CAS number . . . . . . . . . . . 75-07-0
NIOSH REL. . . . . . . . . . . . None established; NIOSH considers
                                 acetaldehyde to be a potential
                                 occupational carcinogen as defined by
                                 the OSHA carcinogen policy [29 CFR 1990].
Current OSHA PEL . . . . . . . . 200 ppm (360 mg/m3) TWA
1989 OSHA PEL. . . . . . . . . . 100 ppm (180 mg/m3) TWA, 150 ppm 
                                 (270 mg/m3) STEL
1993-1994 ACGIH TLV. . . . . . . 25 ppm (45 mg/m3) CEILING, A3
Description of substance . . . . Colorless liquid or gas (above 69øF) with 
                                 a pungent, fruity odor.
LEL. . . . . . . . . . . . . . . 4.0% (10% LEL, 4,000 ppm)
Original (SCP) IDLH. . . . . . . 10,000 ppm
Basis for original (SCP) IDLH. . The chosen IDLH is based on the statements 
                                 by Patty [1963] and ACGIH [1971] that all
                                 rats survived a 4-hour exposure to 8,000 ppm,
                                 but all rats died from a 16,000 ppm exposure
                                 [Smyth 1956].
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      Appelman et al. 1982 13,000  -----  4 hr   26,000 ppm (2.0) 2,600 ppm
Hamster  Feron 1979           17,000  -----  4 hr   34,000 ppm (2.0) 3,400 ppm
Rat      Skog 1950            20,000  ----- 30 min  20,000 ppm (1.0) 2,000 ppm
Rat      Skog 1950            20,536  ----- 30 min  26,536 ppm (1.0) 2,054 ppm

Other animal data. . . . . . . . RD50 (mouse), 4,946 ppm [Alarie 1981].
Human data . . . . . . . . . . . None relevant for use in determining the
                                 revised IDLH.

Revised IDLH: 2,000 ppm
Basis for revised IDLH: The revised IDLH for acetaldehyde is 2,000 ppm based on acute inhalation toxicity data in animals [Alarie 1981; Skog 1950]. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for acetaldehyde at any detectable concentration.]

REFERENCES:

1. ACGIH [1971]. Acetaldehyde. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 1-2.
2. Alarie Y [1981]. Dose-response analysis in animal studies: prediction of human responses. Environ Health Perspect 42:9-13.
3. Appelman LM, Woutersen RA, Feron VJ [1982]. Inhalation toxicity of acetaldehyde in rats. I. Acute and subchronic studies. Toxicology 23(4):293-307.
4. Feron VS [1979]. Effects of exposure to acetaldehyde in Syrian hamsters simultaneously treated with benzo(a)pyrene or diethylnitrosamine. Prog Exp Tumor Res 24:162-176.
5. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1967.
6. Skog E [1950]. A toxicological investigation of lower aliphatic aldehydes. I. Toxicity of formaldehyde, acetaldehyde, and butryaldehyde; as well as acrolein and crotonaldehyde. Acta Pharmacol Toxicol 6(4):299-318.
7. Smyth HF Jr [1956]. Improved communication: hygienic standards for daily inhalation. Am Ind Hyg Assoc Q 17(2):129-185.