TOXICOLOGICAL EVALUATION OF 1,1,1,2,2-PENTAFLUOROETHANE (HFC-125)

Acute, subacute, and subchronic inhalation toxicity studies, developme ntal toxicity studies, a cardiac sensitization evaluation, and mutagen icity assays were conducted with pentafluoroethane (HFC-125), In the a cute study, rats were exposed to a single concentration of 800,000 ppm for 4 hr, Ataxic gait and abnormal respiration were observed during e xposure but not after exposure, There was no mortality or other signs of toxicity. Repeated exposures of rats to 50,000 ppm, 6 hr/day, 5 day s/week for either 4 or 13 weeks elicited no effects on body weight, fo od consumption, clinical signs, hematology, biochemistry, urinalysis, organ weight, or tissue morphology, Positive evidence of cardiac sensi tization in response to an intravenous epinephrine challenge in dogs w as seen at 100,000 ppm and above, but not at 75,000 ppm. HFC-125 was n ot mutagenic in Salmonella typhimurium and Escherichia coli strains at concentrations of 20 to 100% (v/v) with and without activation, No ev idence of clastogenic activity was observed in cultured Chinese hamste r ovary (CHO) cells or human lymphocytes at less than or equal to 70% HFC-125 when treatments were conducted for 3-4 hr with activation or f or 24 and 48 hr (human lymphocytes only) without activation, However, a statistically significant increase in chromosomally aberrant cells w as observed in CHO cells at 60% HFC-125 when treatment without activat ion was extended to 48 hr, The biological significance of this effect is questionable since signs of severe toxicity were also present, In v ivo, no micronuclei were induced in mouse bone marrow at concentration s as high as 600,000 ppm HFC-125 for a 6-hr exposure, In addition, HFC -125 did not induce embryotoxic or teratogenic effects in either the r at or the rabbit at exposure concentrations as high as 50,000 ppm. (C) 1995 Society of Toxicology