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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 historic 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. The SACC, composed of scientists from academia, government, industry, and environmental groups, is charged with reviewing EPA’s draft risk evaluations to ensure that they are based on the best available science and the weight of the scientific evidence as required by the statute. 

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 and that EPA’s estimate of non-cancer risks should be based on other health effects.  (Although the Draft Risk Evaluation does not use the cardiac data as a basis of its risk determination, it does provide detailed analysis of the cardiac risks that the SACC has recommended be removed.)

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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