ACETIC ACID

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: 64-19-7; Chemical Formula: CH₃COOH

The former OSHA PEL for acetic acid was a 10-ppm 8-hour TWA. OSHA proposed to retain the TWA limit and to supplement it with a 15-ppm STEL, based on the acute irritant properties of acetic acid. These limits are consistent with the ACGIH recommended TLVs (1986/Ex. 1-3). NIOSH (Ex. 8-47, Table N1) concurred with these proposed limits. However, OSHA’s review of the evidence for acetic acid has demonstrated that there is no basis at this time for a STEL, and the final rule thus retains the 8-hour TWA PEL. Acetic acid is a clear, colorless, flammable liquid with a pungent odor.

Sterner (1949/Ex. 1-1207) reported that exposures to concentrations of acetic acid ranging from 800 to 1200 ppm cannot be tolerated by humans for longer than three minutes. The AIHA (Ex. 8-16) stated that unacclimatized workers experience eye and nasal irritation at acetic acid levels in excess of 26 ppm, and that exposure to 50 ppm is intolerably irritating. The ACGIH also reported that acclimatized workers are sometimes able to tolerate exposure to concentrations as high as 30 ppm. Guinea pigs exhibited minor changes in respiration after exposure to 5 ppm; exposure to 100 ppm produced a significant increase in pulmonary flow resistance and a decrease in breathing rate and minute volume, which suggests that bronchial constriction is the primary irritant action of acetic acid (Amdur 1961/Ex. 1-601).

The 10-ppm TWA was established on the basis of studies indicating that industrial exposure to acetic acid at 10 ppm was nonirritating (Sterner 1943/Ex. 1-806). However, conjunctival irritation has been reported in humans exposed below 10 ppm (duration not specified) (Baldi 1953/Ex. 1-602), and workers exposed to concentrations of 60 ppm during the workshift, plus one hour daily at 100 to 260 ppm, for 7 to 12 years developed respiratory irritation, conjunctivitis, bronchitis (which was asthma-like in some workers), pharyngitis, erosion of exposed teeth, and gastritis (Parmeggiani and Sassi 1954/Ex. 1-753). Vigliani and Zurlo (1955/Ex. 1-164) observed respiratory, gastrointestinal, and skin irritation in the same group of workers.

In a prehearing comment, Eastman Kodak (Ex. 3-661) argued that there was no toxicologic basis for a 15-ppm STEL, citing Vigliani and Zurlo (1955/Ex. 1-164), who reported that exposure to 20 to 30 ppm is without danger. In addition, Kodak stated that irritation has only been observed “with prolonged and repeated exposures” above the 10-ppm TWA PEL. Eastman Kodak concluded that “[no] significant irritation or other ill effects have been reported by employees that periodically are exposed to levels of acetic acid in excess of the proposed 15-ppm STEL” (Ex. 3-661, p. 4).

OSHA has carefuly reviewed the toxicologic evidence in the record and has determined that the evidence supporting a STEL for acetic acid is equivocal. Because information on exposure durations is lacking in the studies cited above (Baldi 1953/Ex. 1-602; Parmeggiani and Sassi 1954/Ex. 1-753), it is not known whether the conjunctival irritation found among exposed workers was due to short-term or prolonged exposure to acetic acid. Eastman Kodak (Ex. 3-661) has maintained that prolonged exposure to acetic acid at levels above the 10 ppm TWA PEL is necessary to cause irritant responses among exposed workers. Therefore, in the final rule, OSHA is retaining its 10 ppm TWA PEL for acetic acid, but is not supplementing this limit with a STEL.