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: 1929-82-4; Chemical Formula: C6H3Cl4N
OSHA formerly had no specific limit for nitrapyrin, although the Agency’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 nitrapyrin. The proposed PEL was 10 mg/m3; however, in the final rule, OSHA is retaining its former total particulate limit of 15 mg/m3 and the respirable particulate limit of 5 mg/m3. NIOSH concurred with the proposed limit (Ex. 8-47, Table N4). Nitrapyrin is a crystalline substance.
Nitrapyrin’s very low vapor pressure makes hazardous inhalation exposures unlikely. Torkelson (as cited in ACGIH 1986/Ex. 1-3, p. 428) has reported feeding dogs and rats a dosage of 15 mg/kg daily for 93 days. He observed no adverse effects in appearance, behavior, growth, food consumption, body and organ weight, mortality, or blood chemistry, and no tissue or organ changes. In the proposal, OSHA asked for comment on the need for a 20-mg/m3 15-minute STEL for nitrapyrin. The Agency received no comments on this issue. Because OSHA has not determined that short-term exposures to nitrapyrin pose a significant risk to workers, no STEL is included in the final rule (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 this dust; OSHA finds that these limits are protective against the significant risk of physical irritation.