EPA recently issued Proposed Revisions to the Risk Evaluation Framework Rule, which was originally issued in 2017 and established guidelines to govern how EPA conducts risk evaluations under the Toxic Substances Control Act (TSCA). The Proposed Revisions provide critical updates to the original framework rule, that we applaud, but the Revisions fall short in several areas, which could result in TSCA risk evaluations that fail to capture real-world chemical exposures and risks, leading to weak chemical regulation leaving people and communities at risk.
EPA failed to propose adequate guidelines for several critical elements of chemical risk assessment, including:
- A comprehensive and robust statement of systematic review principles;
- A comprehensive definition of potentially exposed or susceptible subpopulations (PESS);
- A requirement to consider aggregate exposures and cumulative risk in each risk evaluation;
- A requirement to quantify the risk of non-cancer health effects at chemical exposure levels commonly experienced by workers, consumers, and susceptible subpopulations.
Collectively, these omissions perpetuate a system of examining single chemical exposures in a manner that is not reflective of the real exposures and risks.
Why this matters
We are exposed to dozens of chemicals and non-chemical stressors every day – some that may have compound health consequences that are not captured when studied or evaluated individually. This is because chemicals interact and can amplify the negative effects of one another. There is also growing evidence that psychosocial stressors impact many of the same bodily systems as chemical stressors. This means that some non-chemical stressors, such as experiencing psychosocial stress from living in poverty, may magnify the adverse effects chemical exposures have on the cardiovascular, neurological, endocrine, immune, and other biological systems.
It is important that EPA’s chemical risk evaluations quantify “real world” risks and to do that, they must rely on unbiased and robust scientific evidence.
Systematic review’s critical role
The Proposed Revisions weaken provisions regarding systematic review, adding to EPA’s history of flawed TSCA systematic review methods that jeopardize its ability to ensure that all relevant evidence is identified and used in conducting a risk evaluation.
Systematic review is essential to making risk-based decisions to protect human health and is a consistent approach with National Academies of Sciences recommendations. Rigorous systematic review methods require:
- publishing a protocol before beginning the systematic review.
- including all relevant studies, and
- assessing study quality and funding bias.
Failure to adhere to these methods may leave out valuable studies and underestimate or miscalculate the weight of scientific evidence.
Importance of cumulative risk assessment
Cumulative risk assessment (CRA) is currently the best approach to estimate how human health may be impacted by these multiple stressors in combination. More than 20 years ago, EPA defined CRA as “the analysis, characterization, and possible quantification of the combined risks to health or the environment posed by multiple agents or stressors” and established guidance for assessing risks from exposures to mixtures of chemicals.
Despite EPA’s established guidance for conducting CRA, the Proposed Revisions fail to make any commitment to conducting CRA in TSCA risk evaluations. Non-chemical stressors are also encompassed in EPA’s CRA definition, but they are not defined in the Proposed Revisions and have rarely been included in TSCA risk evaluations to date.
EPA’s failure to require CRA will result in TSCA risk evaluations that underestimate the true adverse health effects that toxic chemical exposures have on populations experiencing high levels of chemical exposures or greater susceptibility to harm from those exposures, which can arise from intrinsic factors like pre-existing disease or age, and extrinsic factors like poverty or racism.
EPA can fix these problems
The good news is that EPA included consideration of all uses and exposure pathways for each chemical assessed, identification of potentially exposed or susceptible subpopulations, and consideration of aggregate exposures. Those are all steps in the right direction to protect people and communities.
Despite these improvements, EPA missed a critical opportunity to propose improved methods that account for real-world chemical exposures and adhere to the best available science. EPA can fix these problems when it issues the final rule, expected in April 2024. By examining the aggregate effects of multiple exposures, incorporating CRA methods, and following rigorous systematic review methods in its risk evaluations, EPA can improve regulatory decision-making and offer stronger health protections for those disproportionately impacted by chemical exposures.
Read PRHE’s public comments on the revisions to EPA’s Risk Evaluation Framework Rule here.
About the authors
Olivia Stoddard is an MPH student at the University of California, Berkeley, and is an intern for the Science, Policy, and Engagement team at PRHE.
Rashmi Joglekar, PhD is the Associate Director of Science, Policy, and Engagement at PRHE. She has a wealth of knowledge and understanding of how toxic chemicals impact susceptible populations and communities and is skilled in addressing these issues with decision-makers in Washington, DC. Rashmi completed her doctorate in the Integrated Toxicology and Environmental Health Program at Duke University, specializing in neurodevelopmental toxicology.
