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  that rats survived 2,600 ppm for 24 minutes [Irish et al. 1940].
Short-term exposure guidelines: None developed
ACUTE TOXICITY DATA:
Lethal concentration data:
|Species||Reference||LC50 (ppm)||LCLo (ppm)||Time||Adjusted 0.5-hr LC (CF)||Derived value|
|Alexeeff et al. 1985Bakhishev 1973
Honma et al. 1985
Izmerov et al. 1982
Sayers et al. 1929
|1 hr30 min
|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 ppm732 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 ppmBasis 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.]|
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2. Bakhishev GN . Relative toxicity of aliphatic halohydrocarbons to rats. Farmakol Toksikol 8:140-143 (in Russian).
3. Bakhishev GN . 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 . 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 . Neurotoxicity and metabolism of methyl bromide in rats. Toxicol Appl Pharmacol 81:183-191.
6. Irish DD, Adams EM, Spencer HC, Rowe VK . 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 . Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 81.
8. Patty FA, ed. . 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 . Physiological response attending exposure to vapors of methyl bromide, methyl chloride, ethyl bromide, and ethyl chloride. Public Health Bulletin 185:1-56.