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Methylene chloride

methylene dichloride

SPRI Emission Reporting Threshold
10.0 Kg/yr Pollutant Emissions to Land
1,000 Kg/yr Pollutant Emissions to Air
10.0 Kg/yr Pollutant Emissions to Water
10.0 Kg/yr Pollutant Emissions to Waste Water
This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet.
What is it?
Dichloromethane is a clear, colourless liquid with a strong penetrating odour. It easily evaporates to vapour and is only slightly soluble in water. It is non-flammable, but can be explosive when mixed with oxygen. Dichloromethane is part of the group of compounds known as the volatile organic compounds (VOCs).
What is it used for?
The main uses of dichloromethane are as in paint removers, as aerosol solvents, as a flame retardent when mixed with certain propellants, in the manufacture of steroids, antibiotics and vitamins, as an extracting and degreasing agent and in the electronics industry.
Where does it come from?
The majority of direct releases of dichoromethane to air occur from the manufacture and use of solvents and aerosols containing it. There are thought to be no natural sources of dichloromethane to the environment.
How might it affect the environment?
At sufficiently high concentrations, dichloromethane may harm wildlife, but the effects are minimised by the rapid evaporation of the liquid into the air in which it slowly breaks down into other substances. As a VOC, it is thought to contribute only slightly to the formation of potentially damaging ground level ozone or photochemical smogs. The slow degradation of dichloromethane in air means that it can be carried long distances to remote locations. Although it can remove ozone, dichloromethane usually reacts with other air pollutants in the lower atmosphere and so does not significantly deplete the ozone layer in the high stratosphere (which protects the earth from harmful UV sun rays).
How might exposure to it affect human health?
Exposure to normal environmental concentrations of dichloromethane is unlikely to damage human health. However inhalation of high concentrations (following an accidental release for example) for even short amounts of time may damage the nervous system and the heart and may also cause cancer. Inhalation of ground level ozone (in the formation of which dichloromethane is slightly involved) can exacerbate respiratory conditions such as asthma.
What steps are being taken to limit the potential impacts?
In the UK (including Scotland) dichloromethane is regulated through controls of releases of substances to surface waters; and through the pollution prevention and control regulations. European Directives controlling releases of dichloromethane include those concerned with pollution of the aquatic environment (76/464); regulation of solvents; and it is listed as a "priority substance" under the proposed Water Framework Directive. At an international level, releases of dichloromethane are controlled through the Basel convention on transboundary movements and disposal of hazardous wastes; as a VOC, under the UNECE convention on long-range transboundary air pollution; and it is also listed as a candidate substance under the OSPAR and Helsinki conventions, protecting the marine environments of the north-east Atlantic and Baltic sea respectively.