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By Pat Rizzuto
The Environmental Protection Agency released a final human health assessment for trichloroethylene Sept. 28 that for the first time classifies the widely used solvent as “carcinogenic to humans” by all routes of exposure.
The Integrated Risk Information System (IRIS) assessment, which had not been updated since 1989, also concludes trichloroethylene can harm the central nervous system, kidneys, the liver, the male reproductive system, the immune system, and the developing fetus, Paul Anastas, assistant EPA administrator for research and development, told reporters during a briefing.
Lenny Siegel, executive director of the California-based nonprofit group called the Center for Public Environmental Oversight, said the new assessment “will lead directly to more protective exposure standards for vapor intrusion, and it is also likely to cause the re-evaluation and possibly lowering of the drinking water standard for TCE, often used as a remedial action objective for groundwater cleanup.”
State officials, attorneys, environmental consultants, environmental health advocates, and other interested parties BNA has interviewed since mid-September agreed with Siegel that vapor intrusion sites, superfund and brownfields cleanups, and drinking water limits could be tightened due to the final IRIS assessment.
Anastas did not describe specific regulations that would be affected by the final IRIS document. The reason is IRIS assessments are scientific analyses, not regulatory documents. “Our offices of water, air, and solid waste all have interest,” he said.
EPA's central conclusions about carcinogenicity and other health problems TCE can cause have not changed much since 2001, when the agency issued a draft update, but the depth and strength of that scientific evidence supporting them is now much stronger, Anastas said.
The document should spur the development and evaluation of more alternative solvents, Anastas said.
“The most important information within a scientific assessment of a chemical's hazard is not just that it is hazardous but what it is about that chemical that makes it hazardous. That gives insights into the design of the next generation of substances,” said Anastas, who is known as the father of green chemistry.
Joel Tickner, an associate professor of community health at the Lowell Center for Sustainable Production, University of Massachusetts at Lowell, agreed. His university has worked with Massachusetts companies seeking substitutes for TCE.
“Most companies do not want to use TCE if they don't have to” due to paperwork triggered by its use and potential liability, Tickner said.
He said he hopes EPA's Design for the Environment Program will launch a partnership to evaluate TCE alternatives in the wake of the IRIS assessment.
After the release of EPA's 2001 draft IRIS assessment of TCE, the Air Force estimated that cleanup costs for its facilities could increase by $5 billion if the assessment caused EPA to reduce its current Maximum Contaminant Level from five parts per billion (ppb) to one part ppb, Siegel said. The one ppb level was an estimate of what might be issued, he said.
“I'm not convinced there would be that much difference,” Siegel said. “A change in the [risk] number would not necessarily mean a change in the remediation objective.”
Technical issues often limit the extent of groundwater cleanup that is feasible, however, Siegel said. So if it is not possible to meet the one ppb level, a site cannot be required to meet that standard, he said.
Prior to its release, Bill Morris, a vapor intrusion specialist with Vapor Mitigation Sciences and formerly a vapor intrusion expert at the Kansas Department of Health and Environment, weighed in on the assessment's possible impact on vapor intrusion standards.
The impact will vary by state and by site, Morris said.
About 25 states have vapor intrusion guidance, and these include divergent acceptable risk standards.
Those acceptable risk standards may be more important drivers of regulations than EPA's risk values, he said.
For example, New Jersey does not want a contaminant to pose more than a one in 1 million chance of causing cancer, while Kansas accepts a cancer risk of one in 100,000, Morris said. That means Kansas could allow 10 times more contamination than New Jersey, he added.
The impact of EPA's assessment will also depend on the age of the population that could be exposed to TCE, Morris and Siegel agreed.
In some cases, concerns for children's development—the non-carcinogenic health consequences of TCE—could drive a demand for mitigation, for example at schools, Morris and Siegel said.
In other cases, the information about TCE's carcinogenicity will be critical, they said.
EPA's final assessment concludes that TCE is a mutagenic carcinogen. That means risk assessors will have to take into account that early life exposures to the solvent could increase the risk of eventual cancer.
DoD said it does not expect an immediate impact from EPA's IRIS assessment.
The assessment “may or may not lead to eventual changes in cleanup standards or drinking water Maximum Contaminant Levels,” the department said in a statement to BNA. “Such changes, if any, would likely take years to develop and finalize.”
Also, “even if cleanup levels were eventually revised that does not mean that every DoD site will be affected. It depends on site-specific conditions,” the department's statement said.
While EPA has been working on its IRIS assessment, TCE reduction efforts have been underway throughout the department, DoD said. “The Army reduced releases of TCE from 214,223 pounds in 1994 to 62,495 pounds by 2008.”
John Bell, director of scientific programs at the Halogenated Solvents Industry Alliance, which represents manufacturers of TCE and other solvents, said his trade association is disappointed with and does not agree with EPA's cancer classification of the chemical. The association raised objections during an agency peer review of the document (122 DEN A-5, 6/28/10).
EPA's classification of TCE is consistent with the World Health Organization's classification of TCE as a probable human carcinogen and the U.S. National Toxicology Program's listing of it as “reasonably anticipated” to cause human cancer.
William Farland, who directed the EPA office that oversaw IRIS assessments while draft iterations of the document were being prepared, said the TCE assessment was among those that broke scientific ground when it first came out and helped elevate the scientific rigor among federal agencies' analyses of these documents.
These discussions have influenced the way EPA presents its conclusions and extended the time it takes to complete them, but the science that has evolved while the discussions that ensued have generally supported EPA's highest level of concerns, Farland told BNA prior to the TCE assessment's release. Farland is now the vice president for research at Colorado State University.
EPA's Toxicological Review of Trichloroethylene and related documents are available at http://www.epa.gov/iris/subst/0199.htm .
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