Tetrachloroethylene, also known under its systematic name tetrachloroethene and many other names, is a chlorocarbon. It is a colorless liquid widely used for dry cleaning of fabrics and is sometimes called "dry-cleaning fluid". It has a sweet odor detectable by most people at a concentration of 1 part per million (1 ppm). It is also used in the cleaning of metal machinery and to manufacture some consumer products and other chemicals. Confirming longstanding scientific understanding and research, the final EPA risk assessment characterizes this material as a likely human carcinogen. The assessment provides estimates for both cancer and non-cancer effects associated with exposure to it over a lifetime.
Tetrachloroethylene, also known under its systematic name tetrachloroethene and many other names, is a chlorocarbon. It is a colorless liquid widely used for dry cleaning of fabrics and is sometimes called "dry-cleaning fluid". It has a sweet odor detectable by most people at a concentration of 1 part per million (1 ppm). It is also used in the cleaning of metal machinery and to manufacture some consumer products and other chemicals. Confirming longstanding scientific understanding and research, the final EPA risk assessment characterizes this material as a likely human carcinogen. The assessment provides estimates for both cancer and non-cancer effects associated with exposure to it over a lifetime.
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Earlier the International Agency for Research on Cancer has classified tetrachloroethene as a Group 2A carcinogen, which means that it is probably carcinogenic to humans. Like many chlorinated hydrocarbons, tetrachloroethene is a central nervous system depressant and can enter the body through respiratory or dermal exposure.
Animal studies and a study of 99 twins by Dr. Samuel Goldman and researchers at the Parkinson's Institute in Sunnyvale, California determined there is a "lot of circumstantial evidence" that exposure to Tetrachloroethlene increases the risk of developing Parkinson's disease ninefold. Larger population studies are planned.
Tetrachloroethylene should not be used near welding operations, flames, or hot surfaces.
EPA does not believe that wearing clothes dry cleaned with tetrachloroethene (c0mmonly known as perc) will result in exposures which pose a risk of concern. EPA has already taken several significant actions to reduce exposure to perc. EPA has clean air standards for dry cleaners that use perc, including requirements that will phase-out the use of perc by dry cleaners in residential buildings by December 21, 2020.
EPA has also set limits for the amount of perc allowed in drinking water and levels for cleaning up perc at Superfund sites throughout the country, which will be updated in light of the IRIS assessment.
After World War I, dry cleaners began using chlorinated solvents. These solvents were much less flammable than petroleum solvents previously used and had improved cleaning power. By the mid-1930s, the dry cleaning industry had adopted tetrachloroethylene as the ideal solvent. It has excellent cleaning power and is stable, nonflammable, and gentle to most garments.
The toxicity values reported in the perc IRIS assessment will be considered in:
Establishing cleanup levels at the hundreds of Superfund sites where perc is a contaminant
Revising EPA’s Maximum Contaminant Level for perc as part of the carcinogenic volatile organic compounds group in drinking water, as described in the agency’s drinking water strategy
Evaluating whether to propose additional limits on the emissions of perc into the atmosphere, since perc is considered a hazardous air pollutant under the Clean Air Act
The assessment replaces the 1988 IRIS assessment for perc and for the first time includes a hazard characterization for cancer effects. This assessment has undergone several levels of rigorous, independent peer review including: agency review, interagency review, public comment, and external peer review by the National Research Council. All major review comments have been addressed.
EPA continues to strengthen IRIS as part of an ongoing effort to ensure the best possible science is used to protect human health and the environment. In May 2009, EPA streamlined the IRIS process to increase transparency, ensure the timely publication of assessments, and reinforce independent review. In July 2011, EPA announced further changes to strengthen the IRIS program in response to recommendations from the National Academy of Sciences.
For further information: http://yosemite.epa.gov/opa/admpress.nsf/0/E99FD55271CE029F852579A000624956
Photo: http://upload.wikimedia.org/wikipedia/commons/9/93/Dry_clean_rack.jpg
