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February 24, 2005
EPA Science Advisers Suggest Greater Cancer Potency Of C-8
EPA science advisers are recommending that the agency consider elevating its cancer-causing classification of the controversial chemical C-8 and do a more thorough review of the substance, which is used to make numerous consumer products.
The recommendations were made at a Feb. 22-23 meeting of the Science Advisory Board (SAB), which is reviewing a draft EPA risk assessment of perfluorooctanoic acid (PFOA), also known as C-8. EPA in its draft review has tagged the compound as a “suggestive” carcinogen, but SAB members said evidence may indicate the chemical is a “likely” cancinogen, if certain questions are answered.
PFOA is produced by DuPont which is the subject of an EPA enforcement action alleging the company violated toxics and waste reporting laws. In addition, DuPont's handling of the compound is the focus of a class-action lawsuit filed by residents near the company's West Virginia manufacturing plant.
The chemical is used in making nonstick cookware, clothing and carpets and has raised concerns at EPA and among environmentalists because it is persistent and has been found in blood samples across the general population.
EPA's draft risk assessment focuses on developmental toxicity in women and generally dismisses cancer concerns by concluding that there is only “suggestive” evidence that the chemical is carcinogenic. But the agency's science advisers are saying PFOA poses greater cancer threats than EPA estimated, and are warning the agency not to dismiss cancer findings in studies on test animals in its final risk review.
Specifically, the SAB panel in an upcoming report will recommend that EPA examine a broader range of cancers -- including mammary, pancreatic and testicular tumors -- in conducting a more comprehensive review of the chemical.
A draft panel statement considered at the meeting says “the data are stronger than the examples listed under the descriptor 'suggestive evidence of carcinogenic potential',” as outlined by EPA guidelines.
While the panel expressed discomfort with one aspect of elevating the chemical's cancer-causing classification to “likely,” most agreed the data on PFOA are more consistent with this category than the “suggestive” descriptor EPA is proposing. SAB panelists said they had reservations about saying the existing PFOA data supported the finding that the chemical is “more likely than not” to cause cancer in humans, which is part of the definition of the “likely” category outlined by the agency's cancer guidelines.
“We should say we don't know what the likelihood is,” but that cancer potency should be taken more seriously by EPA, according to Ron Melnick of the National Institute of Environmental Health Sciences.
The descriptor used for cancer classifications is a key part of any risk evaluation because it can trigger a host of state and federal regulatory requirements.
But other SAB panelists warned that upgrading the cancer classification would trigger overly protective approaches that may not be appropriate in this case. Mel Andersen of the CIIT Center of Health Research encouraged the panel to recommend that EPA explore a number of risk approaches to PFOA in addition to the “linear” model, which typically results in strict environmental regulations and cleanup standards for chemicals classified as “likely” or “known” human carcinogens.
DuPont said in a statement that the company “continues to support the U.S. Environmental Protection Agency's risk assessment process on PFOA,” but declined to comment on the SAB's deliberations.
According to an Environmental Working Group (EWG) representative, “we believe EPA will now do an adequate cancer assessment after they dismissed these cancer endpoints for a variety of reasons in the draft.” EWG had advocated that a much broader range of cancer endpoints be considered in public comments before the SAB.