OSHA's former 8-hour TWA limit for methyl acetate was 200 ppm; the Agency proposed to retain this limit and to add a STEL of 250 ppm. NIOSH (Ex. 8-47, Table N1) concurred with this proposal. The ACGIH has established an 8-hour TWA limit of 200 ppm and a TLV-STEL of 250ppm. In the final rule, OSHA is establishing an 8-hour TWA of 200 ppm and a 15-minute STEL of 250 ppm. Methyl acetate is a highly volatile, colorless liquid with a pleasant odor.
Methyl acetate is mildly narcotic and is a known irritant to the mucous membranes of the eyes and respiratory passages. Occupational exposure to this substance by vapor inhalation at unreported levels resulted in inflammation of the eyes, nervous irritation, and a sensation of tightness in the chest (Duquenois and Revel 1934/Ex. 1-779; Fairhall 1957f, as cited in ACGIH 1986/Ex. 1-3, p. 367). Duquenois and Revel (1934/ Ex. 1-779) suggested that, like methyl alcohol, methyl acetate may produce atrophy of the optic nerve.
Other researchers have suggested that the methanol formed by hydrolysis in the body may be responsible for the toxicity of methyl acetate and, on this basis, have recommended a limit of 250 ppm in the occupational setting (Henderson and Haggard 1943j, as cited in ACGIH 1986/Ex. 1-3, p. 367). However, Lehmann and Flury (1943d, as cited in ACGIH 1986/Ex. 1-3, p. 367) have attributed toxic effects (e.g.,blood changes, weight loss, lung irritation), as well as some deaths, to chronic exposures to methyl acetate at 6600 ppm.
The ACGIH (1986/Ex. 1-3, p. 367) reports that "no cases of irritation or systemic injury have been reported from industrial exposures to methyl acetate below 200 ppm." There were no record comments on methyl acetate, except for the concurrence from NIOSH (Ex. 8-47, Table N1).
OSHA is establishing an 8-hour TWA PEL of 200 ppm TWA and a 15-minute STEL of 250 ppm for methyl acetate. The STEL is necessary to ensure that exposures do not exceed 250 ppm even for a short time because effects have been reported (ACGIH 1986/Ex. 1-3, p. 367) above 250ppm. The Agency concludes that both of these limits will protect workers from the significant risk of narcosis, eye and skin irritation, andpulmonary irritation, all of which constitute material health impairments.