OSHA formerly had no limit for exposure to carbon tetrabromide. The proposed limits were 0.1 ppm as an 8-hour TWA and 0.3 ppm as a 15-minute STEL; the final rule establishes these limits, which are consistent with those of the ACGIH. NIOSH (Ex. 8-47, Table N1) concurred with OSHA's proposed limits for carbon tetrabromide. At room temperature, pure carbon tetrabromide is a colorless, nonflammable solid. However, samples are usually yellow-brown in color.
Carbon tetrabromide's hepatotoxic effects include both fatty infiltration and necrosis. The 0.1-ppm and 0.3-ppm TWA and STEL levels were selected based on an observed no-effect level of 0.1 ppm; this finding derives from a study in which rats were exposed to carbon tetrabromide by inhalation for seven hours per day, five days per week for six months (Torkelson and Rowe 1981a/Ex. 1-974). Dr. Grace Ziem (Ex. 46) submitted information to OSHA showing that exposure to 0.07 ppm has caused sensory irritation in rats.
The final rule establishes limits of 0.1 ppm as an 8-hour TWA and 0.3 ppm as a 15-minute STEL for carbon tetrabromide. OSHA concludes that establishing these limits for this previously unregulated chemical will protect workers against the significant risk of hepatotoxic effects, which constitute material health impairments.