CAREX Canada

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CAS No. 75-09-2

Photo: Wikimedia Commons^[1]

IARC Monograph Vol. 71, 1999 (Group 2B)

General Information

Dichloromethane is a volatile, clear and colourless liquid that smells similar to chloroform.^[2] Dichloromethane has been an important industrial solvent since the 1940s.^[3] Dichloromethane is also commonly referred to as methylene chloride and DCM.^[4] There are numerous other synonyms and product names; see HSDB for more information.^[4]

In 1999 dichloromethane was classified by IARC as Group 2B, possibly carcinogenic to humans, based on evidence in experimental animals.^[3] In two inhalation studies in mice, increases in lung and liver tumours were observed.^[3] Mammary tumours were seen in female rats in another study.^[2]

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.^[3] Limitations of the available studies include small number of cases and lack of accurate exposure assessments.^[3]

The central nervous system is the primary target of acute inhalation exposure.^[5] Respiratory effects and skin irritation have also been reported.^[5]

Dichloromethane has been ranked by CAREX Canada for both the occupational and environmental settings as Group A (immediate high priority). Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Canadian Jurisdictions	OEL (ppm)
Canada Labour Code	50
BC	25
AB, ON, MB, NL, PE, NB, NS	50
SK	50 75 [stel]
QC	50 [em]
YT	200 250 [stel]
NT, NU	100 500 [stel]
Other Jurisdiction	OEL (ppm)
ACGIH 2011 TLV	50

ppm = parts per million

stel = short term exposure limit (15 min. maximum)

em = exposure must be reduced to the minimum

Canadian Environmental Guidelines

Jurisdiction	Limit	Year
Canadian Drinking Water Guidelines	0.05 mg/L	2010^[6]
Residential Indoor Air Quality	Included under product aerosol recommendations (adequate ventilation and intermittent used advised)	1987^[7]
Cosmetic Ingredients Hotlist	Not Permitted (as ‘methylene chloride’)	2011^[6]
Food Additives Permitted for Use	CE – Carriers or Extraction Solvents	2006^[17]

Canadian Agencies/Organizations

Agency	Designation/Position	Year
Health Canada	DSL – low priority substance (already risk managed)	2006^[8]
CEPA	Schedule 1, paragraphs ‘a’ and ‘c’	1999^[9]
Environment Canada	Pollution Prevention Plans – Part 4 of CEPA 1999	2000^[10]

Dichloromethane was not included in other Canadian government chemical listings reviewed.^[18]

Main Uses

Dichloromethane is used as a paint stripper and varnish remover.^[3] 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.^[14]

Production and Trade

Activity	Quantity	Year
Canadian Production	Not produced since 1985	2000^[13]
Domestic Demand	5,100 t	2002^[13]
Export: Mainly to US	196 t of ‘dichloromethane (methylene chloride)’	2010^[19]
Import: Mainly from US	3,272 t of 'dichloromethane (methylene chloride)'	2010^[19]

t = tonne

Occupational Exposures

Inhalation is the most important route of occupational exposure. Dermal absorption has also been observed.^[2]

In 1995 it was estimated that 15,985 facilities in Canada were using DCM.^[14] Approximately 32,000 Canadians were considered to be occupationally exposed to dichloromethane at that time.^[14]

Workers at risk of exposure to DCM include furniture refinishers, chemical manufacturers, and painters.^[2] 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.

Environmental Exposures

An estimated 80% of dichloromethane produced globally is released to the environment.^[20]

Based on data gathered in the early 1990’s, indoor air is likely to be the most significant source of exposure for Canadians.^[12] Ambient air may be of greater concern in industrialized urban areas and areas in close proximity to waste or disposal sites.^[2,20]

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.^[14] Data on levels of dichloromethane in food is limited; it has been detected in several products including cereal and butter.^[12]

Soil analysis data on DCM levels is limited to contaminated sites.^[12] Dichloromethane has been detected in groundwater in Canada, usually associated with nearby landfills and waste disposal sites.^[12]

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.^[12]

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

NPRI 2009^[21]
Search term: ‘dichloromethane'
Category	Quantity	Industry
Released into Environment	84 t	Plastic and urethane foam manufacture and pharmaceutical manufacture (45 companies)
Disposed of	128 t
Sent to off-site recycling	201 t

US Household Products 2010^[22]
Search Term	Quantity	Product Type
'dichloromethane'	30	Heavy-duty automotive cleaners and degreasers (10), home and hobby paints or adhesives (13), lubricant remover (1), and herbicide (1)