Previously, OSHA had no permissible exposure limit for acrylic acid. The ACGIH has an 8-hour TLV-TWA of 10 ppm. The proposed PEL was 10 ppm as an 8-hour TWA, and the final rule establishes this limit and adds a skin notation. Acrylic acid is a colorless, corrosive liquid with a distinctive acrid odor.
Acrylic acid is known to polymerize explosively with amines, ammonia, oleum, and chlorosulfonic acid, and it is incompatible with strong alkalis and pure nitrogen. Occupational exposure to acrylic acid usually occurs when the chemical is used in the form of methyl, ethyl, or butyl esters in the manufacture of acrylic resins.
Data indicate that the oral LD(50) in rats is between 0.25 and 0.5 mg/kg (Dow Chemical Company 1977f, as cited in ACGIH 1986/Ex. 1-3, p. 14), and the skin absorption LD(50) in rabbits is 0.95 ml/kg (Smyth, Carpenter, Weil et al. 1962/Ex. 1-441). Another study indicates that rabbits given acrylic acid orally had no ill effects at a level of 0.025 mg/kg (Klimkina et al. 1969, as cited in ACGIH 1986/Ex. 1-3, p. 14), and Gage (1970/Ex. 1-318) reports that rats exposed to 80 ppm for 6 hours daily for 20 days showed no adverse effects.
Case reports indicate that acute exposures to acrylic acid in workers have caused skin burns, eye burns, and upper respiratory effects (ACGIH 1986/Ex. 1-3, p. 14). OSHA received a comment from the Basic Acrylic Monomer Manufacturers (Ex. 184) supporting the proposed 10-ppm TWA limit. The New Jersey Department of Health (Ex. 144) discussed acrylic acid in connection with the Department's recommendation that OSHA use EPA's IRIS data as the basis for limit-setting; OSHA has discussed this approach in Section VI.A of this preamble. NIOSH (Ex. 8-47, Table N2) believes that the limit being established by OSHA for acrylic acid should be lower, based on recent studies demonstrating degeneration of the nasal mucosa, changes in pulmonary function, and skin absorption (Miller, Ayres, Jersey, and Mckenna 1981 and Silver, Leith, and Murphy 1981, both as cited in ACGIH 1986/Ex. 1-3, p 14.1). OSHA is aware of the recent literature on acrylic acid and will continue to monitor it in the future.
OSHA concludes that an 8-hour TWA PEL of 10 ppm and a skin notation are necessary to protect workers from the significant risk of nasal and eye irritation, which constitute material health impairments that are potentially associated with exposure to acrylic acid at levels above the new limit. The Agency has determined that this limit will substantially reduce this risk and prevent recurrences of the burns and irritation previously associated with industrial exposures to acrylic acid.