March 2, 2023

EPA Proposes Principles, Approach for Cumulative Risk Assessment

EPA on Friday published a set of principles for evaluating cumulative risks under the Toxic Substances Control Act (TSCA), a move the agency characterizes as a step toward “developing [its] capability under TSCA to examine risk to people from exposure to multiple chemicals with similar effects.” EPA outlines its approach for applying these new principles in an accompanying draft proposal for the cumulative risk assessment of certain phthalate chemicals undergoing risk evaluation related to TSCA section 6, which provides EPA with authorities for addressing risks from chemical substances. According to the agency, phthalates are used in many industrial and consumer products and are concerning to EPA due to their toxicity and the potential for high exposure to these chemicals from their widespread use.

EPA has previously approached TSCA risk assessments by evaluating the risk posed by single chemical substances under their conditions of use. The agency’s recent proposal recognizes that people are often exposed to multiple chemicals that have similar effects on human health at the same time.

“In some of these cases, EPA believes that the best approach to evaluate risk to human health may be to look at the combined risk to health from these chemicals,” an agency press release explains. “[W]hen chemicals are sufficiently similar toxicologically and are found to present co-exposures—meaning people are at exposed to multiple chemicals at the same time—a cumulative risk assessment may be appropriate.”

EPA proposes in its approach to group the substances di-ethylhexyl phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), di-isobutyl phthalate (DIBP), dicyclohexyl phthalate (DCHP), and di-isononyl phthalate (DINP) together for cumulative risk assessment under TSCA because they are toxicologically similar and the U.S. population is co-exposed to them.

Both the proposed cumulative risk assessment principles and EPA’s proposed phthalate approach are available for public comment. A public virtual meeting of the Science Advisory Committee on Chemicals, a federal advisory committee charged with providing scientific advice, information, and recommendations to EPA on chemicals regulated under TSCA legislation, will be held May 8–11, 2023, to peer review these proposals.

Further details on EPA’s proposals regarding cumulative risk assessment can be found in the agency’s press release, and the draft documents are available for download from the EPA website.

Related: An article published in the May 2017 issue of The Synergist focuses on addressing cumulative risk in the occupational environment.