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Trichloroethene

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Introduction

Trichloroethene is also known as Triclene and Vitran and by other trade names in industry. It is a nonflammable, colorless liquid at room temperature with a somewhat sweet odor and a sweet, burning taste. This manmade chemical does not occur naturally in the environment. Trichloroethene is now mainly used as a solvent to remove grease from metal parts. It is also used as a solvent in other ways and is used to make other chemicals. Trichloroethene can also be found in some household products, including typewriter correction fluid, paint removers, adhesives, and spot removers. Most people begin to smell trichloroethene in air when there are around 100 parts of trichloroethene per a million parts of air (ppm).

Fate & Transport

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 is found in some foods; the trichloroethene found in foods is believed to come from contamination of the water used in food processing, or from the food processing equipment cleaned with trichloroethene. 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 Pathways

Trichloroethene is found in the outdoor air at levels far less than 1 ppm. When measured several years ago, some of the water supplies in the United States were found to have trichloroethene. The most recent monitoring study found mean levels in surface water ranging from 0.0001 to 0.001 parts of trichloroethene per million parts (ppm) of water and a mean level of 0.007 ppm in groundwater. About 400,000 workers are exposed to trichloroethene in the United States on a full-time (i.e., a 40-hour workweek) basis. The chemical can also get into the 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. Products that may contain trichloroethene are some types of typewriter correction fluids, paints and paint removers, glues, spot removers, rug cleaning fluids, and metal cleaners.

Metabolism

Trichloroethene enters your body when you breathe air or drink water containing it. It can also enter your body if you get it on your skin. You could be exposed to contaminated water or air if you live near or work in a factory that uses trichloroethene or if you live near a waste disposal site that contains trichloroethene. 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

Trichloroethene was once used as an anesthetic for surgery. People who are exposed to large amounts of trichloroethene can become dizzy or sleepy and may become unconscious when exposed to very high levels. Death may occur from inhalation of large amounts. Many people have jobs where they work with trichloroethene and can breathe it or get it on their skin. Some people who get concentrated solutions of trichloroethene on their skin develop rashes. People who breathe moderate levels of trichloroethene may have headaches or dizziness. Some people who breathe high levels of trichloroethene may develop damage to some of the nerves in the face. Humans have reported health effects when exposed to the level of trichloroethene at which its odor is noticeable. Effects have also occurred at much higher levels. Animals that were exposed to moderate levels of trichloroethene had enlarged livers, and high-level exposure caused liver and kidney damage. However, we do not know if these changes would occur in humans.

It is uncertain whether people who breathe air or drink water containing trichloroethene are at higher risk of cancer or if their children have more birth defects. People who used water for several years from two wells that had high levels of trichloroethene may have had a higher incidence of childhood leukemia than other people. Increased numbers of children were reported to be born with cardiac abnormalities, a finding which is supported by data from some animal studies showing developmental effects of trichloroethene on the heart. However, other chemicals were also in the water from this well. We do not have any clear evidence that trichloroethene alone can cause leukemia or any other type of cancer in humans. As part of the National Exposure Registry, the Agency for Toxic Substances and Disease Registry (ATSDR) compiled data on 4,280 residents of three states (Michigan, Illinois, and Indiana) who had environmental exposure to trichloroethene. It found no definitive evidence for an excess of cancers from trichloroethene exposure. In studies using high doses of trichloroethene in rats and mice, tumors in the lung, liver, and testes were found, providing some evidence that high doses of trichloroethene can cause cancer in experimental animals. We do not know if trichloroethene affects human reproduction.

Information excerpted from:

Toxicological Profile for Trichloroethene August 1995 Draft Update

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services

Structural diagram:

National Institutes of Health