Health effects of 1,1,2-trichloroethane
Contents
Introduction
1,1,2-Trichloroethane is a colorless, sweet-smelling liquid that does not burn easily and boils at a higher temperature than water. It is made by two companies in the United States. It is used mostly where 1,1-dichloroethane (vinylidene chloride) is made. 1,1,2-Trichloroethane is used as a solvent. Because information about how much is made and how it is used is not available, we cannot say how much 1,1,2-trichloroethane is used, where it is used, or in what products it is found. 1,1,2-Trichloroethane may also be formed in landfills when 1,1,2,2-tetrachloroethane is broken down. When it is released into the environment, most 1,1,2-trichloroethane finally ends up in the air, but some may enter groundwater (Health effects of 1,1,2-trichloroethane) . Breakdown in both the air and groundwater is slow.
In the air, half the 1,1,2-trichloroethane is expected to breakdown in 49 days, and so it is likely to spread far from where it is released before breaking down. A few studies show that 1,1,2-trichloroethane below the soil surface or in groundwater does not breakdown within 16 weeks, and other studies suggest that it will last for years. Some studies show that breakdown of 1,1,2-trichloroethane occurs in landfills, but how fast this happens is not known.
Exposure to 1,1,2-trichloroethane
Low levels of 1,1,2-trichloroethane may be found in outdoor air. The main source of this 1,1,2-trichloroethane is thought to be industries that use it as a solvent. Because the industries that produce 1,1,2-trichloroethane or use it to make other chemicals often recycle or burn their waste, releases of 1,1,2-trichloroethane by these industries should not be major sources of pollution.
From surveys of industrial wastewater, we learn that some of the industries that discharge 1,1,2-trichloroethane are the timber products industry, plastics and synthetics industry, and laundries. Limited data show that 1,1,2-trichloroethane is present in a quarter to a half of city air samples. Where 1,1,2-trichloroethane is found, the samples tested usually contain 10 to 50 parts of 1,1,2-trichloroethane per trillion parts of air (ppt).
Though exposure to contaminated drinking water taken from groundwater sources is possible, such exposure appears to be rare. A nationwide survey did not find 1,1,2-trichloroethane in drinking water, but well water in some areas has been found to contain it. Surveys found 1,1,2-trichloroethane in well water in Wisconsin, New =Jersey, Rhode Island, and Suffolk County, New York. The largest amount in these supplies was 31 parts of 1,1,2-trichloroethane per one billion parts of water (ppb).
1,1,2-Trichloroethane has not been reported in food or soil. Besides the air and drinking water sources, people may be exposed to 1,1,2-trichloroethane from spills and in the workplace, where it may be used as a solvent. Exposure would most likely be from breathing vapors of the chemical or from skin contact.
When a chemical like 1,1,2-trichloroethane is utilized to make other chemicals, it is usually used in tightly closed automatic systems, so that workers are not usually exposed to high levels of it. A national survey conducted in 1981-1983 estimated that 1,036 workers were exposed to 1,1,2-trichloroethane. 1,1,2-Trichloroethane has been found thus far at 45 of 1,177 hazardous waste sites on the National Priorities List (NPL) in the United States. Landfill gases from these sites may contain 1,1,2-trichloroethane.
Pathways for 1,1,2-trichloroethane in the body
1,1,2-Trichloroethane can enter the body when a person breathes air containing 1,1,2-trichloroethane, or when a person drinks water containing this compound. It can also enter the body through the skin. After it enters the body, it is carried by the blood to organs and tissues such as the liver, kidney, brain, heart, spleen, and fat.
Experiments in which animals were given 1,1,2-trichloroethane by mouth have shown that most 1,1,2-trichloroethane leaves the body unchanged in the breath and as other substances that it was changed into in the urine in about 1 day. Very little stays in the body more than 2 days.
Health effects of 1,1,2-trichloroethane
1,1,2-Trichloroethane can cause temporary stinging and burning pain on the skin when humans touch it. There is no other information on the health effects of 1,1,2-trichloroethane in humans.
You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
Most of what we know about the health effects of this chemical comes from experiments in animals. As is true with most chemicals, a large amount of 1,1,2-trichloroethane produces more damage than a small amount. Short-term exposure to high levels of 1,1,2-trichloroethane in air or high doses given by mouth or applied to the skin has caused death in animals.
Long-term exposure of animals to high doses given by mouth has also shortened the lifespan. These levels and doses are much higher than would be found in the air, water, or food to which humans might be exposed. Breathing high levels in air can affect the nervous system and cause sleepiness. 1,1,2-Trichloroethane may also affect the liver, kidney, and digestive tract, produce skin irritation, and affect the body's ability to fight infections. Mice, but not rats, that were given high doses of 1,1,2-trichloroethane by mouth for most of their life developed liver cancer, but we do not know whether humans exposed to this chemical would develop cancer. From the limited information available in animals, it appears that 1,1,2-trichloroethane does not cause birth defects or otherwise inhibit normal development.
1,1,2-trichloroethane exposure levels with harmful effects
It is not known what levels of 1,1,2-trichloroethane cause harmful health effects in people. In animals, liver effects, central nervous system depression, and death occurred at levels greater than 416 parts per million (ppm) 1,1,2-trichloroethane in air. At levels of 200 ppm in water, effects on the immune system and liver were seen.
Medical tests for 1,1,2-trichloroethane
Although chemists have ways of measuring some chemicals in body fluids (through biomonitoring, there is no commonly used medical test to find out whether a person has been exposed to 1,1,2-trichloroethane.
Further Reading
- The Agency for Toxic Substances and Disease Registry
- Interagency Coordinating Committee on the Validation of Alternative Methods
- European Centre for the Validation of Alternative Methods
- Institute for Laboratory Animal Research
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