OSHA formerly had no specific limit for clopidol; however, OSHA's generic total particulate limit of 15 mg/m3 TWA applied. The ACGIH has a TLV-TWA of 10 mg/m3 and a TLV-STEL of 20 mg/m3 for clopidol, which is a solid. The proposed total particulate PEL was an 8-hour TWA of 10 mg/m3; NIOSH (Ex. 8-47, Table N4) agreed that this limit is appropriate. However, in the final rule, OSHA is retaining the former 15-mg/m3 limit (total particulate) and 5-mg/m3 limit (respirable fraction), both 8-hour TWAs.
The oral LD(50) for clopidol in rats, rabbits, and guinea pigs is greater than 8 g/kg (Dow Chemical Company 1973c, as cited in ACGIH 1986/Ex. 1-3, p. 141). Long-term (two-year) studies of rats and dogs fed at levels of 15 mg/kg and 5 mg/kg per day, respectively, showed no adverse effects. Similarly, there were no adverse effects on fertility, gestation, viability, or lactation in rats and rabbits, and no increase in teratogenicity (Dow Chemical Company 1973c, as cited in ACGIH 1986/Ex. 1-3, p. 141). The chronic toxicity of clopidol is reported to be low (ACGIH 1986/Ex. 1-3, p. 141).
In the proposal, OSHA solicited comment on the need for a STEL for clopidol, but no comments were received on this issue. Because OSHA finds no evidence to suggest that short-term exposures pose a significant risk to workers, the final rule contains no STEL (see Section VI.C.17 for a discussion of the Agency's policies on STELs).
In the final rule, OSHA is retaining 8-hour TWA PELs of 15 mg/m3 (total particulate) and 5 mg/m3 (respirable particulate) for clopidol. OSHA concludes that these limits will protect workers from the significant risk of eye, skin, and other physical irritation.