Acetic anhydride

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

ACUTE TOXICITY DATA

Lethal concentration data:

                                                       Adjusted               
                             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.

REFERENCES:

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.