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(up to 2.5 h) to FC-12 at 10,000 ppm could be tolerated without adverse health effects.

Kehoe (1943) reported that exposure to FC-12 at up to 60,000 ppm was tolerated for 80 min by one human subject. When exposed at 40,000 ppm for 14 min and then at 20,000 ppm for 66 min, a second subject developed EEG changes and had slurred speech and decreased scores in psychologic tests. At 110,000 ppm, amnesia and cardiac arrhythmia occurred within about 10 min.

Mergner et al. (1975) exposed a male and a female volunteer to radiolabeled FC-12 at 1,000 ppm for 7–17 min. Recovery of administered radioactivity in exhaled air was essentially complete. Radioactivity in urine and exhaled CO2 together amounted to less than 0.2% of administered radioactivity.

EFFECTS ON ANIMALS

FC-12 has not shown appreciable oral toxicity in laboratory animals in either acute or chronic exposures. These included 18-wk rat and dog feeding studies (fed at 160–379 mg/kg per day) and 2-yr rat feeding studies (up to 150 mg/kg per day) (Haskell Laboratory, 1955a; Hood, 1956; Sherman, 1974; Sherman and Barnes, 1966).

No skin irritation was observed after contact of the gas with the skin of rats, rabbits, or guinea pigs. Transient eye irritation followed application of a 50% solution to rabbit eyes. Treated eyes were normal 24 h later. No eye irritation was seen after an aerosol mixture containing FC-12 was sprayed into the eyes of rabbits (Haskell Laboratory, 1955b; Hood, 1956).

The lethal concentration of FC-12 for rats in a 3-h exposure was 620,000 ppm (Shugaev, 1963). Two-hour exposure at 600,000 ppm was lethal to rats, but not to guinea pigs (Scholz, 1962). Central nervous system effects were observed in all exposed species. In rats exposed for 30 min, there were no reactions at 200,000 ppm (Lester and Greenberg, 1950). At higher concentrations, the following effects were observed: muscular twitching and tremors at 300,000–400,000 ppm, loss of postural reflex at 500,000 ppm, and loss of righting reflex at 600,000 ppm. Guinea pigs were similarly affected at 200,000–300,000 ppm (Nuckolls, 1933). Mice survived a 24-h exposure at 10,000 ppm, but microscopic examination revealed nonspecific lung changes (Quevauviller et al., 1963).

Rats, guinea pigs, monkeys, rabbits, and dogs were exposed to FC-12 continuously at 810 ppm for 90 d (Prendergast et al., 1967). Although 2 of 15 rats and 1 of 15 guinea pigs died during exposure, there were no visible signs of toxicity. During the course of the experiment—which involved tests of several other chemicals, such as trichloroethylene, carbon tetrachloride, and other fluorocarbons—7 of 304 control rats and 2 of 34 control guinea pigs died. Pathologic examination revealed focal necrosis in the livers of the guinea pigs. This change was thought to be due to the continuous nature of the exposure or the high degree of susceptibility of the guinea pig. No pathologic changes were seen in the tissues of the other four species. In another experiment, test animals were exposed at 840 ppm for 8 h/d, 5 d/wk, for 6 wk (Nuckolls, 1933). No signs of toxicity were seen,



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