Hepatotoxicity associated with overexposure to 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123)

1,1-Dichloro-2,2,2-trifluoroethane (HCFC-123) was evaluated as a substitute for trichlorofluoromethane (CFC-11), and it appeared that a permissible exposure limit of 50 ppm was justified. When HCFC-123 was introduced as a precision cleaning agent in a controlled operation, marked elevations in serum alanine transaminase and serum aspartase transaminase were noted in exposed workers. Sampling taken during start-up documented personal samples from 24-480 ppm (375 and 21 min, respectively) and area samples of 18-180 ppm (375 and 21 min, respectively). Personal and area samples collected after the liver abnormalities were identified ranged from 5-12 ppm. Exposure data were not available for the period when the abnormalities are suspected to have developed. Two models were developed to estimate exposure during the unmonitored period: (1) the entire plant as a homogenous box and (2) evaporation into smaller work zones. Modeling using the entire building estimated 8-hour time-weighted average (TWA) exposures of 10-35 ppm. Modeled estimates of work area and air exchange rates indicated that degreaser exposed workers could have experienced peak levels of 280-2,100 ppm (8-hour TWAs 252-1,630 ppm). Modeling of the work environment, estimated to be one-third of the volume of the entire open building, indicated peak exposures of 28-210 ppm (8-hour TWAs 25-163 ppm). These ranges estimate the minimum and maximum exposure levels. The best estimates, using 12 air changes per day, suggest peak levels around the degreaser of 635-2,100 ppm (8-hour TWA 499-1,630 ppm) and 63-207 ppm (8-hour TWAs 50-163 ppm) in the work area. These are the first estimates of exposure level associated with these hepatotoxic effects; all are significantly higher than personal and area samples collected for HCFC-123 after the liver abnormalities were identified.