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Methylene chloride

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

CAS number: 75–09–2

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

Current OSHA PEL: 500 ppm TWA, 1,000 ppm CEILING,

2,000 ppm 5-minute MAXIMUM PEAK IN ANY 2 HOURS

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 50 ppm (174 mg/m3) TWA, A2

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

LEL: . . . 13% (10% LEL, 13,000 ppm)

Original (SCP) IDLH: 5,000 ppm

Basis for original (SCP) IDLH: Negherbon [1959] reported that a 10-minute exposure to 2,330 ppm produces vertigo in man [Lehmann et al. 1936]. However, Sax [1975] stated that at 2,300 ppm there was no feeling of dizziness during 1-hour exposures. Thienes and Haley stated that no dizziness, but slight nausea, is caused by exposure to 2,300 ppm for 1 hour and that methylene chloride is not lethal at 25,000 ppm. Considering the data cited above, an IDLH of 5,000 ppm is chosen.

Short-term exposure guidelines: None developed


Lethal concentration data:

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





Clayton 1967Fiz Akt Vesh 1975

Heppel et al. 1944

Lehmann et al. 1936

von Oettingen 1949

von Oettingen 1949











2 hr30 min

7 hr

4.5 hr

7 hr

7 hr

8,000 ppm (1.6)24,929 ppm (1.0)

24,000 ppm (2.4)

25,820 ppm (2.1)

34,560 ppm (2.4)

33,859 ppm (2.4)

800 ppm2,493 ppm

2,400 ppm

2,582 ppm

3,456 ppm

3,386 ppm

Human data: Volunteers exposed at 1,000 ppm for 2 hours had carboxyhemoglobin levels in excess of those permitted in industry from exposure to carbon monoxide alone [Stewart et al. 1972]. A 10-minute exposure at 2,330 ppm has produced vertigo [Lehmann et al. 1936]. However, it has also been reported that no feeling of dizziness was noted after 1 hour of exposure to 2,300 ppm [Sax 1975]. It has been stated that no dizziness, but slight nausea, is caused by exposure to 2,300 ppm for 1 hour and that methylene chloride is not lethal at 25,000 ppm [Thienes and Haley].

Revised IDLH: 2,300 ppmBasis for revised IDLH: The revised IDLH for methylene chloride is 2,300 ppm based on acute inhalation toxicity data in humans [Sax 1975]. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for methylene chloride at any detectable concentration.]


1. Clayton JW [1967]. Fluorocarbon toxicity and biological action. Fluor Chem Rev 1:197-252.

2. Fiz Akt Vesh [1975]; 7:35-36 (in Russian).

3. Heppel LA, Neal PA, Perrin TL, Orr ML, Porterfield VT [1944]. The toxicology of dichloromethane (methylene chloride). I. Studies on effects of daily inhalation. J Ind Hyg Toxicol 26(1):8-16.

4. Lehmann KB, Schmidt-Kehl L, Ruf H, Crescitelli, Dahl, Eppinghausen, Eshe, Falker, Grotefendt, Junkenita, Maier, Mergner, Pantehtsch, Schlitzer, Shoenes, Spettmann, Wirges, Bamsreiter, Benninger, Lazarus, Manasse, Kummeth, Reuss, Schwarzweller [1936]. Die 13 wichtisgsten chlorkohlenwasserstoffe der fettreihe vom standpunkt der gewerbehygiene (The 13 most important chlorinated hydrocarbons of the aliphatic series from the standpoint of occupational medicine). Arch Hyg Bakteriol 116:131-200 (translated).

5. Negherbon WO [1959]. Handbook of toxicology. Vol. III. Insecticides, A compendium. Wright-Patterson Air Force Base, OH: U.S. Air Force, Air Research and Development Command, Wright Air Development Center, Aero Medical Laboratory, WADC Technical Report 55-16, p. 485.

6. Sax NI [1975]. Methylene chloride. In: Dangerous properties of industrial materials. 4th ed. New York, NY: Van Nostrand Reinhold Company, p. 921.

7. Stewart RD, Fisher TN, Hosko JJ, Peterson JE, Baretta ED, Dodd HC [1972]. Carboxyhemoglobin elevation after exposure to dichloromethane. Science 176:295-296.

8. Thienes CH, Haley TJ [?].

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