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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2
Underwriters’ Laboratories, Inc., (1933) has placed FC-114 in Category 6 of its classification of life hazards. This category contains the least toxic gases and vapors; i.e., they do not appear to produce injury or death in test animals as a result of exposures at 200,000 ppm for about 2 h.
The lethal concentration of FC-114 for rats in a 2-h exposure is greater than 600,000 ppm, and for guinea pigs, greater than 500,000 ppm (Scholz, 1962). The LC50 in mice exposed for 30 min is 700,000 ppm (Paulet and Desbrousses, 1969). A dog survived an 8-h exposure at 200,000 ppm, but a 16-h exposure was lethal to another dog (Yant et al., 1932). Exposure of dogs at 150,000 ppm for 24 h was not lethal and resulted only in a loss of appetite (Yant et al., 1932). Exposure at 200,000 ppm caused pupillary dilation, convulsions, opisthotonus, and unconsciousness in dogs. However, exposure at 400,000–600,000 ppm was necessary to cause mild CNS effects in rats and guinea pigs. Recovery was rapid and complete in all species.
FC-114, like other chlorofluorocarbons and hydrocarbons, is capable of sensitizing the beagle heart to exogenous epinephrine in standard 5-min cardiac-sensitization screening studies. The concentration needed to elicit marked responses in 50% of a group of beagles is 45,000 ppm (Reinhardt et al., 1971). However, dogs exposed to FC-114 while running on a treadmill to increase their own epinephrine concentration were not sensitized until exposures reached 50,000–100,000 ppm. In another endogenous-epinephrine study, a concentration of 800,000 ppm (80% FC-113:20% oxygen) was shown to sensitize the beagle heart after its epinephrine concentration was increased by fright (Mullin et al., 1972).
Rats and mice were exposed at 200,000 ppm for 2.5 h/d, 5 d/wk, for 2 wk (Paulet and Desbrousses, 1969). Slight blood and body-weight changes were seen, as well as slight evidence of lung irritation. Exposure at 100,000 ppm had no effect, even after 2 mo of exposure (Paulet and Desbrousses, 1969). Dogs and guinea pigs were exposed at 141,600 ppm for 8 h/d for 21 d (Yant, 1933). The severity of the clinical signs attributable to CNS effects decreased during the 21 d of exposure. In the dogs, slight hematologic changes were observed, but the measures in question returned to normal 15–17 d after exposure; no gross pathologic changes were seen.
No effects were seen in dogs, cats, guinea pigs, or rats exposed at 100,000 ppm for 3.5 h per exposure for 20 exposures (Scholz, 1962). No effects were seen in rats and rabbits exposed at 10,000 ppm for 2 h/d, 5 d/wk, during 8–9 mo (Desoille et al., 1973).
INHALATION EXPOSURE LIMITS
The ACGIH TLV-TWA (ACGIH, 1980, 1983) and the OSHA Federal Standard (OSHA, 1983) for FC-114 are both 1,000 ppm. ACGIH recommended a TLV-STEL for 15-min excursions of 1,250 ppm (ACGIH, 1983). The TLV-TWA was “recommended as exposure level which should provide a margin of safety in preventing systemic toxicity and an adequate margin in preventing cardiac sensitization” (ACGIH, 1980).