Atmosphere

Air toxics and indoor air quality in Australia

State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4

Part C: Factsheets (continued)

Dichloromethane

Substance name: Dichloromethane
CASR number: 75-09-2
Molecular formula: CH2Cl2
Synonyms: Methylene chloride, methylene dichloride, methane dichloride, methylene bichloride, dichloromethane, aerothene MM

Physical and chemical properties

Dichloromethane is an organic solvent that is clear and colourless and has a mild sweet odour. It is a volatile liquid.

Melting point: -96.7°C
Boiling point: 39.8°C
Specific gravity: 1.3255
Vapour density: 2.93

Dichloromethane is chemically stable. It is slightly soluble in water.

Common uses

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. It is used in aerosol products, including paints and automotive spray products.

Sources of emissions

Point sources

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 manufacturers, 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 point sources included in aggregated emissions data

Commercial and household paint removal, electronic cleaners and aerosols result in emissions to air.

Natural sources

Dichloromethane does not occur naturally in the environment.

Mobile sources

There are no known mobile sources of dichloromethane.

Consumer products that may contain 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.

Health effects

How might I be exposed to dichloromethane?

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.

By what pathways might dichloromethane enter my body?

Dichloromethane will enter the body if we breathe in contaminated air. It can also pass through the skin.

Health guidelines

National Occupational Health and Safety Commission (NOHSC):

Dichloromethane is listed as a substance under review by the NOHSC regarding skin absorption.

Australian Drinking Water Guidelines (NHMRC and ARMCANZ 1996):

What effect might dichloromethane have on my health?

Dichloromethane can affect people if it is breathed in or passes 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'. Dichloromethane is classified by the NOHSC as a Category 3 carcinogen (substance which causes concern for humans owing to possible carcinogenic effects but in respect of which the available information is not adequate for making a satisfactory assessment).

Environmental effects

Environmental fate

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 bioaccumulate. It is not expected to react with ozone in the upper atmosphere since most of it will decompose in the lower atmosphere.

Environmental transport

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. Since dichloromethane is used in many consumer products, short-term indoor concentrations may be elevated above the levels considered safe for workers.

Environmental guidelines

The 1992 Australian Water Quality Guidelines for Fresh and Marine Waters reports that halogenated methanes should be limited to 0.016 mg/L (0.000016 grams per litre) of water in order to protect human consumers of fish and other aquatic organisms.

What effect might dichloromethane have on the environment?

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 the body being deprived of oxygen. Very high levels of dichloromethane (25 300 ppm concentration of air breathed) were lethal to 50% of rats tested. Lower long-term concentrations caused problems with the liver and kidneys in rats. Dichloromethane has low acute toxicity to aquatic organisms.

Key

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