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HYDROFLUOROCARBON-23 31 ed at each of the six concentrations used. No positive responses were observed in any of the dogs. Branch et al. (1994) evaluated the acute cardiac and central-nervous- system effects of HFC-23 in eight anesthetized baboons. An intravenous injection of 1 µg/kg epinephrine was given after 3 min of exposure to HFC-23 at concentrations of 600,000 ppm or 700,000 ppm. The effects of a control injection of epinephrine had been previously evaluated. Premature ventricular activity totaling four beats was observed in one animal 1 min after the epinephrine injection during inhalation of HFC-23 at 700,000 ppm. No other arrhythmic activity was observed during this study. Ewing et al. (1990) exposed anesthetized cats to HFC-23 at a concentration of 700,000 ppm for 10 min and observed cardiac sensitization in three of five cats after an intravenous injection of epinephrine. Two of the three sensitized cats received 1 µg/kg and the other one received 10 µg/kg. Two other cats that given epinephrine at 0.1 µg/kg did not develop any cardiac arrhythmias. Branch et al. (1990) exposed anesthetized cats to HFC-23 at a concentration of 700,000 ppm for 10 min and observed cardiac sensitization in three of seven cats after an intravenous injection of epinephrine. All seven cats received 1 µg/kg. Two other cats that received epinephrine at 0.1 µg/kg did not develop any cardiac arrhythmias. In both of these studies, the epinephrine was given immediately after exposure. Subchronic Toxicity Leuschner et al. (1983) exposed groups of 20 male and 20 female rats to HFC-23 at 10,000 ppm for 6 hr per day for 90 consecutive days. Likewise, they exposed groups of three male and three female beagle dogs to HFC-23 at 5,000 ppm for 6 hr per day for 90 consecutive days. Clinical signs, food and water consumption, changes in body weight, clinical chemistry, gross and microscopic pathology, and ECGs on the dogs were evaluated. No abnormalities attributable to the test compound were observed and no premature deaths occurred. The investigators concluded that HFC-23 did not produce any adverse effects in the rats or dogs under the test conditions used. Reproductive Toxicity No reproductive toxicity studies of HFC-23 are currently available.
