Trichloroethene


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What is Trichloroethene?

Tricloroethene is a manufactured chemical that does not occur naturally in the environment. It is a colorless liquid with a sweet odor and taste. Synonyms include trichloroethylene, TCE, Triclene and Vitran [1]

Structural diagram: National Institutes of Health


Uses of Trichloroethene

Trichloroethene is a highly effective solvent, most often used to remove oils and grease from metal. Though such uses are generally declining, it is still sometimes found in products like typewriter correction fluid, adhesives, paints, glues, rug cleaners, and spot and paint removers. Trichloroethene was once used as an anesthetic for surgery. [1]

Trichloroethene in the Environment

By far, the biggest source of trichloroethene in the environment is evaporation from factories that use it to remove grease from metals. It can also enter the air and water when it is disposed of at chemical waste sites. It evaporates easily but can stay in the soil and in groundwater. Once it is in the air, about half will be broken down within a week. When trichloroethene is broken down in the air, phosgene, a lung irritant, can be formed. Under certain conditions found in the workplace, trichloroethene can break down into chemicals such as dichloroacetylene and phosgene. In the body, trichloroethene may break down into dichloroacetic acid (DCA), trichloroacetic acid (TCA), chloral hydrate, and 2-chloroacetaldehyde. These chemical products have been shown to be toxic to animals and are probably toxic to humans. Once trichloroethene is in water, much will evaporate into the air; again, about half will break down within a week. It will take days to weeks to break down in surface water; in groundwater the breakdown is much slower because of the much slower evaporation rate. Very little trichloroethene breaks down in the soil, and it can pass through the soil into underground water. It does not build up in fish, but it has been found at low levels in them. It is not likely to build up in your body.

Exposure to Trichloroethene

Trichloroethene can get into air or water in many ways, for example, at waste treatment facilities; by evaporation from paints, glues, and other products; or by release from factories where it is made. Another way you may be exposed is by breathing the air around factories that use the chemical. People living near hazardous waste sites may be exposed to it in the air or in their drinking water, or in the water used for bathing or cooking.

Metabolism

If you breathe the chemical, about half the amount you breathe in will get into your bloodstream and organs; you will exhale the rest. If you drink trichloroethene, most of it will be absorbed into your blood. If trichloroethene comes in contact with your skin, some of it can enter your body, although not as easily as when you breathe or swallow it.

Once in your blood, your liver changes much of the trichloroethene into other chemicals. The majority of these breakdown products leave your body in the urine within a day. You will also quickly breathe out much of the trichloroethene that is in your bloodstream. Some of the trichloroethene or its breakdown products can be stored in body fat for a brief period, and thus may build up in your body if exposure continues.

Health Effects of Trichloroethene

The NIOSH Pocket Guide to Chemical Hazards [3] lists the following symptoms related to trichloroethene exposure:

  • Eye, skin irritation

  • Headache, vision problems

  • Weakness, dizziness

  • Tremor, drowsiness

  • Nausea, vomiting

  • Dermatitis

  • Irregular heart rhythm

  • Paresthesia

  • Liver damage

  • Potential occupational carcinogen

  • When checked on 12 December 2015, US EPA's IRIS Database states that trichloroethene is "carcinogenic to humans by all routes of exposure", based on epidemiological studies that found increased incidence of renal cell carcinoma, non-Hodgkin's lymphoma, and liver tumors. [4] When checked on 7 April 2015, the International Agency for Research on Cancer had determined that trichloroethene is carcinogenic to humans. [2]

    References

    [1] "Toxicological Profile for Trichloroethene August 1995 Draft Update", published by the Agency for Toxic Substances and Disease Registry, U.S. Dept. of Health and Human Services

    [2] International Agency for Research on Cancer

    [3] NIOSH Pocket Guide to Chemical Hazards, published by the National Institute for Occupational Safety and Health

    [4] Integrated Risk Information System, published by the United States Environmental Protection Agency