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August 26, 2019

EPA Proposes to Designate 20 Chemical Substances as High-Priority Substances for Risk Evaluation under TSCA

The ACTA Group

The U.S. Environmental Protection Agency (EPA) published a Federal Register notice on August 23, 2019, proposing to designate 20 chemical substances as high-priority substances for risk evaluation under the Toxic Substances Control Act (TSCA).  84 Fed. Reg. 44300.  The notice and supporting docket materials identify the proposed designation for each of the chemical substances and instructions on how to access the chemical-specific information, analysis, and basis used by EPA to support the proposed designation for each chemical substance.  EPA requests information that would inform the exposure and hazard assessments and the identification of conditions of use for the 20 chemical substances.  Comments are due November 21, 2019.
As reported in our March 22, 2019, memorandum, “EPA Releases List of 40 Chemicals Undergoing Prioritization for Risk Evaluation,” EPA released in March 2019 a list of 40 chemicals for which it initiated the prioritization process for risk evaluation.  EPA selected 20 chemical substances as candidates for designation as high-priority substances and now proposes to designate the same 20 chemical substances as high-priority substances:

Chemical NameDocket Number
Dibutyl phthalate (DBP) (1,2-Benzenedicarboxylic acid, 1,2- dibutyl ester)EPA-HQ-OPPT-2018-0503
Butyl benzyl phthalate (BBP) (1,2-Benzenedicarboxylic acid, 1-butyl 2-(phenylmethyl) ester)EPA-HQ-OPPT-2018-0501
Di-ethylhexyl phthalate (DEHP) (1,2-Benzenedicarboxylic acid, 1,2-bis(2-ethylhexyl) ester)EPA-HQ-OPPT-2018-0433
Di-isobutyl phthalate (DIBP) (1,2-Benzenedicarboxylic acid, 1,2-bis-(2-methylpropyl) ester)EPA-HQ-OPPT-2018-0434
Dicyclohexyl phthalateEPA-HQ-OPPT-2018-0504
4,4′-(1-Methylethylidene)bis[2,6-dibromophenol] (TBBPA)EPA-HQ-OPPT-2018-0462
Tris(2-chloroethyl) phosphate (TCEP)EPA-HQ-OPPT-2018-0476
Phosphoric acid, triphenyl ester (TPP)EPA-HQ-OPPT-2018-0458
Ethylene dibromideEPA-HQ-OPPT-2018-0488
1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta [g]-2-benzopyran (HHCB)EPA-HQ-OPPT-2018-0430
Phthalic anhydrideEPA-HQ-OPPT-2018-0459

The supporting materials for the 20 proposed high-priority chemical substances are available for comment in their respective dockets.
EPA states that it generally used reasonably available information to screen the candidate chemical substances against the following criteria and considerations:

  • The chemical substance’s hazard and exposure potential;
  • The chemical substance’s persistence and bioaccumulation;
  • Potentially exposed or susceptible subpopulations;
  • Storage of the chemical substance near significant sources of drinking water;
  • The chemical substance’s conditions of use or significant changes in conditions of use;
  • The chemical substance’s production volume or significant changes in production volume; and
  • Other risk-based criteria that EPA determines to be relevant to the designation of the chemical substance’s priority.

In conducting the screening review during the prioritization process, EPA states that it considered sources of information relevant to the screening-review criteria as outlined in TSCA Section 6(b)(l)(A) and 40 C.F.R. Section 702.9(a) and consistent with the scientific standards of TSCA Section 26(h), including, as appropriate, sources for hazard and exposure data listed in Appendices A and B of EPA’s 2012 TSCA Work Plan Chemicals:  Methods Document.  In addition, EPA considered the hazard and exposure potential of the chemical substances and states that it did not consider costs or other non-risk factors in making the proposed priority designations.
EPA’s initiation of the prioritization process in March 2019 included a 90-day comment period for the submission of relevant information on the 20 chemical substances identified as candidates for high-priority substance designation.  EPA states that it received 125 submissions from commenters that addressed the overall prioritization process (e.g., the collection and consideration of relevant information), the review process (e.g., the use of data and approaches in risk evaluation), information specific to the candidate chemical substances (e.g., relevant studies, assessments, and conditions of use), and topics not germane to the prioritization process (e.g., scheduling future chemicals for prioritization and concerns about risk evaluation fees).  To the extent that comments provided information on additional conditions of use for the 20 candidate high-priority chemical substances, EPA discusses those conditions of use in the proposed designation documents for each chemical substance.  EPA will respond to those and any additional comments in conjunction with the final priority designation of the chemical substances.
According to the notice, under TSCA Section 6(b)(1)(B) and 40 C.F.R. Section 702.3, a high-priority substance is defined as “a chemical substance that EPA determines, without consideration of costs or other non-risk factors, may present an unreasonable risk of injury to health or the environment because of a potential hazard and a potential route of exposure under the conditions of use, including an unreasonable risk to potentially exposed or susceptible subpopulations identified as relevant by EPA.”  EPA notes that a proposed designation of a chemical substance as a high-priority substance is not a finding of unreasonable risk.  EPA states that instead, when prioritization is complete, it will have evidence that the chemicals it designated as high-priority substances may present an unreasonable risk of injury to health or the environment because of a potential hazard and a potential route of exposure under the conditions of use.  Final designation of a high-priority substance initiates the risk evaluation process, culminating in a finding of whether the chemical substance presents an unreasonable risk of injury to health or the environment under the conditions of use.


EPA continues to develop the prioritization process.  EPA suggested the 20 high- and 20 low-priority candidate substances in March in what it deemed an “initiation” of the prioritization process.  EPA invited stakeholders to submit comments or information related to the proposed designations.  EPA reports that it received 125 comment submissions touching on a variety of topics, including information on additional conditions of use.  EPA states that it discussed the additional conditions of use in the proposed designation documents but does not otherwise discuss or deal with the comments.  The high- and low-priority designations seem to have been a foregone conclusion.  In the formal proposed designation for prioritization, EPA does not directly respond to comments it received in the “initiation” phase, but EPA states that it will respond to those comments along with other comments it receives in this 90-day comment period.  EPA does not defend its selection of the “next 20” in any robust way; rather, EPA seems to restate its justifications from the “initiation” phase.  If comments received in response to the initiation stage are not addressed in proposing the designations, the value of the “initiation” phase seems questionable, except to extend the comment period for prioritization. 
The prioritization-risk evaluation-risk management clock is relentless and puts EPA in a difficult position if data gaps are identified in any phase.  Going forward, EPA may have to initiate data gathering activities before EPA initiates or proposes substances for prioritization because once EPA starts the prioritization process, it is essentially too late to generate new information other than the most basic data.  EPA can extend the prioritization deadline for three months if it requires information development under Section 4(a)(2)(B), a process that involves issuing the test order requiring industry to conduct and report the testing, followed by EPA review of the information and issuance of its final designation within 90 days of receiving the new information.  TSCA Section 6(b)(1)(C) further requires that if EPA cannot support a low-priority designation during this 90-day period, it must designate the chemical as high-priority. Perhaps EPA can identify a way to time all of these steps in the process that would allow for data generation to occur while still providing the required comment periods before issuing a final designation.  Then again, perhaps the complications and requirements that attend to this prioritization-related data development process are why EPA has not yet used this additional new Section 4 authority.
EPA seems to have ample evidence that the 20 high-priority candidates are worthy of that designation.  Some may question whether EPA selected the “right” 20, but EPA does have some discretion on which substances it designates for prioritization, even if EPA has not thoroughly explained why it selected these 20 among the dozens of other Work Plan chemicals.  The prioritization “preference” guidance found in Section 6(b)(2)(D) seems to be of limited value in sorting this out, as relatively few 2014 Work Plan substances have persistence and bioaccumulation scores of three or are known human carcinogens and have high acute and chronic toxicity. 
Perhaps the more interesting outcome will be the low-priority designations.  EPA will have to establish, subject to legal challenge, that it has sufficient data to establish that each substance does not meet the criteria for high-priority designation.  If EPA cannot adequately satisfy the criteria for low-priority designation, EPA will have more than 20 high-priority substances in its risk evaluation queue while at the same time missing the statutory deadline to designate 20 low-priority substances.