EPA May Face New Data Challenge Over Changes To Key Dioxane Study

Posted: August 23, 2010

The Defense Department (DOD) is warning EPA that its just-issued risk assessment of dioxane, a chemical found in industrial solvents and personal care products, is vulnerable to a Data Quality Act (DQA) challenge because EPA completed the assessment without external review of a revised version of a key study the agency relied on.

EPA says changes to the study are "minor" and did not affect the final risk assessment.

But the agency is already facing criticism from industry over a draft version of the risk assessment as well as a growing number of DQA challenges from industry over chemical and other issues since a federal court suggested for the first time that agency decisions under DQA may be judicially reviewable.

At issue is EPA's Integrated Risk Information System (IRIS) assessment for 1,4 dioxane, which regulators will use to set regulatory standards for products containing the chemical and cleanup standards at contaminated waste sites. The assessment, unveiled Aug. 11, labels the chemical as "likely" to cause cancer in humans despite claims from some industry groups that the classification is not justified by available data.

EPA released a draft version of the assessment in May 2009 and the document subsequently went through an external peer review process. After the peer review was complete, results from one of the studies on which the assessment is based -- a study on the effects of 1,4 dioxane in drinking water conducted by the Japan Bioassay Research Center (JBRC) originally reported in 1994 -- was republished in 2009 as a peer-reviewed manuscript in Food & Chemical Toxicology by H. Kano.

In light of the Kano 2009 publication, EPA made what an agency spokeswoman describes as "minor changes" to the risk assessment document that the spokeswoman says "did not significantly affect the qualitative or quantitative cancer assessment for 1,4 dioxane."

But in June 8 comments released alongside EPA's final risk assessment, DOD characterizes the study updates as "major changes in critical data" that were made "after completion of the interagency and external peer reviews." The changes included "the number of animals, the number of animals that had tumors, the doses given to the animals, and changes in both the statistical procedures and . . . calculations," DOD says.

DOD suggests "use of an additional external peer review to preclude a data quality challenge based on the fact that the original panel did not have accurate data at the time of their review." DOD also suggests "that both the data reviewed by the external panel as well as the data on which EPA bases its analysis, be presented in the final report."

Clarifying Changes

In response to DOD's concerns, EPA added text to the final assessment meant to clarify the changes and "clearly state which report . . . was the source for the data discussed," the agency spokeswoman says. The agency also added Appendix E to the document, which provides a side-by-side comparison of the data from the various versions of the JBRC study.

However, the EPA spokeswoman says "[a]dditional peer review was not warranted considering the data reported by [Kano 2009] did not significantly change compared to earlier reports . . . reviewed by the external peer review panel."

The DQA generally requires EPA and other federal agencies to ensure that scientific and other data used to develop policy stances are objective, reproducible and peer-reviewed. The law requires agencies to accept and respond to petitions to correct allegedly flawed data used in rulemakings and other decisions.

Industry efforts to use the authority to challenge agency decisions had been stymied by a 2006 federal appellate ruling in Salt Institute v. Leavitt that DQA petitions are not subject to judicial review. But proponents of the law say a more recent ruling has opened the door to judicial review. The U.S. Court of Appeals for the District of Columbia Circuit May 10 denied a Justice Department petition in Prime Time Int'l Co. v. Vilsack asking the court to clarify that a ruling in the suit did not address whether the DQA creates judicially enforceable rights.

While critics say the D.C. Circuit ruling does not set any new precedent, supporters have already filed a flurry of petitions challenging data EPA relied on in chemical risk assessments of key chemicals like methanol, arsenic and phthalates, as well as climate change, coal ash and other decisions.

The dioxane petition could also be ripe for a data quality challenge given long-standing industry opposition. EPA in the assessment classifies the chemical as a "likely" carcinogen using its 2005 Guidelines for Carcinogenic Risk Assessment, which allows the agency to designate chemicals as either "known" carcinogens, "likely" carcinogens, "suggestive" carcinogens, or as not having enough data to make a determination that the substance is a carcinogen.

But this classification was challenged in July 6 comments filed by the aerospace industry group Alliance for Environmental Responsibility and Openness (AERO), which argued that the "only studies that show 1,4 dioxane causes tumors are very high dose rodent studies."

AERO argued available data shows 1,4 dioxane is not genotoxic or mutagenic, and therefore there is no reason to assume, as EPA did in the draft assessment, that there is a "proportional or linear relationship between health problems experienced in rodents at high doses and those that would be expected to occur in humans exposed to the chemical in more typical environmental circumstances. EPA guidelines suggest it should assess chemicals that may be mutagenic with the more conservative linear modeling.

Non-Linear Model

The industry group advocated that EPA use a non-linear model, such as the physiologically based pharmacokinetic (PBPK) model to assess how the chemical would react in the human body. AERO argued EPA should include more of the data underlying the risk assessment in the assessment document, arguing the current draft "hides" information from regulatory policy makers.

But in its finalized IRIS assessment EPA maintains 1,4 dioxane is "likely to be carcinogenic to humans" based on "inadequate evidence of carcinogenicity in humans" and "sufficient evidence in animals (i.e., hepatic tumors in multiple species [three strains of rats, two strains of mouse, and in guinea pigs]; mesotheliomas of the peritoneum, mammary, and nasal tumors have also been observed in rats following 2 years of oral exposure to 1,4- dioxane)."

The final assessment says the PBPK "models available for 1,4 dioxane were found unsuitable and could not be used for interspcies oral extrapolation."

The final assessment's finding that the chemical is a "likely" human carcinogen is consistent with statements peer review panelists made last year that to consider it only a "suggestive" carcinogen would be likely inappropriate. While some of the panelists said much is still unknown about the chemical and how it causes health problems, classifying a chemical as only a "suggestive" carcinogen is usually only appropriate under EPA's guidelines in situations where only one study has suggested a link between a chemical and cancer, which they noted is not the case with 1,4, dioxane.

AERO representatives could not be reached for comment by press time. -- Douglas P. Guarino

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