1,1,2-TRICHLOROETHANE
OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
CAS: 76-13-1; Chemical Formula: CCl2FCClF2
1,1,2-Trichloro-1,2,2-trifluoroethane (FC-113) is a member of the chlorofluorocarbon family. The former OSHA PEL was an 8-hour TWA of 1000 ppm. The Agency proposed to retain this limit and to add a STEL, and NIOSH (Ex. 8-47, Table N1) concurred that these limits are appropriate. The final rule retains the 8-hour TWA of 1000 ppm and supplements it with a 1250-ppm STEL. The ACGIH has an 8-hour TLV-TWA of 1000 ppm and a 15-minute STEL of 1250 ppm for FC-113. FC-113 is a colorless, noncombustible liquid.
Cardiac sensitization following the administration of epinephrine is the most significant effect observed after exposure to FC-113. Reinhardt, Mullin, and Maxfield (1973/Ex. 1-114) observed that 10 out of 29 dogs exposed to 5000 ppm FC-113 for 5 minutes and simultaneously injected with epinephrine developed serious arrhythmias. Similar experiments, in which the dogs were exposed to 2000 to 2500 ppm of this substance for longer periods of time (from 30 minutes to 6 hours) and simultaneously administered epinephrine, resulted occasionally in arrhythmia (Aviado 1975, as cited in ACGIH 1986/Ex. 1-3, p. 603). However, when the experiment was repeated using four 6-hour exposures to 1000 ppm in conjunction with an injection of epinephrine, no arrhythmias were observed.
A study by Stopps and McLaughlin (1967/Ex. 1-122) of human volunteers revealed that exposure to 2500 ppm FC-113 for 1.5 hours resulted in impairment of psychomotor performance (described as lethargy and inability to concentrate). This effect was not observed at concentrations below 2500 ppm. Within the first one-half to one hour of exposure to 2500 ppm or more, subjects reported subjective sensations including loss of concentration, a tendency to somnolence, and a feeling of “heaviness” in the head. Dr. Lawrence Hecker of Abbott Laboratories (Ex. 3-678) commented that there was no basis for a STEL for FC-113. OSHA does not agree with Dr. Hecker’s assessment because the results of the Stopps and McLaughlin (1967/Ex. 1-122) study described above demonstrate that FC-113 can induce subjective effects in humans on short-term exposure. Thus, OSHA finds that a STEL is necessary to prevent these effects. The UAW (Tr. pp. 7-67 to 7-69) and the AFL-CIO (Ex. 194) supported short-term or ceiling limits for FC-113 lower than the proposed STEL.
The evidence described above demonstrates that FC-113 can exert toxic effects at levels of exposure comparable to the levels that were formerly permitted by excursions above the former OSHA TWA limit of 1000 ppm; such levels thus pose a significant risk of cardiac sensitization to exposed workers. The Agency considers cardiac sensitization induced by FC-113 as material impairment of health and functional capacity. OSHA concludes that a STEL of 1250 ppm will provide a wider margin of safety against cardiac sensitization and will reduce the risk of impaired psychomotor performance by limiting the potentially high, short-term exposures formerly permitted by the 8-hour TWA limit alone. The final rule establishes limits of 1000 ppm TWA and 1250 ppm STEL for 1,1,2-trichloro-1,2,2-trifluoroethane to substantially reduce the significant risks associated with exposure to this substance.