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May 1994

Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)

Methylene chloride

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:


SpeciesReferenceLC50 (ppm)LCLo (ppm)TimeAdjusted 0.5-hr LC (CF)Derived value
G. pig






Clayton 1967

Fiz Akt Vesh 1975

Heppel et al. 1944

Lehmann et al. 1936

von Oettingen 1949

von Oettingen 1949













2 hr

30 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 ppm

2,493 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 ppm

Basis 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.

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