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 |