Health effects of 1,1,1-trichloroethane
1,1,1-Trichloroethane is a synthetic chemical that does not occur naturally in the environment. It also is known as methylchloroform, methyltrichloromethane, trichloromethylmethane, and ?-trichloromethane. Its registered trade names are chloroethene NU® and Aerothene TT®. It is a colorless liquid with a sweet, sharp odor. 1,1,1-Trichloroethane dissolves slightly in water. The liquid evaporates quickly and becomes a vapor. Most people begin to smell 1,1,1-trichloroethane in the air when its levels reach 120–500 parts per million (ppm). If the chemical makes up 8–10.5% (80,000– 105,000 ppm) of the air, it can burn easily when it contacts a spark or flame. A poisonous gas known as phosgene can be produced during welding if 1,1,1-trichloroethane is used to clean the metal. 1,1,1-Trichloroethane also can be found in soil and water, particularly at hazardous waste sites. Because of its tendency to evaporate easily, the vapor form is most commonly found in the environment.
1,1,1-Trichloroethane had many industrial and household uses. It was often used as a solvent to dissolve other substances, such as glues and paints. In industry, it was widely used to remove oil or grease from manufactured parts. In the home, it used to be an ingredient of such products as spot cleaners, glues, and aerosol sprays. No 1,1,1-trichloroethane is supposed to be manufactured for domestic use in the United States after January 1, 2002, because it affects the ozone layer. However, until 2005, limited amounts were still allowed to be produced for essential purposes, and until 2012, production of 1,1,1-trichloroethane is allowed for export. About 300 million pounds were produced in 2000, but less is being made today. Most of the 1,1,1-trichloroethane that is manufactured today is exported.
Pathways for 1,1,1-trichloroethane in the environment
Most of the 1,1,1-trichloroethane released into the environment enters the air. Once in the air, it can travel to the upper part of the earth's atmosphere, which is called the stratosphere. There, sunlight breaks it down into other chemicals that may reduce the stratospheric ozone layer. This ozone layer blocks certain damaging ultraviolet rays of the sun from reaching the earth's surface. Some scientists think the gradual thinning of the ozone layer is increasing the number of skin cancer cases in humans.
Spills, improper disposal, industrial emissions, and consumer use can release 1,1,1-trichloroethane into the environment. Contaminated water from landfills and hazardous waste sites can contaminate surrounding soil and nearby surface water or groundwater. However, most of the chemical probably will evaporate eventually into the air. It will not build up in plants or animals. Industrial operations release the largest amount of 1,1,1-trichloroethane into the environment, mostly by emissions into the air. The vapor also enters the air because many products containing the chemical were used in the home and workplace.
We do not know how long 1,1,1-trichloroethane lasts in water or soil. In surface waters, such as lakes and rivers, where it partially mixes with water, much of the chemical evaporates quickly. 1,1,1-Trichloroethane also evaporates from soil surfaces. Water can easily carry it through soil into groundwater. 1,1,1-Trichloroethane in groundwater can evaporate and pass through soil as a gas and finally be released to the air. Also, organisms that live in soil and water may break down 1,1,1-trichloroethane. One study suggests that half of the chemical takes 200–300 days to break down in contaminated groundwater. However, the number of days can vary widely, depending on specific site conditions.
Exposure to 1,1,1-trichloroethane
You are not likely to be exposed to large enough amounts of 1,1,1-trichloroethane to cause adverse health effects. 1,1,1-Trichloroethane has been found in air samples taken from all over the world. In the United States, city air typically contains about 0.1–1.0 parts per billion (ppb) of 1,1,1-trichloroethane; rural air usually contains less than 0.1 ppb. Because 1,1,1-trichloroethane was used so frequently in home and office products, much more was found in the air inside buildings (0.3–4.4 ppb) than in the outside air (0.1–0.9 ppb). Since this chemical was found in many building materials, new buildings used to have higher indoor levels than old buildings. Thus, you were likely to be exposed to 1,1,1-trichloroethane vapor at higher levels indoors than outdoors or near hazardous waste sites. However, since 2002, 1,1,1-trichloroethane is not expected to be commonly used, and therefore, the likelihood of being exposed to it is remote.
Common consumer products that used to contain 1,1,1-trichloroethane included glues, household cleaners, and aerosol sprays. In the workplace, you could have been exposed to 1,1,1-trichloroethane while using some metal degreasing agents, paints, glues, and cleaning products. You could have been exposed to 1,1,1-trichloroethane by breathing the vapors from these products or by letting the liquid contact your skin. High levels of exposure have occurred in people who deliberately inhaled the vapors, as in glue-sniffing or solvent abuse.
1,1,1-Trichloroethane has 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 5.4 ppm). In one case, drinking water from a private well contained up to 12 ppm, possibly as a result of illegal discharge or spill from a nearby industrial plant. Releases during manufacture and transportation and during industrial or household use can cause these high levels, but the levels vary substantially from one location to another. Certain foods you eat and water you drink or bathe in may be contaminated with 1,1,1-trichloroethane.
However, you can be exposed to 1,1,1-trichloroethane primarily by drinking contaminated water and eating contaminated food.
Pathways for 1,1,1-trichloroethane in the body
1,1,1-Trichloroethane can quickly enter your body if you breathe in air containing it in vapor form. It also enters your body if you drink water or eat food containing 1,1,1-trichloroethane. If you spill 1,1,1-trichloroethane on your skin, most of it quickly evaporates into the air, but small amounts enter your body through your skin. Regardless of how 1,1,1-trichloroethane enters your body, nearly all of it quickly leaves your body in the air you exhale. The small amount that is not breathed out can be changed in your body into other substances, known as metabolites. Most of the metabolites leave your body in the urine and breath within a few days.
Health effects of 1,1,1-trichloroethane
Scientists use many tests to protect the public from harmful effects of toxic chemicals and to find ways for treating people who have been harmed.
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 health effects such 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).
If you breathe air containing high levels of 1,1,1-trichloroethane (1,000 ppm or higher) for a short time, you may become dizzy and lightheaded and possibly lose your coordination. These effects rapidly disappear after you stop breathing contaminated air. If you breathe in much higher levels of 1,1,1-trichloroethane, either intentionally or accidentally, you may become unconscious, your blood pressure may decrease, and your heart may stop beating. Whether breathing low levels of 1,1,1-trichloroethane for a long time causes harmful effects is not known. Studies in animals show that breathing air that contains very high levels of 1,1,1-trichloroethane (higher than 2,000 ppm) damages the breathing passages and causes mild effects in the liver, in addition to affecting the nervous system. There are no studies in humans that determine whether eating food or drinking water contaminated with 1,1,1-trichloroethane could harm health. Placing large amounts of 1,1,1-trichloroethane in the stomachs of animals has caused effects on the nervous system, mild liver damage, unconsciousness, and even death. If your skin contacts 1,1,1-trichloroethane, you might feel some irritation. Studies in animals suggest that repeated exposure of the skin might affect the liver and that very large amounts on the skin can cause death. These effects occurred only when evaporation was prevented.
Available information does not indicate that 1,1,1-trichloroethane causes cancer. The International Agency for Research on Cancer (IARC) has determined that 1,1,1-trichloroethane is not classifiable as to its carcinogenicity in humans. EPA has also determined that 1,1,1-trichloroethane is not classifiable as to its human carcinogenicity. The likelihood is very low that exposure to 1,1,1-trichloroethane levels found near hazardous waste sites would cause significant health effects.
Medical tests for 1,1,1-trichloroethane
Samples of your breath, blood, and urine can be tested to determine if you have recently been exposed to 1,1,1-trichloroethane. In some cases, these tests can estimate how much 1,1,1-trichloroethane has entered your body. To be of any value, samples of your breath or blood have to be taken within hours after exposure, and samples of urine have to be taken within 2 days after exposure. However, these tests will not tell you whether your health will be affected by exposure to 1,1,1-trichloroethane. The exposure tests are not routinely available in hospitals and clinics because they require special analytical equipment.
- 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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