OSHA had no former limit for carbonyl fluoride. The ACGIH has an 8-hour TWA limit of 2 ppm and a 15-minute STEL of 5 ppm for this colorless and essentially odorless gas. The proposed PELs were an 8-hour TWA of 2 ppm and a 15-minute STEL of 5 ppm. NIOSH (Ex. 8-47, Table N1) concurred with these limits, and they are established in the final rule.
The 1-hour LC(50) for rats is 360 ppm, and the 4-hour LC(50) for the same species is 90 ppm (ACGIH 1986/Ex. 1-3, p. 111). Carbonyl fluoride hydrolyzes instantly on contact with moisture. The ACGIH (1986/Ex. 1-3, p. 14) reports that carbonyl fluoride is "about as toxic as hydrogen fluoride as a respiratory irritant gas."
Repeated exposure of animals to carbonyl fluoride is known to have metabolic effects; it inhibits the fluoride-sensitive enzyme succinic dehydrogenase via hydrolysis of carbonyl fluoride to hydrogen fluoride (Scheel, McMillan, and Phipps 1968/Ex. 1-364). Carbonyl fluoride is also a strong irritant to the eyes, skin, mucous membranes, and respiratory tract (Dangerous Properties of Industrial Materials, 6th ed., Sax 1984). The only comment on carbonyl fluoride came from NIOSH.
In the final rule, OSHA is establishing an 8-hour TWA limit of 2 ppm and a 15-minute 5-ppm STEL for carbonyl fluoride; these limits are based on analogy with the 3-ppm TWA limit being established for hydrogen fluoride. The Agency concludes that both a TWA and a STEL are necessary to provide protection against the significant risks of marked irritation and metabolic effects, which constitute material health impairments that are associated with exposure to carbonyl fluoride at levels above the new PELs.