EPA must improve its TSCA systematic review method, scientific review says again

Six years have passed since Congress updated the Toxic Substances Control Act (TSCA), yet EPA still does not have an appropriate method for conducting systematic reviews of chemical risks – the method by which EPA evaluates potential health harms – which is critical to protecting the public’s health.

This is the clear conclusion taken from reading the most recent peer review of EPA’s methods, released on July 21, 2022 by EPA’s Science Advisory Committee on Chemicals (SACC). EPA’s failure to establish scientifically defensible systematic review methods for its TSCA risk evaluations means further delays in EPA action to protect the public from toxic chemical exposures. 

Here is the timeline of six years that brought us to this point:

EPA may say it is adopting a systematic review approach, but many aspects of its TSCA method are still inconsistent with established best practices.

Here is what the new SACC peer review report says about some of the key problems previously identified by PRHE.

Need for a pre-published protocol for each chemical risk evaluation

A critical step to conducting a transparent and unbiased review is establishing a pre-published protocol that details the specific methods to be used in conducting the systematic review. EPA created confusion by calling its 2021 draft document a ”systematic review protocol,” when it was actually a generic description of methods to be applied across assessments. EPA did not develop assessment-specific protocols for the 23 ongoing chemical risk evaluations.

The SACC says that “The purpose, objective, and audience of the document should be defined,” “the purpose of the document [is] confusing” and “chemical specific protocols should be developed, and peer reviewed.”

Need to improve study inclusion criteria to include all toxicity findings

A PECO (Population, Exposure, Comparator, Outcome) statement provides criteria that researchers use to decide which studies are relevant to include in a systematic review. EPA’s PECO statements for most of the 23 chemicals under evaluation placed limitations on the types of health effects that would be included by excluding studies demonstrating early biological changes (like reduced thyroid hormone levels or reduced red blood cell counts) that represent health hazards.

The SACC says: “PECO statements appear to inappropriately exclude important toxicity endpoints from the TSCA hazard assessments” and “this document should include a generic PECO statement that includes all possible health outcomes.”

Need for improved approaches to study quality assessment that don’t use scoring

Study quality refers to assessing if a study was conducted to the highest possible standard and is important for understanding the strengths and limitations of a study when synthesizing evidence regarding a chemical. The NASEM previously identified several problems with the 2018 TSCA method’s approach to assessing study quality, in particular objecting to EPA’s use of quantitative scoring for study quality assessment and exclusion from a systematic review of studies deemed to be flawed. These problems with EPA’s approach to study quality assessment continued in its 2021 TSCA method.

The SACC says: “EPA should follow NASEM recommendations and best practices of systematic review by removing its approach to determine an overall quality score,” “The protocol should not use the results of study evaluation as eligibility criteria for the systematic review,” and “As recommended by NASEM…the results of study evaluation should not be used as exclusionary criteria.”

Need to account for funding bias in individual studies

Industry-sponsored studies or authors with a financial conflict of interest (COI) are more likely to have results and conclusions in favor of the sponsor’s product than studies without. This bias must be identified and accounted for when evaluating studies in EPA risk assessments so that evidence is not inappropriately skewed away from identifying hazards.

The SACC says: “The systematic review should assess funding bias for all included studies.”

Why this matters

The most recent TSCA systematic review document has significant problems in its approaches to identifying and evaluating evidence for inclusion in a chemical risk evaluation. Many of these problems have been previously identified – and ways to address those problems have also been identified. The SACC report notes:

Previous recommendations from SACC and NASEM pointed out existing methodologies that could, and should, be used to both improve the basis for the decisions made and to save time and money. These recommendations should be re-reviewed.

EPA must not get this wrong again. The document reviewed by the SACC was EPA’s presentation of methods being used for ongoing risk evaluations of 23 chemicals. The need to fix the methods will undoubtedly add to delays in assessing these chemicals, but continued failure to adopt appropriate methods for TSCA systematic review will further delay regulations to reduce toxic chemical exposures for workers, consumers and vulnerable communities.

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.