Today, the U.S. Environmental Protection Agency (EPA) released for public comment and peer review a set of principles for evaluating cumulative risks under the Toxic Substances Control Act (TSCA) and an approach for applying those principles to the evaluation of the cumulative risk posed by certain phthalate chemicals undergoing TSCA section 6 risk evaluation. This is an important step in the process of EPA developing the capability under TSCA to examine risk to people from exposure to multiple chemicals with similar effects.
Until now, EPA has generally approached TSCA risk assessments by looking at the risk posed by a single chemical. However, in many cases people are exposed to multiple chemicals with similar effects 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. This cumulative risk assessment approach can help more appropriately evaluate risks people face and may be helpful in more effectively mitigating the identified unreasonable risks. Evaluating cumulative chemical risks may also provide particularly useful information for communities that are overburdened by chemical pollution. Ultimately, cumulative risk assessment will help EPA better understand and address risks from chemicals as required by the law.
Chemicals such as some of the phthalates have particularly similar effects on human health and have been found in the human body at the same time. 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. Today’s principles and approach documents are the first steps towards EPA conducting a cumulative risk assessment under TSCA.
“Workers, consumers and communities don’t just face risks from a single chemical,” said Assistant Administrator for the Office of Chemical Safety and Pollution Prevention Michal Freedhoff. “If we can develop the scientific tools to allow us to consider the risks people are facing from multiple chemicals at once, we will be able to more effectively protect them from those risks.”
Principles of Cumulative Risk Assessment
EPA’s “Draft Proposed Principles of Cumulative Risk Assessment Under the Toxic Substances Control Act” discusses what cumulative risk assessment is and how it could be used in the scientific and regulatory context of TSCA. A cumulative risk assessment will not always be the best approach, or possible to complete in the statutory timeframes provided for TSCA risk evaluations. But when 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.
Cumulative Risk Assessment of Phthalates
Phthalates are a group of chemicals used in many industrial and consumer products, including polyvinyl chloride (PVC) products, to make plastics more flexible and durable. Because of their widespread use in industrial and consumer products, people can be exposed to many phthalates. Phthalates have been found in food and have also been measured in human blood samples. Numerous laboratory animal studies have demonstrated that prenatal phthalate exposure can impact male development and reproduction, in a phenomenon known as “phthalate syndrome.”
EPA is currently conducting risk evaluations for five phthalates designated as high-priority substances under TSCA, including di-ethylhexyl phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), di-isobutyl phthalate (DIBP), and dicyclohexyl phthalate (DCHP), and two phthalates subject to manufacturer-requested risk evaluation, including di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP).
In the “Draft Proposed Approach for Cumulative Risk Assessment of High-Priority Phthalates and a Manufacturer Requested Phthalate Under the Toxic Substances Control Act,” EPA proposes a methodology for evaluating cumulative risk for the phthalate chemicals currently under review.
EPA proposes in its approach submitted for public comment and peer review that DEHP, BBP, DBP, DIBP, DCHP and DINP (but not DIDP) are toxicologically similar (and pose an additive hazard) and that the U.S. population is co-exposed to these phthalates. Therefore, EPA is proposing to group these phthalates for cumulative risk assessment under TSCA as described in the “Draft Proposed Approach” document.
This proposed approach is not itself a cumulative risk assessment nor does it make a finding of risk, but rather is a methodology that EPA proposes to use and seeks public input about and peer review on. Additionally, since risk estimates have not yet been developed for the individual chemicals, EPA cannot predetermine the results of that work in this cumulative risk assessment approach. The cumulative risk assessment for phthalates and individual risk evaluations are being conducted in parallel, and those risk evaluations will undergo their own public comment and peer review, as appropriate. By releasing this approach for public comment and peer review now, EPA is assuring that the methods used to conduct the cumulative risk assessment will be based on the best available science. The results of the phthalate cumulative risk assessment may help inform EPA’s individual phthalate risk evaluations and ultimately the unreasonable risk determinations.
EPA will hold a public virtual meeting of the SACC on May 8-11, 2023, to peer review the cumulative risk assessment principles and framework. This review will ensure that the approach incorporates independent scientific advice and recommendations, and that EPA follows a transparent process. Information on registering to attend the public virtual meeting will be available in April 2023 on the SACC website.
Upon publication of the Federal Register notice, written comments on the documents undergoing peer review will be accepted for 60 days through www.regulations.gov (Docket No. EPA-HQ-OPPT-2022-0918).
Original source can be found here.
