Cumulative Risk Assessment Under the Toxic Substances Control Act
In May 2023, EPA held a virtual public meeting of the Science Advisory Committee on Chemicals (SACC) to peer review a set of principles for evaluating cumulative risks under the Toxic Substances Control Act (TSCA) and a proposed approach for applying those principles to the evaluation of the cumulative risk posed by certain phthalate chemicals undergoing TSCA section 6 risk evaluation. EPA had released these draft principles for public comment in February 2023.
Draft Proposed Principles of Cumulative Risk Assessment Under the Toxic Substances Control Act (pdf)
Previously, EPA has approached TSCA section 6 risk evaluations by looking at the risk posed by a single chemical substance under the conditions of use. However, chemicals such as some of the phthalates have similar effects on human health and have been found in the human body at the same time. For these chemicals, EPA believes that the best approach to evaluate risk to human health may be to look at the combined risk to health from multiple chemicals with similar effects simultaneously. Public comments received by the agency, other federal and international regulatory agencies and authoritative bodies support a cumulative approach to assessing the risks of phthalate chemicals.
Following the May 2023 SACC meeting, EPA incorporated feedback from the SACC and public comments into its proposed principles, which provide details on the implementation of cumulative risk assessment approaches within individual chemical risk evaluations.
Cumulative Risk Assessment for Phthalates
EPA used its cumulative risk assessment principles to inform its draft technical support document for cumulative risk analysis for di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), diisobutyl phthalate (DIBP), dicyclohexyl phthalate (DCHP), and diisononyl phthalate (DINP) under TSCA.
EPA also used the cumulative risk assessment principles to inform its individual chemical risk assessments for DEHP, DBP, BBP, DIBP, and DCHP.
- View the draft risk evaluation for DEHP.
- View the draft risk evaluation for DBP.
- View the draft risk evaluation for BBP.
- View the draft risk evaluation for DIBP.
- View the draft risk evaluation for DCHP.
On August 4-8, 2025, EPA held a SACC meeting to review the draft cumulative risk analysis for DEHP, DBP, BBP, DIBP, DCHP, and DINP, as well as the draft risk evaluations for DEHP, DBP, and DCHP. Although the SACC did not review the draft risk evaluations for BBP or DIBP, it reviewed several technical support documents that support the draft risk evaluations for these two chemicals. EPA will consider the SACC recommendations from this peer review when finalizing the risk evaluations and unreasonable risk determinations for BBP and DIBP. Therefore, EPA does not expect the need for an additional peer review of the risk evaluations for BBP or DIBP.
EPA released the final risk evaluation for DINP in January 2025.
Learn more about risk evaluations for existing chemicals under TSCA.