OSHA formerly regulated dicyclopentadienyl iron (ferrocene) under its generic total particulate limit of 15 mg/m3. The ACGIH has a TLV-TWA of 10 mg/m3 for this bright orange crystalline solid that smells like camphor. The proposed and final-rule PEL for dicyclopentadienyl iron is 10 mg/m3 (total particulate) as an 8-hour TWA. The 5-mg/m3 PEL for the respirable fraction is retained. NIOSH (Ex. 8-47, Table N4) supports the selection of these PELs.
Available evidence in animals suggests that dicyclo-pentadienyl iron has a moderate order of oral toxicity but a high order of intravenous and intraperitoneal toxicity. In mice, the oral LD(50) has been reported as 600 mg/kg (Madinaveitia 1965/Ex. 1-862). In rats, 1000 mg/kg has been reported as the lethal dose, but subacute oral toxicity tests have shown no fatalities when 10 feedings of 200 mg/kg were given over a two-week period (E.I. du Pont de Nemours and Co., Inc. 1955, as cited in ACGIH 1986/Ex. 1-3, p. 195). Ferrocene has been found to be mutagenic in bioassays involving several species ( Dangerous Properties of Industrial Materials, 7th ed., Sax and Lewis 1989). NIOSH was the only commenter to the rulemaking record on this substance.
In the final rule, OSHA is establishing 8-hour TWA limits of 10 mg/m3 (total particulate) and 5 mg/m3 (respirable fraction) for dicyclopentadienyl iron. The Agency concludes that these limits will substantially reduce the significant risk of material health impairments, in the form of mutagenic and other effects, that are associated with occupational exposure to this substance.