EPA’s final risk evaluation of trichloroethylene is scientifically flawed and understates risks to workers, the general public and those most susceptible

Jennifer McPartland, Ph.D., is a Senior Scientist.  Richard Denison, Ph.D.is a Lead Senior Scientist.

Today the Trump Environmental Protection Agency (EPA) issued its final risk evaluation for trichloroethylene (TCE).  It largely tracks the agency’s draft document, retaining numerous flaws that severely understate the highly toxic chemical’s risks to workers, the general public and those most susceptible to its health impacts.

Among the evaluation’s most serious deficiencies is the abandonment of a bedrock principle of chemical risk assessment: that risk estimates be based on the most sensitive health effect.  Sadly, the final document retains the unprotective approach the Trump White House forced EPA to adopt, as reported in detail by Elizabeth Shogren of Reveal News.

Exposure to TCE is ubiquitous, coming from ambient and indoor air, vapor intrusion from contaminated sites, groundwater and drinking water wells, and food – yet EPA’s evaluation ignores or downplays each of these exposure sources and pathways.

Below we summarize some of the major concerns in EPA’s evaluation that we addressed in detail in our comments.

One silver lining:  Despite its glaring deficiencies, the risk evaluation did find that the great majority of TCE’s conditions of use present unreasonable risks—even as it grossly understated the extent of those risks.  As a result, EPA must now proceed to regulate those activities, providing the new Administration an opportunity to rectify the serious problems created by the Trump EPA. 

Failure to protect against the most sensitive endpoint, fetal cardiac malformations:  EPA’s reliance on immune-related endpoints instead of fetal cardiac malformations for its determinations of acute and chronic risk deviates from scientific best practices, defies requirements under the law, ignores longstanding agency policy, and is as much as 500-fold less protective of public health.

EPA now falsely claims that its Science Advisory Committee on Chemicals (SACC) supported this decision (see p. 33 of the final evaluation).  In fact, the SACC was conflicted and did not reach consensus on this question.  The Executive Summary of the SACC peer review report stated (p. 21) that “the Committee was divided on reliance on fetal heart malformations for risk characterization.”  And while some committee members supported EPA’s decision, others did not (p. 94):  “To base unreasonable risks on immunosuppression and not on fetal heart malformations appears to some Committee members (and to some public commenters) to accept less protective concentration levels.”  Unfortunately, the review panel lacked anyone with specific expertise in cardiac development.

Exclusion of known uses and exposures:  EPA has again abdicated its responsibility under TSCA to identify and evaluate the risks the chemical presents to the general population as well as communities near industrial sites and other contamination sources.  It did so by excluding from its risk evaluation conditions of use and exposures that are known or reasonably foreseen, including exposures from releases of TCE to air, water, and land – amounting to nearly 3 million pounds annually.  EPA has also failed to consider exposure to background levels of TCE.

Underestimation of occupational risks:  EPA continues to severely underestimate occupational risks in several major ways: its unsupported assumptions regarding worker use of personal protective equipment in many scenarios; its use of a overly lax cancer risk level for workers that fails to protect them as a vulnerable subpopulation as required by TSCA; and its failure to consider combined exposures of workers from multiple sources.


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