The 2016 Toxic Substances Control Act (TSCA) amendments require EPA to establish a more standardized and efficient process to: prioritize existing chemicals for risk evaluations; conduct those evaluations; and take regulatory actions to manage or control chemicals that are found to present an “unreasonable risk.”
EPA has recently put out a call for nomination of experts to serve as ad hoc members of the TSCA Science Advisory Committee on Chemicals (SACC). The SACC will be tasked with the review of an updated TSCA systematic review protocol that EPA is expected to release soon. It is critical that this updated approach to systematic review address important considerations for the application of systematic review methods to risk assessment such as evaluation of study quality, relevance, and reliability of different types of studies (epidemiology, in vivo toxicology, in vitro toxicology and mechanistic studies); and integration of data and information. These improvements in systematic review procedures are essential for the Agency to meet TSCA’s science provisions.
Importantly, EPA’s systematic review polices, practices and procedures must use objective scientific information, transparent methods that meet the “weight of the scientific evidence” and “best available science” standards required in the 2016 amendments to TSCA. This should include applying a scientifically-solid framework for integrating study results based on the weight of scientific evidence to establish cause and effect and incorporating modern knowledge of mode of action (MOA) to determine if any unreasonable risks exists.
EPA finalized its TSCA risk evaluation procedures in 2017 and began drafting the first 10 risk evaluations later that same year. In 2018, EPA also developed a supplementary “systematic review” guidance document to meet the new science requirements of the law that described, in general terms, how EPA would identify, evaluate, and integrate scientific evidence from the health and safety studies that form the basis of the risk evaluations.1 Systematic review can be a powerful tool to provide transparency into the methods EPA uses for study evaluation and evidence integration. It also helps ensure that EPA meets the scientific standards of TSCA.
The National Academies of Sciences, Engineering, and Medicine reviewed EPA's 2018 TSCA systematic review guidance document and found that EPA’s approach needed significant improvement. In ACC’s review of the first 10 risk evaluations that EPA finalized in 2020 and 2021, we have concluded that in some cases the agency gave inappropriate consideration and weight to studies of inferior data quality and/or questionable relevance in its risk evaluations. The 2018 TSCA guidance document also does not provide details on how the agency integrates the data to develop the required weight of evidence conclusions, which is critical when considering different types of evidence such as mechanistic information, studies in laboratory animals, and studies of the health-related states and events in humans. The systematic review approaches that EPA has implemented to date in TSCA lack appropriate consideration of study quality, relevance, and integration of data and information. These critical shortcomings have led to TSCA risk evaluations of questionable scientific quality that, in some cases, fall well short of meeting the scientific standards prescribed in the 2016 law.
The result: most of EPA’s final TSCA risk evaluations to date have overestimated the risks of these chemicals under their conditions of use. In practical terms, this means that EPA’s unreasonable risk determinations will likely trigger more onerous regulatory actions than are actually warranted by a full and objective consideration of the science. Failure of EPA to use best available science and objective weight of the scientific evidence integration procedures when evaluating studies for use in the risk evaluations can lead to undue concerns for health effects and may trigger costly and unjustified regulatory measures.
Congress required EPA to use “best available science” and objective “weight of scientific evidence” integration procedures in its evaluations of the studies that form the basis of TSCA risk evaluations. It’s past time for EPA to implement these modern scientific policies, practices and procedures in its analysis and decision-making under TSCA. Improving the technical quality of EPA’s TSCA systematic review approach, particularly by ensuring transparency in what science is being considered, how it is being interpreted, and how it is integrated within risk evaluation, EPA can ensure that risks are objectively, consistently and appropriately evaluated.
1These studies address the inherent “hazards” of the chemical and the relevant “exposures” to the chemical under its conditions of use (i.e., circumstances of manufacturing, processing, distribution, use or disposal).
