EPA Issues Final Risk Management Rules for Trichloroethylene, Perchloroethylene, and Carbon Tetrachloride

The U.S. Environmental Protection Agency (EPA) released final risk management rules under the Toxic Substances Control Act (TSCA) for trichloroethylene (TCE) and perchloroethylene (PCE) on December 9, 2024, and for carbon tetrachloride (CTC) on December 11, 2024. EPA states that all uses of TCE will be banned over time, with “the vast majority of identified risks eliminated within one year,” and safer alternatives readily available for the majority of uses. The PCE rule will ban manufacture, processing, and distribution in commerce of PCE for all consumer uses and many commercial uses, while allowing some workplace uses to continue only where robust workplace controls can be implemented. The CTC rule will require “robust worker safety programs” while banning some uses.

TCE

EPA’s December 9, 2024, press release states that TCE is used as a solvent in consumer and commercial products such as cleaning and furniture care products, degreasers, brake cleaners, sealants, lubricants, adhesives, paints and coatings, and arts and crafts spray coatings, and is also used in the manufacture of some refrigerants. According to EPA, “[s]afer alternatives are readily available for the majority of these uses.”

The final rule (89 Fed. Reg. 102568) states that to address unreasonable risk, EPA is:

EPA notes that all TSCA COUs of TCE are subject to the final rule. The final rule will be effective January 16, 2025.

PCE

EPA’s December 9, 2024, press release states that PCE is a solvent that is widely used for consumer uses such as brake cleaners and adhesives, in commercial applications such as dry cleaning, and in many industrial settings. According to EPA, “[s]afer alternatives are readily available for the majority of these uses.”

The final rule (89 Fed. Reg. 103560) states that to address unreasonable risk, EPA is:

EPA notes that all TSCA COUs of PCE are subject to the final rule. The final rule will be effective January 17, 2025.

CTC

EPA’s December 11, 2024, press release states that CTC is a solvent used in commercial settings as a raw material for producing other chemicals like those used in refrigerants, aerosol propellants, and foam-blowing agents. EPA notes that the U.S. Consumer Product Safety Commission banned the use of CTC in consumer products in 1970. According to EPA, requirements under the Montreal Protocol on Substances that Deplete the Ozone Layer and the Clean Air Act phased out CTC production in the United States in 1996 for most domestic uses that did not involve manufacturing other chemicals. The continued, safe use of CTC in the manufacture of low global warming potential chemicals used in refrigerants, aerosol propellants, and foam-blowing agents “is particularly important in the agency’s efforts to support the American Innovation and Manufacturing Act of 2020 (AIM Act) and the Kigali Amendment to the Montreal Protocol.”

The final rule (89 Fed. Reg. 103512) states that to address unreasonable risk, EPA is:

EPA notes that all TSCA COUs of CTC are subject to the final rule. The final rule will be effective January 17, 2025.

Commentary

Bergeson & Campbell, P.C. (B&C®) is pleased that EPA completed its risk management activities but disappointed with the approach EPA has taken. It is vitally important that EPA take action to protect health and the environment, especially workers who may be exposed to these three substances, but EPA fails to follow the statutory standard and meet its own regulations, and neglects to use the best available science. As with the other risk management rules, EPA remains vulnerable to legal challenges for not meeting the scientific standards under TSCA Section 26. In addition, EPA failed to comply with its own regulations for following the procedures for conducting risk evaluations. We discuss each of these points in more detail below. B&C expects entities impacted by these final rules to seek petitions for review, further delaying the implementation of the measures necessary to protect against unreasonable risk.

Under TSCA Section 6(b)(4)(C), EPA is required to “conduct and publish risk evaluations” in accordance with a rulemaking that establishes procedures for such evaluations. The relevant rulemaking cited in the final risk evaluations for TCE, PCE, and CTC was the 2017 Procedures for Chemical Risk Evaluation Under the Amended Toxic Substances Control Act (the Risk Evaluation Rule). The Risk Evaluation Rule codified regulatory definitions (e.g., weight of scientific evidence) and required application of a systematic review method that “uses a preestablished protocol…and integrate[s] evidence…”.

EPA was informed publicly about issues with its systematic review method as early as July 2019 by a public commenter at a meeting of the TSCA Science Advisory Committee on Chemicals (SACC). The public commenter made the following statements about EPA’s use of the 2018 Application of Systematic Review in TSCA Risk Evaluations (the 2018 TSCA SR document), including:

The first critical piece of missing information is creating a protocol which is used to review all the evidence and outline the process for conducting the review. This helps minimize bias and ensure transparency in the decision-making process. It’s also required by law to have a preestablished protocol, and there’s not one for 1,4-Dioxane or the other TSCA chemicals. [see pp. 125-126 of the meeting transcript.]

EPA was informed in February 2021 by the U.S. National Academies of Sciences, Engineering, and Medicine (NASEM) that its 2018 TSCA SR document did not meet the criteria of “comprehensive, workable, objective, and transparent” and that “The OPPT approach to systematic review does not adequately meet the state-of-practice.”

EPA acknowledged in its December 2021 Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for Chemical Substances Version 1.0 that it “did not have a complete clear and documented TSCA systematic review (SR) Protocol [in the first ten risk evaluations].” EPA further acknowledged that an “Evidence Integration process…was not previously included in the 2018 TSCA SR document [used for TCE, PCE, and CTC].”

Despite public comments, NASEM’s review, and EPA’s acknowledgements, EPA did not remedy these issues in the first ten risk evaluations, including the risk evaluations for TCE, PCE, and CTC. Rather, EPA re-issued final unreasonable risk determinations with the following unsupported blanket statement in each: “EPA views the peer reviewed hazard and exposure assessments and associated risk characterization [for TCE, PCE, and CTC] as robust and upholding the standards of best available science and weight of the scientific evidence per TSCA sections 26(h) and (i).”

In addition to these weaknesses that apply to all the completed risk management rules, each of these three rules suffers from additional weaknesses.

TCE

EPA stated in the preamble of the final rule that it “recognizes that the interim ECEL of 0.2 ppm as an 8-hr TWA does not fully address the unreasonable risk from TCE, hence, the term ‘interim.’’’ EPA further stated that “Potentially exposed persons may continue to be at risk for the developmental [i.e., fetal cardiac defects] and immunotoxicity effects that provide the basis for EPA’s ultimate prohibition.” In comparison, EPA concluded in the 2020 Final Risk Evaluation for Trichloroethylene “that acute immunosuppression and chronic autoimmunity were the best overall non-cancer endpoints for use in Risk Evaluation under TSCA, based on the best available science and weight of the scientific evidence, and were used as the basis of risk conclusions…”.

EPA subsequently departed from its statements about the best available science and weight of scientific evidence for TCE in the proposed and final risk management rules. As noted above, EPA stated on January 9, 2023, in the final revision to the risk determination for TCE that the 2020 Final Risk Evaluation for Trichloroethylene upheld the scientific standards under TSCA Section 26. Also on January 9, 2023, EPA issued a press release stating that it will develop “existing chemical exposure limits [ECELs] based on both the immune endpoint [i.e., a generally agreed upon effect by the TSCA SACC; see p. 70 of the TSCA SACC final report and consistent with the final risk evaluation] and the CHD endpoint [i.e., fetal cardiac defects, which EPA had rated previously as a lower quality study] in support of risk management.” EPA clarified this decision by stating that the fetal cardiac defects endpoint “was not relied on to determine whether there is unreasonable risk from TCE [in the 2020 Final Risk Evaluation for Trichloroethylene] because of direction not to do so that was provided by the previous political leadership.” For discussion of this claim, see our memorandum dated January 19, 2023. Because Section 6(a) mandates that EPA regulate to the extent necessary to mitigate the risk identified in the risk evaluation, it is not clear that EPA can promulgate a rule to protect against hazards not identified as representing the best available science and weight of scientific evidence in the final risk evaluation.

PCE

EPA stated the following in the final risk management rule for PCE:

EPA is finalizing as proposed an ECEL under TSCA section 6(a) of 0.14 ppm (0.98 mg/m3) as an 8-hour TWA based on the chronic non-cancer human equivalent concentration for neurotoxicity.

EPA’s ECEL was derived using studies (i.e., Cavalleri et al., 1994 and Echeverria et al., 1995) judged by NASEM as “appropriate to use as a point of departure [POD] for derivation of the [Integrated Risk Information System’s (IRIS) reference concentration] RfC…[see p. 5 of the NASEM report].” The TSCA SACC concluded that EPA’s use of these studies and deriving a midpoint value as the POD was “appropriate [see pp. 62-63 of the TSCA SACC final report].” We, therefore, do not anticipate successful challenges of EPA’s ECEL, based on the scientific standards under TSCA Section 26. Given the scientific robustness of the ECEL, it is not clear why EPA elected to ban COUs that might be undertaken in compliance with a WCPP that includes that ECEL. As with other of EPA’s final risk management rules, EPA seems to be issuing regulations with prohibitions that go beyond the extent necessary to protect against the unreasonable risks identified in the final risk evaluation.

CTC

EPA stated the following in the final risk management rule for CTC:

EPA is finalizing as proposed an ECEL under TSCA section 6(a) of 0.03 ppm (0.2 mg/m3) for inhalation exposures to CTC as an 8-hour TWA based on the threshold POD for liver cancer (assuming a margin of exposure of 300) and the [inhalation unit risk] IUR for adrenal cancer.

EPA derived the ECEL using a POD of 6 mg/m3 based on liver tumor data from female mice chronically exposed to CTC via inhalation. As EPA stated, it applied a benchmark margin of exposure (MOE) of 300 to this POD, which consisted of 10× for intraspecies (human to human) uncertainty (i.e., UFH), 3× for interspecies (animal to human) uncertainty (i.e., UFA), and 10× for uncertainty with extrapolating from a lowest-observed-adverse-effect-concentration (LOAEC) to a no-observed-adverse-effect-concentration (NOAEC) (i.e., UFLOAEC to NOAEC or UFL).

We agree with EPA’s use of a threshold approach for carcinogenicity of CTC as recommended by the TSCA SACC. See p. 51 of the TSCA SACC’s final report to “Consider adoption of a threshold-type [mode of action] MOA in estimating the carcinogenic risks of carbon tetrachloride.” Unfortunately, EPA did not follow its own guidance for developing the POD and benchmark MOE.

During the public comment period on the proposed risk management rule for CTC, members of the public commented on EPA’s threshold approach, specifically noting that application of the LOAEC-to-NOAEC (UFL) approach rather than using benchmark dose (BMD) modeling was inconsistent with EPA’s own guidance documents (see slides 15 and 16 of the public comments). Note, when BMD modeling is used, a UFL is not applied because BMD modeling reduces the uncertainty represented by the UFL. The public commenters performed BMD modeling on the liver tumor data from female mice and concluded that their results “were statistically valid and identical to EPA’s 2010 BMD results” (see slide 11 of the public comments). Using the BMD approach, rather than the UFL approach, the public commenters derived an ECEL of 1.5 ppm (i.e., 9.5 mg/m3) (see slide 12 of the public comments). EPA did not explain why it did not use the BMD modeling approach.

EPA’s statement about the “IUR for adrenal cancer” is questionable, given that these tumors were evaluated recently by carcinogenicity experts who concluded that “The pheochromocytomas in rodents are not relevant to human cancer risk.” EPA has yet to refute that conclusion.

Conclusions

B&C anticipates that the common procedural issues with the final risk evaluations for TCE, PCE, and CTC may serve as an underlying basis for challenging the final risk management rules on these substances. We acknowledge that courts will generally give deference to EPA’s interpretation of science, but we question whether this will occur, particularly with the issues discussed above with TCE and CTC, when EPA departs from its own standards. We anticipate that EPA may be challenged for prohibiting occupational COUs when EPA concludes that compliance with the WCPP and ECELs protects against the unreasonable risks identified. EPA’s own conclusion about the protective effect of a WCPP undermines any argument that a ban is required to protect to the “extent necessary” under TSCA Section 6(a).

Leave a Reply

Your email address will not be published. Required fields are marked *