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

CAS number: 71-43-2

NIOSH REL: 0.1 ppm TWA, 1 ppm STEL; NIOSH considers benzene to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 1 ppm TWA, 5 ppm STEL

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 10 ppm (32 mg/m3) TWA, A2

Description of substance: Colorless to light-yellow liquid with an aromatic odor.

LEL: 1.2% (10% LEL, 1,200 ppm)

Original (SCP) IDLH: 3,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the report in Patty [1963] that for man, a single exposure to 3,000 ppm is endurable for 0.5 to 1 hour [Flury 1928].

Existing short-term exposure: National Research Council [NRC 1986] guidelines

Emergency Exposure Guidance Levels (EEGLs):
1-hour EEGL: 50 ppm
24-hour EEGL: 2 ppm


Lethal concentration data:

LC50 LCLo 0.5-hr Derived
Species Reference (ppm) (ppm) Time LC (CF) Value
Rabbit Carpenter et al. 1944 —– 44,000 30 min 45,000 ppm (1.0) 4,500 ppm
Dog Spector 1955 —– 44,923 ? ? ?
Cat Spector 1955 —– 52,308 ? ? ?
Human Tab Biol Per 1933 —– 20,000 5 min 11,000 ppm (0.55) 1,100 ppm

Other human data: It has been stated that 3,000 ppm is endurable for 0.5 to 1 hour [Flury 1928]. It has also been stated that exposure at 19,000 to 20,000 ppm for 5 to 10 minutes is fatal; exposure at 7,500 ppm for 30 minutes is dangerous; exposure at 1,500 ppm for 60 minutes induces serious symptoms; exposure at 500 ppm for 60 minutes leads to symptoms of illness; exposure at 50 to 150 ppm for 5 hours produces headache, lassitude, and weakness; and exposure at 25 ppm for 8 hours has no effect [Gerarde 1960].


  1. Carpenter CP, Shaffer CB, Weil CS, Smyth HF Jr [1944]. Studies on the inhalation of 1:3-butadiene; with a comparison of its narcotic effect with benzol, toluol, and styrene, and a note on the elimination of styrene by the human. J Ind Hyg Toxicol 26(3):69-78.
  2. Flury F [1928]. Moderne gewerbliche vergiftungen in pharmakologisch-toxikologischer hinsicht (Pharmacological-toxicological aspects of intoxicants in modern industry). Arch Exp Pathol Pharmakol 138:65-82 (translated).
  3. Gerarde HW [1960]. Toxicology and biochemistry of aromatic hydrocarbons. New York, NY: Elsevier Publishing Company.
  4. NRC [1986]. Emergency and continuous exposure guidance levels for selected airborne contaminants. Vol. 6. Benzene and ethylene oxide. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 7-33.
  5. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1221.
  6. Spector WS, ed. [1955]. Handbook of toxicology. Vol. 1. Acute toxicities of solids, liquids and gases to laboratory animals. Philadelphia, PA: W.B. Saunders Co., p. 324.
  7. Tab Biol Per [1933]; 3:231 (in German).