella/microsome plate assays in Salmonella typhimurium tester strains TA98, TA100, TA1535, TA1537, and TA1538 showed no evidence of mutagenicity with exposure to 7 graded doses of 7.1 to 5200 ug/plate. A mouse lymphoma forward mutation assay conducted at test concentrations up to 100 ug/ml in the presence of S9 gave negative results. An in vitro sister chromatid exchange test was conducted in Chinese hamster ovary cells exposed to concentrations up to 25 ug/ml; negative results were seen.