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Methyl chloride

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

CAS number: 74–87–3

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

Current OSHA PEL: 100 ppm TWA, 200 ppm CEILING,

300 ppm 5-minute MAXIMUM PEAK IN ANY 3 HOURS

1989 OSHA PEL: 50 ppm (105 mg/m3) TWA, 100 ppm (210 mg/m3) STEL

1993-1994 ACGIH TLV: 50 ppm (103 mg/m3) TWA, 100 ppm (207 mg/m3) STEL [skin]

Description of substance: Colorless gas with a faint, sweet odor which is not noticeable at dangerous concentrations.

LEL: . . . 8.1% (10% LEL, 8,100 ppm)

Original (SCP) IDLH: 10,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Patty [1963] that 20,000 to 40,000 ppm is dangerous to animals in 30 to 60 minutes [Flury and Zernik 1931] and the report by MacDonald [1964] that a worker repeatedly walked in and out of an area in which concentrations greater than 10,000 ppm were measured.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50




Time Adjusted 0.5-hr


Derived value
Rat Bakhishev 1975 72,000 ----- 30 min 72,000 ppm (1.0) 7,200 ppm
Mouse Chellman et al. 1986 2,200 ----- 6 hr 5,060 ppm (2.3) 506 ppm
Mammal Clayton & Clayton 1981 2,760 ----- 4 hr 5,520 ppm (2.0) 552 ppm
G. pig Clayton 1967 ----- 20,000 2 hr 32,000 ppm (1.6) 3,200 ppm
Rat Izmerov et al. 1982 2,524 ----- 4 hr 5,048 ppm (2.0) 505 ppm
Dog von Oettingen 1949 ----- 14,661 6 hr 33,720 ppm (2.3) 3,372 ppm

Other animal data: It has been reported that 20,000 to 40,000 ppm is dangerous in 30 to 60 minutes [Flury and Zernik 1931].

Human data: It has been reported that a worker repeatedly walked in and out of an area in which concentrations greater than 10,000 ppm were measured; symptoms included blurring of vision, dizziness, and a slight headache [MacDonald 1964]. A worker exposed to concentrations of 2,000 to 4,000 ppm for 13 days stated that during the first week he was very sleepy and became quite dizzy; during the second week headache, blurring of vision, slurring of speech, dizziness, mental confusion, and a staggering gait occurred [MacDonald 1964]. Another worker exposed to concentrations of 1,000 to 2,000 ppm during the workshift experienced dizziness, blurring of vision, headache, nausea, and vomiting [MacDonald 1964]. It has been stated that exposures to 20,000 ppm for 2 hours may be fatal [Deichmann and Gerarde 1969].

Revised IDLH: 2,000 ppm

Basis for revised IDLH: The revised IDLH for methyl chloride is 2,000 ppm based on acute inhalation toxicity data in humans [MacDonald 1964]. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for methyl chloride at any detectable concentration.]


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

2. Chellman GJ, White RD, Norton RM, Bus JS [1986]. Inhibition of the acute toxicity of methyl chloride in male B6C3F1 mice by glutathione depletion. Toxicol Appl Pharmacol 86:93-104.

3. Clayton GD, Clayton FE, eds. [1981]. Patty's industrial hygiene and toxicology. 3rd rev. ed. Vol. 2B. Toxicology. New York, NY: John Wiley & Sons, Inc., pp. 3436-3442.

4. Clayton JW Jr [1967]. Fluorocarbon toxicity and biological action. Fluor Chem Rev 1(2):197-252.

5. Deichmann WB, Gerarde HW [1969]. Methyl chloride. In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., pp. 386-387.

6. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, p. 309 (in German).

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. 86.

8. MacDonald JDC [1964]. Methyl chloride intoxication: report of 8 cases. J Occup Med 6:82-83.

9. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1249.

10. von Oettingen WF [1949]. Studies on the relation between the toxic action of chlorinated methanes and their chemical and physicohemical properties. NIH Bulletin 191:1-85.