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Carbon tetrachloride

carbon tetrachloride

SPRI Emission Reporting Threshold
10.0 Kg/yr Pollutant Emissions to Air
1.00 Kg/yr Pollutant Emissions to Water
1.00 Kg/yr Pollutant Emissions to Waste Water
Disclaimer
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?
Tetrachloromethane (TCM) is a clear, non-flammable, volatile (easily vapourisable) liquid with a sweet smell, which does not mix with water. TCM is part of the group of compounds known as the volatile organic compounds (VOCs).
What is it used for?
Nowadays TCM is only used in a small number of industrial applications. In the past TCM was widely used: as a propellant in aerosol cans, as a refrigerant, as a dry cleaning agent, as a degreasing agent, in fire extinguishers, as a pesticide and it was also used by farmers to control liver fluke in sheep.
Where does it come from?
Today the major sources of TCM are from industrial spillages and from landfill sites where waste containing TCM has been buried. In the past, when TCM was widely used, it was a major contaminant of indoor air. There are thought to be no natural sources of TCM.
How might it affect the environment?
Releases of TCM evaporate easily into the air and can also accumulate in water bodies, but it does not bind to soil or sediments. The time taken for TCM to break down in lakes and groundwater depends on the conditions, but can be up to a year. In rivers, breakdown generally occurs faster. As a VOC, TCM (in combination with other air pollution) plays a significant role in the formation of ground level ozone which can damage crops and materials. TCM also has global environmental effects. Air-borne TCM is very stable in the lower atmosphere and can persist for up to 30-50 years. When it reaches the upper atmosphere it breaks down to give chlorine which damages the stratospheric ozone layer and hence reduces the protection from harmful UV sun rays which this offers. TCM is also a "greenhouse gas", contributing to global warming.
How might exposure to it affect human health?
Exposure to normal environmental concentrations of TCM is unlikely to damage health. Inhalation or ingestion of higher levels (in contaminated drinking waters or through occupational exposure for example) can however be detrimental to health: causing damage to the liver, kidneys, lungs and central nervous system, possibly being carcinogenic and in severe cases even causing coma or death. Inhalation of ground level ozone (in the formation of which TCM is significantly involved) can exacerbate respiratory conditions such as asthma. Depletion of the stratospheric ozone layer (in which TCM plays a part) means that humans may be exposed to high doses of UV sunlight which might cause skin cancers.
What steps are being taken to limit the potential impacts?
In the UK (including Scotland) the main legislation controlling releases of TCM are those regulating releases of substances to surface waters (SI 1997/2560); food and environmental protection (FEPA 1985); pesticide releases (COPR 1986); the National Air Quality Strategy control (as a VOC); and it is not listed as a safe pesticide for use in the UK. European Directives controlling emissions of TCM include those concerned with its use and manufacture (2037/2000); and pollution of the aquatic environment (76/464). Internationally, releases of TCM are regulated under the UNECE convention on long-range transport of transboundary air pollution; the Basel convention on transboundary movements and disposal of hazardous wastes; and it is listed as a candidate substance for inclusion in the OSPAR and Helsinki conventions protecting the marine environments of the north-east Atlantic and Baltic sea respectively.