ACETIC ANHYDRID

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: 108-24-7; Chemical Formula: CH₃CO₂O

The former OSHA PEL for acetic anhydride was 5 ppm as an 8-hour TWA. The ACGIH has a TLV of 5 ppm as a ceiling, based on analogy with acetic acid’s (TLV = 5 ppm ceiling) irritant potential. The proposed PEL was 5 ppm as a ceiling, and NIOSH (Ex. 8-47, Table N1) concurs with this limit, which is established by the final rule. Acetic anhydride is a colorless, mobile, strongly refractive liquid with a strong odor.

In one study, rats inhaling 1000 ppm of acetic anhydride for four hours survived, but 2000 ppm was fatal (Smyth 1956/Ex. 1-759). In human studies, eye, nose, and throat irritation has been observed, and it has been suggested that bronchial and lung injury may occur as a consequence of exposure (Henderson and Haggard 1943j, as cited in ACGIH 1986/Ex. 1-3, p. 5). Skin burns and serious corneal injury have been reported in industrial settings when workers came into contact with the liquid (McLaughlin 1946/Ex. 1-641), and acetic anhydride is a marked lacrimator (Fairhall 1949b, as cited in ACGIH 1986/Ex. 1-3, p. 5).

In light of acetic anhydride’s potential for acute toxicity, OSHA is replacing the former 5-ppm 8-hour TWA with a 5-ppm ceiling. The Agency concludes that this limit will protect workers from the significant risk of ocular and respiratory effects associated with high, short-term exposures to acetic anhydride at the former level. Ocular and respiratory effects constitute material impairments of health. The final rule’s limit will substantially reduce these risks among industrially exposed workers.