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: 463-51-4; Chemical Formula: CH2 = C = O
OSHA's former 8-hour TWA limit for ketene was 0.5 ppm. The ACGIH has a TLV-TWA of 0.5 ppm and a TLV-STEL of 1.5 ppm for this colorless gas with a sharp, penetrating odor. The proposal retained the 8-hour TWA and added a STEL of 1.5 ppm; NIOSH (Ex. 8-47, Table N-1) concurs. The final rule retains an 8-hour TWA PEL of 0.5 ppm and adds a STEL of 1.5 ppm for ketene.
Ketene is highly irritating to the respiratory tract (Mendenhall and Stokinger 1959/Ex. 1-428), and the effects of its action are delayed (Treon, Sigmon, Kitzmiller 1949/Ex. 1-769). Mendenhall and Stokinger (1959/Ex. 1-428) have reported a 10-minute LC(50) for mice of 17 ppm. Chronic exposure at 1 ppm for six months on a schedule of six hours daily, five days per week, was tolerated by animals of several species (Mendenhall and Stokinger 1960, as cited in ACGIH 1986/Ex. 1-3, p. 341). Similar results have been reported in monkeys exposed repeatedly (55 exposures) for seven hours (Treon, Sigmon, and Kitzmiller 1949/Ex. 1-769). Evidence strongly suggests that the development of emphysema and fibrosis may occur in individuals who have developed a tolerance to the acute effects of ketene exposure (Stokinger, Wagner, and Dobrogarski 1957/Ex. 1-139). No comments other than NIOSH's were received on ketene.
In the final rule, OSHA is retaining the 8-hour TWA PEL of 0.5 ppm and adding a 15-minute STEL of 1.5 ppm for ketene. The Agency concludes that workers exposed to this highly irritating and toxic gas are at significant risk of developing respiratory irritation, pulmonary edema, and other severe pulmonary effects that constitute material health impairments. OSHA finds that a TWA and STEL are required to protect against both acute and chronic health effects. The final rule's limits will substantially reduce these risks.
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