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Acetic anhydride

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 108-24-7

NIOSH REL: 5 ppm (20 mg/m3) CEILING

Current OSHA PEL: 5 ppm (20 mg/m3) TWA

1989 OSHA PEL: 5 ppm (20 mg/m3) CEILING

1993-1994 ACGIH TLV: 5 ppm (21 mg/m3) TWA

Description of substance: Colorless liquid with a strong, pungent, vinegar-like odor.

LEL: 2.7% (10% LEL, 2,700 ppm)

Original (SCP) IDLH: 1,000 ppm

Basis for original (SCP) IDLH: According to AIHA [1971], all rats exposed for 4 hours to 2,000 ppm were dead within 14 days while all rats exposed for 4 hours to 1,000 ppm survived the 14-day observation period [Capellini and Sartorelli 1967]. Because 2,000 ppm is obviously too high to be selected as the IDLH, 1,000 ppm has been chosen.

Short-term exposure guidelines: None developed


Lethal concentration data:
LC50 LCLo 0.5-hr Derived
Species Reference (ppm) (ppm) Time LC (CF) Value
Rat Deichmann and 1,000 ----- 4 hr 2,000 ppm (2.0) 200 ppm

Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 200 ppm

Basis for revised IDLH: The revised IDLH for acetic anhydride is 200 ppm based on acute inhalation toxicity data in animals [Deichmann and Gerarde 1969]. This may be a conservative value due to the lack of relevant acute toxicity data for workers.


  1. AIHA [1972]. Acetic anhydride. In: Hygienic guide series. Am Ind Hyg Assoc J 32(1):64-67.
  2. Capellini A, Sartorelli [1967]. Episodio di intossicazione collettiva da anidride acetica ed acido acetico. Med Lav 58:108-112 (in Italian).
  3. Deichmann WB, Gerarde HW [1969]. Trifluoroacetic acid (3FA). In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., p. 607.