COBALT HYDROCARBONYL

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: 16842-03-8; Chemical Formula: HCo(CO)₄

OSHA had no former limit for cobalt hydrocarbonyl. The ACGIH has a TLV-TWA of 0.1 mg/m³ (measured as cobalt) for this flammable and toxic gas. The proposed PEL was an 8-hour TWA of 0.1 mg/m³; NIOSH (Ex. 8-47, Table N1) concurs with this limit. The final rule promulgates an 8-hour TWA PEL of 0.1 mg/m³ (measured as cobalt) for cobalt hydrocarbonyl.

Cobalt hydrocarbonyl is approximately half as toxic as nickel carbonyl in terms of acute effects; in animals, it produces clinical signs and symptoms very similar to those produced by nickel carbonyl (ACGIH TLV-TWA of 0.007 mg/m³) and iron pentacarbonyl (ACGIH TLV-TWA of 0.8 mg/m³)(ACGIH 1986/Ex. 1-3, p. 145). These include headache, dizziness, and, after a delay in onset, liver, brain, and lung damage. The 30-minute LC(50) in rats is 165 mg/kg (Palmes, Nelson, Laskin, and Kuschner 1959/Ex. 1-430). There is no evidence of chronic toxicity or of carcinogenicity.

In the final rule, OSHA establishes an 8-hour TWA limit of 0.1 mg/m³ for cobalt hydrocarbonyl. The Agency concludes that this limit will protect exposed employees from the significant risk of pulmonary, brain, and liver damage, as well as that of acute effects such as headaches and dizziness, which constitute material health impairments that are associated with exposures to levels above the new PEL.