Science Advisors Reject EPA’s Analysis of TCE Cardiac Study
There was big news last month that should affect how the government
regulates the industrial solvent trichloroethylene (TCE), including how it
conducts clean-ups at Superfund sites.
Members of a key Environmental Protection Agency (EPA)
science advisory panel rejected the Agency’s analysis of a controversial study suggesting
a link between exposure to TCE and fetal cardiac effects in laboratory animals.
The panel’s consensus on the cardiac issue represents a significant
departure from EPA’s approach, as previous EPA assessments of TCE have leaned
heavily on the cardiac study. The clear conclusion to be drawn from the Committee’s
rejection is that the Agency’s assessment of the non-cancer risks of TCE should
no longer be based on the single cardiac study.
The discussion of health effects of TCE occurred during a
virtual public meeting of the Toxic Substances Control Act (TSCA) Science
Advisory Committee on Chemicals (SACC). The meeting was held on March 24-27,
2020, to review EPA’s draft risk evaluation for TCE, which is one of the first
ten chemicals to be evaluated by EPA under amendments to TSCA passed in 2016.
Under the amended law, EPA is required to conduct a risk
evaluation of the conditions of use of chemicals in commerce to determine
whether risk management regulations are required. TSCA risk evaluations must be
consistent with the requirements in TSCA to use and base decisions on the best
available science and the weight of scientific evidence. The SACC, composed of
scientists from academia, government, industry, and environmental groups, is
charged with reviewing EPA’s draft risk evaluations and providing
recommendations for improvements.
Previous EPA assessments of TCE in 2011 and 2014 cited a controversial
2003 study by University of Arizona researchers that reported cardiac birth
defects in offspring of rats exposed to TCE. An early draft of the current TSCA
evaluation continued the emphasis on this study, but in a subsequent draft
released earlier this year, the agency shifted its focus away from cardiac
birth defects and toward prioritizing immunosuppression risks.
SACC member concerns about the Arizona study echoed those
from other scientific reviews, including those conducted by the National
Academy of Sciences and California’s Office of Environmental Health Hazard
Assessment, as well as industry scientists.
During the March peer review meeting, SACC members agreed
that the Arizona study was too flawed to form the basis of an agency review. SACC
member James Bruckner (University of Georgia) stated that the study has
multiple problems. He argued that the way in which it was conducted was faulty,
specifically describing it as a combination of experiments conducted years
apart and then combined to reach the fetal cardiac risk conclusion.
Another SACC member, Charles Vorhees (University of Cincinnati),
called the study “the strangest experimental design I’ve ever seen. If someone
brought me that … I’d say it’s an improper design.” SACC panelist Kathleen
Gilbert (University of Arkansas – retired), who had expressed some concern about
developmental effects of TCE, concluded that use of the Arizona study for EPA’s
risk evaluation was not appropriate.
The SACC is expected to develop a report on the draft TCE
evaluation, including the recommendation not to use the Arizona study in its
risk calculations, for submission to EPA in late May. The agency will then take
those recommendations and finalize its risk evaluation, although a timetable
for that step is still up in the air.
ACC’s Steve Risotto noted that the SACC recommendation should
impact other aspects of EPA policy on TCE. In particular, he noted that EPA’s
dependence on the cardiac studies has caused significant disruption of remediation
efforts at federal and state contaminated sites. “EPA’s use of the flawed
cardiac data has resulted in the reopening of completed remediation sites, relocation
of residents and workers, and unnecessary expense and effort,” Risotto said.
“We are heartened that the TSCA peer review process has focused
EPA on sound science for its 2020 evaluation of TCE,” he said. “We look forward
to reviewing the SACC report and the revision of EPA’s TCE evaluation to include
the best available science and consideration of the weight of evidence as
required by the statute.”
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