Tetrachloromethane (TCM)

The substance
Tetrachloromethane (carbon tetrachloride) is a manufactured compound consisting only of carbon and chlorine. It is usually found as a clear non-flammable volatile liquid, immiscible with water, with a sweet smell that can be detected at low levels.

In the past tetrachloromethane was produced in large quantities to make refrigerants and propellants for aerosol cans (such as CFC 11 & 12). It was also commonly used as a dry cleaning agent, a degreasing agent, a fire extinguisher, and a pesticide. Because of its harmful effects, these uses are now banned and it is only used in some limited industrial applications as feedstock in chemical manufacture (e.g. in the manufacture of Polyphenylene-terephthalamide and for the elimination of nitrogen trichloride in the production of chlorine and caustic soda in the chlor-alkali industry) including the formulation of petrol additives, catalyst regeneration and the production of CFC 11 and 12, which are in turn used as intermediate for other chemicals. Tetrachloromethane is regulated under the Montreal Protocol.

Major emissions
Individuals may be exposed to tetrachloromethane in the air from accidental releases from production. The major source of emissions to air is from industrial sites. In the past tetrachloromethane was also a common contaminant of indoor air, the sources of exposure being building materials or products such as cleaning agents. These uses are now banned. Release to the soil can occur due to spills, and through landfill leaching. Surface waters can be polluted as a result of these activities. However, it evaporates very quickly from soil and surface water. The only natural source of releases to the environment are volcanoes.

Impacts on human health and environment
Excessive exposure to tetrachloromethane may cause health effects on the brain, digestive system, eyes, kidney, liver, skin, and may cause cancer. Tetrachloromethane is a Volatile Organic Compound (VOC) but is completely un-reactive and consequently does not contribute to the formation of ground-level ozone. Releases or spills of tetrachloromethane on soil will likely result in rapid evaporation although some leaching to groundwater causing contamination will also occur, as it does not adsorb to soil well. Biodegradation has been demonstrated under anaerobic conditions, but under aerobic conditions such as in lakes and groundwater, the process is usually very slow, i.e. from weeks to greater than a year depending on the conditions. Its lifetime in rivers is expected to be much shorter (weeks). Adsorption to sediment and bioconcentration are not expected to be significant. Tetrachloromethane is an ozone depleting substance controlled under the Montreal Protocol. In the lower atmosphere (troposphere), it is extremely stable (residence time 30-50 years). The chemical stability of tetrachloromethane allows it to reach the upper atmosphere (stratosphere), where intense ultraviolet radiation causes it to break apart and release chlorine. The chlorine reacts with ozone and causes depletion of the Earth's stratospheric ozone layer, which shields life on earth from harmful ultraviolet radiation. Tetrachloromethane is also a weak greenhouse gas, contributing to global warming.

Emission to air reporting threshold: 100 kg/year

Data source: European Pollutant Emission Register