TRIMELLITIC ANHYDRIDE

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: 552-30-7; Chemical Formula: C₉H₄O₅

OSHA previously had no exposure limit for trimellitic anhydride. In 1981, the ACGIH set 0.005 ppm (0.04 mg/m³) as the 8-hour TWA limit for this substance. The proposed PEL was 0.005 ppm as an 8-hour TWA, and the final rule promulgates this limit. NIOSH (Ex. 8-47, Table N1) concurs with this limit. Trimellitic anhydride is a colorless solid.

Exposure to trimellitic anhydride (TMAN) causes irritation of the eyes, nose, skin, and pulmonary tract. NIOSH (1978n, as cited in ACGIH 1986/Ex. 1-3, p. 606) reported in a current intelligence bulletin that trimellitic anhydride should be considered an extremely toxic workplace hazard, because exposure to it can cause noncardiac pulmonary edema and immunological sensitization, as well as upper respiratory tract irritation.

Pulmonary edema has occurred in workers exposed to TMAN at unreported air concentrations; the development of pulmonary edema in these workers without upper respiratory tract irritation suggests that TMAN is a sensitizer (Rice, Jenkins, Gray, and Greenburg 1977/Ex. 1-358). Zeiss, Patterson, Pruzansky, and colleagues (1977/Ex. 1-501) described TMAN-related illnesses among a group of workers synthesizing TMAN. These authors believe there are three separate syndromes associated with TMAN exposure: rhinitis/asthma; a flu-like condition; and irritation of the upper respiratory tract. Another case of TMAN-related occupational sensitization occurred in a worker exposed during the application of an epoxy resin coating (Fawcett, Taylor, and Pepys 1977/Ex. 1-636).

At levels averaging 1.5 and 2.8 mg/m³ in two processes, NIOSH reported that employees reported eye and nose irritation, shortness of breath, coughing, nausea, headache, skin irritation, and throat irritation (NIOSH 1974c/Ex. 1-1181). Pulmonary hemorrhage and hemolytic anemia have been reported in workers exposed to TMAN at unspecified levels (Ahmad, Morgan, Patterson et al. 1979/Ex. 1-460).

Rats have shown intraalveolar hemorrhage after TMAN exposures to concentrations of 0.01 ppm (Amoco Chemical Corporation 1978, as cited in ACGIH 1986/Ex. 1-3, p. 606).

Based on this study, in the final rule OSHA is revising the PEL for trimellitic anhydride to an 8-hour TWA level of 0.005 ppm. The Agency concludes that this limit will protect workers from the severe pulmonary effects, sensitization, and skin and upper respiratory tract irritation observed in workers exposed to this extremely toxic substance. The Agency has determined that these effects constitute material impairments of health. OSHA finds that this limit will substantially reduce these significant risks, which were formerly not controlled because of the absence of any OSHA PEL.