Industrial Chemicals– Possible Carcinogen (IARC 2B)
CAS No. 75-09-2
Photo: Wikimedia Commons
IARC Monograph Vol. 71, 1999 (Group 2B)
Dichloromethane is a volatile, clear and colourless liquid that smells similar to chloroform. Dichloromethane has been an important industrial solvent since the 1940s. Dichloromethane is also commonly referred to as methylene chloride and DCM. There are numerous other synonyms and product names; see HSDB for more information.
In 1999 dichloromethane was classified by IARC as Group 2B, possibly carcinogenic to humans, based on evidence in experimental animals. In two inhalation studies in mice, increases in lung and liver tumours were observed. Mammary tumours were seen in female rats in another study.
Although several epidemiological studies have reported increased incidence of cancer associated with DCM exposure, multiple sites are identified, with no single site showing a consistent excess risk. Limitations of the available studies include small number of cases and lack of accurate exposure assessments.
The central nervous system is the primary target of acute inhalation exposure. Respiratory effects and skin irritation have also been reported.
Dichloromethane was not included in other Canadian government chemical listings reviewed.
Dichloromethane is used as a paint stripper and varnish remover. It has also been used as a flexible urethane blowing agent, in aerosol formulations, as a solvent in the production of pharmaceuticals and film coatings, and as an extraction medium (used in the food industry for extraction of spices, caffeine and hops).[2,5] Other uses include metal degreasing, electronics manufacturing, in adhesives manufacture, plastics processing, and as a refrigerant.[5,11]
Historically, dichloromethane has been used as a fumigant. However, it is not currently registered as a pest-control product in Canada.[5,12]
Canadian Production and Trade
Canada does not produce dichloromethane, but meets domestic requirements through imports.
Production and Trade
Not produced since 1985
Export: Mainly to US
196 t of ‘dichloromethane (methylene chloride)’
Import: Mainly from US
3,272 t of 'dichloromethane (methylene chloride)'
t = tonne
Inhalation is the most important route of occupational exposure. Dermal absorption has also been observed.
CAREX Canada estimates that approximately 25,000 Canadians are exposed to DCM in their workplace. The largest industrial groups exposed are automotive repair and maintenance, followed by building finishing contractors and plastic product manufacturers. Other important industries that are likely exposed to DCM include paint removal, personal and household goods maintenance and repair, and automotive parts manufacturing.
In terms of exposure groups by occupations, the largest exposed group are motor vehicle body repairers, followed by painters and decorators, and then machinists and machining and tooling inspectors. Other important occupations that may be exposed are furniture refinishers and chemical manufacturers. Workers may be exposed when spraying urethane foam, removing paint or varnish from equipment or furniture, or using products that use DCM as a propellant or degreasing agent.
An estimated 80% of dichloromethane produced globally is released to the environment.
Based on data gathered in the early 1990’s, indoor air is likely to be the most significant source of exposure for Canadians. CAREX Canada’s environmental estimates indicate that DCM levels in indoor air may be sources of elevated cancer risk (moderate data quality).
Ambient air may be of greater concern in industrialized urban areas and areas in close proximity to waste or disposal sites.[2, 20] CAREX Canada’s environmental estimates indicate that DCM levels in outdoor air are not resulting in increased cancer risk (high data quality).
Environment Canada estimated that 2 million people were exposed to DCM through use of consumer products including paint strippers, aerosol paints, and insecticides and cleaning solutions. Data on levels of dichloromethane in food is limited; it has been detected in several products including cereal and butter. Total daily intakes of DCM for the Canadian general population are estimated to range from 3.96 to 6.62 micrograms/kilogram of body weight per day. Currently, no recent Canadian studies have been identified for DCM estimates in food, beverages, and drinking water.
Soil analysis data on DCM levels is limited to contaminated sites. Dichloromethane has been detected in groundwater in Canada, usually associated with nearby landfills and waste disposal sites.
For more information, see CAREX Canada’s environmental exposure estimates for dichloromethane. Searches of environmental and consumer product databases yielded the following results on current potential for exposure to dichloromethane in Canada:
NPRI and US Household Products Database
Search term: ‘dichloromethane'
Released into Environment
Plastic and urethane foam manufacture and pharmaceutical manufacture (45 facilities)
Sent to off-site recycling
US Household Products 2013
Heavy-duty automotive cleaners and degreasers, home and hobby paints or adhesives, lubricant remover, and herbicide
t = tonne
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. To learn more about policies specific to dichloromethane on the Directory, click here. For questions about this resource, please contact Michelle Halligan, from the prevention team at the Canadian Partnership Against Cancer.
Long, G., et al (1994), ‘Dichloromethane: evaluation of risks to health from environmental exposure in Canada,’ Environmental Carcinogenesis & Ecotoxicology Reviews, Vol. 12, No. 2 (3 p.1/4), pp. 305-318
Moore, R.M., (2004), ‘Dichloromethane in North American Waters, Journal of Geophysical Research, Vol. 109, C09004.