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: 8002-05-9; Chemical Formula: None
For petroleum distillates (naphtha), also identified as rubber solvent, OSHA proposed to reduce its former 8-hour limit of 500 ppm to 400 ppm. The final rule establishes an 8-hour TWA PEL of 400 ppm for petroleum distillates. The ACGIH has a TLV-TWA of 400 ppm, and NIOSH recommends a TWA of 87 ppm and a 15-minute ceiling of 450 ppm for these substances.
A study performed by Carpenter, Kinkead, Geary et al. (1975b/Ex. 1-53) exposed rats to between 2800 and 24,200 ppm of naphtha. Motor incoordination occurred at 5300 ppm, and convulsions and death occurred in all animals at 24,200 ppm. Animals exposed to 480 ppm for 63 days showed no signs of toxicity (Carpenter, Kinkead, Geary et al.1975b/Ex. 1-53).
NIOSH (1977g, as cited in ACGIH 1986/Ex. 1-3, p. 516) noted that rubber solvent (naphtha) is composed primarily of C5 - C8 alkanes and, thus, that the limit of 350 mg/m3 (85 ppm) recommended for C5 -C8 alkanes should apply to naphtha. This recommendation presumes that all C5 - C8 alkanes possess equivalent neurotoxicity; however, as discussed above in Section V (Summary of Commenters' Responses to NPRM Questions), OSHA has concluded that not all of the C5 - C8 alkanes are neuropathic agents.
In establishing the 400-ppm TLV-TWA for petroleum distillates, the ACGIH relied on observations showing that slight irritation occurs in humans exposed to 430 ppm and that no signs of toxicity occur in animals exposed to 480 ppm. The NIOSH-recommended 85-ppm ceiling limit is based on the assumption that all C5 - C8 alkanes possess equivalent neuropathic properties. As discussed above, OSHA has rejected this hypothesis and is therefore reducing the PEL for petroleum distillates to an 8-hourTWA limit of 400 ppm to protect workers against the significant risk of irritation, which constitutes a material health impairment that is associated with exposure to these substances. OSHA has determined that this limit will substantially reduce this risk.
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