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

CAS number: 75–52–5

NIOSH REL: The 1989 OSHA PEL may not be protective to workers.

Current OSHA PEL: 100 ppm (250 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 100 ppm (250 mg/m3) TWA

Description of substance: Colorless, oily liquid with a disagreeable odor.

LEL:. . 7.3% (10% LEL, 7,300 ppm)

Original (SCP) IDLH: 1,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Browning [1965] that with concentrations above 1,000 ppm, if the product of this and the time of exposure was greater than 1 (e.g., 1,000 ppm for 3 hours) some of the animals, including 1 monkey, died. Also, AIHA [1961] reported severe eye irritation at 500 ppm [Machle et al. 1940]. [Note: The statement by Browning [1965] regarding the product of the concentration and the time of exposure is apparently in error; the value “greater than 1” should probably be “greater than 1,000”.]

Short-term exposure guidelines: None developed


Lethal concentration data:

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



Izmerov et al. 1982Skinner 1947

Weatherby 1955

Weatherby 1955







2 hr?

12 hr

6 hr

11,339 ppm (1.6)?

7,250 ppm (2.9)

11,500 ppm (2.3)

1,134 ppm?

725 ppm

1,150 ppm

Lethal dose data:

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



Machle et al. 1940Subbotin 1967

Subbotin 1967

Weatherby 1955










2,067 ppm2,590 ppm

2,618 ppm

344 ppm

207 ppm259 ppm

262 ppm

34 ppm

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

Revised IDLH: 750 ppmBasis for revised IDLH: The revised IDLH for nitromethane is 750 ppm based on acute inhalation toxicity data in animals [Weathery 1955].


1. AIHA [1961]. Nitromethane. In: Hygienic guide series. Am Ind Hyg Assoc J 22:518-520.

2. Browning E [1965]. Toxicity and metabolism of industrial solvents. New York, NY: Elsevier Publishing Company, p. 282.

3. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 93.

4. Machle W, Scott EW, Treon J [1940]. The physiological response of animals to some simple mononitroparaffins and to certain derivatives of these compounds. J Ind Hyg Toxicol 22(8):315-332.

5. Skinner JB [1947]. The toxicity of 2-nitropropane. Ind Med 16:441-443.

6. Subbotin VG [1967]. Hygienic assessment of nitromethane and ether nitroparaffins in connection with sanitary protection of water bodies. Gig Sanit 32(9):9-13 (in Russian).

7. Weatherby JH [1955]. Observations on the toxicity of nitromethane. AMA Arch Ind Health 11:102-106.