By Pat Rizzuto and Patrick Ambrosio
The Environmental Protection Agency formally concluded Feb. 10 that a widely used dry cleaning solvent is a likely human carcinogen, paving the way for the agency to reconsider drinking water and other standards for the chemical.
The agency released its final assessment of perchloroethylene, or perc (CAS No. 127-18-4). That assessment had not been updated since 1988.
The agency's decision to classify perc as a likely human carcinogen is consistent with its finding in 2008, when it released a draft assessment of perchloroethylene (32 CRR 641, 6/30/08)
The National Academies also supported that classification in a 2010 report.
In EPA's new assessment, the agency also concluded that laboratory animal testing and other data on perc show lifetime daily ingestion at far lower levels of the solvent than estimated in 1988 could cause neurological, kidney, immune, or other problems other than cancer.
Specifically, the final assessment provides a reference dose of 0.006 milligram per kilogram body weight per day compared to the RfD of 0.1 mg/kg/day set by the agency in 1988.
EPA's assessment sets its first reference concentration, or RfC, for perchloroethylene. The RfC is an estimate of a lifelong concentration of perchloroethylene in air that people could breathe over their lifetimes without the expectation that solvent would cause neurological, kidney, immune, or other noncancer problems. Previously EPA did not have an RfC for perchloroethylene.
Environmental health advocates quickly praised EPA's final assessment.
“The evidence against this ubiquitous dry cleaning chemical piled up for years, like dirty laundry in the corner of the room,” David Andrews, a senior scientist with Environmental Working Group, said in a statement. “It's encouraging that EPA is completing this assessment so that health measures can be taken to protect workers and the public,” he continued.
The Halogenated Solvents Industry Alliance Inc., which represents companies that make perchloroethylene and other chlorinated solvents, said it is “pleased that EPA has completed the review and removed some of the uncertainties related to evaluating human health exposures to the solvent, and [we] also appreciate EPA's reassurance that wearing clothes dry cleaned with perchloroethylene is not a human health concern.”
A fact sheet EPA issued together with its assessment stressed: “EPA does not believe that wearing clothes cleaned with perc poses a risk of concern.”
John Bell, HSIA science program director, voiced concerns, however, about what he called inconsistencies between the agency's assessments of perchloroethylene and other volatile organic compounds being analyzed by EPA's Office of Water. That office has said it is developing a maximum contaminant level for carcinogenic VOCs that could be 0.05 parts per billion, Bell said. Yet, this review “establishes a negligible human health risk at 20 ppb or higher.”
EPA said it will use its classification decision and the risk values in the assessment to develop drinking water standards for perchloroethylene and other carcinogenic volatile organic compounds.
“Typically, it takes about 2 to 2.5 years to develop a proposed rule and about 2 years to promulgate a final rule,” EPA said.
The assessment also will be used to derive cleanup levels for indoor air contaminated by vapor intrusion, EPA said.
The assessment could provide valuable guidance to cleanup managers who have been remediating homes near superfund sites where perchloroethylene contaminates indoor air due to its presence in groundwater. EPA's superfund program has been basing its vapor intrusion standards on an assessment developed by California's Environmental Protection Agency for vapor intrusion, EPA said in a fact sheet.
California's analysis found perc to be more hazardous than EPA's assessment concluded, EPA said. Where a state, such as California, has a more stringent standard, that will be considered the cleanup goal, EPA's fact sheet said.
Elsewhere, however, vapor intrusion standards will be less stringent, meaning “no additional cleanup will need to be done at any previously cleaned superfund sites,” the fact sheet said, adding there are many reasons why one agency's analysis will differ from another's.
Perchloroethylene is produced commercially for use in dry cleaning, textile processing, and metal-cleaning operations, although its primary use is to make other chemicals, EPA's assessment said.
Perchloroethylene, also known as tetrachloroethylene, has been detected in hundreds of hazardous waste sites, in groundwater, in surface water as well as in air, soil, food, and breast milk,
EPA's assessment of perchloroethylene is available at http://www.epa.gov/iris/toxreviews/0106tr.pdf.
EPA's summary of that document is available at http://www.epa.gov/iris/subst/0106.htm.