IRON PENTACARBONYL

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: 13463-40-6; Chemical Formula: Fe(CO)₅

OSHA previously had no exposure limit for iron pentacarbonyl. The ACGIH has a TLV-TWA of 0.1 ppm with a TLV-STEL of 0.2 ppm, measured as iron, for this highly flammable, oily, colorless to yellow liquid. The Agency proposed, and the final rule establishes, permissible exposure limits of 0.1 ppm TWA and 0.2 ppm STEL for iron pentacarbonyl, measured as Fe. NIOSH (Ex. 8-47, Table N1) concurs that these limits are appropriate.

In studies of rats, iron pentacarbonyl has been reported to have approximately one-third the acute toxicity of nickel carbonyl (for which the ACGIH has recommended a TLV of 0.05 ppm TWA) (Sunderman, West, and Kincaid 1959/Ex. 1-384). In 1970, Gage found that a 5.5-hour exposure at 33 ppm caused fatalities in three of eight rats; four of eight animals died after two 5.5-hour exposures at 18 ppm. At 7 ppm, no ill effects were observed in rats exposed 18 times in 5.5 hours (Gage 1970/ Ex. 1-318). There are no reports of long-term dose-response exposure studies in laboratory animals, and no evidence exists that iron pentacarbonyl is carcinogenic in either humans or animals (ACGIH 1986/Ex. 1-3, p. 327).

Immediate symptoms of acute exposure to high concentrations of iron pentacarbonyl include headache and dizziness, followed in 12 to 36 hours by fever, cyanosis, cough, and shortness of breath. Another clinical effect of overexposure to this substance is lung injury, and degenerative changes in the central nervous system have also been reported (ACGIH 1986/Ex. 1-3, p. 327). No comments (other than NIOSH’s) on the health effects of iron pentacarbonyl were submitted to the rulemaking record.

In the final rule, OSHA establishes a permissible exposure limit of 0.1 ppm TWA and a STEL of 0.2 ppm for iron pentacarbonyl. The Agency concludes that these limits will protect workers from the significant risks of material health impairment in the form of headache, dizziness, fever, dyspnea, cyanosis, pulmonary injury, and central nervous system effects, which are potentially associated with exposures at levels above the new limits.