Methyl bromide

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

CAS number: 74–83–9

NIOSH REL: None established; NIOSH considers methyl bromide to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 20 ppm (80 mg/m3) CEILING [skin]

1989 OSHA PEL: 5 ppm (20 mg/m3) TWA [skin]

1993-1994 ACGIH TLV: 5 ppm (19 mg/m3) TWA [skin]

Description of substance: Colorless gas with a chloroform-like odor at high concentrations.

LEL: . . . 10% (10% LEL, 10,000 ppm)

Original (SCP) IDLH: 2,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Patty [1963] that rats survived 2,600 ppm for 24 minutes [Irish et al. 1940].

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50 (ppm) LCLo (ppm) Time Adjusted 0.5-hr LC (CF) Derived value





G. pig

Alexeeff et al. 1985

Bakhishev 1973

Bakhishev 1975

Honma et al. 1985

Izmerov et al. 1982

Sayers et al. 1929













1 hr

30 min

30 min

8 hr

2 hr

9 hr

1,500 ppm (1.25)

7,316 ppm (1.0)

2,833 ppm (1.0)

755 ppm (2.5)

624 ppm (1.6)

780 ppm (2.6)

150 ppm

732 ppm

283 ppm

76 ppm

62 ppm

78 ppm

Other animal data: It has been reported that rats have survived an exposure to 2,600 ppm for 24 minutes [Irish et al. 1940].

Human data: It has been stated that 220 ppm can be endured for several hours without serious effects [Clarke et al. 1945].

Revised IDLH: 250 ppm

Basis for revised IDLH: The revised IDLH for methyl bromide is 250 ppm based on acute inhalation toxicity data in humans [Clarke et al. 1945]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 220 ppm. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for methyl bromide at any detectable concentration.]


1. Alexeeff GV, Kilgore WW, Munoz P, Watt D [1985]. Determination of acute toxic effects in mice following exposure to methyl bromide. J Toxicol Environ Health 15:109-123.

2. Bakhishev GN [1973]. Relative toxicity of aliphatic halohydrocarbons to rats. Farmakol Toksikol 8:140-143 (in Russian).

3. Bakhishev GN [1975]. Relationship between chemical structure and toxicity for some halogenated aliphatic hydrocarbons. Fiz Akt Vesh 7:35-36 (in Russian).

4. Clarke CA, Roworth CG, Holling HE [1945]. Methyl bromide poisoning. An account of four recent cases met with in one of H.M. ships. Brit J Ind Med 2:17-23.

5. Honma T, Miyagawa M, Sato M, Hasegawa H [1985]. Neurotoxicity and metabolism of methyl bromide in rats. Toxicol Appl Pharmacol 81:183-191.

6. Irish DD, Adams EM, Spencer HC, Rowe VK [1940]. The response attending exposure of laboratory animals to vapors of methyl bromide. J Ind Hyg Toxicol 22(6):218-230.

7. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 81.

8. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1252.

9. Sayers RR, Yant WP, Thomas BGH, Berger LB [1929]. Physiological response attending exposure to vapors of methyl bromide, methyl chloride, ethyl bromide, and ethyl chloride. Public Health Bulletin 185:1-56.

Page last reviewed: December 4, 2014