When reviewing long, technical EPA science documents it helps to have an idea of what to look for. If you begin on page 1 and read everything in order, you may never get to some of the most critical content. The buried details can ultimately determine whether EPA’s actions will protect people’s health or leave us exposed.
In the case of EPA’s recent Draft Toxic Substances Control Act (TSCA) Systematic Review Protocol, some of the most important aspects of EPA’s approach to conducting chemical risk evaluations are not presented until Appendix H.5, beginning on page 345.
Appendix H.5 presents EPA’s PECO statements for assessing the hazards of 23 industrial chemicals. A PECO statement – which is short for “population, exposure, comparator, and outcome” – lays out the rules for deciding which studies are relevant (and thus included in the assessment) and which studies are not relevant (and thus excluded).
A well-crafted PECO statement is a critical foundation for conducting a good systematic review as it determines what studies will be evaluated. EPA has appropriately developed individual PECO statements for each of its ongoing risk evaluations. Unfortunately, these PECO statements do not provide a clear, consistent, reasonable, or appropriate basis for determining which studies to include. As we discuss in detail in our comments, EPA’s approach is likely to result in exclusion of critical health effects studies, which ultimately leads to underestimating the risks to human health from industrial chemical exposures.
EPA’s PECO statements appear to inappropriately exclude important toxicity endpoints from the TSCA risk evaluations
All health outcomes should be included in EPA’s PECO statements. In some instances, EPA appropriately includes studies of “all health outcomes” and “all biological effects.” However, for 20 out of 23 chemicals currently undergoing risk evaluation, the inclusion criteria are narrowed to “All apical biological effects (effects measured at the organ level or higher).” This means health effects that are observable, such as birth defects and cancer. Hidden in this technical language is a critical decision – EPA appears to be excluding important health studies reporting biological changes observed at the cellular level that are also reflective of health hazards and have been used in previous EPA assessments. Examples of outcomes that may be excluded by these new TSCA criteria include reduced thyroid hormone levels, reduced red blood cell counts, reduced immune system function, and reduced sperm quality. If EPA does not consider evidence of these more sensitive measures of toxicity, its risk evaluations will underestimate the risk to human health.
EPA’s approach also excludes consideration of the most current scientific approaches to identifying chemical hazards. Considering only apical outcomes will substantially bias the evidence base of TSCA risk evaluations toward insensitive industry-funded guidelines studies and away from non-industry studies. Industry-sponsored research is more likely to produce results that are favorable to industry.
EPA disregarded the National Academies’ warning to avoid changing PECO statements after starting a systematic review
For 21 out of 23 ongoing risk evaluations, EPA presents one PECO statement for the initial stage of screening studies for inclusion or exclusion, and a different PECO statement for the more detailed review.
Changing PECO statements while a review is in progress disregards the previous criticisms of the TSCA systematic review method by the National Academies of Science, Engineering, and Medicine, which observed that “In the TSCA evaluation process, eligibility criteria are not predefined in the protocols and shift during the systematic review process” and recommended “Eligibility criteria need to be based on PECO statements that are formulated in a standard way and need to be predefined in the protocol…to prevent a systematic exclusion of outcomes that could bias the results.”
Changing the PECO mid-stream can also result in inappropriate study exclusions, as whether an important study is included or excluded in the systematic review can depend on which version of the PECO criteria is applied.
There are unexplained inconsistencies across EPA’s PECO statements for different chemicals
A consistent approach should be applied to all of EPA’s TSCA risk evaluation PECO statements and differences should be found only to account for chemical-specific considerations.
However, there are numerous unexplained differences in the PECO statements for the 23 ongoing TSCA risk evaluations. For example, two organophosphate flame retardants, TCEP and TPP, are chemically similar and have similar uses. However, the PECOs for these chemicals differ regarding inclusion of studies with biomonitoring measures of exposure, cellular-level outcomes, and studies of chemical mixtures. Different rules are therefore being applied to the risk evaluations for these two similar chemicals, without any explanation.
PRHE recommendations for improved PECO statements
- EPA should include studies of cellular-level changes and other sensitive outcomes as relevant, instead of using only studies with apical outcomes.
- EPA should apply a single PECO statement throughout each risk evaluation, with consistent approaches to PECO statements across all ongoing TSCA risk evaluations.
Without these changes, EPA’s PECO statements could result in TSCA risk evaluations that exclude critical scientific evidence, leading to EPA decisions that will fail to protect public health from hazardous industrial chemicals.
About the author
Daniel Axelrad worked at the U.S. Environmental Protection Agency for 33 years in the Office of Pollution Prevention and Toxics (1987-1993) and the Office of Policy (1993-2020). His areas of expertise include science policy, children’s environmental health, benefit-cost analysis and risk assessment. He has a bachelor’s degree in economics from Occidental College and a master’s in public policy from Harvard University.
