Methylene chloride

Synonyms

DCM; Methylene di- (or bi-) chloride; Dichloromethane; [NIOSH]

Category

Chlorinated Aliphatics

Description

Colorless liquid with a chloroform-like odor. [Note: A gas above 104 degrees F.] [NIOSH]

Sources/Uses

Used as a paint stripper and an extraction solvent; [LaDou, p. 552] Also used as a blowing agent for polyurethane foam and a propellant for insecticides; [ATSDR Medical Management] No longer used as a fumigant in the U.S. [EPA Pesticides]

Comments

Evidence of liver injury in exposed workers has been reported. Some of the methylene chloride absorbed is metabolized to carbon monoxide. Non-smoking workers exposed to average concentrations of 66 ppm had carboxyhemoglobin levels of 3.6 %. This is above that permitted for exposure to carbon monoxide (3.5 %). [ACGIH] Dichloromethane causes "trivial hepatotoxicity, unless exposure is very heavy or agent ingested." [Zimmerman, p. 333] "In one study, 24 healthy workers chronically exposed to methylene chloride at concentrations averaging from 60 to 475 ppm were electrocardiographically monitored and showed neither an increase in ventricular or supraventricular ectopic activity nor episodic ST segment depression. Likewise, there was no evidence of cardiac susceptibility or electrographic abnormalities in several case reports of otherwise healthy persons rendered unconscious from acute exposure to methylene chloride." [ATSDR Case Studies #3] Methylene chloride is in the list of "Some volatile substances which may be abused by inhalation" published on the web site of the U.N. International Drug Control Programme, indicating its potential to cause narcosis in workers. [Flanagan et al. Volatile Substance Abuse]

In US industries, the process use of methylene chloride ended in the mid-1990s; [PMID 24224613] Methylene chloride standard (29 CFR 1910.1052) requires medical surveillance if >action level >30 days/yr of >STEL >10 days/yr;

Reference Link #1

Biomedical References

Dichloromethane in urine = 0.3 mg/L at end of shift;

Insufficient data

50 ppm

25 ppm, STEL(OSHA) = 125 ppm

50 ppm

2300 ppm

Excerpts from Documentation for IDLHs

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 10­minute 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]

435 mm Hg

1.2 ppm

Odor Threshold High

440 ppm

LC50 (mice) = 14,400 ppm/7H

Explanatory Notes

Detection odor threshold from AIHA (mean = 160 ppm); VP from HSDB;

For carboxyhemoglobin in blood: 12-16 hours; [TDR, p. 862]

Reference Link #2

must be preheated

300 ppm

750 ppm

4,000 ppm

Acute solvent syndrome

Hepatoxic (a) from occupational exposure (secondary effect) or (b) in animal studies or in humans after ingestion

Probable (2a)

Anticipated human carcinogen

Confirmed Animal

Diseases

Occupational diseases associated with exposure to this agent:

• Encephalopathy, chronic solvent
• Fumigants, acute toxic effect
• Solvents, acute toxic effect

Processes

Industrial Processes with risk of exposure:

• Leather Tanning and Processing
• Metal Degreasing
• Painting (Solvents)

Activities

Activities with risk of exposure:

• Lithography printing
• Preparing and mounting animal skins (taxidermy)
• Sculpturing plastics
• Woodworking