OSHA had an 8-hour TWA limit of 2 ppm for phthalic anhydride. The ACGIH has a limit of 1 ppm TWA for phthalic anhydride, which exists in the form of white crystalline needles with a mild odor. The proposed PEL was 1 ppm as an 8-hour TWA, and NIOSH (Ex. 8-47, Table N1) concurs that this limit is appropriate. The final rule establishes an 8-hour TWA PEL of 1 ppm for phthalic anhydride.
The primary exposure hazards associated with phthalic anhydride are severe skin, eye, and respiratory irritation. The substance can also produce skin and, perhaps, pulmonary sensitization (Patty 1963i, as cited in ACGIH 1986/Ex. 1-3, p. 487). Baader (1955/Ex. 1-1139) has reported irritant effects in animals exposed to 30 mg/m3 (approximately 5 ppm) phthalic anhydride in air.
In studies of workers exposed to phthalic anhydride, symptoms of respiratory tract injury as well as bronchitis, eye irritation, and nasal bleeding have been reported. Precise exposure concentrations were not detectable by the analytic method being used, which had a limit of detection of 25 mg/m3 (i.e., of 4 ppm or lower) (Baader 1955/Ex. 1-1139; Menschick 1955/Ex. 1-1091). Other industrial acid anhydrides (e.g., tetrachlorphthalic anhydride and maleic anhydride) are considered more irritating than phthalic anhydride (ACGIH 1986/Ex. 1-3, p. 489). Only NIOSH commented on this substance.
OSHA is establishing an 8-hour TWA limit of 1 ppm for phthalic anhydride in the final rule. The Agency concludes that this 1-ppm limit will reduce the significant risk of respiratory irritation and skin and pulmonary sensitization, all of which constitute material impairments of health that are associated with exposure to levels above the new PEL.