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October 30, 2023

EPA Proposes to Amend TSCA Risk Evaluation Framework Rule

The ACTA Group

The U.S. Environmental Protection Agency (EPA) announced on October 19, 2023, a proposed rule that would amend the procedural framework rule for conducting risk evaluations under the Toxic Substances Control Act (TSCA). Published in the Federal Register on October 30, 2023, the proposed rule states that the purpose of risk evaluations under TSCA is to determine whether a chemical substance presents an unreasonable risk of injury to health or the environment, without considering costs or non-risk factors, including unreasonable risk to potentially exposed or susceptible subpopulations identified as relevant to the risk evaluation by EPA, under the conditions of use (COU). 88 Fed. Reg. 74292. EPA states that it has reconsidered the procedural framework rule for conducting such risk evaluations and determined that certain aspects of that framework should be revised to align better with applicable court decisions and the statutory text, to reflect its experience implementing the risk evaluation program following enactment of the 2016 TSCA amendments, and to allow for consideration of future scientific advances in the risk evaluation process without the need to amend further the Agency’s procedural rule. Comments are due December 14, 2023. EPA notes that under the Paperwork Reduction Act, comments on the information collection provisions are best assured of consideration if the Office of Management and Budget (OMB) receives a copy of the comments on or before November 29, 2023.

Proposed Amendments

Policy Objectives

EPA states that it will propose targeted changes and clarifying edits to the existing process by which it evaluates risk from chemical substances for purposes of TSCA Section 6, as well as structural changes to the regulatory text to accomplish these goals. EPA notes that due to the rapid advancement of the science of risk evaluation and the science and technology that inform risk evaluation, the proposed rule “seeks to ensure that the risk evaluation process is transparent, without unduly restricting the science that will be used to conduct the evaluations, allowing the Agency flexibility to adapt and keep pace with changing science as it conducts TSCA risk evaluations into the future.”

General Provisions

Applicability of Updated Procedures

EPA is proposing that the changes to the procedures as part of the rulemaking would be applied to all risk evaluations initiated on or after the date of the final rule. For risk evaluations in process as of the date of the final rule, EPA states that it would expect to apply the proposed changes to those risk evaluations “only to the extent practicable, taking into consideration the statutory requirements and deadlines.” According to the proposed rule, as a general matter, “EPA believes that most of its ongoing risk evaluations, including the ongoing supplement to the 1,4-Dioxane risk evaluation and part two of the Asbestos risk evaluation, will likely conform to the changes contemplated” in the proposed rule and “does not anticipate significant challenges in this area.” EPA notes that it does not expect to apply these procedures retroactively to risk evaluations already completed.

Categories of Chemical Substances

EPA is proposing to clarify the regulations with respect to their applicability to risk evaluations on categories of chemical substances. According to EPA, pursuant to TSCA Section 26(c), wherever TSCA requires or authorizes EPA to take action on a chemical substance, “EPA can take that same action with respect to a category of chemical substances (i.e., groups of chemical substances which are, for example, similar in molecular structure, in physical, chemical, or biological properties, in use, or in mode of entrance into the human body or into the environment).” EPA states that although the rule’s procedural requirements generally refer to “chemicals” or “chemical substances,” it will propose to clarify in the regulatory text at 40 C.F.R. Section 702.31(d) that those references also apply to categories of chemical substances.


EPA is proposing changes to a number of definitions codified in the existing regulatory text, including the elimination of the codified definitions for “best available science” and “weight of scientific evidence.” According to the proposed rule, EPA “believes that defining these concepts in the rule is both unnecessary and inhibits the Agency’s flexibility to quickly adapt to and implement changing science.” EPA is proposing to add “overburdened communities” to the examples identified in the definition of “potentially exposed or susceptible subpopulation” that currently includes “infants, children, pregnant women, workers, or the elderly.” EPA states that this addition better reflects its intent to consider risks to particular communities in the United States that potentially experience disproportionate environmental harms and risks, while also ensuring environmental justice is considered where appropriate, “including as part of any subsequent risk management action.” EPA notes that it is proposing minor updates to a number of other definitions to align better with existing Agency guidance. Specifically, the proposed rule would adjust the definitions for “pathways” and “routes” for consistency with EPA’s Exposure Factors Handbook. EPA is also proposing clarifying edits to the definitions for “aggregate exposure” and “sentinel exposure” to align with Agency guidance, and to make clear that the terms can apply to populations and environment when doing so is consistent with the best available science. EPA states that it is not proposing to amend the definitions for “act,” “conditions of use,” “reasonably available information,” “sentinel exposure,” “uncertainty,” or “variability.”

Technical Corrections and Reorganization

EPA states that the proposed rule “reflects a number of minor updates and corrections and general organizational restructuring.” As part of this effort, EPA is proposing to reorganize the sequence and structure of regulatory provisions to, for example, establish sections that distinguish between the components of the risk evaluation, the analytic considerations to be applied in the risk evaluation, and the associated procedural timeframes and actions.

Scope of TSCA Risk Evaluations

Inclusion of All Conditions of Use

EPA states that it is proposing a number of changes to the regulatory text “to make clear that the scope of TSCA risk evaluations will not exclude any ‘conditions of use’ (i.e., any circumstance, based on reasonably available information, under which a chemical substance is known, intended or reasonably foreseen to be manufactured, processed, distributed in commerce, used, or disposed of) to better align with the statutory text and structure, including modification to various provisions in the current rule that state or imply that EPA has broad discretion to choose which conditions of use it will or will not evaluate.” According to EPA, the proposed amendments are intended to ensure that the scopes of future risk evaluations are determined in accordance with the law. While EPA at one time interpreted the language differently, the proposed rule notes that EPA “no longer believes that the ‘expects to consider’ language in TSCA section 6(b)(4)(D) gives the Agency broad discretion to choose among conditions of use that it will include in a risk evaluation of a chemical substance.”

Determination of “Conditions of Use”

EPA states that although it no longer interprets TSCA to allow the Agency to exclude any intended, known, or reasonably foreseen conditions of use from the scope of a risk evaluation, it “nonetheless retains authority to exercise judgment in making its determination as to whether a particular circumstance is intended, known, or reasonably foreseen, and therefore falls within the definition of ‘condition of use’ for a particular chemical.” According to the proposed rule, for each risk evaluation, “EPA has and will continue to undergo a process to determine each chemical’s conditions of use, analyzing reasonably available information and applying the facts, Agency expertise and professional judgment on a case-by-case basis.”

Inclusion of All Exposure Pathways

As announced on June 30, 2021, EPA states that it will no longer narrow the scope of its TSCA risk evaluations by excluding analysis of certain exposures to the general population from releases to air, water, and land. According to the proposed rule, EPA “has reconsidered the text of the relevant statutory provisions, overarching statutory structure and context, and legislative history, and no longer interprets the law to authorize exclusion of exposure pathways from the scope of TSCA risk evaluations because other EPA offices have already or could in the future regulate those chemicals.” EPA is proposing to require explicitly that each risk evaluation assess all exposure routes and pathways relevant to the chemical substance under the COUs, including those that are regulated under other federal statutes.

Comprehensive but Fit-for-Purpose

EPA states that for TSCA implementation efforts to be sustainable, “risk evaluations must be fit-for-purpose such that the Agency meets both the substantive statutory and regulatory requirements for conducting risk evaluations, while completing those evaluations within the statutory deadlines.” EPA is proposing changes to the framework rule that are intended to ensure consistency with TSCA’s text, structure, and purpose, while also clarifying where TSCA provides flexibilities in how EPA conducts risk evaluations. For example, according to EPA, the proposed rule “makes clear that a risk evaluation must assess the full range of conditions of use and all exposure routes and pathways, and that a single risk determination will be made on the chemical substance, but these can be accomplished with a fit-for-purpose approach that allows for varying types and levels of analysis.”

Additional Efficiencies

EPA states that in the interest of creating additional efficiencies, it is proposing a process in which the Agency would publish and take comment during prioritization on preliminary information to inform the scope of the potential risk evaluation, acknowledging that this may result in the publication of the “draft scope” before the initiation of the subsequent risk evaluation. EPA notes that more specifically, “when early indications suggest the chemical is likely to meet the criteria for a high-priority designation, EPA expects to publish the draft scope for public comment, to correspond with one of the two statutorily required 90-day comment periods associated with prioritization.” According to EPA, publishing this information early will allow it to give an early indication as to the COUs, hazards, exposures, and potentially exposed or susceptible subpopulations that it expects to consider and may provide early indications as to how it expects to conduct a fit-for-purpose risk evaluation. The proposed rule will maintain the requirement to publish a draft scope but set forth an expectation to publish the information as early as the prioritization process (e.g., concurrent with the proposed high-priority designation), to allow EPA more time to review and use effectively the public input in the development of the risk evaluation’s scope.

Risk Determinations

Determinations on the “Chemical Substance”

EPA is proposing to clarify the regulations with respect to the way EPA makes a risk determination at the conclusion of the TSCA risk evaluation process (i.e., to make a single risk determination on the whole chemical substance). EPA states that based on the text and structure of TSCA, EPA now reads it as requiring the Agency, in each risk evaluation, to make a single risk determination of the chemical substance. According to EPA, although it previously referred to this as a “whole chemical” approach, “this descriptor may have created some confusion regarding the Agency’s intent and purpose. EPA believes that a more accurate description of the approach is simply one where the Agency makes its risk determination for the chemical substance.” EPA notes that a determination that a chemical substance presents an unreasonable risk does not mean that the entirety or whole of that chemical’s uses — or even a majority of uses — presents an unreasonable risk. Instead, “EPA may determine that a chemical substance presents an unreasonable risk based on risk associated with even a single condition of use.”

“Unreasonable Risk” Considerations

The proposed rule clarifies that “overburdened communities” are one example of a group that may be considered as potentially exposed or susceptible subpopulations within a given risk evaluation. EPA states that “overburdened communities” may include various populations or communities in the United States that potentially experience disproportionate environmental harms and risks or multiple burdens from chemical exposure. According to EPA, the proposed change will clarify that EPA will consider the risk to potentially exposed or susceptible subpopulations as part of its determination of whether the chemical presents unreasonable risk. EPA notes that its determination of unreasonable risk from the chemical substance will also consider, where relevant, the Agency’s analyses on aggregate exposures and cumulative risk.

Risk Evaluation Considerations

Occupational Exposure Assumptions

EPA is proposing regulatory amendments to clarify that, in future risk evaluations, its consideration of occupational exposure scenarios in the exposure assessments will take into account reasonably available information, including information regarding known and reasonably foreseen circumstances where subpopulations of workers are exposed due to absence or ineffective use of personal protective equipment (PPE). EPA states that it intends to assess and include in the risk evaluation the use of PPE, any engineering controls, and other industrial hygiene practices at industrial, commercial, and federal facilities. Where information is made available, EPA will take into account known occupational control measures in the exposure assessments. EPA notes that it will not consider, as part of the unreasonable risk determination, exposure reduction based on assumed use of PPE by workers. For purposes of the risk determination at 40 C.F.R. Section 702.39(f)(2), EPA will distinguish between an “assumed” use of PPE and a use that is supported by the reasonably available information and therefore known to be inherent in the performance of an activity.

Aggregate Exposure

EPA is proposing “slight revisions” to the definition of “aggregate exposure.” According to EPA, aggregate exposure analysis is not only used to assess exposure to an individual, but may also be used to assess exposure for a population, subpopulation, or the environment. Thus, EPA is proposing to strike “to an individual” from the definition. EPA notes that additionally, it is proposing to strike “single” chemical, as TSCA allows the Agency to conduct risk evaluations on categories of chemicals.

Cumulative Risk

EPA states that although TSCA does not mandate that EPA must conduct cumulative risk assessments, “TSCA does require that EPA, when conducting TSCA risk evaluations in 3 to 3.5 years, consider the reasonably available information, consistent with the best available science, and make decisions based on the weight of the scientific evidence.” (Citations omitted.) EPA notes that it recognizes that for some chemical substances undergoing risk evaluation, the best available science may indicate that the development of a cumulative risk assessment is appropriate to ensure that risk to human health and the environment is adequately characterized. TSCA also gives the Agency the authority to consider the combined risk from multiple chemical substances or a category of chemical substances.

According to the proposed rule, EPA expects to use available EPA, Organization for Economic Cooperation and Development (OECD), and World Health Organization/International Programme on Chemical Safety (WHO/IPCS) guidances that outline two principal considerations for grouping chemicals for inclusion in a cumulative risk assessment: (1) toxicologic similarity; and (2) evidence of co-exposure over a relevant timeframe. EPA states that to date, it has not considered cumulative impacts in TSCA risk evaluations, “but may in the future as appropriate data, methods, and guidance are available.”

Potentially Exposed or Susceptible Subpopulations

According to EPA, TSCA allows it to evaluate any subpopulation that may be at greater risk due to greater susceptibility or exposure, and to identify additional subpopulations other than those examples listed in the statute, where warranted. To ensure that the TSCA risk evaluations conducted for existing chemicals fully consider and evaluate the risks to these vulnerable communities, EPA is proposing to amend the regulatory definition of “potentially exposed or susceptible subpopulations.” Specifically, EPA is proposing to add “overburdened communities” — communities that may be disproportionately exposed or impacted by environmental harms — to the list of example subpopulations.

EPA states that to identify overburdened communities when conducting a risk evaluation, it will engage the public throughout the TSCA prioritization and risk evaluation processes, work with EPA offices such as the Office of Environmental Justice and External Civil Rights and the Office of Research and Development (ORD), and may use available screening tools.

Science Policy and Scientific Standards

Scientific Guidelines and Procedures

The proposed rule is codifying the use of appropriate Agency guidance in the development of risk evaluations (proposed 40 C.F.R. Section 702.37(a)(1)). EPA states that it “may develop and use additional guidance as needed using a transparent process.”

Peer Review.

EPA states that it “remains committed to using peer review in the development of TSCA risk evaluations and any associated methods or approach type documents and proposes to retain the provision to require peer review in the risk evaluation process.” EPA is proposing modifications to the language from the 2017 final rule to provide increased clarity on both the guidance it will use to conduct peer review and on what peer review will be conducted, however. EPA is proposing removing the reference to specific versions of guidance documents and is proposing at 40 C.F.R. Section 702.41 to refer instead to “applicable peer review policies, procedures, guidance documents, and methods” adopted by EPA and OMB to serve as the guidance for peer review activities. EPA notes that it interprets “applicable” to reference the most current versions “and believes this change will appropriately incorporate any future versions of peer review guidance documents.”

According to the proposed rule, rather than peer reviewing an entire risk evaluation, in adhering to applicable guidance, it may be appropriate for EPA to conduct peer review on only portions or sections that constitute unreviewed influential information. EPA states that the proposed regulatory text at Section 702.41 provides its expectation that peer review activities could be conducted on risk evaluations “or portions thereof.” EPA “believes this provides the needed flexibility to conserve Agency resources and avoid redundant peer review.”

Scientific Standards

EPA is proposing to eliminate the following definitions from the regulatory text:

  • Best available science: EPA states that it believes that codifying a definition of “best available science” in the risk evaluation procedural rule “is unnecessary and potentially problematic as it could limit the Agency’s ability, flexibility, and mandate to incorporate the best available science into TSCA risk evaluations.”
  • Systematic review and fit-for-purpose systematic approaches: EPA states that it “will look to streamline chemical-specific protocols and approaches while remaining consistent with systematic review principles.” According to EPA, these systematic approaches “will be transparent, fit-for-purpose, and specific to the needs of each chemical/category, while better aligning with the schedules for completion of the risk evaluation.” EPA notes that it is also exploring how to leverage consideration of systematic reviews and systematic review approaches from other EPA offices and authoritative bodies, or portions thereof, to achieve greater efficiencies in the process.
  • Weight of scientific evidence: The final rule defines weight of scientific evidence as “a systematic review method, applied in a manner suited to the nature of the evidence or decision, that uses a pre-established protocol to comprehensively, objectively, transparently, and consistently identify and evaluate each stream of evidence, including strengths, limitations, and relevance of each study and to integrate evidence as necessary and appropriate based upon strengths, limitations, and relevance.” EPA states that it believes the current definition “is problematic and inconsistent with typical risk assessment practice and is therefore proposing to eliminate the definition from the regulatory text — instead relying on long-established Agency guidance documents to guide weight of scientific evidence analyses under TSCA.”

Process for EPA Revisions to Scope or Risk Evaluation Documents

EPA is proposing some new procedures and criteria for whether and how EPA would endeavor to revise or supplement final scope documents, and draft or final risk evaluations. With respect to final scope documents, EPA is proposing that subsequent changes — if any — to the scope of the risk evaluation after publication of the final scope be reflected and described in the draft risk evaluation instead of a revised final scope document. If changes to the risk evaluation scope during that period are more significant, EPA could, in its discretion, publish a Federal Register notice notifying the public that EPA has made information regarding changes to the risk evaluation scope available in the docket before releasing the draft risk evaluation. EPA is proposing to refrain from reissuing draft risk evaluations in a second draft form. EPA states that rather than spending time and resources to develop and issue a revised draft risk evaluation, it “instead expects to reflect and describe any changes to the draft document in the final risk evaluation.” Where changes are “significant in nature,” EPA notes that “nothing in the proposed rule would prevent EPA from seeking additional advice or feedback from its independent scientific advisors or additional public comment on relevant topics, provided that such actions can be completed within the timeframes Congress contemplated for TSCA risk evaluations.”

EPA is proposing a general practice for how and when to revisit final risk evaluations, and certain exceptions to that practice. According to EPA, as general practice, where circumstances warrant revisiting a chemical risk evaluation that has already been issued in final, EPA “may identify that chemical as a potential candidate for high-priority designation, and follow the procedures at 40 CFR Part 702, Subpart A.” EPA states that where it endeavors to revise or supplement a final risk evaluation outside of reprioritization, the proposed rule will further require it to follow the same process and requirements for TSCA risk evaluations described in this proposed rule, including publication of a new draft and final risk evaluation, solicitation of public comment, and, as appropriate, peer review.

Process and Requirements for Manufacturer-Requested Risk Evaluations (MRRE)

EPA is proposing a number of changes to the process and requirements for manufacturers to request a risk evaluation.

  • Submission of MRRE: In cases where multiple manufacturers jointly submit an MRRE (i.e., a consortium), EPA states that it expects to treat a consortium as a single entity for purposes of any regulatory determinations with regard to the requests, fee payments, and other general communication regarding the MRRE request and/or the risk evaluation. Joint submitters must designate a single point of contact for Agency engagement, and are otherwise collectively responsible for providing complete and sufficient information to the Agency to support the risk evaluation.
  • Scope of request: EPA is proposing that manufacturers only be permitted to make requests for evaluations of entire chemical substances — not individual COUs or subsets of COUs.
  • Contents of request: EPA is proposing to require that manufacturers include a listing of the chemical’s COUs (i.e., the circumstances under which the chemical substance is intended, known, or reasonably foreseen to be manufactured, processed, distributed in commerce, used, or disposed of), and all information known to or reasonably ascertainable by the requesting manufacturer that supports the identification of those circumstances. EPA is also proposing that incoming requests include “all information known to or reasonably ascertainable by the requesting manufacturer on the health and environmental hazard(s) of the chemical substance, human and environmental exposure(s), and exposed population(s).”
  • EPA process for reviewing requests: EPA is proposing a number of changes to how it will review MRREs:

    • Notice of receipt: EPA will provide the public with notice within 15 days that it has received an MRRE. EPA states that it expects to provide notice through updates to its website and e-mail listserv notifications.

    • Initial review for completeness: EPA will begin reviewing the request and supporting information against the requirements in the proposed rule to determine whether the request appears complete. EPA will reject and return to the submitter requests that are clearly missing key required information in 40 C.F.R. Section 702.45(c) or are otherwise not well-supported.

    • Public notice and comment: Where EPA initially determines the request to be complete, it will submit a notice of receipt of the MRRE for publication in the Federal Register within 90 days. EPA will also open a docket that includes all non-confidential business information (CBI) and CBI-sanitized information included in the request and provide no less than a 60-day public comment period. EPA states that it may also solicit specific comments on the request, including feedback on the COUs listed by the manufacturer and information regarding sufficiency of available information to support a risk evaluation.

    • Secondary review for sufficiency: From the start of the public comment period, EPA states that it would expect to begin conducting a more in-depth review of the request to determine whether there is sufficient information to support a reasoned evaluation on the chemical substance. Concurrently, EPA expects to conduct an internal cursory review of other reasonably available information, with a more comprehensive information collection occurring after granting the request. For requests determined not to be supported by sufficient information during this period, EPA will reject the request and notify the requesting manufacturer. The requesting manufacturer would have the opportunity to supplement and resubmit their request to EPA. EPA notes that additionally, where the submitter believes that the information is not reasonably ascertainable by them, they can include in their resubmission a request that EPA exercise its information gathering authorities to collect and/or develop information necessary to remedy the deficiency. For requests determined to be supported by sufficient information, EPA will proceed with granting the request and continuing the review process.

    • Grant: Subject to the percentage limitations in TSCA Section 6(b)(4)(E)(i)(II), EPA will grant MRRE requests that are both complete and supported by sufficient information.

    • Publication of draft conditions of use and request for information: EPA will next publish a Federal Register notice setting out, in draft form, its preliminary determination on the chemical’s COUs, taking into account information provided in the MRRE request, information received during the first public comment period, and EPA’s own further review efforts. EPA will request relevant information from the public and provide no less than a 60-day public comment period.

    • Initiation of risk evaluation: Upon initiation of the MRRE, EPA will follow all requirements in the proposed rule, including but not limited to proposed Sections 702.37 through 702.49. EPA will notify the manufacturer that the MRRE has been initiated, and similarly expects to keep the public apprised of the status through updates to its website. EPA notes that it is reserving the right to identify additional information needs at any time during the risk evaluation process, including post-initiation.

    • Identification of information needs: Where EPA identifies additional information needs at any time before granting the MRRE, the proposed rule provides a process for supplementing and resubmitting the request. Where EPA identifies additional information needs at any point following its grant of the MRRE, EPA will notify the requesting manufacturer(s) and set a reasonable amount of time, as determined by EPA, for manufacturers to respond. In response to EPA’s notice, the manufacturer can choose to: (1) provide the necessary information to EPA; (2) if the risk evaluation has not yet been initiated, withdraw the MRRE request; or (3) request that EPA obtain the information using authorities under TSCA Section 4, 8, or 11.

    • Unfulfilled information needs: EPA states that it believes it is important that the procedures in the proposed rule account for a scenario in which information needs are not met, and the Agency “is simply unable to complete the risk evaluation.” In circumstances where EPA has identified additional data needs, but the requesting manufacturer(s) is unable or unwilling to fulfill those needs in a timely manner, has produced information that is insufficient to meet the need as determined by EPA, or where EPA determines that a request to use its information gathering authorities under TSCA Section 4, 8, or 11 is not warranted (e.g., where the information is ascertainable by the manufacturer or the request does not provide a sufficient rationale), the proposed rule at 40 C.F.R. Section 702.45(g) “contemplates that EPA can deem the MRRE request to be constructively withdrawn (i.e., EPA would construe the MRRE request to be withdrawn even in the absence of a request to withdraw).” EPA notes that any fees to be collected or refunded would be determined in accordance with the proposed rule and the TSCA fee provisions in 40 C.F.R. Section 700.45.

Requests for Comment

EPA requests comment on all aspects of the proposed rule, including comment on whether the proposed rule would enhance transparency and public understanding of EPA’s TSCA risk evaluation process and better align with the 2016 amendments to TSCA under the Frank R. Lautenberg Chemical Safety for the 21st Century Act. Additionally, EPA is soliciting feedback on specific issues, as summarized below:

  • EPA requests comment on how the Agency could consider potential climate-related risks in a risk evaluation;
  • EPA requests comment on the proposed approach of publishing a draft scope during the prioritization process when it is clear that the chemical undergoing the prioritization process will be designated as a high-priority chemical;
  • EPA requests public comment on the proposed elimination of the definitions of best available science and weight of scientific evidence, the need for such definitions, and the utility of definitions as the state of science evolves;
  • EPA requests comments on the proposed changes to the process of an MRRE. In regard to cost, while the costs to EPA would be reflected in the final invoice to the requesting manufacturer, EPA seeks comment on, to the extent that test orders are issued to support an MRRE, whether the entire test order fee should also be directed to the requesting manufacturer, even where the order is also issued to another entity. Additionally, EPA requests specific comment on the burden estimate of an MRRE, including the assumptions used in estimating the burden (e.g., number of requests EPA expects);
  • EPA requests comment on general approaches or best practices for improving engagement with small entities. Early engagement with and feedback from all those who manufacture, process, distribute, use, or dispose of a chemical is critical for the Agency to be able to identify and characterize accurately that chemical’s COUs for consideration in the risk evaluation. EPA seeks comment on how to improve its outreach to the stakeholder community, including education on the TSCA risk evaluation process for small entities; and
  • EPA requests public comment on how the Agency can provide a transparent and detailed basis for the proposed unreasonable risk determination and existing chemical exposure limits derived from the risk evaluation process.

Reliance Interests

EPA states that the proposed rule includes some statutory interpretations that differ from those it held at the time it issued the 2017 final rule, and, as part of developing the proposed rule, EPA has considered to what extent stakeholders may have reliance interests in those previous interpretations. According to the proposed rule, “EPA believes that there are either no reliance interests on those past statutory interpretations, or that any such interests are minor” and the current rule and proposed changes “mostly do not directly impact external parties, with one exception being modified procedural requirements for voluntary requests for risk evaluation submitted by manufacturers.” To the extent there were any reliance interests on the prior interpretations, or the risk evaluations that were developed based on the previous procedural requirements, EPA notes that it does not intend anything in the proposed rule to apply retroactively.


The Acta Group (Acta®) acknowledges that the proposed rule is potentially the most impactful that the Biden-Harris Administration has issued under TSCA. We agree that it is appropriate for EPA to consider exposures that are managed by other statutes in its TSCA risk evaluations. It is reasonably foreseeable that an individual might be exposed at home via ambient air and drinking water and potentially also be exposed at work and/or from consumer products. Such exposures (up to the level permitted under, for example, the Clean Air Act or Safe Drinking Water Act (SDWA)) could effectively be a baseline exposure that EPA then considers in the context of other exposures. We also hope that if EPA concludes that exposure via a particular pathway (e.g., drinking water) is an unreasonable risk driver, EPA would consider using another authority (e.g., the SDWA) to address the unreasonable risk, rather than TSCA, especially if exposures might result from non-TSCA uses (either for example from legacy pollution or food, drug, or cosmetic uses). A TSCA ban on manufacture, processing, or use of a substance will have no protective effect if there is legacy pollution or if there might be unreasonable risk from exposures that may occur from non-TSCA uses.

On the other hand, we are concerned that if EPA’s proposal to eliminate the definitions for “best available science” and “weight of scientific evidence” is promulgated as final, it will allow EPA to lower the scientific rigor of its risk evaluations performed under TSCA Section 6. We would hope this proposal troubles stakeholders across the spectrum of interests. Lack of rigor can be abused to be either over- or under-protective. It will also provide EPA with latitude with identifying and incorporating previously peer-reviewed information into its draft risk evaluations without justifying the use of such information when conflicting peer-reviewed information exists. Below, we have highlighted several representative issues with this proposed rule that warrant public comment from interested parties.

EPA’s stated rationale for its proposal to eliminate the definitions for “best available science” and “weight of scientific evidence” is that these definitions inhibit “the Agency’s flexibility to quickly adapt to and implement changing science.” The issue here is that EPA did not provide examples of how these definitions inhibited its flexibility with adapting to changing science on the first ten final risk evaluations and other activities it has undertaken in support of its risk evaluations.

Our concern is that EPA codified the definitions for these terms, yet now seeks to eliminate those definitions apparently because EPA repeatedly failed to meet the requirements it established. It may be that revising regulatory definitions to accommodate flexibility with incorporating scientific changes is a valid and defensible reason for a proposed update, but we do not see evidence of this need. Rather, it is our view that EPA has frequently failed to meet the definitions it established, suggesting that EPA simply seeks to lower the standard and paper-over issues related to lapses in scientific integrity.

Representative examples in support of the latter determination are available from the first ten final risk evaluations, the TSCA Section 4 test orders on high-priority substances, and the 2023 Draft Supplement to the Risk Evaluation for 1,4-Dioxane (the 2023 Draft Supplement on 1,4-DX), as summarized below.

  • Colour Index Pigment Violet 29 (PV29) and EPA’s use of deposited dose rather than retained dose for a poorly soluble and low toxicity particle (PSLT), which conflicts with the best available science that supports retained dose, is the appropriate dose metric for PSLTs. For discussion, see the commentary to our memorandum dated September 9, 2022.
  • trans-1,2-Dichloroethylene and EPA’s requirement for acute/chronic toxicity testing on benthic invertebrates, which reverses without justification EPA’s previous conclusion that such testing was not necessary. For discussion, see Section I.B.1.a. of our 2023 forecast.
  • The 2023 Draft Supplement on 1,4-DX and EPA’s conclusion that a linear low-dose (non-threshold) approach for carcinogenicity assessment is appropriate, despite reasonably available information, which EPA failed to review, that supports a threshold. For discussion, see public comments on EPA’s 2023 Draft Supplement on 1,4-DX.

Second, EPA stated “there may be situations when repeated peer review is not warranted…Rather than peer reviewing an entire risk evaluation, in adhering to applicable guidance, it may be appropriate for EPA to conduct peer review on only portions or sections that constitute unreviewed influential information. EPA also expects that a TSCA risk evaluation may use peer reviewed products (e.g., risk assessments, hazard assessments, models), or portions thereof, conducted by another EPA office or other authoritative body (e.g., state, national, or international programs), for which both the best available science and weight of scientific evidence standards were adhered to.”

We agree with EPA’s position that previously peer-reviewed documents may not warrant additional peer review. The issue here is that EPA may end up “cherry picking” older peer-reviewed documents in preference for newer information without providing a scientific justification (as EPA did for 1,4-DX). Between the time that EPA issued the 2013 Integrated Risk Information System (IRIS) assessment and the 2020 Final Risk Evaluation for 1,4-DX, Health Canada and the European Chemicals Agency (ECHA) released assessments on 1,4-DX in which each agency concluded that 1,4-DX was a threshold carcinogen. Despite these conclusions from competent authorities, EPA did not reassess its conclusions in either the 2020 Final Risk Evaluation or the 2023 Draft Supplement on 1,4-DX. Rather, it stated that it relied upon the previous conclusions from the 2020 Final Risk Evaluation for 1,4-DX. We acknowledge the challenge for EPA that science often continues to evolve during EPA’s risk evaluation and risk management, but in this instance, EPA was supplementing its risk evaluation, so for EPA to only update parts of its risk evaluation (exposures) and ignore such a significant update in the best available science related to hazard strikes us as unjustified. EPA then specifically excluded its evaluation of the hazard from the charge questions to peer reviewers.

The above example illustrates two important considerations with EPA’s proposed revisions to the risk evaluation rule. First, it emphasizes the importance of exhausting administrative remedies on draft and final IRIS assessments, which are not regulations but may be used in EPA’s assessments that form the basis for regulatory actions. Second, it suggests that the Office of Pollution Prevention and Toxics (OPPT) will incorporate IRIS hazard and dose response assessments verbatim and without subsequent peer review despite the availability of other “reasonably available information” that suggests the IRIS assessments may no longer represent the best available science and meet the standard of the weight of scientific evidence. OPPT already does not hew to IRIS assessments that OPPT views as insufficiently protective because of recent science. For EPA to not also update IRIS values with new science if the change would lead to lower concern is scientifically disingenuous and outcome determinative.

Third, EPA stated that it will “rely on established Agency guidance documents to guide the required application of [weight of scientific evidence (WOSE)] in TSCA risk evaluations. At this time, EPA will primarily look to four documents for implementing WOSE in TSCA risk evaluations: 2016 Weight of Evidence in Ecological Assessment [citation omitted], Guidelines for Carcinogen Risk Assessment [citation omitted], 2011 Endocrine Disruptor Screening Program Weight-of-Evidence: Evaluating Results of EDSP Tier 1 Screening to Identify the Need for Tier 2 Testing [citation omitted], and 2022 ORD Staff Handbook for Developing IRIS Assessments [citation omitted].”

Our concern with the above approach is that the documents EPA cites are focused primarily on hazard and dose response and do not provide metrics for informing the weight of scientific evidence for other evidence streams (e.g., exposure). We recognize that EPA issued the 2021 Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for Chemical Substances (the 2021 Draft SR Protocol). For discussion, see our commentary dated December 21, 2021. We note, however, that EPA has not issued this document in final. We further note that the TSCA Science Advisory Committee on Chemicals (SACC) concluded that the approaches in the 2021 Draft SR Protocol for integrating evidence in exposure and hazard “presents a complicated and potentially inefficient method for integrating data within the various disciplines.”

We note that EPA’s use of the 2021 Draft SR Protocol would not satisfy its codified definitions of “best available science” and “weight of scientific evidence,” yet with the elimination of these terms, EPA will have free reign to adjust the benchmark for how it determines scientific information meets the description of these terms under TSCA Sections 26(h) and 26(i), in the absence of codified definitions. Again, we would hope that this concerns stakeholders across the spectrum. We suspect that other external stakeholders will agree that their views are not always aligned with EPA’s scientific conclusions and that EPA must be held to an objectively high scientific standard and not simply what EPA concludes is the “best available science” in any  action or based on the preferences of any administration.

A contemporary example of this is provided in OPPT’s proposed risk management rule on trichloroethylene, which was released as a pre-publication draft on October 23, 2023. We mention this because OPPT, under the Trump-Pence Administration, excluded the fetal cardiac defects endpoint, as reported by Johnson et al. (2003), under Section of the 2020 Final Risk Evaluation for Trichloroethylene titled “Best Overall Non-Cancer Endpoints for Risk Conclusions.” OPPT re-affirmed these conclusions, under the Biden-Harris Administration, in the notice for the 2023 Final Revised Risk Determination on Trichloroethylene stating that it “views the peer reviewed hazard and exposure assessments and associated risk characterization [in the Final Risk Evaluation for Trichloroethylene] as robust and upholding the standards of best available science and weight of the scientific evidence per TSCA sections 26(h) and (i).”

Despite these conclusions, OPPT’s proposed risk management rule on trichloroethylene uses the point of departure for fetal cardiac defects as the basis for its proposed existing chemical exposure limit (ECEL). This decision appears to support a pre-determined outcome that is not supported by the 2020 Final Risk Evaluation for Trichloroethylene and conflicts with OPPT’s own statements from September 2023 that “The risk evaluation is the primary decision support document the U.S. Environmental Protection Agency uses if it must issue regulations to address unreasonable risks identified as part of the evaluation. ” (Emphasis in original.)

It is also unclear how the proposed rule will increase efficiencies. EPA stated that it will “assess all exposure routes and pathways relevant to the chemical substance under the conditions of use, including those that are regulated under other federal statutes.” Though we agree with this approach, the reality of such an approach is that it will significantly increase the workload, may lead to missed deadlines, and delay the implementation of public health protection through risk mitigation for those COUs where EPA identifies unreasonable risks. EPA fails to explain why meeting objective criteria for “best available science” and “weight of scientific evidence” is too burdensome, but significantly broadening the scope of its risk evaluations to include all COUs is not.

Further, EPA’s stated improvements to the MRRE process/requirements appear to establish an approach that deters submission of MRREs. Our experience to date is that EPA’s review for MRRE completeness focuses primarily on data gaps, not true data needs. EPA’s proposed improvements will not remedy this. EPA may be intentionally raising the bar for MRREs, which is a valid policy position to take. There is no question that MRREs add to EPA’s burden of completing risk evaluations. On the other hand, the scientific standards for MRREs and EPA-initiated risk evaluations should not be different.

Since its announcement on June 30, 2021, we have been troubled by EPA’s “whole chemical” approach, which EPA is now memorializing in this proposed rule. EPA had previously stated that if EPA found the majority of COUs present unreasonable risks, EPA would conclude that the whole chemical was an unreasonable risk; this begged the question at the margins, why would 51 percent of COUs trigger a whole chemical being an unreasonable risk, while 49 percent would not? In this proposal, EPA takes the whole chemical approach to the logical conclusion — that if EPA finds any COU presents an unreasonable risk, the chemical substance, as a whole, presents an unreasonable risk. EPA waves away concerns that such a conclusion misrepresents the actual risk from a substance. EPA states that it will endeavor to do better with its risk communication to explain to external audiences that only some COUs present an unreasonable risk. This is a naïve conclusion that the press and general public understand the nuance of EPA’s headline position that EPA concluded a substance presents an unreasonable risk. It also provides no assurance or protection to manufacturers that EPA’s communications will accurately and clearly represent EPA’s view of individual COUs. After all, if EPA makes a single risk determination that a substance, as a whole, presents an unreasonable risk, any subsequent reporting or statements by EPA or others would be accurate even if EPA goes on for pages to explain that only a small number of COUs present an unreasonable risk.

EPA’s whole chemical approach is even more troubling when considering that EPA has yet to limit what COUs are “reasonably foreseen.” EPA simply assumes that there might be COUs that would exceed any particular concern level that EPA identifies. This is most evident in EPA’s implementation of TSCA Section 5, but it appears to be true for its TSCA Section 6 risk evaluations as well. EPA has yet to propose risk management that does not also include banning some, most, or all COUs, even when EPA concludes that a workplace chemical protection plan (WCPP) is sufficiently protective to mitigate the unreasonable risks identified. This means that once EPA identifies a hazard other than low hazard, EPA will necessarily conclude that there might be an exceedance of EPA’s hazard threshold, therefore there is an unreasonable risk, which would then trigger risk management.

As a result, we expect EPA to conclude that essentially every chemical it reviews (because EPA will not prioritize low hazard substances) will be an unreasonable risk. In our view, this is an impermissible hazard-based approach, not a risk-based approach explicitly required by TSCA. It might be true for highly hazardous substances, such as many of those currently undergoing risk evaluation and risk management, but if it were Congress’s intent that EPA protect against all possible risks, Congress would have so specified in the statutory language.

The Acta Group encourages interested parties to review carefully EPA’s proposed rule and to provide comments as appropriate. This is potentially the most impactful TSCA rule proposed to date this year. Regulated entities should consider carefully the prospective impacts of this proposed rule, even if their chemistries are not currently on EPA’s TSCA Work Plan, the IRIS Program Outlook, or EPA’s list of high-priority substances undergoing risk evaluation.