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: 108-44-1; Chemical Formula: C7H9N

m-Toluidine formerly had no OSHA permissible exposure limit. The ACGIH has a 2-ppm 8-hour TWA, with a skin notation. The proposed PEL was 2 ppm as an 8-hour TWA, with a skin notation, and the final rule establishes these limits. m-Toluidine is a light yellow liquid.

When m-toluidine was tested on the eyes and skin of rabbits, moderate to strong irritation effects resulted (NIOSH 1979b, as cited in ACGIH 1986/Ex. 1-3, p.589). A mean maximal methemoglobinemia of 60.2 percent was reported to occur following the intravenous administration of 27 mg m-toluidine per kilogram of body weight in cats (McLean, Starmer, and Thomas 1969/Ex. 1-425). Rodent carcinogenicity studies cited by the ACGIH (1986/Ex. 1-3, p. 589) were either inconclusive or negative.

The effects in humans of exposure to m-toluidine, when it is either absorbed through the skin or delivered via inhalation, are hematuria and methemoglobinemia. Exposure to 40 ppm for 60 minutes causes severe poisoning (Goldblatt 1955/Ex. 1-417). There are no epidemiological studies of workers exposed only to m-toluidine (ACGIH 1986/Ex. 1-3, p. 589).

NIOSH does not concur with OSHA’s limit (Ex. 8-47, Table N2; Tr. III, p. 86) and reports that, although the evidence for the carcinogenicity of m-toluidine is inconclusive (Weisberger, Russfield, Homburger et al. 1978/Ex. 1-535), it is important to remember that this substance is an aromatic amine, like o- and p-toluidine, both of which are carcinogenic. NIOSH commented that a lower PEL might be appropriate for this substance.

In the final rule, OSHA is establishing a 2-ppm 8-hour TWA and a skin notation for this previously unregulated chemical. The Agency concludes that this limit will protect workers from the significant risk of metabolic effects, such as hematuria and methemoglobinemia, associated with exposure to m-toluidine at the levels formerly permitted in the absence of any OSHA PEL. OSHA finds that hematuria, methemoglobinemia, and the other metabolic effects associated with exposure to m-toluidine constitute material impairments of health.

Page last reviewed: September 28, 2011