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Methyl chloroform

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

CAS number: 71–55–6

NIOSH REL: 350 ppm (1,900 mg/m3) 15-minute CEILING

Current OSHA PEL: 350 ppm (1,900 mg/m3) TWA

1989 OSHA PEL: 350 ppm (1,900 mg/m3) TWA, 450 ppm (2,450 mg/m3) STEL

1993-1994 ACGIH TLV: 350 ppm (1,910 mg/m3) TWA, 450 ppm (2,460 mg/m3) STEL

Description of substance: Colorless liquid with a mild, chloroform-like odor.

LEL:. 7.5% (10% LEL, 7,500 ppm)

Original (SCP) IDLH: 1,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by MCA [1965] that “humans exposed to 900 to 1,000 ppm experience prompt, though minimal impairment of coordination. Above 1,700 ppm, obvious disturbances of equilibrium in humans have been observed.” Deichmann and Gerarde [1969] stated that “the earliest symptoms of a single vapor exposure are lightheadedness and lassitude. The earliest sign of intoxication is an impaired Romberg test. In humans an abnormal Romberg test is usually observed shortly after exposures to 900 to 1,700 ppm.” Because data are not available to indicate at what concentrations above 1,000 ppm a person’s equilibrium would be affected enough to impede escape, 1,000 ppm is used as the IDLH. AIHA [1961] reported that humans exposed to 800 to 1,000 ppm exhibit early anesthetic effects including incoordination [Stewart et al. 1961; Torkelson et al. 1958]. Browning [1965] reported that several human subjects exposed to 920 ppm for periods ranging from 5 to 45 minutes showed a slight loss of coordination and equilibrium [Stewart et al. 1961].

Existing short-term exposure guidelines: American Industrial Hygiene Association [AIHA 1964] Emergency Exposure Limits (EELs):

5-minute EEL: 2,500 ppm

15-minute EEL: 2,000 ppm

30-minute EEL: 2,000 ppm

60-minute EEL: 1,000 ppm


Lethal concentration data:

Species Reference LC50 (ppm) LCLo (ppm) Time Adjusted 0.5-hrLC (CF) Derived value
MouseRat AIHA 1964Sangyo Igaku 1971 3,91118,000 ———- 2 hr4 hr 6,258 ppm (1.6)36,000 ppm (2.0) 626 ppm3,600 ppm

Lethal dose data:

Species Reference Route LD50 (mg/kg) LDLo (mg/kg) Adjusted LD Derived value


Pal’gov et al. 1990Pal’gov et al. 1990

Torkelson et al. 1958







12,108 ppm7,568 ppm

7,139 ppm

1,211 ppm757 ppm

714 ppm

Other animal data: No significant signs of intoxication were seen in rats inhaling 500 ppm, 6 hours per day for 4 days [Savolainen et al. 1977]; in mice inhaling up to 1,300 ppm for 1 hour [Kjellstrand et al. 1985]; in rats inhaling up to 3,000 ppm for 0.5 to 4 hours [Mullin and Krivanek 1982]; or in baboons inhaling up to 1,400 ppm for 4 hours [Geller et al. 1982].

Human data: The onset of central anesthesia has occurred in individuals exposed for up to 7 hours to concentrations approaching 500 ppm [Stewart et al. 1969]. It has been stated that exposure to 900 to 1,000 ppm causes prompt, though minimal impairment of coordination; obvious disturbances in equilibrium have been noted above 1,700 ppm [MCA 1965]. Those exposed to 800 to 1,000 ppm have exhibited early anesthetic effects including incoordination [Stewart et al. 1961]. Volunteers exposed to 920 ppm for 5 to 45 minutes showed a slight loss of coordination and equilibrium [Stewart et al. 1961].

Revised IDLH: 700 ppmBasis for revised IDLH: The revised IDLH for methyl chloroform is 700 ppm based on acute inhalation toxicity data in humans [MCA 1965; Stewart et al. 1961, 1969].


1. AIHA [1961]. 1,1,1-Trichloroethane (methyl chloroform) (revised 1961). In: Hygienic guide series. Am Ind Hyg Assoc J 22:509-511.

2. AIHA, Toxicology Committee [1964]. Emergency exposure limits. Am Ind Hyg Assoc J 25:578-586.

3. Browning E [1965]. Toxicity and metabolism of industrial solvents. New York, NY: Elsevier Publishing Company, p. 257.

4. Deichmann WB, Gerarde HW [1969]. Methylchloroform. In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., pp. 387-388.

5. Geller I, Mendez V, Rippstein W Jr [1982]. Effects of 1,1,1-trichloroethane on a match-to-sample discrimination task in the baboon. J Toxicol Environ Health 9:783-795.

6. Kjellstrand P, Holmquist B, Jonsson I, Ramare S, Mansson L [1985]. Effects of organic solvents on motor activity in mice. Toxicology 35:35-46.

7. Marhold JV [1972]. Sbornik Vysledku Toxixologickeho Vysetreni Latek A Pripravku. Czechoslovakia: Institut Pro Vyshovu Vedoucien Pracovniku Chemickeho Prumyclu Praha, p. 28 (in Czechoslovakian).

8. MCA [1965]. Chemical safety data sheet SD-90: properties and essential information for safe handling and use of 1,1,1-trichloroethane. Washington, DC: Manufacturing Chemists Association, pp. 1-14.

9. Mullin LS, Krivanek ND [1982]. Comparison of unconditioned reflex and conditioned avoidance tests in rats exposed by inhalation to carbon monoxide, 1,1,1-trichloroethane, toluene, or ethanol. Neurotoxicol 3:126-137.

10. Pal’gov VI, Khananaev LI, Goinatskii MG, Gavrilyuk VM, et al. [1990]. Hygienic substantiation of content of methylchloroform in water bodies. Gig Nas Mest 29:45-49 (in Russian).

11. Sangyo Igaku (Japanese Journal of Industrial Health) [1971]. An experiment of 1,1,1-trichloroethane vapor exposure to mice (supplementary report on the toxicity of 1,1,1-trichloroethane). 13:226-227 (in Japanese).

12. Savolainen H, Pfaffli P, Tengen M, Vainio H [1977]. Trichloroethylene and 1,1,1-trichloroethane effects on the brain and liver after 5 days intermittent inhalation. Arch Toxicol 38:229-237.

13. Stewart RD, Gay HH, Erley DS, Hake CL, Schaffer AW [1961]. Human exposure to 1,1,1-trichloroethane vapor: relationship of expired air and blood concentrations to exposure and toxicity. Am Ind Hyg Assoc J 22:252-262.

14. Stewart RD, Gay HH, Schaffer AW, Duncan SE, Rowe VK [1969]. Experimental human exposure to methyl chloroform vapor. Arch Environ Health 19:476-472.

15. Torkelson TR, Oyen F, McCollister DD, Rowe VK [1958]. Toxicity of 1,1,1-trichloroethane as determined on laboratory animals and human subjects. Am Ind Hyg Assoc J 19:353-362.