Dichloromethane is principally used as a solvent in paint removers and as an aerosol propellant. It is used as a blowing and cleaning agent in the production of urethane foam and plastic fabrication and in paint stripping operations. It is used in metal cleaning, as a solvent in the production of polycarbonate resins, in film processing, and in ink formulations. Dichloromethane is used in the food industry as an extraction solvent for spices, caffeine (decaffeinated coffee), and hops. Dichloromethane's use in aerosol products includes paints and automotive spray products.
Substance name: Dichloromethane
CASR number: 75-09-2
Molecular formula: CH2Cl2
Synonyms: Methylene chloride, Methylene dichloride, Methane dichloride, Methylene bichloride, dichloromethane, Aerothene MM
Dichloromethane is an organic solvent that is clear and colourless and has a mild sweet odour. It is a volatile liquid (that is, it evaporates quickly).
Melting Point: -96.7°C
Boiling Point: 39.8°C
Vapour Density: 2.93
Specific Gravity: 1.3255
Dichloromethane is chemically stable. It is slightly soluble in water.
The National Pollutant Inventory (NPI) holds data for all sources of dichloromethane emissions in Australia.
Dichloromethane can affect you if breathed in and by passing through the skin. Exposure to high concentrations may cause unconsciousness and death. Exposure may irritate the lungs, which can cause a build up of fluid (pulmonary oedema). Lower doses may cause headaches, fatigue, and behaviour similar to being drunk. Dichloromethane exposure may cause the heart to beat irregularly or stop. Long term exposures at high levels may damage the liver and brain. The International Agency for Research on Cancer classifies dichloromethane as a 'possible human carcinogen'. Worksafe Australia categorises dichloromethane into Category 3, a 'suspected human carcinogen'. It is possible that there is no safe level of exposure to a carcinogen.
Entering the body
Dichloromethane will enter the body if we breathe in contaminated air. It can also pass through the skin.
Workers in the industries that use or produce dichloromethane are at risk of exposure. Consumers can be exposed to dichloromethane by exposure to air from production and processing facilities using dichloromethane. Consumers may also be exposed to dichloromethane when using consumer products containing dichloromethane, especially if there is not good ventilation. Note above the large number of consumer products containing dichloromethane.
According to Worksafe Australia it is allowable for workers to be exposed to 50 parts per million dichloromethane over an eight hour workshift. Worksafe Australia has determined that dichloromethane is a Category 3, suspected carcinogen. It is possible that there is no safe level of exposure to a carcinogen.
Australian Drinking Water Quality Guidelines (NHMRC and ARMCANZ, 1996):
0.004 mg/L (i.e. 0.000004 g/L).
Dichloromethane evaporates when exposed to air. It dissolves when mixed with water and also evaporates from the water. In animals, as well as humans dichloromethane is metabolised into carbon monoxide, which results in depriving the body of oxygen. Very high levels of dichloromethane (25,300 parts per million concentration of air breathed) were lethal to 50% of the rats tested. Lower long-term concentrations caused problems with the liver and kidneys in rats. Dichloromethane has low acute toxicity to aquatic organisms.
Entering the environment
Industrial emissions of dichloromethane can produce elevated, but still low level concentrations in the atmosphere around the source. Because of its short life expectancy in the atmosphere dichloromethane is expected to be confined to the local area within which it is emitted. Because dichloromethane is used in many consumer products, short-term indoor concentrations may be elevated above the levels considered safe for workers.
Where it ends up
Dichloromethane quickly evaporates to a gas if released as a liquid. It will then degrade by reacting in the air with photochemically produced products. The expected lifetime in the air is 130 days. Dichloromethane has low acute toxicity to aquatic organisms. There is not enough information to predict the effect dichloromethane has on land animals and birds. Dichloromethane is not expected to bio-accumulate. It is not expected to react with ozone in the upper atmosphere since most of it will decompose in the lower atmosphere.
The 1992 Australian Water Quality Guidelines for Fresh and Marine Waters reports halogenated methanes should be limited to 0.016 milligrams per litre (that is, 0.000016 grams per litre) of water in order to protect human consumers of fish and other aquatic organisms.
The primary stationary sources of dichloromethane are the industries that manufacture it or use it in production. Some of the industries that use it in production are plastic product manufactures, manufacturers of synthetics, urethane foam production, the electronics industry (electroplating, circuit board manufacturing, and metal degreasing) and the paint industry. These may result in emissions to air.
Diffuse sources, and industry sources included in diffuse emissions data
Commercial and household paint removal, electronic cleaners and aerosols result in emissions to air.
Dichloromethane does not occur naturally in the environment.
There are no known sources of mobile emissions of dichloromethane.
Aerosol paints, automotive and machinery refinish paints and primers, automotive body polish and cleaners, aerosol air fresheners and deodorants, furniture polish and cleaners, hairsprays, household hard surface cleaners (aerosol and liquid), household insecticides, household tints and dyes, lubricating greases and oils, automotive chemicals, paint and varnish removers and thinners, shoe polish and cleaners, pet flea and tick products, waterproofing compounds.
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