Screening Process for Existing Chemicals Proposed

High-priority substances to undergo full risk evaluation

EPA’s proposed Procedures for Prioritization of Chemicals for Risk Evaluation under the Toxic Substances Control Act (TSCA) comprises the Agency’s steps for selecting chemicals it will subject to full risk evaluations, as required by the June 2016 amendments to TSCA. The main objective of the selection or screening process is to guide the Agency toward identifying the high-priority substances that pose the greatest hazard and exposure potential first.


TSCA Section 6(b)(1) requires that the EPA establish, by rule, “a risk-based screening process, including criteria for designating chemical substances as high-priority substances for risk evaluations or low-priority substances for which risk evaluations are not warranted at the time.” TSCA Sections 6(b)(1) through (3) provide further specificity on the screening process, including the prioritization steps, screening criteria and statutory preferences, use of EPA’s March 2007 Framework for Metals Risk Assessment when prioritizing metals or metal compounds, time limits on both the prioritization process and the risk evaluations, and opportunities for public comment.The proposed rule incorporates these and all the other elements required by statute and also supplements those provisions with additional criteria the Agency expects to consider at its discretion during screening, as well as additional procedural steps to ensure effective implementation.

The EPA notes that all 85,000 chemical substances in the TSCA Inventory are subject to screening and prioritization. Another EPA proposal would require that manufacturers and importers notify the Agency about chemicals in the Inventory that are still being produced. A third proposal would establish how the Agency evaluates the risk from existing chemicals. The three proposals are available here.  

EPA granted ‘broad discretion’

Even before passage of the TSCA Amendments, the EPA had acted to identify existing chemicals and chemical uses for risk evaluation and potential regulation. In writing the amendments, Congress incorporated some of these actions. For example, in designating high-priority substances, Congress specified that the EPA must give preference to chemicals listed in the Agency’s 2014 Update of the TSCA Work Plan and also draw50 percent of all ongoing risk evaluations from the Work Plan. (In November 2016, the EPA chose the first 10 chemicals for risk evaluations from the list of 90 chemicals in the Work Plan. Risk evaluations for these chemicals and for those chemical substances for which the EPA has initiated a risk evaluation in response to manufacturer requests would be conducted according to the proposed risk evaluation rule noted above.

The actual criteria the EPA will use to screen a candidate chemical for a risk evaluation are specified in TSCA Section 6(b)(1)(A as follows:

  • The hazard and exposure potential of the chemical substance (e.g., persistence and bioaccumulation)
  • Potentially exposed or susceptible subpopulations and storage near significant sources of drinking water
  • The conditions of use or significant changes in the conditions of use of the chemical substance
  • The volume or significant changes in the volume of the chemical substance manufactured or processed

The amendments also provide the EPA with broad discretion to choose which chemicals to put into the priority-risk evaluation process. Accordingly, the Agency is proposing to include additional exposure and hazard considerations that can be used to narrow the field of potential candidates. These considerations include use in children’s products, use in consumer products, detected in human and/or ecological biomonitoring programs, potential concern for children’s health, high acute and chronic toxicity, probable or known carcinogen, and neurotoxicity. The Agency is further exercising its discretion by proposing to identify potential candidates where available information suggests that the chemical may present a hazard and that exposure is present under “one or more conditions of use,” but where an “unreasonable risk” determination cannot be made without a more extensive or complete assessment in a risk evaluation.

Steps in the process

The specific components of EPA’s proposed prioritization approach are as follows:

Policy objective. The overall objective of the process is to guide the Agency toward identifying high-priority substances that have the greatest hazard and exposure potential first. The EPA may also consider the relative hazard and exposure of a potential candidate’s likely substitute(s) to avoid moving the market to a chemical of equal or greater risks. The level of analysis necessary to support an exact ranking system is not appropriate at the prioritization stage, says the EPA, since the sole outcome of screening is a decision on whether to further evaluate the chemical substance. The EPA intends to conserve its resources and deeper analytic efforts for the actual risk evaluation.

Scope of designations. The EPA will designate the priority of a chemical as a whole and will not limit its designation to a specific use or subset of uses of a chemical. The Agency says it is proposing this approach in response to clear statutory directives. Specifically, the relevant provisions of TSCA Section 6 repeatedly refer to both the designation and evaluation of chemical substances under the conditions of use. “Conditions of use” is broadly defined as “the circumstances, as determined by the Administrator, under which a chemical substance is intended, known, or reasonably foreseen to be manufactured, processed, distributed in commerce, used, or disposed of.” The EPA believes that the addition of the phrase “conditions of use” was intended to move the Agency away from its past practice of assessing only narrow uses of a chemical substance, toward a comprehensive approach to chemical substance management.

Time frame. Initiation of prioritization begins upon publication of a notice in the Federal Register (FR), which identifies a chemical for prioritization and provides the results of the screening review. The process is complete upon publication in the FR of a notice announcing a final priority designation. The proposed rule specifies that the process—from initiation to final designation—will last between 9 and 12 months.

Categories of chemical substances. TSCA Section 26 provides the EPA with authority to take action on categories of chemical substances. Although the proposed rule most often references “chemical substances,” the Agency is also proposing to include a clear statement in the regulation that nothing in the proposed rule shall be construed as a limitation on EPA’s authority to take action with respect to categories of chemical substances and that, where appropriate, the EPA can prioritize and evaluate categories of chemical substances.

Chemicals subject to prioritization. Generally, all chemical substances listed on the TSCA Inventory are subject to prioritization. TSCA contemplates that, over time, all chemical substances on the TSCA Inventory will be prioritized into either high- or low-priority substances and that all high-priority substances will be evaluated. The Agency notes that chemicals newly added to the TSCA Inventory following EPA’s completion of premanufacture review under Section 5 of TSCA are also candidates for prioritization. But the Agency expects that such substances are not likely to be high-priority candidates in light of the risk-related determination that the EPA must make for new chemicals and new chemical uses.

Preprioritization considerations. Aside from the statutory preferences for chemical substances in the 2014 Work Plan, the statute leaves the EPA with broad discretion to choose the chemical substances to prioritize for risk evaluation. The proposed rule includes a discussion of the criteria the Agency expects to use to cull through chemicals in the TSCA Inventory. For example, as noted above, in identifying potential candidates for high-priority designations, the Agency is proposing to seek to identify substances where available information suggests that the chemical substance may present a hazard and that exposure is present under “one or more conditions of use” but where an “unreasonable risk” determination cannot be made without a more extensive or complete assessment in a risk evaluation. This is one proposed consideration that may generate resistance from the regulated community.

Information availability. The EPA will generally review the available hazard and exposure-related information and evaluate whether that information will be sufficient to allow completion of both the prioritization and risk evaluation processes. As part of such an evaluation, the Agency expects to consider the quality, objectivity, utility, and integrity of the available information. To the extent the information is not currently available or is insufficient, the EPA will determine whether or not information can be developed and collected, reviewed, and incorporated into analyses and decisions in a timely manner.

Selection and screening of a candidate chemical substance. TSCA requires that the EPA give preference to chemical substances listed in the 2014 Work Plan thathave a persistence and bioaccumulation score of 3, are known human carcinogens, and have high acute and chronic toxicity. But, again, TSCA does dictate how the Agency must ultimately select a candidate chemical substance to put into the prioritization process.

Also, the EPA says it fully recognizes the important role stakeholders can play in helping to identify candidates for prioritization or better understand the unique uses or characteristics of a particular chemical. “EPA continues to welcome this type of engagement and dialogue early in the process, including during the pre-prioritization phase,” says the Agency.

Once a single candidate chemical substance (or category of chemical substances) is selected, the EPA will screen the selected candidate against the following specific criteria and considerations in TSCA Section 6(b)(1)(A):

  • Hazard and exposure potential
  • Persistence and bioaccumulation
  • Potentially exposed or susceptible subpopulations
  • Storage near significant sources of drinking water
  • Conditions of use or significant changes in conditions of use
  • Production volume or significant changes in production volume
  • At EPA’s discretion, any other risk-based criteria relevant to the designation of the chemical substance’s priority

Initiation of prioritization. For purposes of triggering the 9- to 12-month statutory time frame, the prioritization process officially begins when the EPA publishes a notice in the FR identifying a chemical substance for prioritization.

Proposed priority designation. Based on the results of the screening review, relevant information received from the public during the initial comment period, and other information, the EPA will propose to designate the chemical substance as either a high-priority substance or low-priority substance. TSCA prohibits considering costs or other nonrisk factors in making a proposed designation.

Final priority designation. The last step is for the EPA to finalize its designation. Again, TSCA prohibits costs or other nonrisk factors from being considered in the designation.

Repopulation of high-priority substances. Upon completion of a risk evaluation for a chemical substance, TSCA requires the EPA to finalize a designation for at least one new high-priority substance, other than a risk evaluation requested by a manufacturer.

Effect of final priority designation. Final designation of a chemical as a high-priority substance requires that the EPA immediately begin a risk evaluation on that substance. The designation does not mean that the Agency has determined that the chemical substance presents a risk to human health or the environment—only that the Agency intends to consider the chemical substance for further risk review and evaluation. Furthermore, a high-priority substance designation is not a final Agency action and is not subject to judicial review or review under the Congressional Review Act.

Final designation of a chemical substance as a low-priority substance does not preclude EPA from later revising the designation if warranted. The proposed rule outlines the revision process the Agency will take.