Dichloromethane Profile
INDUSTRIAL CHEMICALS – PROBABLE CARCINOGEN (IARC 2A)
Contents
Dichloromethane Profile
General Information
Dichloromethane is a volatile, clear, and colourless liquid with a smell similar to chloroform.[1] It has been an important industrial solvent since the 1940s.[2] Dichloromethane is also commonly referred to as methylene chloride and DCM.[3]
There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.[3]
Dichloromethane is classified by the International Agency for Research on Cancer (IARC) as Group 2A, probably carcinogenic to humans, based on limited evidence that it causes biliary-tract cancer and non-Hodgkin lymphoma in humans, and sufficient evidence of carcinogenicity in experimental animals (malignant lung and hepatocellular tumours in male and female mice).[2] This assessment also considered the strong mechanistic evidence that dichloromethane is broken down into reactive metabolites by an enzyme called glutathione-S-transferase T1 (GSTT1), and that this activity is strongly associated with genotoxicity in vitro and in vivo.[2]
The central nervous system is the primary target of acute inhalation exposure.[4] Respiratory effects and skin irritation have also been reported.[4]
Regulations and Guidelines
Occupational exposure limits (OEL) [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]
| Canadian Jurisdictions | OEL (ppm) |
|---|---|
| Canada Labour Code | 50 |
| BC | 25 |
| AB, ON, MB, NL, PE, NB, NS | 50 |
| NT, NU, SK | 50 75 [stel] |
| QC | 50 [em] |
| YT | 200 250 [stel] |
| Other Jurisdiction | OEL (ppm) |
| ACGIH 2020 TLV | 50 |
ppm = parts per million
stel = short term exposure limit (15 min. maximum)
em = exposure must be reduced to the minimum
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian environmental guidelines and standards*
| Jurisdiction | Limit | Year |
|---|---|---|
| Drinking Water Guidelines (Canada, BC, MB) and Standards (ON, QC, SK) | 0.05 mg/L | 2003-2020 [20,21,22,23,24,25] |
| Ontario Ambient Air Quality Criteria | 24-hour: 220 µg/m3 Annual: 44 µg/m3 (as ‘methylene chloride’) | 2016[26] |
| Quebec’s Clean Air Regulation | 1 hour limit: 14,000 µg/m3 1 year limit: 3.6 µg/m3; Prohibited discharge into the air if the concentration of dichloromethane exceeds the standards | 2014[27] |
| Government of Canada’s Indoor Air Reference Levels | 600 µg/m3 (critical effect: liver effects) | 2018[28] |
| Cosmetic Ingredients Hotlist | Not permitted in aerosol preparations (as “methylene chloride”) | 2004[29] |
| Food Additives Permitted for Use | Permitted for use as as Carrier or Extraction Solvents. 30 ppm allowed in natural extractives and spice extracts; 2.2% in hop extract; 10 ppm in decaffeinated roasted coffee, instant coffee, or tea | 2012[30] |
| BC’s Contaminated Sites Regulation, BC Reg 375/96 | Sets soil standards for the protection of human health: Agricultural and low density residential sites: 250 μg/g Urban park and high density residential sites: 500 μg/g Commercial sites: 1,500 μg/g Industrial sites: 40,000 μg/g Drinking water standard: 0.05 mg/L Sets vapour standards for the protection of human health: | 2017[31] |
*Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
mg/L = milligrams per litre
µg/m3= micrograms per cubic metre
µg/g = micrograms per gram
Canadian agencies/organizations
| Agency | Designation/Position | Year |
|---|---|---|
| Health Canada | DSL – low priority substance (already risk managed) | 2006[32] |
| CEPA | Schedule 1, paragraphs ‘a’ and ‘c’ | 1999[33] |
| Environment Canada | Pollution Prevention Plans – Part 4 of CEPA 1999 | 2000[34] |
| National Classification System for Contaminated Sites | Rank = “High hazard”, potential human carcinogen | 2008[35] |
| Environment Canada’s National Pollutant Release Inventory | Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than 10 tonnes | 2016[36] |
Dichloromethane was not included in other Canadian government chemical listings reviewed.[37]
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
Dichloromethane was not included in other Canadian government guidelines, standards, or chemical listings reviewed.
Main Uses
Dichloromethane is used to strip paint and remove varnish.[2] It has also been used as a flexible urethane blowing agent, in aerosol formulations, as a solvent in producing pharmaceuticals and film coatings, and as an extraction medium (used in the food industry to extract spices, caffeine, and hops).[1,4] Other uses include degreasing metals, manufacturing electronics and adhesives, processing plastics, and refrigerating.[4,38]
Historically, dichloromethane has been used as a fumigant. However, it is not currently registered as a pest-control product in Canada.[39]
Canadian Production and Trade
Canada does not produce dichloromethane, but meets domestic requirements through imports.[40]
Production and trade
| Activity | Quantity | Year |
|---|---|---|
| Canadian Production | Not produced since 1985 | 2000[41] |
| Domestic Demand | 5,100 t | 2002[41] |
| Export | 33 t of ‘dichloromethane (methylene chloride)’ | 2021[42] |
| Import | 12,118 t of ‘dichloromethane (methylene chloride)’ | 2021[42] |
t = tonne
Environmental Exposures Overview
An estimated 80% of dichloromethane produced globally is released to the environment.[43]
Based on data gathered in the early 1990’s, indoor air is likely the most significant source of exposure for Canadians.[44] CAREX Canada’s environmental estimates indicate that dichloromethane levels in indoor air result in an increased risk of cancer (moderate data quality).
Ambient air may be of greater concern in industrialized urban areas and in close proximity to waste or disposal sites.[1,43] CAREX Canada’s environmental estimates indicate that dichloromethane levels in outdoor air do not result in an increased risk of cancer (high data quality).
Environment Canada estimated that 2 million people were exposed to dichloromethane by using consumer products including paint strippers, aerosol paints, and insecticides and cleaning solutions.[40] Data on levels of dichloromethane in food is limited; however, it has been detected in several products including cereal and butter.[44,45] Potential for bioaccumulation in foods is low.[45] Dichloromethane levels are below the detection limit in the majority of drinking water samples collected in Canada, and are more frequently associated with groundwater sources.[45,46] Total daily intakes of dichloromethane for the Canadian general population are estimated to range from 3.96 to 6.62 micrograms/kilogram of body weight per day.[44] No recent Canadian studies have been identified for dichloromethane estimates in food and beverages.
Soil data on dichloromethane levels is limited to contaminated sites.[44,45] Dichloromethane has been detected in groundwater in Canada, and is usually associated with nearby landfills and waste disposal sites.[44]
Searches of the National Pollutant Release Inventory (NPRI) and US Consumer Product Information Database yielded the following results on current potential for exposure to dichloromethane in Canada:
NPRI and US Consumer Product Information Database
| NPRI 2015[47] | ||
|---|---|---|
| Search term: ‘dichloromethane’ | ||
| Category | Quantity | Industry |
| Released into Environment | 20 t | Office furniture manufacturing, pharmaceutical and chemical manufacture, pulp and paper mills, paint, coating and adhesive manufacturing (24 facilities) |
| Disposed of | 328 t | |
| Sent to off-site recycling | 267 t | |
| US Consumer Products 2015[48] | ||
|---|---|---|
| Search Term | Quantity | Product Type |
| ‘Methylene chloride’ | 55 | Heavy-duty automotive cleaners and degreasers (11), paint and adhesive remover (39), paint brush cleaner (2), furniture cleaner (1), deglosser (1), and herbicide (1) |
t = tonne
For more information, see CAREX Canada’s environmental exposure estimate for dichloromethane.
Occupational Exposures
Inhalation is the most important route of occupational exposure, however dermal absorption is also possible.[1]
CAREX Canada estimates that approximately 22,000 Canadians are exposed to dichloromethane 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 include building equipment contractors and personal and household goods maintenance and repair.
The largest exposed occupational groups are motor vehicle body repairers, followed by painters and decorators, construction traders helpers and labourers, and machinist and machining and tooling inspectors. Other occupations that may be exposed include furniture refinishers and chemical manufacturers.[1] Workers may be exposed when spraying urethane foam, removing paint or varnish from equipment or furniture, or using products that use dichloromethane as a propellant or degreasing agent.
For more information, see the occupational exposure estimate for dichloromethane.
Sources
Other Resources
- Long, G. et al. “Dichloromethane: evaluation of risks to health from environmental exposure in Canada.” J. Geophys. Res.1994;12(2):305-318.
- Moore, R.M. “Dichloromethane in North American Waters.” Journal of Geophysical Research 2004;109:C09004.
- Environment and Climate Change Canada. Frequently Asked Questions: Pollution Prevention Planning Requirements for Dichloromethane (2010)
- Agency for Toxic Substances and Disease Registry (ATSDR). ToxFAQs Sheet for dichloromethane/ methylene chloride (2001) (PDF)
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