Trichloroethylene
Trichloroethylene (TCE) is a colorless, synthetic chemical solvent with the molecular formula C2HCl3, commonly used in industrial applications for cleaning and degreasing metal items. It has a chloroform-like smell and is slightly soluble in water, meaning it can mix with various solvents. TCE has been frequently utilized in the production of household products such as paint strippers, adhesives, and spot removers, and in the past, it served as a general anesthetic during certain medical procedures. However, TCE is recognized as a hazardous substance, with significant health risks associated with exposure, including skin irritation, central nervous system effects, and potential links to cancer.
The chemical poses environmental concerns, as it is a prevalent contaminant in groundwater and has been identified at numerous contaminated sites, including Superfund locations. Its vapors can remain in the atmosphere for up to seven days and pose explosive risks under certain conditions. To mitigate the dangers of TCE, safety precautions such as protective clothing and proper ventilation are essential during its use. Understanding TCE's risks and applications is crucial for those who may encounter this chemical in industrial or environmental contexts.
Trichloroethylene
Trichloroethylene, or TCE, is a chemical solvent with a number of industrial uses. TCE is considered a hazardous substance, and exposure to large amounts of it can have dangerous effects on human life. Although TCE is not flammable, the vapors or fumes from it could ignite in the presence of an open flame.
Description and Uses
The molecular formula of TCE is C2HCl3. The colorless, synthetic chemical is sensitive to light and has a smell similar to that of chloroform. It is only slightly soluble in water but mixes with a number of other solvents. Its main use is in the cleaning and degreasing of metal items. It also is used in the manufacture of a many products used in homes and offices, such as paint strippers, carpet shampoos, spot removers, adhesives, waterproofing agents, and correction fluids.
In the past, TCE was used as an inhalable anesthesia for short medical procedures that required light sedation with good pain control. Sometimes known as Trilene, this form of TCE often was used during labor and some dental procedures. Because of its relatively low cost, it is still sometimes used as an anesthesia in developing countries.
Environmental Hazards
TCE has been recognized as a significant source of environmental contamination by the U.S. Environmental Protection Agency (EPA) and has been identified in thousands of contaminated sites. The EPA's 2011 Final Health Assessment for TCE reported that it was the most commonly found environmental contaminant and was present in 761 of approximately 1,300 Superfund sites (sites designated as environmental hazards in need of cleanup in compliance with the Comprehensive Environmental Response, Compensation, and Liability Act of 1980). Many military bases also have been found to be contaminated by TCE. In addition to threatening the groundwater on and near these sites, TCE vapors can rise from the contaminated ground and water and affect the air, especially the air inside buildings located on the site.
The majority of TCE is used as a vaporous degreaser in industrial settings. It is a highly volatile chemical and very readily evaporates, releasing vapors into the atmosphere where they can linger for up to seven days. Because it has some ability to mix with water, TCE that lands in the soil often migrates into groundwater supplies. As a result, it is the most frequently identified organic contaminant of underground water supplies. Although most municipal water systems contain less than the maximum allowed amount of TCE, between 9 and 34 percent of drinking water sources in the United States are contaminated with at least some of the chemical.
Industrial waste disposal sites are another potential source of TCE environmental contamination; waste materials can seep into the ground and reach water supplies. In some cases, illegal dumping has contaminated the ground and water and affected whole communities who were exposed unknowingly.
While TCE itself is not a fire risk, its vapors can ignite when exposed to flame. TCE vapors are heavier than air and can become explosive if they collect in an area before exposure to a flame. When ignited vapors are exposed to aluminum, copper, iron, or zinc, they can form another gas, phosgene, which is highly toxic. Heat and/or strong oxidizers mixed with TCE can potentially form dichloroacetylene, which is flammable, explosive, and toxic.
TCE presents a serious hazard to aquatic life forms and poses long-term consequences to their environment.
Health Hazards
Exposure to TCE poses a number of health hazards, depending on the type and duration of exposure. Direct exposure can cause skin and eye irritation. Swallowing TCE can irritate the mucous membranes and can cause harm to the airway.
The most common form of exposure to TCE is by inhalation. Someone who is exposed to a large amount of the chemical's vapors or to the toxic gases that are released when the vapors ignite can experience immediate and acute effects to the central nervous system. Symptoms of TCE inhalation include irritation to the nose and throat, nausea, and blurred vision. Inhaling the vapors can induce fatigue and sleepiness, confusion, a sense of euphoria or irresponsibility, and headaches. Significant exposure can lead to cardiac arrest. Vapor exposure also can affect the skin, gastrointestinal system, kidneys, and liver.
TCE poses hazards to those who are exposed to it continually, such as those who work in places where it is used as a degreaser or in factories that use it in manufacturing. Regularly breathing the vapors can affect the central nervous system, causing headaches, dizziness, sleepiness and fatigue, confusion, vision problems, and numbness of the face. Chronic exposure through industrial sources or contaminated drinking water has been shown to affect the liver and kidneys and the immune and endocrine systems. Some studies have indicated an increase in miscarriages among women exposed to TCE vapors on a regular basis; it is considered a hazard to the developing organs of fetuses whose mothers have been exposed.
Other studies have indicated that TCE may increase the risk of cancer in both humans and animals. Human studies show the strongest association with kidney cancer, while animal studies have shown increased incidents of kidney, liver, lung, and testicular tumors and lymphoma.
Safe Handling
Safety precautions can reduce the danger of TCE exposure. These include wearing neoprene gloves and protective clothing, such as a full worksuit or apron. A face shield or safety goggles can protect against accidental splashes. Exhaust systems equipped with a vacuum can minimize exposure to vapors. The sweet ether or chloroform-like odor, which can become obnoxiously strong, can alert to the presence of dangerous levels of TCE vapors. Precautions such as careful storage in steel drums kept in well-ventilated, cool, dry areas are necessary to minimize fire hazards.
Bibliography
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"Trichloroethylene Safety FactSheet." National Industrial Chemicals Notification and Assessment Scheme. Australian Government Department of Health. 2013. Web. 27 Jan. 2016. http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/trichloroethylene-safety-factsheet