Charting a Path Forward: Assessing the Science of Chemical Risk Evaluations under the Toxic Substances Control Act in the Context of Recent National Academies Recommendations

BACKGROUND: In 2016, Congress enacted the Frank R. Lautenberg Chemical Safety for the 21st Century Act (the Lautenberg Act), which made major revisions to the main U.S. chemical safety law, the 1976 Toxic Substances Control Act (TSCA). Among other reforms, the Lautenberg Act mandates that the U.S. Environmental Protection Agency (U.S. EPA) conduct comprehensive risk evaluations of chemicals in commerce. The U.S. EPA recently finalized the first set of such chemical risk evaluations. OBJECTIVES: We examine the first 10 TSCA risk evaluations in relation to risk science recommendations from the National Academies to determine consistency with these recommendations and to identify opportunities to improve future TSCA risk evaluations by further implementing these key approaches and methods. DISCUSSION: Our review of the first set of TSCA risk evaluations identified substantial deviations from best practices in risk assessment, including overly narrow problem formulations and scopes; insufficient characterization of uncertainty in the evidence; inadequate consideration of population variability; lack of consideration of background exposures. combined exposures, and cumulative risk; divergent approaches to dose-response assessment for carcinogens and noncarcinogens; and a flawed approach to systematic review. We believe these deviations result in underestimation of population exposures and health risks. We are hopeful that the agency can use these insights and have provided suggestions to produce chemical risk evaluations aligned with the intent and requirements of the Lautenberg Act and the best available science to better protect health and the environment-including the health of those most vulnerable to chemical exposures.

Automated summary

The first set of TSCA risk evaluations showed significant deviations from the recommendations of the National Academies, including narrow problem scopes, inadequate characterization of uncertainty, insufficient consideration of population variability, and lack of consideration for background exposures and cumulative risk. These deviations result in underestimation of population exposures and health risks.