1,1,1-Trichloroethane


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Introduction

1,1,1-Trichloroethane is a colorless liquid that evaporates quickly and has a sweet odor. It does not occur naturally, but industry produces millions of pounds of 1,1,1-trichloroethane every year. Industrial uses include degreasing metal parts, or serving as a solvent for products like paints and glues. It has seen use in spot cleaners and aerosol sprays.

Structural diagram: National Institutes of Health


Fate & Transport

Many home and workplace uses result in 1,1,1-trichloroethane vapor entering the air, where it lasts for about 2-10 years. It is not known how long 1,1,1-trichloroethane lasts in water or soil. From surface waters such as lakes and rivers, where 1,1,1-trichloroethane will partially mix with water, it will probably evaporate quickly to the air. It will not stick to soil, and can be carried by water through soil and into groundwater. Once there, it may be broken down by naturally occurring organisms, which take 200-300 days to remove half of the chemical.

Exposure Pathways

Because of its widespread industrial use and past disposal practices, 1,1,1-trichloroethane is sometimes found at industrial and hazardous waste sites - typically in ground water, but occasionally as a liquid in soil or as a vapor. You can be exposed to 1,1,1-trichloroethane daily from a wide variety of sources. 1,1,1-Trichloroethane is found in air samples taken all over the world. In the United States, urban air typically contains about 0.0001-0.001 parts of 1,1,1-trichloroethane per million parts air (ppm); rural air usually contains less than 0.0001 ppm. Because 1,1,1-trichloroethane is used so much in home and office products, there may be much more of it in inside air than outside air. New buildings can have high indoor levels, since this chemical is found in many building materials. Thus, you are more likely to be exposed to the vapor form of this chemical indoors.

Common consumer sources of 1,1,1-trichloroethane include glues, household cleaners, and aerosol sprays. If you eat foods contaminated with 1,1,1-trichloroethane, you will be exposed to it. Workplace exposure to 1,1,1-trichloroethane can occur during the use of metal degreasing agents, paints, glues, and cleaning products. You can be exposed to 1,1,1-trichloroethane by breathing the vapors from these products. Industrial uses of 1,1,1-trichloroethane probably make up the largest amount of release to the environment. High levels of exposure can occur during glue sniffing or solvent abuse.

1,1,1-Trichloroethane has also been found in rivers and lakes (up to 0.01 ppm), in soil (up to 120 ppm), in drinking water (up to 0.0035 ppm), and in drinking water from underground wells (up to 12 ppm). These amounts vary widely by location, and can be caused by releases during manufacture and transportation and during industrial or household use. You can be exposed to 1,1,1-trichloroethane by drinking contaminated water. Release of large amounts of the chemical can be caused by spillage, improper disposal, or industrial emissions. High levels of 1,1,1-trichloroethane in soil, surface water, or groundwater can also be caused by water from landfills and hazardous waste sites.

Metabolism

1,1,1-Trichloroethane can quickly enter your body if you breathe in air containing 1,1,1-trichloroethane vapor. It can also enter your body if you drink water or eat food containing 1,1,1-trichloroethane. If you were to spill it on your skin, most of it would quickly evaporate into the air and small amounts would enter your body through the skin. The most likely way you would be exposed to 1,1,1-trichloroethane at a hazardous waste site would be to breathe in 1,1,1-trichloroethane vapors in the air or drink water contaminated with 1,1,1-trichloroethane. Regardless of how 1,1,1-trichloroethane enters your body, nearly all of it will quickly leave your body in the air you breathe out. The small amount that is not breathed out changes in your body into other substances, known as metabolites. Most of the metabolites will leave your body in urine and breath in a few days. If you are exposed to 1,1,1-trichloroethane for a long time, some metabolites will begin to collect in your body. These metabolites rapidly leave your body when exposure stops.

Health Effects

If you were to breathe air containing high levels of 1,1,1-trichloroethane for a short time you might experience dizziness, lightheadedness, and loss of balance and coordination. These effects would rapidly "disappear" after you stop breathing in the contaminated air. If you were to breathe in much higher levels of 1,1,1-trichloroethane, either intentionally or accidentally, you might become unconscious, your blood pressure might decrease, and your heart might stop beating. We do not know whether any health effects would happen if you were to breathe in low levels of 1,1,1-trichloroethane for a long time. Studies in animals have shown that damage to the breathing passages and lungs, as well as mild liver effects, can result from breathing air with high levels of 1,1,1-trichloroethane. Exposure of pregnant rats to high levels of 1,1,1-trichloroethane in air slowed development of their offspring during pregnancy. Similarly, when pregnant rabbits breathed air containing high levels of 1,1,1-trichloroethane their offspring had changes in their bone structure.

So far, other studies in animals have not shown 1,1,1-trichloroethane in the air or water to cause cancer or affect their ability to produce offspring, but some of these studies were not complete enough to be absolutely sure. There are no studies in humans that can tell us whether health effects will occur if you were to eat food or drink water contaminated with 1,1,1-trichloroethane. However, swallowing large amounts of 1,1,1-trichloroethane caused liver damage and death in animals and could hurt humans.

Information excerpted from:

Toxicological Profile for 1,1,1-Trichloroethane December 1990

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