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Basic Information
On this page:
About perchloroethylene,
or "perc"
EPA's role in regulating perc
About perchloroethylene, or "perc"
The chemical formula of perc isC2Cl4 - two carbon and four chlorine atoms. |
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Perchloroethylene, also known as perc, PCE, tetrachloroethyene and tetracholorethylene, is a solvent used in dry cleaning. Approximately 28,000 U.S. dry cleaners use perchloroethylene, which is the only air toxic emitted from the dry cleaning process.
EPA's Science Advisory Board has identified perchloroethylene as a possible to probable human carcinogen. Exposure to perchloroethylene has been linked to the development of liver tumors in mice. Epidemiological studies have shown mixed results, with some studies reporting increased incidence of a variety of tumors and other studies not reporting carcinogenic effects.
Exposure to perchloroethylene also is associated with chronic, non-cancer health effects, including liver and kidney damage in rodents, and neurological effects in humans. Acute exposures can result in loss of coordination; eye, nose and throat irritation; and headache. Technical risk information about perc (tetrachloroethylene).
EPA's role in regulating perc
The role of standards:
The Clean Air Act requires EPA to regulate air toxics from large industrial facilities in two phases. Perchloroethylene, or perc, is one of the air toxics emissions that EPA regulates. More information about air toxics.
First phase: In the first, technology-based phase, EPA develops particular standards for controlling the emissions of air toxics from sources in an industry group, or a "source category." One such example of a source category is dry cleaners.
- MACT standards: These standards, termed "maximum achievable control technology", or “MACT” standards, are based on the emissions levels acheived by facilities that emit the lowest among ALL facilities in that industry. For dry cleaners, EPA finalized the perchloroethylene dry cleaning MACT standards in September of 1993. MACT dry cleaning standards apply to the largest dry cleaning facilities.
- GACT standards: allowed for smaller "area" sources, are more flexible requirements than MACT standards. For example, GACT standards do not have a requirement to set a control baseline or “floor” equal to the controls used for the best performing 12 percent of a type of facility. GACT standards also allow cost- effectiveness of air pollution controls to be considered.
Second phase: In the second phase, EPA is required under the Clean Air Act to conduct two reviews.
Technology review: EPA is required to review the technology-based standards and revise them, if necessary, to account for improvements in air pollution controls and/or prevention. EPA is to conduct this assessment every eight years.
Residual Risk Review: EPA is required to assess the risk remaining after the application of the 1993 MACT standards to determine whether the standards protect public health with an ample margin of safety. If more protective standards are needed, EPA amends the MACT standards to add what is known as “residual risk standards.” EPA has discretion as to whether it conducts this review for GACT standards.
In developing risk-based standards to reduce health risks from air toxics, EPA strives to ensure that those standards provide the maximum feasible amount of protection by:
- Limiting an individual’s cancer risk to approximately 100 in 1 million. This means that a person living near a facility and exposed to maximum concentrations of a pollutant for a 70-year-lifetime would have no more than a 100 in 1 million chance of getting cancer as a result.
- Protecting the largest number of people possible so that their individual cancer risks are no higher than approximately one in 1 million.
It is important to note that all risk estimates contain uncertainties. It is impossible to know, for example, exactly how many people may get cancer from breathing certain concentrations of a chemical (in this case, perc). Health effects information about perc is available on EPA's IRIS database.
Regulating "Perc" Drycleaners under the Clean Air Act:
There are three types of perchloroethylene dry cleaners.
- Large Industrial & Commercial Dry Cleaners
- Large industrial and commercial dry cleaners are classified as “major sources,” meaning they emit more than 10 tons of perchloroethylene a year. There are 12 of these large dry cleaners in the United States. These dry cleaners are covered by EPA’s 1993 maximum achievable control technology (MACT) standards.
- Freestanding Small Drycleaners
- Freestanding small dry cleaners are the type of dry cleaner you might see in a strip shopping center or as a stand-alone building. These dry cleaners are classified as "area sources," which means they emit less than 10 tons of perchloroethylene each year. These smaller dry cleaners are covered by emissions standards known as generally available control technology (GACT) standards, issued in 1993.
- Small Drycleaners in Apartment Buildings
- About 1,300 small "area source" dry cleaners using perchloroethylene are located on the ground floor of residential buildings. Like freestanding small dry cleaners, these co-residential cleaners are covered by emissions standards known as generally available control technology (GACT) standards, issued in 1993.
- Co-residential facilities pose a unique exposure scenario. Because apartments in these buildings are located very close to these dry cleaners, residents' exposures and their estimated cancer risks can be much higher than for typical area sources.