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  reported that a 10-minute exposure to 2,330 ppm produces vertigo in man [Lehmann et al. 1936]. However, Sax  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
ACUTE TOXICITY DATA:
Lethal concentration data:
|Species||Reference||LC50 (ppm)||LCLo (ppm)||Time||Adjusted 0.5-hr LC (CF)||Derived value|
|Clayton 1967Fiz Akt Vesh 1975
Heppel et al. 1944
Lehmann et al. 1936
von Oettingen 1949
von Oettingen 1949
|2 hr30 min
|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
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.]|
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