Methyl iodide

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

CAS number: 74–88–4

NIOSH REL: 2 ppm (10 mg/m3) TWA [skin]; NIOSH considers methyl iodide to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 5 ppm (28 mg/m3) TWA [skin]

1989 OSHA PEL: 2 ppm (10 mg/m3) TWA [skin]

1993-1994 ACGIH TLV: 2 ppm (12 mg/m3) TWA [skin], A2

Description of substance: Colorless liquid with a pungent, ether-like odor.

LEL: . . . Noncombustible Liquid

Original (SCP) IDLH: 800 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the mouse 57-minute LC50 of 860 ppm [Buckell 1950 cited by Patty 1963].

Existing short-term exposure guidelines: 1991 American Industrial Hygiene Association (AIHA) Emergency Response Planning Guidelines (ERPGs):

ERPG-1: 25 ppm (60-minute)

ERPG-2: 50 ppm (60-minute)

ERPG-3: 125 ppm (60-minute)


Lethal concentration data:

Species Reference LC50 (ppm) LCLo (ppm) Time Adjusted 0.5-hr LC (CF) Derived value
Rat Bakhishev 1975 1,550 —– 30 min 1,550 ppm (1.0) 155 ppm
Mouse Buckell 1950 860 —– 57 min 1,065 ppm (1.24) 107 ppm
Rat Deichmann & Gerarde 1969 220 —– 4 hr 440 ppm (2.0) 44 ppm
Rat von Oettingen 1955 —– 3,800 15 min 3,017 ppm (0.79) 302 ppm

Other animal data: In a subchronic study, no rats died following exposures to 150 ppm for 6 hours/day for 3 days [Monsanto 1986].

Human data: None relevant for use in determining the revised IDLH.


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

2. Buckell M [1950]. The toxicity of methyl iodide: I. Preliminary survey. Br J Ind Med 7:122-124.

3. Deichmann WB, Gerarde HW [1969]. Table 67. Acute inhalation toxicity of alkyl iodides. In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., p. 756.

4. Monsanto [1986]. Methyl iodide: pilot, 4-week, and 13-week inhalation toxicity studies in rats (ML-81-015, ML-81-084, ML-81-274). 1982-1986. [Unpublished report]. St. Louis, MO: Monsanto Company, Department of Medicine and Environmental Health.

5. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1256.

6. von Oettingen WF [1955]. The halogenated aliphatic, olefinic, cyclic, aromatic, and halogenated insecticides, their toxicity and potential dangers. Washington, DC: U.S. Government Printing Office, U.S. Public Health Service Publication No. 414, pp. 30-32.

Page last reviewed: December 4, 2014