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: 88-72-2 (o-isomer); 99-08-1 (m-isomer); 99-99-0 (p-isomer); Chemical Formula: CH3C6H4NO2
OSHA formerly had an 8-hour TWA limit of 5 ppm, with a skin notation, for nitrotoluene. The ACGIH has a TLV-TWA of 2 ppm, also with a skin notation. The proposed PEL was 2 ppm as an 8-hour TWA, with a skin notation, and NIOSH concurred with this limit (Ex. 8-47, Table N1). The final rule establishes an 8-hour TWA PEL for nitrotoluene of 2 ppm and retains the skin notation. The ortho- and meta-isomers of nitrotoluene are yellow liquids; the para-isomer is also yellow, but exists in crystalline form.
Nitrotoluene is one of the aromatic nitrogen compounds that may cause methemoglobin formation. Linch (1974/Ex. 1-747) has studied the nitrotoluene isomers and reported that they have relatively low emiagenic potential; he considered nitrotoluene comparable to aniline in its toxic effects (Linch 1974/Ex. 1-747). Cases of poisoning as a result of exposure to nitrotoluene are rare (von Oettingen 1941/Ex. 1-874). Only NIOSH commented on this substance.
In the final rule, OSHA establishes an 8-hour TWA limit of 2 ppm and retains the skin notation for nitrotoluene. The Agency concludes that this limit will protect workers against the significant risk of methemoglobinemia, a material health impairment that is associated with exposure to this substance; the skin notation is retained because of nitrotoluene’s capacity to penetrate the skin.