On September 28, 2018, the U.S. Environmental Protection Agency (EPA) released the general approaches that the Office of Pollution Prevention and Toxics (OPPT) may use to identify potential candidate chemicals for prioritization under the Toxic Substances Control Act (TSCA). EPA notes that it will seek public comment on the approach document and on which chemicals should be identified as potential candidates for the initial 20 high-priority and 20 low-priority chemicals that must be identified pursuant to TSCA Section 6(b)(2)(B).

The document, A Working Approach for Identifying Potential Candidate Chemicals for Prioritization, lays out EPA’s thinking regarding a near-term approach for identifying potential chemicals for prioritization, the initial step in evaluating the safety of existing chemicals under TSCA. The approach document also includes a longer-term risk-based strategy for managing the larger TSCA chemical landscape that, according to the portion of the TSCA Chemical Substance Inventory (Inventory) that includes the substances designated as active (TSCA Active Inventory), is expected to include over 38,000 chemicals reported as “active” under the TSCA Inventory Notification (Active-Inactive) Requirements final rule. According to EPA, the longer-term approach proposes parsing chemicals into “bins” that can be used to inform multiple activities and priorities throughout EPA, including within the TSCA program.

EPA also posted a pre-publication version of the Federal Register notice that, upon its publication, takes three actions:

• Announces the availability of the approach document;

• Opens a public docket to accept comments on the longer-term risk-based strategy, which will inform its continued development and help outline a public meeting to be held in early 2019; and

• Opens 73 chemical-specific public dockets, one for each of the remaining chemicals on the 2014 TSCA Work Plan (the 2012 TSCA Work Plan that was updated in 2014) (the chemicals are listed in the notice), as well as a general docket to suggest additional candidate chemicals that are not on the Work Plan.

EPA’s Approach Document

The approach document lays out EPA’s near-term approach for identifying potential chemicals for prioritization, the initial step in evaluating the safety of existing chemicals under TSCA. Building on EPA’s commitment to work with the public to select the next chemicals for risk evaluation, the approach reflects public input received at a December 2017 meeting and through the public docket. EPA also published a summary of public comments.

EPA anticipates using the near-term approach to inform the identification of potential candidates for the initial 20 high-priority and 20 low-priority chemical substances that must be identified pursuant to TSCA Section 6(b)(2)(B). EPA states that it expects its approach for identifying candidates for prioritization to evolve over time as it develops expertise in identifying chemicals to enter prioritization, as well as in conducting prioritization and risk evaluations. EPA looks to preserve its flexibility to ensure that it can incorporate newly developed and updated information, including analytical methods, and consider policy developments, including any future EPA or other federal agency and U.S. government priorities. According to EPA, it expects to use lessons learned from the process of selecting the first 40 priority chemicals in identifying the next set of priority chemicals.

EPA states that it is considering a longer-term approach to bin the remaining chemicals (those not included on the 2014 TSCA Work Plan) on the TSCA Active Inventory. EPA currently expects to use an approach that integrates available information from both New Approach Methods (NAM) and traditional approaches, covering the domains of hazard, exposure, persistence, and bioaccumulation for human and ecological domains, to group chemicals based on information availability and hazard and exposure potential. The term NAM was introduced previously by EPA to cover any in vitro, in silico, or in chemico techniques used to provide data or information as an alternative to animal testing. The approach document describes the first step of developing this approach. According to EPA, subsequent steps will include a white paper describing a proof-of-concept for the binning approach using a relatively small number of chemicals and future public workshops on and discussion of the planned approach and the results obtained.

Near-Term Approach for Identifying Potential Candidate Chemicals for High-Priority Designation

EPA’s working approach is to look primarily to the 2014 TSCA Work Plan for high-priority potential candidates, as TSCA requires that at least 50 percent of the chemicals undergoing risk evaluation as of December 2019 must come from the 2014 TSCA Work Plan. EPA generally intends to consider the three factors, described below, for selecting potential chemicals for prioritization:

1. EPA and Federal Priorities: In selecting chemicals as potential candidates for prioritization, EPA expects to consider its overarching priorities. This may include, but is not limited to, a chemical or group of chemicals that are priorities for EPA, including chemicals that other EPA program offices have deemed a priority for their program and suitable for current prioritization. In addition, EPA intends to consult and collaborate with other federal agencies to identify candidate chemicals and any information that may be useful in their selection and during subsequent prioritization and risk evaluation. While EPA intends to look first to the 2014 TSCA Work Plan for potential high-priority chemical candidates, EPA acknowledges that active chemicals not listed on the 2014 TSCA Work Plan may also be selected as candidates for prioritization in cases where other federal agencies, the general public, or the EPA Administrator have identified these chemicals as particularly suitable. In such cases, EPA will open dockets for all potential candidate chemicals not listed on the 2014 TSCA Work Plan. EPA will also consider public input received, such as during any public consultations and through the dockets, for each of the 2014 TSCA Work Plan chemicals and chemicals not included on the Work Plan.

2. Quantity and Quality of Information: EPA intends to consider the quantity and quality of information in a step-wise approach to ensure responsible and timely completion of the process when identifying potential candidate chemicals for prioritization. According to EPA, the approach is intended to screen out information-deficient candidate chemicals that would hinder its ability to perform scientifically sound risk evaluations from the initial selection of the 20 high-priority and the 20 low-priority candidates. EPA notes that the scientific underpinnings of a risk evaluation need to be strong enough to support a risk evaluation determination and inform potential future risk management activities in a way that allows EPA to meet the tight TSCA deadlines for these actions. 
   Additional information may need to be developed for information-deficient chemical substances and EPA outlines its approach to develop necessary information for a chemical substance or chemical category. Once generated, the new information will feed into analyses and decisions supporting the selection of candidate chemicals beyond the initial high- and low-priority candidates and the prioritization process within the statutory timeframes.

3. Work Load: According to EPA, as it explained during the December 11, 2017, public meeting, it must be mindful of its workload and resource constraints, given the statutory deadlines and other requirements. Once a chemical is designated high-priority for risk evaluation, the maximum 3.5-year statutory deadline for completing the risk evaluation begins with no opportunity for interruption or further extension.
   To address workload issues, EPA states that it could use diverse approaches to consider current expertise or facilitate the analysis of candidate chemicals. For example, EPA could identify potential candidate chemicals that share certain characteristics with the first ten chemical substances undergoing risk evaluation, such as solvents, since focusing on the solvents remaining on the 2014 TSCA Work Plan would take advantage of the expertise developed on the six solvents currently undergoing risk evaluation (e.g., development of exposure scenarios).
   EPA could also consider selecting a category of chemicals for prioritization. As stated in the July 20, 2017, Procedures for Prioritization of Chemicals for Risk Evaluation final rule, “TSCA section 26 provides EPA with authority to take action on categories of chemical substances.” Furthermore, “should EPA determine to prioritize a category of chemical substances, EPA would describe the basis for such a determination in the Federal Register notice published to initiate prioritization” and, as part of the initiation notice, “EPA will provide an explanation of the rationale for initiating the process on the chemical substance, thus ensuring the public has notice and an opportunity to comment on any decision to prioritize a category of chemical substances.”

Under the near-term approach, EPA’s general goal is to determine whether the information is sufficient and relevant to: (1) evaluate information availability for prioritization and risk evaluation; and (2) identify gaps that may be filled through future information gathering activities. EPA notes that the survey is meant only to identify data availability and gaps, and to assess whether the amount of data available is sufficient for prioritization and risk evaluation of candidate chemicals. This process and the data surveyed are not meant to supplant the prioritization process or the risk evaluation process.

EPA intends to begin actively gathering information for the 73 remaining chemicals listed under the 2014 TSCA Work Plan. EPA intends generally to use reasonably available and frequently used data sources, including but not limited to those already identified in the TSCA 2012 Work Plan Methods Document, public literature, and “gray literature” sources as deemed necessary. Gray literature refers to sources of scientific information that are not formally published and distributed in peer reviewed journal articles and can include theses and dissertations, technical reports, guideline studies, conference proceedings, publicly-available industry reports, unpublished industry data, trade association resources, and government reports. According to EPA, these references “are still valuable and consulted in the TSCA risk evaluation process.”

Near-Term Approach for Identifying Potential Candidate Chemicals for Low-Priority Designation

EPA must also designate 20 low-priority chemical substances by December 2019. EPA states that it intends to select candidates that appear to be most suitable for low-priority designation. According to EPA, the most suitable candidates “are those likely to be favored by the considerations in the act (Section 6(b)(1)(A)) [and the regulations at 40 CFR 702.5].” In identifying potential candidates for low-priority chemical designation, EPA will use the best available science, consistent with TSCA Section 26(h). EPA may identify substances from multiple sources, including one or more of the following chemical information resources: EPA’s Safer Chemical Ingredients List (SCIL); EPA’s Chemical Assessment Management Program (ChAMP); and the Organization for Economic and Cooperation Development (OECD) Screening Information Data Sets (SIDS) assessment documents. EPA states that these resources “reference useful information on chemical hazard and, in some cases, on conditions of use and exposure,” and that “[u‌]sing all resources is important, since the different sources will provide different information to support assessment of the elements in the prioritization process (40 CFR §702.9 (a)).”

At this time, EPA intends to select low-priority candidate chemicals from the TSCA Active Inventory (as of April 2018 or the most recent version). In general, EPA states that it intends to preferentially select Chemical Abstracts Service (CAS) numbers that represent discretely defined structures, which can be more confidently associated with information on hazard, conditions of use, and exposure. EPA intends to select candidate low-priority chemicals with robust data sets for hazard and exposure, with respect to the range of the substances’ conditions of use.

Proposed Longer-Term Approach

The approach document presents a proposed longer-term, risk-based approach that EPA is considering to “bin” chemicals on the TSCA Active Inventory, meaning that EPA would loosely group chemicals on the Inventory into pools that could inform potential prioritization based on risk-based data and information availability. The approach document is intended to begin a public discussion, beginning in late 2018, regarding the implementation of this longer-term approach. With publication of the Federal Register notice announcing the approach document, EPA will open a docket to accept initial comment on this longer-term approach that will inform expansion of this approach and proof of concept. When complete, the binning approach will help inform which chemicals EPA may choose for prioritization.

The binning scores included in this approach will incorporate human hazard relative to exposure, ecological hazard, genotoxicity, persistence, and bioaccumulation, further building upon prioritization approaches used in the TSCA 2012 Work Plan process and the objectives identified for integrating NAMs in the Canadian Chemicals Management Plan (CMP). Consistent with stakeholder feedback, this approach integrates NAMs to fill gaps when traditional testing data are not available. Through the binning approach, EPA also plans to apply U.S. and international data sources for hazard and exposure information and incorporate cutting-edge tools developed by OPPT and especially the EPA’s Office of Research and Development (ORD) in areas such as human and environmental toxicity predictions, exposure estimations, human hazard-to-exposure ratios, and predictions of persistence and bioaccumulation. Estimates concerning susceptible human subpopulations will be included but initially will be limited to the potential for exposure to children. The document outlines an iterative approach to improve and strengthen future binning efforts by applying the experience gained and through the development of updated and improved tools. Specific areas for improvement include the ability to model, score, and bin mixtures and UVCBs (chemical substances of unknown or variable composition, complex reaction products and biological materials; according to EPA these make up approximately half of the Active Inventory chemicals), updating and improving occupational exposure estimates and models, developing tools to integrate ecological hazard-to-exposure ratio information, and others. The approach document also identifies a number of caveats and potential limitations of the proposed strategy.

While the approach of binning the TSCA Inventory will help to reduce the size of the pool from which EPA will draw chemicals for potential prioritization, EPA notes that its purpose “is not to identify a list of high-priority candidates. Nor is its purpose to signal that the EPA has concerns with particular chemicals or categories of chemical substances.” Through the approach, EPA states that it will attempt to identify a portion of the TSCA Active Inventory that can be set aside as not containing candidates for high-priority designation, so that EPA can focus on chemicals that are most likely to meet the statutory standard of high priority chemicals.

According to EPA, it will be transparent in its implementation of the binning approach and will actively engage with the public on both the application and interpretation of the results of the approach. EPA intends to hold public meetings, provide comment opportunities, and employ other engagement activities to ensure that stakeholders’ expertise and perspectives are considered. The anticipated process in the development and implementation of this approach includes the following:

• Public release of the approach document, outlining the higher-level strategy for parsing the chemicals on the TSCA Active Inventory into bins. EPA has also opened a docket (EPA-HQ-OPPT-2018-0659) to take initial high-level comment on this approach and on how the resulting bins and the remaining 2014 TSCA Work Plan chemicals will inform selection of the next chemicals for prioritization, as well as a methodology to address information gaps identified during the binning process.

• EPA will use these initial comments to inform preparation and release of a white paper that describes a proof-of-concept for the binning approach using a relatively small number of substances. The white paper will provide additional details on data integration and scoring, how the resulting bins will inform selection of candidate chemicals, and how information gaps identified during the binning process will be addressed.

• A public meeting to discuss and receive feedback on the planned approach, as will be described in the forthcoming white paper, and also to discuss the results of the proof-of-concept exercise.

• Finally, application of the binning approach to the TSCA Active Inventory.

Next Steps

Upon publication of the Federal Register notice announcing the approach document, EPA will take comment on the document until November 15, 2018. A public meeting will then be held in early 2019. EPA will also open 73 chemical-specific public dockets, one for each of the remaining chemicals on the 2014 TSCA Work Plan, as well as a general docket for the public to suggest additional chemicals that are not on the Work Plan. With these latter two actions, EPA will provide the public an opportunity to submit use, hazard, and exposure information on these chemicals. EPA states that it will use these data to inform TSCA prioritization and risk evaluation for these chemicals. These dockets will be open until December 1, 2019.

Commentary

EPA has outlined a near-term working approach for identifying potential candidate chemicals for prioritization that, in our view, is well-constructed and thoughtful. EPA complements this with an outline of a future-oriented and cutting edge approach that applies existing tools and models and embraces “learning by doing,” continuous improvement, and future research efforts to strengthen and expand the available capabilities. EPA also fully embraces transparency by affording multiple opportunities for public input as well as scientific workshops.

We appreciate the pragmatism evidenced by the three factors identified for consideration in selecting potential chemicals for prioritization; these consisted of federal government priority, the quantity and quality of the available data, and EPA’s work load and resource constraints. While the latter two were well known and previously recognized, we are impressed by the recognition that, first and foremost, these TSCA efforts needed to support a broader set of federal government priorities than might be identified by OPPT alone. We have long wished that the federal government would take a more coordinated approach to its health and environmental assessment and regulatory efforts. The commitment EPA expresses in the document to both intra- and interagency federal cooperation may plant seeds with the potential for greater future coordination and coherence in areas of critical public and environmental import. Just last week we took note of and applauded the decision by EPA in its Final TSCA fees rule to apply the Small Business Administration’s (SBA) employee-based standard for defining small businesses rather than proceeding with a different (revenue-based) EPA method. Regarding the present matter, we commend OPPT for breaking out of EPA’s silo-based thinking by applying tools developed and supported by ORD over many years. The underlying research was paid for and conducted in the expectation that program offices would use the tools in their work and the applied experience gained by OPPT and ORD will provide invaluable input into ORD’s future research and development in these areas. We hope we are seeing an emerging theme of OPPT using and applying to the greatest extent possible the work and approaches developed by intra- or interagency colleagues as OPPT undertakes its TSCA responsibilities. In making this point, we note that EPA’s approach does not give similar recognition to state or tribal government priorities, although these entities can provide input via the public commenting opportunities.

The near-term approach does a good job of applying existing understanding and approaches such as that provided by the 2014 TSCA Work Plan, SCIL, ChAMP, and OECD SIDS evaluations in identifying high- and low-priority candidate chemicals. Consideration by EPA of the results of these, in some cases, hazard-based assessment efforts will be strengthened and be made explicitly risk-based when combined with the most recent information obtained by the Chemical Data Reporting (CDR) rule and other available exposure/release information.

The intermediate- and longer-term approach also considers and addresses the informational gaps and uncertainties that will affect future efforts to bin the TSCA Active Inventory. Here the document proposes use of new and emerging tools developed by OPPT and ORD, and by Canadian authorities for use in their CMP, as well as OPPT’s recent efforts regarding alternative animal testing and NAMs. EPA’s plan to develop and release a proof-of-concept white paper for the binning approach following its application to a small number of chemicals is likely to be an important milestone. This forthcoming paper will undoubtedly receive close scientific and public scrutiny. In general, although optimistic, we caution that a number of these new/emerging tools, while offering the potential for sophisticated comparative screening results and understanding, have been applied largely if not exclusively in a research context. At a minimum they have not been used and have no precedent in TSCA regulatory screening and assessment work (including in the TSCA new chemicals program).

We also note that most of the tools focus on hazard endpoints which suggests that exposure assessments will continue to be the weakest component in the process. In making this point we hasten to add that we do not believe that EPA has figured out how to fully utilize the CDR and other available exposure data to inform its assessment work, so, recognizing this, we temper somewhat our pessimism. Thus, while we believe that the approaches outlined may prove useful in meeting EPA’s goal to inform multiple activities and priorities throughout EPA, including the identification and selection of candidates for TSCA prioritization, we recognize the many unknowns and expect that experience will be a valuable teacher.

EPA’s approach document describes an important and forthcoming companion document on systematic review, Application of Systematic Review in TSCA Risk Evaluations. This document will, among other things, provide discussion of the types and sources of information that will be excluded based on data quality criteria that, in EPA’s judgment, would make the information unreliable to use for risk evaluation purposes.

As readers of our postings will recognize, we have pointed out issues and discrepancies in OPPT’s treatment of certain types of chemicals/uses under the Safer Choice program (based on the SCIL list) versus the treatment of similar chemicals when submitted under Section 5 as new chemicals. Perhaps a more fulsome accounting and reckoning between the treatment of new and existing chemicals, and increased intra-OPPT coherence will result when low-priority candidates identified from SCIL are taken through the TSCA prioritization process.