On September 26, 2024, the U.S. Environmental Protection Agency (EPA) released the final risk evaluation for Tris(2-chloroethyl) phosphate (TCEP), a flame retardant and plasticizer. 89 Fed. Reg. 78868. EPA states that it determined that TCEP poses an unreasonable risk of injury to human health and the environment. According to EPA’s September 23, 2024, press release, TCEP “has the potential to cause kidney cancer, damage the nervous system and kidneys, and harm fertility.” EPA notes that this is the first risk evaluation issued in final for the 20 high-priority substances designated in 2019. EPA incorporated improvements into the risk evaluation process that were announced in June 2021 and in an April 2024 final rule. As part of these improvements, EPA assessed TCEP exposure to potentially exposed or susceptible subpopulations like workers, pregnant women, infants that breastfeed, children, people living in fenceline communities near facilities that emit TCEP, and people and Tribes whose diets include large amounts of fish.

Uses and Risks Associated with TCEP

According to EPA’s press release, TCEP is used in paints and coatings, aerospace and automotive applications, and was historically used in fabrics and textiles, foam seating, and construction materials. It is also found in a range of goods that are imported into the United States. EPA states that domestic production has decreased by about 99 percent since 2014, but that it “is still used in the United States to make some paints and coatings for structural and automotive applications and as a flame retardant and plasticizer for specific aerospace applications.”

EPA states that TCEP can leach out of products and into the environment because it is not chemically bonded to the materials into which it is mixed. TCEP released into the environment from manufacturing processes or leaching from products primarily ends up in water, sediment, soil, or dust. According to EPA, TCEP may leach out of materials disposed of in landfills and get into ground water or surface water. It can also be released into the air.

EPA states that it found that TCEP presents unreasonable risk of kidney cancer and noncancer health effects to workers and consumers. EPA determined that seven out of 21 conditions of use (COU) of TCEP contribute significantly to the unreasonable risk to workers:

• Manufacturing imports;
• Paint and coating manufacturing;
• Polymers used in aerospace equipment and products;
• Aerospace equipment and products and automotive articles and replacement parts containing TCEP;
• Paints and coatings for industrial use;
• Paints and coatings for commercial use; and
• Laboratory chemicals.

EPA notes that it found unreasonable risk from both inhalation and dermal exposures when workers are handling or applying liquid formulations containing TCEP. According to EPA, “[w]orkers with the greatest potential for exposure to TCEP are those who spray TCEP-containing paints or coatings, and workers who are involved in processing a 2-part resin used in paints, coatings, and polyurethane resin castings for aerospace applications.”

EPA found unreasonable risk to consumers from three out of 21 COUs: fabric and textile products; foam seating and bedding products; and wood and engineered wood products. According to EPA, consumers are most at risk when they breathe or ingest dust from TCEP that comes from fabrics, textiles, foam, and wood products. EPA states that infants and children may also be at risk if they frequently mouth products containing foam, textiles, or wood that contain TCEP.  EPA notes that “[a] single instance of exposure, such as a child mouthing a TCEP-containing product once, does not mean an individual will definitely suffer adverse health effects.”

EPA found unreasonable risks for people who eat large amounts of fish contaminated with TCEP. According to EPA, TCEP can accumulate in fish if they live in a stream or other waterbody with high concentrations of TCEP. EPA states that these concerns are particularly notable for groups that eat higher quantities of fish, such as subsistence fishers and Tribes. EPA notes that “Tribal populations for whom fish is important dietarily and culturally have greater risk than the general population and subsistence fishers.”

EPA also found that TCEP presents unreasonable risk to the environment, specifically to fish chronically exposed to TCEP through surface water and sediment. EPA states that it assessed TCEP exposures to the aquatic environment when TCEP leaches or is released into water through the manufacturing, processing, or use of TCEP or TCEP-containing materials. EPA notes that it did not find unreasonable risk to land-dwelling animals from exposure to TCEP.

Next Steps

EPA states that it “is now moving forward on risk management to address the unreasonable risk presented by TCEP.” EPA will release a proposed rule under Toxic Substances Control Act (TSCA) Section 6 to protect people and the environment from the risks EPA identified.

Commentary

Bergeson & Campbell, P.C. (B&C^®) applauds EPA with completing the final risk evaluation on TCEP. As noted above, this is the first of the “Next 20” chemical substances EPA designated as high-priority substances for risk evaluation in December 2019. We commented previously on EPA’s draft risk evaluation for TCEP, noting that existing prohibitions on this substance appeared to be limiting significantly its commercial applicability. For discussion, see our memorandum dated December 21, 2023. We, therefore, limit our discussion below on TCEP, as a representative example, for overarching issues with EPA’s systematic review in TSCA risk evaluations.

EPA’s 2023 document on TCEP titled “Systematic Review Supplemental File: Data Quality Evaluation Information for Environmental Hazard” includes an assigned overall data quality determination of “High” for an aquatic toxicity study performed by Sun et al. (2016). During the letter peer review on the draft risk evaluation for TCEP, one of the peer reviewers stated that “these results [i.e., Sun et al., 2016] should not have been given a ‘High’ rating.” EPA was also provided an expert review of Sun et al. (2016) shortly after the close of the public comment period on the draft risk evaluation for TCEP. The expert reviewer concluded that “[Sun et al., 2016] does not justify a US EPA Systematic Review rating of ‘High’ due to a wide range of relevant and consequential weaknesses and errors and should in fact be rated ‘Low’.” Despite this feedback, EPA retained the “High” data quality rating for Sun et al. (2016) in the final risk evaluation for TCEP.

EPA’s data quality ratings have been a source of contention in its draft and final risk evaluations on TCEP and other chemical substances. This may, however, be due to changes in EPA’s systematic review methods, which were initially heavily scrutinized by the U.S. National Academy of Sciences, Engineering, and Medicine (NASEM) for “not adequately meet[ing] the state-of-practice,” and subsequently issued anew and in draft form in December 2021 but never finalized. The issues do, however, go beyond data quality ratings. For example, one peer reviewer on the draft risk evaluation for TCEP identified several studies that were not cited in the document and commented that:

The ability to find, without much difficulty, multiple relevant studies that are missing from the document suggests significant limitations with the current literature review approach.

The same peer reviewer further stated:

This may be because most of the newly identified studies have recently been published. However, the studies cited within the articles and in the European Chemicals Agency (ECHA) database are older and do not appear to have been retrieved with the search strategy that was used.

Aside from the above issues, we acknowledge the improvements EPA made in the final risk evaluation for TCEP. For example, in the draft risk evaluation for TCEP, EPA stated the following:

Overall, EPA concluded that evidence indicates that TCEP likely causes developmental toxicity in humans under relevant exposure circumstances [emphasis added].

B&C raised concern over this statement previously based on its “scant evaluation of the available data.” For discussion, see our memorandum dated December 21, 2023. We, therefore, were pleased to see in the final risk evaluation for TCEP that EPA “[c]hanged the evidence integration/conclusion for developmental toxicity from likely to cause the effect to suggestive for the effect.”

B&C encourages readers to review the letter peer-review comments on TCEP. This document provides a wealth of information on issues that experts in the field communicated back to EPA and may aid public commenters with focusing their attention on relevant issues in future draft risk evaluations. We acknowledge that EPA is not always responsive to peer reviewers’ comments. For example, one peer reviewer of the draft risk evaluation for TCEP expressed this concern by stating that “It is disturbing that these recommendations [by the TSCA Science Advisory Committee on Chemicals] are persistently ignored [by EPA].” Public commenters should not, however, be dissuaded by this. Public comments serve to build an administrative record; having such information on the record will assist in ensuring that EPA meets its statutory obligations under TSCA.