[Federal Register Volume 88, Number 208 (Monday, October 30, 2023)]
[Proposed Rules]
[Pages 74292-74326]
[FR Doc No: 2023-23428]

Vol. 88

Monday,

No. 208

October 30, 2023

Part III

Environmental Protection Agency

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40 CFR Part 702

Procedures for Chemical Risk Evaluation Under the Toxic Substances
Control Act (TSCA); Proposed Rule

Federal Register / Vol. 88 , No. 208 / Monday, October 30, 2023 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 702

[EPA-HQ-OPPT-2023-0496; FRL-8529-01-OCSPP]
RIN 2070-AK90

Procedures for Chemical Risk Evaluation Under the Toxic
Substances Control Act (TSCA)

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA, ``the Agency'') is
proposing to amend the procedural framework rule for conducting risk
evaluations under the Toxic Substances Control Act (TSCA). 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 consideration of 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. EPA has reconsidered the procedural
framework rule for conducting such risk evaluations and determined that
certain aspects of that framework should be revised to better align
with applicable court decisions and the statutory text, to reflect the
Agency's 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
need to further amend the Agency's procedural rule.

DATES: Comments must be received on or before December 14, 2023. 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 your comments on or
before November 29, 2023.

ADDRESSES: Submit your comments, identified by docket identification
(ID) number EPA-HQ-OPPT-2023-0496, through the Federal eRulemaking
Portal at https://www.regulations.gov. Follow the online instructions
for submitting comments. Do not submit electronically any information
you consider to be Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Additional
instructions on commenting or visiting the docket, along with more
information about dockets generally, is available at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT:
    For technical information contact: Susanna W. Blair, Immediate
Office, Office of Pollution Prevention and Toxics, Environmental
Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC 20460-
0001; telephone number:<PHONE_NUMBER>; email address:
[email protected].
    For general information contact: The TSCA-Hotline, ABVI-Goodwill,
422 South Clinton Ave., Rochester, NY 14620; telephone number: (202)
554-1404; email address: [email protected].

SUPPLEMENTARY INFORMATION:

I. Executive Summary

A. Does this action apply to me?

    EPA is primarily proposing to amend procedural requirements that
apply to the Agency's activities in carrying out TSCA risk evaluations.
However, EPA is also proposing certain amendments to the process and
requirements that manufacturers (including importers) would be required
to follow when they request an Agency-conducted TSCA risk evaluation on
a particular chemical substance. You may be potentially affected by
this action if you manufacture or import chemical substances regulated
under TSCA. Since other entities may also be interested, the Agency has
not attempted to describe all the specific entities and corresponding
NAICS codes for entities that may be interested in or affected by this
action. The following list of North American Industrial Classification
System (NAICS) codes is not intended to be exhaustive, but rather
provides a guide to help readers determine whether this document
applies to them. Potentially affected entities may include:
     Petroleum Refineries (NAICS code 324110);
     Chemical Manufacturing (NAICS code 325);
     Unlaminated Plastics Film and Sheet (except Packaging)
Manufacturing (NAICS code 326113);
     Unlaminated Plastics Profile Shape Manufacturing (NAICS
code 326121);
     Plastics Pipe and Pipe Fitting Manufacturing (NAICS code
326122);
     Laminated Plastics Plate, Sheet (except Packaging), and
Shape Manufacturing (NAICS code 326130);
     Polystyrene Foam Product Manufacturing (NAICS code
326140);
     Urethane and Other Foam Product (except Polystyrene)
Manufacturing (NAICS code 326150);
     Plastics Bottle Manufacturing (NAICS code 326160);
     Plastics Plumbing Fixture Manufacturing (NAICS code
326191);
     All Other Plastics Product Manufacturing (NAICS code
326199);
     Tire Manufacturing (except Retreading) (NAICS code
326211);
     Tire Retreading (NAICS code 326212);
     Rubber and Plastics Hoses and Belting Manufacturing (NAICS
code 326220);
     Rubber Product Manufacturing for Mechanical Use (NAICS
code 326291);
     All Other Rubber Product Manufacturing (NAICS code
326299);
     Pottery, Ceramics, and Plumbing Fixture Manufacturing
(NAICS code 327110);
     Clay Building Material and Refractories Manufacturing
(NAICS code 327120);
     Flat Glass Manufacturing (NAICS code 327211);
     Other Pressed and Blown Glass and Glassware Manufacturing
(NAICS code 327212);
     Glass Container Manufacturing (NAICS code 327213);
     Glass Product Manufacturing Made of Purchased Glass (NAICS
code 327215);
     Cement Manufacturing (NAICS code 327310);
     Ready Mix Concrete Manufacturing (NAICS code 327320);
     Concrete Block and Brick Manufacturing (NAICS code
327331);
     Concrete Pipe Manufacturing (NAICS code 327332); and
     Other Concrete Product Manufacturing (NAICS code 327390).
    If you have any questions regarding the applicability of this
proposed action to a particular entity, consult the technical
information contact listed under FOR FURTHER INFORMATION CONTACT.

B. What is the Agency's authority for taking this action?

    EPA is issuing this Notice of Proposed Rulemaking (NPRM) pursuant
to the authority in TSCA section 6(b)(4) (15 U.S.C. 2605(b)(4)). EPA
has inherent authority to reconsider previous decisions and to revise,
replace, or repeal a decision to the extent permitted by law and
supported by reasoned explanation. See FCC v. Fox Television Stations,
Inc., 556 U.S. 502, 515 (2009); see also Motor Vehicle Mfrs. Assn v.
State Farm Mutual Auto. Ins. Co., 463 U.S. 29, 42 (1983). See also the
discussion in Units II.A. and B.

C. What action is the Agency taking?

    EPA is proposing to amend regulations that address how the Agency
conducts risk evaluations on chemical

substances under TSCA. These changes include, but are not limited to,
targeted changes to certain definitions, clarifications regarding the
required scope of risk evaluations, considerations related to peer
review and the Agency's implementation of the scientific standards, the
approach for risk determinations on chemical substances and
considerations related to unreasonable risk, and the process for
revisiting a completed risk evaluation. EPA is also proposing to amend
the process and requirements for manufacturers making a voluntary
request for an Agency-conducted risk evaluation on a particular
chemical substance. EPA is requesting public comment on all aspects of
this proposal.

D. Why is the Agency taking this action?

    As further explained in Units I., II., and III., EPA reexamined the
July 20, 2017, final rule (Ref. 1) (hereinafter ``2017 final rule'')
that established procedures and requirements for chemical risk
evaluation under TSCA, in consideration of:
     The statutory text and structure and Congressional intent.
     The November 14, 2019, opinion issued by U.S. Court of
Appeals for the Ninth Circuit in response to petitions for judicial
review, consolidated under Safer Chemicals, Healthy Families v. USEPA
(Ref. 2), of the 2017 final rule and related court orders.
     Executive Order 13990, Protecting Public Health and the
Environment and Restoring Science to Tackle the Climate Crisis (Ref.
3).
     Lessons learned from the Agency's implementation of the
risk evaluation program to date including feedback from the National
Academies of Science Engineering and Medicine and scientific peer
reviewers.
    As a result of this reexamination, the Agency is proposing targeted
amendments of the 2017 final rule.

E. What are the estimated incremental impacts of this action?

    The incremental impacts of this action are associated with
procedural requirements, as described in Unit III.K., which apply to
manufacturers when manufacturers (including importers) elect to request
that EPA perform a risk evaluation on a particular chemical substance.
EPA has estimated the potential burden and costs associated with the
proposed requirements for submitting a request for an Agency-conducted
risk evaluation on a particular chemical substance. These estimates of
burden and costs are available in the docket, and are discussed in Unit
V. and briefly summarized here (Ref. 4).
    The total estimated annual burden is 166 hours and $115,711 (per
year), which is based on an estimated per request burden of 166 hours.
    In addition, EPA's evaluation of the potential costs associated
with this action is discussed in Unit VI.B. Since this rulemaking
focuses on the activities that a manufacturer must perform, the
estimated incremental costs to the public are expected to be
negligible. EPA requests specific comment on the burden estimate and
assumptions associated with the calculation associated with the burden
(e.g., number of requests EPA expects).

F. What should I consider as I prepare my comments for EPA?

1. Submitting CBI
    Do not submit CBI to EPA through https://www.regulations.gov or
email. If you wish to include CBI in your comment, please follow the
applicable instructions at https://www.epa.gov/dockets/commenting-epa-dockets#rules and clearly mark the part or all of the information that
you claim to be CBI. In addition to one complete version of the comment
that includes information claimed as CBI, a copy of the comment that
does not contain the information claimed as CBI must be submitted for
inclusion in the public docket. Information so marked will not be
disclosed except in accordance with procedures set forth in 40 CFR part
2.
2. Tips for Preparing Your Comments
    When preparing and submitting your comments, see the commenting
tips at https://www.epa.gov/dockets/commenting-epa-dockets.html.

II. Background

A. Statutory Requirements for Risk Evaluation

    TSCA section 6(b)(4) requires EPA to establish, by rule, a process
to conduct risk evaluations. Specifically, EPA is directed to use this
process to ``determine whether a chemical substance presents an
unreasonable risk of injury to health or the environment, without
consideration of costs or other non-risk factors, including an
unreasonable risk to a potentially exposed or susceptible subpopulation
identified as relevant to the risk evaluation by the Administrator,
under the conditions of use.'' (15 U.S.C. 2605(b)(4)(A)). TSCA sections
6(b)(4)(A) through (H) enumerate the deadlines and minimum requirements
applicable to this process, including provisions that direct which
chemical substances must undergo risk evaluation, the development of
criteria for manufacturer-requested risk evaluations, the minimum
components of an Agency risk evaluation, and the timelines for public
comment and completion of the risk evaluation. The law also requires
EPA to consider reasonably available information and operate in a
manner that is consistent with the best available science and make
decisions based on the weight of the scientific evidence. (15 U.S.C.
2625(h) and (i)).

B. Judicial Review of the 2017 Final Rule

    In the preamble of the 2017 final rule, EPA explained that it
interpreted the requirements of TSCA section 6 to apply to conditions
of use for which manufacturing, processing, or distribution in commerce
is intended, known to be occurring, or reasonably foreseen to occur,
rather than to legacy uses, which EPA used as a term for continuing,
in-situ uses of chemicals for which manufacturing, processing, or
distribution in commerce had ceased (e.g., certain phased-out flame
retardants present in textiles or furniture that continue to be used,
asbestos-containing pipe wrap, etc.), or associated disposal. In
addition, among other regulatory provisions, the 2017 final rule
established that the submission of inaccurate, incomplete, or
misleading information pursuant to a manufacturer-requested risk
evaluation is a prohibited act subject to penalties under title 18 of
the U.S. Code. The 2017 final rule also established requirements for
information that must be submitted by a manufacturer when requesting
that EPA conduct a risk evaluation (40 CFR 702.37(b)(4)) and that the
submitted information be held to the scientific standards established
in TSCA section 26(h) (40 CFR 702.37(b)(6)).
    Several non-governmental organizations filed petitions for judicial
review of the 2017 final rule, which were consolidated in the U.S.
Court of Appeals for the Ninth Circuit (hereafter, the ``Ninth
Circuit'') under Safer Chemicals, Healthy Families v. USEPA, on August
10, 2017 (Ref. 2). The Ninth Circuit issued its opinion on November 14,
2019, holding that the EPA unlawfully excluded ``legacy uses and
associated disposals'' from the conditions of use that the agency would
consider in any risk evaluation (Ref. 2). Also, at the Agency's
request, the Ninth Circuit (1) vacated and remanded the rule provisions
applying criminal penalties to the submission of inaccurate or
incomplete information to

EPA pursuant to a manufacturer-requested risk evaluation, and (2)
remanded without vacatur the rule provisions addressing the information
requirements for, and application of the TSCA section 26 scientific
standards to, a manufacturer-requested risk evaluation (Ref. 5).
    The Court declined to rule on several other aspects of the
challenge, including that the rule suggested EPA would make risk
determinations on individual uses of a chemical instead of on the
chemical itself, and statements in the preamble regarding broad
discretion to choose to exclude conditions of use from the scope of the
risk evaluations. The Court reasoned that petitioners' claim that EPA
would make risk determinations on individual uses instead of on the
chemical itself as the law required was not justiciable due to
ambiguity in the 2017 final rule text. The Court noted it was unclear
``whether the Agency will actually conduct risk evaluations in the
manner [those litigants] fear[ed]'' and that the claim was therefore
not justiciable (Ref. 2). With regard to petitioners' claim that EPA
intended to exclude conditions of use out of the scope of the risk
evaluations, the court held that claim not ripe, but noted that it did
``not interpret the language in the [2017 final rule] to say anything
about exclusion of conditions of use'' (Ref. 2).

C. Review of the 2017 Final Rule Under Executive Order 13990

    Executive Order 13990 instructs that the Federal Government be
guided by the best science and be protected by processes that ensure
the integrity of Federal decision-making, and established the
Administration's policy of, among other concerns, following the
science, improving public health and protecting the environment,
limiting exposure to dangerous chemicals, reducing greenhouse gas
emissions, and prioritizing environmental justice (EJ) when delivering
on these concerns. Executive Order 13990 also instructs agencies to (1)
review actions issued between January 20, 2017, and January 20, 2021,
that may be inconsistent with or present obstacles to implementing the
policy established in the order and, (2) consider suspending, revising,
or rescinding such actions. Also on January 20, 2021, the Biden-Harris
Administration issued a list of specific actions to be reviewed in
accordance with Executive Order 13990 that included the 2017 final rule
(Ref. 6).
    EPA announced certain policy changes for TSCA risk evaluations on
June 30, 2021 (Ref. 7) to ensure that risk evaluations follow the
science and the law, including:
1. Expanded Consideration of Exposure Pathways
    Prior to June 30, 2021, the first 10 risk evaluations did not
consistently assess air, water or disposal exposures to the general
population based on an argument that these exposure pathways were
already regulated, or could be regulated, under other statutes
administered by EPA, such as the Clean Air Act, Safe Drinking Water
Act, Clean Water Act, Resource Conservation and Recovery Act, or
Comprehensive Environmental Response, Compensation, and Liability Act.
The approach to exclude certain exposure pathways conflicted with the
plain language of the law to evaluate chemical substances under the
known, intended or reasonably foreseen circumstances associated with
the full lifecycle of the chemical substance. It prevented
consideration of relevant exposure information (e.g., information
indicating presence of the chemical in air or water) in spite of
statutory requirements that the Agency base its decisions on the best
available science. The approach also resulted in a failure to
consistently and comprehensively address potential exposures to the
general population, as well as to certain potentially exposed or
susceptible subpopulations. EPA announced it would no longer exclude
consideration of such exposure pathways from TSCA risk evaluations.
2. Assumptions About Use of Personal Protective Equipment (PPE)
    Prior to June 30, 2021, EPA's TSCA risk evaluations generally
assumed that workers were always provided and appropriately used PPE.
However, as described in Unit III.G.1., data on violations of PPE use
suggest that assumptions that PPE is always provided to workers, worn
properly, and effective at eliminating exposures are not justified. In
addition, TSCA requires that risk evaluations consider the known,
intended or reasonably foreseen circumstances associated with the
chemicals substance--including circumstances that result or could
result in exposures to workers. For the reasons described further in
Unit III.E.1., EPA believes that circumstances that result in
occupational exposures to chemicals are reasonable to foresee, and, in
many cases, known. As such, continued application of this general
assumption could result in risk evaluations that underestimate risks,
and in turn, prevent risk management rules from affording necessary
protections. EPA announced that it would no longer assume that PPE is
always used in occupational settings when making unreasonable risk
determinations for a chemical.
3. ``Whole Chemical'' Risk Determination Approach
    Prior to June 30, 2021, EPA made separate unreasonable risk
determinations for each condition of use identified in the risk
evaluation scope. EPA announced that, going forward, it would make the
determination of unreasonable risk on ``the chemical substance,''
rather than for each individual condition of use in isolation. As
described further in Unit III.F.1., doing so going forward better
aligns with the statute and Congress' intent, and enables the Agency's
risk determinations to better reflect the potential for combined
exposures across multiple conditions of use.
    EPA invites public comment on the adoption of these changes in the
amended procedural rule.

D. Agency Implementation

    Since the 2017 final rule, EPA has finalized ten chemical risk
evaluations under TSCA and published a draft supplement to the risk
evaluation for 1,4-Dioxane. Additionally underway are 20 more risk
evaluations on high-priority substances, a part 2 of the asbestos risk
evaluation that will cover additional fiber types and ``legacy''
conditions of use, and several manufacturer-requested risk evaluations
(Ref. 8). EPA is also developing a number of rulemakings to address
unreasonable risks identified in these risk evaluations. The Agency has
gained valuable experience in carrying out these actions and received a
wealth of feedback on our procedures from public commenters and through
scientific peer review. The proposed rule reflects lessons learned,
efforts to increase efficiencies, and includes improvements to the
process and requirements for manufacturer-requested risk evaluations
that are more consistent with Agency scientific practices and policies.
The proposed rule also includes some structural and substantive
revisions for greater clarity and readability, and, more generally, to
enhance the public's understanding of how EPA expects to carry out TSCA
risk evaluations.
    EPA intends that the provisions of this rulemaking be severable. In
the event that any individual provision or part of this rulemaking is
invalidated, EPA intends that this would not render the entire
rulemaking invalid, and that any individual provisions that can
continue to operate will be left in place.

III. Proposed Amendments

A. Policy Objectives

    The risk evaluation process established in 40 CFR part 702, subpart
B outlines how EPA will determine, pursuant to TSCA section 6(b)(4)(A),
whether a chemical substance presents an unreasonable risk of injury to
health or the environment. EPA's general objectives for the proposed
amendments, in keeping with the considerations addressed in Unit II,
are to (1) better align the TSCA risk evaluation process with the
statutory text and structure and Congressional intent, (2) ensure that
the risk evaluation process under TSCA is consistent with the best
available science and based on the weight of the scientific evidence,
maintains the integrity of Federal decision-making, and upholds the
policy in various Executive orders, (3) address the outcome of the
Ninth Circuit litigation on the 2017 final rule, (4) apply lessons
learned to date to improve the Agency's processes moving forward, and
(5) enhance the public's understanding of how EPA expects to carry out
subsequent TSCA risk evaluations. Through improvements to the risk
evaluation process in these proposed amendments, EPA anticipates that
any risk management actions following any determination that a chemical
substance presents unreasonable risk will result in needed public
health and environmental protections that limit exposure to dangerous
chemicals, and, where applicable, address the climate crisis and
advance environmental justice.
    To accomplish these objectives, EPA is proposing targeted changes
and clarifying edits to the existing process by which the Agency
evaluates risk from chemical substances for purposes of TSCA section 6.
Additionally, this proposal includes structural changes to the
regulatory text to accomplish these goals. EPA is not proposing to
establish highly detailed provisions that will address every
eventuality or possible consideration that might arise. Due to the
rapid advancement of the science of risk evaluation and the science and
technology that inform risk evaluation, this 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.

B. General Provisions

1. Applicability of Updated Procedures
    EPA is proposing that the changes to the procedures as part of this
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 would expect to apply the proposed
changes to those risk evaluations only to the extent practicable,
taking into consideration the statutory requirements and deadlines.
Where a change to a risk evaluation would prevent the Agency from
meeting the statutory deadline, for example, EPA would generally not
view that change as practicable. However, where applying a proposed
change would impact timeliness but also ensure compliance with other
statutory obligations (e.g., conducting an appropriately scoped risk
evaluation), EPA would make a judgment on practicability by weighing
the implications for public health and environment, defensibility from
both a scientific and legal perspective, Agency priorities and the
availability of resources. 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 this
NPRM, and does not anticipate significant challenges in this area.
Finally, EPA does not expect to apply these procedures retroactively to
risk evaluations already completed.
2. Categories of Chemical Substances
    EPA is proposing to clarify the regulations with respect to their
applicability to risk evaluations on categories of chemical substances.
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).
Although the rule's procedural requirements generally refer to
``chemicals'' or ``chemical substances,'' EPA is proposing to clarify
in the regulatory text at Sec.  702.31(d) that those references also
apply to categories of chemical substances.

C. Definitions

    EPA is proposing changes to a number of definitions codified in the
existing regulatory text. EPA is proposing to eliminate the codified
definitions for ``best available science'' and ``weight of scientific
evidence.'' As described in greater detail in Unit III.I., EPA believes
that defining these concepts in the rulemaking is both unnecessary and
inhibits the Agency's flexibility to quickly adapt to and implement
changing science. Not codifying regulatory definitions of these
scientific terms is consistent with the approach in the 2017 proposed
rule (Ref. 9) (hereinafter ``2017 proposed rule'') and was supported by
public comment. Instead, as described in Unit III.I. EPA intends to
ensure that its risk evaluations are consistent with Agency guidance
and methodologies in applying these terms. As TSCA requires, at 15
U.S.C. 2625(h), EPA's risk evaluations will continue to use scientific
information, technical procedures, measures, methods, protocols,
methodologies, or models, employed in a manner consistent with the best
available science. Further, both risk evaluation and risk management
decisions under TSCA section 6 will be based on the weight of the
scientific evidence, as required by 15 U.S.C. 2625(i). EPA's expected
application of these terms is more fully described in Unit III.G.
regarding Risk Evaluation Considerations.
    Second, and as described further in Unit III.G.4., EPA is proposing
an addition to the examples identified in the definition of
``potentially exposed or susceptible subpopulation'' which currently
include ``infants, children, pregnant women, workers, or the elderly.''
The Agency proposes to add ``overburdened communities'' to better
reflect the Agency's intent to consider risks to particular communities
in the United States that potentially experience disproportionate
environmental harms and risks, while also ensuring environmental
justice--the fair treatment and meaningful involvement of all people
regardless of race, color, culture, national origin, income, and
educational levels with respect to the development, implementation, and
enforcement of protective environmental laws, regulations, and
policies--is considered where appropriate, including as part of any
subsequent risk management action.
    Finally, EPA is proposing minor updates to a number of other
definitions to better align with existing Agency guidance.
Specifically, the definitions for ``pathways'' and ``routes'' have been

adjusted for consistency with EPA's Exposure Factors Handbook (Ref.
10). Additionally, 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
not only to individual persons, but to the populations and environment
when doing so is consistent with the best available science. EPA is not
proposing to amend the definitions for ``act,'' ``conditions of use,''
``reasonably available information,'' ``sentinel exposure,''
``uncertainty,'' or ``variability.''

D. Technical Corrections and Reorganization

    The proposed rule reflects a number of minor updates and
corrections and general organizational restructuring. For example,
references to 15 U.S.C. 2605(b)(2)(A) have been removed in light of the
fact that the law's one-time requirement related to identification of
the first group of 10 chemicals for risk evaluation has been satisfied
and is no longer applicable for purposes of the procedural rule.
Additionally, EPA made minor updates to the regulatory text to correct
typos and to ensure consistency in use of certain phrases (e.g.,
manufacturer-requested risk evaluations). More generally, EPA aimed to
improve the readability of certain provisions, and, ultimately, enhance
the public's ability to understand how EPA will undertake TSCA risk
evaluations. 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. EPA
welcomes comment on these changes to enhance clarity and readability.
EPA has provided a short description of the reorganization:
     Proposed Sec. Sec.  702.31, 702.33, and 702.35 have
retained the same organization.
     Proposed Sec.  702.37 ``Evaluation requirements'' includes
many of the components of Sec.  702.41 of the 2017 final rule,
including statutory requirements of a risk evaluation, upholding the
science requirements of section 26(h), inclusion of conditions of use,
and clarity regarding making an unreasonable risk determination on the
chemical substance. This section also includes EPA's approach to
information and information sources, much of which is moved from Sec.
702.41(b) in the 2017 final rule. New proposed language included in
this proposed section is EPA's approach to conducting a fit-for-purpose
risk evaluation, addressing information gaps, and use of data gathering
authorities.
     Proposed Sec.  702.39 is a newly titled section
``Components of risk evaluation'' that is composed of 2017 final rule
Sec. Sec.  702.41, 702.43, 702.45. This one section includes the
components of a risk evaluation (e.g., scope, hazard assessment,
exposure assessment, risk characterization, risk determination) and
what they must contain. Some of the specific requirements of the hazard
and exposures assessment have been streamlined and reconfigured from
the 2017 final rule.
     Proposed Sec.  702.41 ``Peer review'' was Sec.  702.47 in
the 2017 final rule.
     Proposed Sec.  702.43 contains the parts of a risk
evaluation (e.g., draft scope, final scope, draft risk evaluation and
final risk evaluation) and the process and timelines associated with
the development and publication of these parts. Much of this section
was moved from the 2017 final rule Sec.  702.41. This proposed section
now includes provisions pertaining to substantive revisions to these
documents post publication.
     Proposed Sec.  702.45 is the revised process for
submitting a manufacturer requested risk evaluation, moved from the
2017 final rule 702.37.
     Proposed Sec.  702.47 ``Interagency collaboration''
remains unchanged from 2017 final rule Sec.  702.39. As part of EPA's
commitment to identify information earlier in the prioritization and
risk evaluation processes, the Agency expects to continue to engage and
enhance coordination with other Federal agencies that may have
chemical-specific information. Doing so will not only serve to inform
the Agency's work in the risk evaluation, but can also help to
proactively identify conditions of use that may be essential to
national security, critical infrastructure, and/or mission critical
uses, identify existing safety measures Federal agencies already have
in place for their uses, and inform any subsequent risk management
approaches.
     Proposed Sec.  702.49 ``Publicly available information''
remains substantively unchanged from Sec.  702.51 from the 2017 final
rule.

E. Scope of TSCA Risk Evaluations

1. Inclusion of All Conditions of Use
    EPA 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. These proposed amendments are intended to ensure that the
scopes of future risk evaluations are determined in accordance with the
law.
    When TSCA was originally signed into law in 1976, there were tens
of thousands of chemicals in commerce and the law imposed no mandate
that EPA conduct any assessments to determine whether those existing
chemicals present unreasonable risk of injury to health or the
environment. While EPA did conduct some risk assessments on a handful
of these existing chemicals prior to 2016, those assessments were
focused on a specific subset of individual conditions of use of
chemicals (e.g., paint and coating removal, vapor degreasing, etc.).
The net effect of this use-by-use approach was that--even if EPA were
to identify risks through a risk assessment and successfully promulgate
a rule under TSCA to manage those particular risks--the public would
still not have certainty regarding risks from the full spectrum of uses
of the chemical substance. This uncertainty, in turn, would continue to
erode public confidence in the safety of chemicals pervasive in our
households, communities and the environment, and encourage states to
adopt an increasingly complex patchwork of regulatory measures to
address chemical risks.
    One of the defining features of the 2016 amendments to TSCA was the
mandate for EPA to systematically prioritize those thousands of
existing chemicals for review, and then to evaluate their risks,
holistically, under the chemical's ``conditions of use''--a phrase that
Congress defined to capture a chemical's full lifecycle, i.e., ``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.'' (15 U.S.C. 2602(4)). While clearly a significant undertaking,
Congress recognized that comprehensive progress on evaluating the
universe of thousands of existing chemicals would not be made without
this mandate, coupled with a strong risk-based safety standard and
deadlines

for completing the work (Ref. 11). To allow EPA to continue to address
only a subset of each chemical's uses as part of the new TSCA process
would deny such comprehensive progress.
    The question of whether the Agency has broad discretion under the
law to exclude conditions of use from the scope of risk evaluations was
the source of much discussion publicly during the development of the
2017 proposed and final rules. EPA believes the approach proposed
herein is more consistent with congressional intent and reflects
consensus of technical discussion with congressional negotiators
leading up to the passage of the 2016 amendments. See also Ref. 11 at
p. S3516 (implying the lack of discretion in the ``mandate to consider
conditions of use'') and p. S3519 (referencing the prior TSCA risk
assessments that did not consider ``all conditions of use'' and
Congress' desire to nonetheless allow EPA to proceed with risk
management based on those select ``partial'' risk evaluations).
However, in the preamble to the 2017 final rule the Agency asserted
that it retained discretion to exclude conditions of use from the scope
of TSCA risk evaluations. Ref. 1 at p. 33729.
    In support of this assertion of discretionary scoping authority in
the 2017 final rule, EPA pointed to language in TSCA section 6(b)(4)(D)
that requires EPA to identify the conditions of use in a scope document
that the Agency ``expects to consider'' in a risk evaluation and the
``as determined by the Administrator'' phrasing in the statutory
definition of ``conditions of use'' itself (Ref. 1 at p. 33729). EPA
argued that such language gave the Agency discretion to select among
the conditions of use and, ultimately, to exclude conditions of use
from the scope of TSCA risk evaluations. EPA expressed at that time
that those provisions empowered the Agency to exclude, for example,
conditions of use that the Agency deemed ``de minimis'' in nature, or
conditions of use where opportunities for exposure were likely to be
limited (e.g., closed system or intermediate) (Ref. 1 at p. 33729). As
discussed further in Unit III.E.3., EPA has also relied on this
interpretation to exclude consideration of exposure pathways in TSCA
risk evaluations where EPA or another regulatory agency had or could
assess and regulate the same chemical--a policy that excluded exposures
to the general population through air, water and disposal, and left
potential risks unaccounted for.
    Upon further review, and as described in the preamble to the 2017
proposed rule and supported by legislative history, EPA believes that
the better reading of TSCA's statutory text and structure is that EPA
does not have discretionary scoping authority, and that risk
evaluations are to be conducted on the circumstances under which the
chemical is known, intended and reasonably foreseen to be manufactured,
processed, distributed in commerce, used, and disposed of (i.e.,
activities that constitute the ``conditions of use'' within the meaning
of TSCA section 3(4)) (15 U.S.C. 2602(4)). The plain language of TSCA
section 6(b)(4)(A) specifies that EPA must determine in a risk
evaluation whether ``a chemical substance'' presents an unreasonable
risk of injury to health or the environment ``under the conditions of
use.'' Similar language appears throughout section 6 of the law. See,
for example, 15 U.S.C. 2605(b)(4)(G)(i) and (ii) stating that the risk
evaluation ``for a chemical substance'' must be completed within 3 to
3.5 years of initiation. As such, while EPA at one time interpreted the
statue to permit a different approach, the statute is better
interpreted as requiring that the evaluation must be on the chemical
substance--not a subset of individual conditions of use of the chemical
substance. EPA also believes the purpose of the requirement to evaluate
the ``chemical substance'' was to ensure that the Agency, through the
risk evaluation process, would comprehensively determine whether a
chemical substance, under the known, intended, and reasonably foreseen
circumstances of manufacture, processing, distribution in commerce, use
and disposal, presents an unreasonable risk. This reading also aligns
with the requirements under the 2016 TSCA amendments to establish a
constant pipeline of activity on assessing chemical substances and
managing risks, effectively driving forward progress on the tens of
thousands of unreviewed existing chemical substances in commerce (15
U.S.C. 2605(b)(2) and (b)(3)(C)). In the absence of comprehensive risk
evaluations on chemical substances (i.e., an approach that considered
only a subset of a chemical's uses), the unevaluated uses would create
uncertainty as to whether EPA had fully addressed a chemical's
unreasonable risk and further delay progress on the backlog of existing
chemicals.
    Given these considerations, EPA believes that the phrase ``as
determined by the Administrator'' in the statutory definition of
``conditions of use'' requires application of fact and professional
judgment in determining whether or not a particular circumstance is
known, intended or reasonably foreseen--and should not be viewed as
license to select among those circumstances in determining which should
be included or excluded from the scope of a risk evaluation that is to
be completed on a chemical substance (15 U.S.C. 2602(4)). Likewise, the
instruction in TSCA section 6(b)(4)(D) for the Agency to--during the
scoping phase--identify the conditions of use it ``expects to
consider'' in a risk evaluation, is best read as directing the Agency
to identify the uses and other activities that it has determined
constitute the conditions of use of the chemical substance, while
acknowledging that the Agency's expectations at the scoping phase may
not always align perfectly with the conditions of use actually
considered and assessed in draft and final risk evaluations. EPA may,
for example, mistakenly identify a condition of use in the scope
document, and later remove it from analysis in the risk evaluation.
Alternatively, EPA might be unaware of or inadvertently exclude a
condition of use during the scoping phase, but later incorporate it
into its risk evaluation. While EPA at one time interpreted the
language differently, 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. The Ninth Circuit agreed with
this view, noting that the phrase ``conditions of use that the EPA
plans to consider'' in the 2017 final rule and the similar phrase
``expects to consider'' in TSCA section 6(b)(4)(D) simply refer to the
Agency's role in determining what the conditions of use are for a
particular substance, and do not grant EPA discretion to exclude
conditions of use from the scope of a risk evaluation (Ref. 2).
    Consideration of all conditions of use in TSCA risk evaluations is
also necessary from a scientific perspective to ensure development of a
technically sound determination as to whether a chemical substance
presents an unreasonable risk of injury to health or the environment.
Thus, consideration of all conditions of use ensures risk evaluations
are consistent with the best available science and based on the weight
of scientific evidence (15 U.S.C. 2625(h) and (i)). As discussed
further in Unit III.G.2., there may be situations where certain
conditions of use are associated with relatively lower exposures, but
nonetheless in the aggregate those uses may contribute to

unreasonable risk. Exclusion of conditions of use from risk
evaluations--irrespective of the Agency's intention in so doing--
deprives the public of a complete picture of the chemical's risk, and
may leave significant risk to human health or the environment
unaccounted for and ultimately unaddressed.
    For these reasons, the proposed rule clarifies that EPA will not
exclude conditions of use (i.e., any circumstances under which the
chemical is known, intended or reasonably foreseen to be manufactured,
processed, distributed in commerce, used or disposed of) from the scope
of a risk evaluation by amending the regulatory text where it was
either stated or implied that the Agency had broad discretion to
exclude certain conditions of use from analysis.
2. Determination of ``Conditions of Use''
    Although EPA 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, EPA 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. As such, 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. As described previously, the phrase ``as determined
by the Administrator'' in the statutory definition of ``conditions of
use'' requires EPA to review the reasonably available information and
exercise judgment in determining whether a particular circumstance is
intended, known or reasonably foreseen. For example, when information
suggests that a circumstance of manufacture, processing, distribution
in commerce, use or disposal is known to be occurring, EPA will
determine that known circumstance to be a condition of use and include
it within the scope of the risk evaluation, irrespective of other
factors like the likelihood of that particular condition of use to be a
significant contributor to risk. Likewise, where, in the Agency's
professional judgment, a circumstance is reasonably foreseen to occur
in the future, EPA will determine that circumstance to be a condition
of use and include it within the scope of the risk evaluation, even
where that condition of use may not contribute significantly to the
Agency's ultimate conclusions on risk.
    In the preamble to the 2017 final rule (Ref. 1) EPA identified
legacy disposal as falling outside the definition of ``conditions of
use.'' EPA interpreted the TSCA definition for ``conditions of use'' as
focusing on circumstances that are prospective or on-going, rather than
reaching back to evaluate risks associated with legacy disposal (i.e.,
disposal that has already occurred) (Ref. 1 at p. 33730). The Ninth
Circuit agreed, holding that TSCA unambiguously does not require legacy
disposals to be considered as conditions of use (Ref. 2 at pp. 425-
426). The Court reasoned that a substance that has already been
disposed of will not ordinarily be intended, known, or reasonably
foreseen to be prospectively manufactured, processed, distributed in
commerce, used, or disposed of again (Ref. 2). EPA is not reconsidering
that issue in this proposal. However, EPA generally does not view any
other categorical exclusions from the definition of condition of use as
appropriate.
    With respect to legacy use and associated disposal, however, EPA
now believes that such circumstances are, in fact, ``conditions of
use'' and must be considered in risk evaluations. (Ref. 2, pp. 420-
421). An example would be in-situ asbestos insulation, a product no
longer manufactured but nevertheless an ongoing downstream use. Future
disposal of asbestos insulation is clearly an example of a chemical
substance being ``disposed of'' and to the extent it is ``intended''
that such a substance be disposed of, or ``known'' that it will be, or
if such disposal is ``reasonably foreseen,'' that circumstance
unambiguously falls within TSCA's definition of ``conditions of use.''
(Ref. 2, pp. 420-421). As such, EPA is already developing a ``part 2''
of the TSCA risk evaluation for asbestos in order to include analysis
of exposures and potential risks from legacy uses and expects future
risk evaluations to also consider legacy uses and associated disposals
as conditions of use (i.e., circumstances associated with ``use'' and
``disposal''). EPA believes that this approach is consistent with the
statutory text and structure, as well as Congressional intent.
    There are other categories of circumstances that EPA intends to
consider in future risk evaluations associated with conditions of use
that also bear mention. The known, intended, and reasonably foreseen
production of a chemical as a byproduct or the known presence of a
chemical as an impurity or within an article, for example, are squarely
``conditions of use'' that generally must be included within the scope
of risk evaluations.
    Likewise, where EPA has reasonably available information
demonstrating that certain exposures associated with a spill or leak
are known or reasonably foreseen to occur during a condition of use
that is part of a risk evaluation (e.g., regular or predictable
exposures from equipment leaks as part of the manufacturing process),
EPA would expect to include that exposure within the scope of the risk
evaluation. However, EPA would not expect to include within the scope
of the risk evaluation exposures from releases of a chemical substance
that are unsubstantiated, speculative or otherwise not likely to occur.
For example, a future one-time accident involving the chemical
substance that could be caused by an atypical one-time set of
circumstances would generally not be assessed as part of a risk
evaluation. Additionally, EPA would generally not include within the
scope of the risk evaluation exposures associated with future extreme
weather events (e.g., hurricanes and wildfires). However, if
information reasonably available to the Agency indicated that factors
such as rising sea levels or extreme temperatures made worse by climate
change were leading to regular and predictable changes in exposures
associated with a given condition of use of a chemical substance, EPA
would expect to consider those exposures within the scope of the risk
evaluation. EPA requests comment on alternative proposals for
considering potential climate-related risks. As discussed further in
Units III.E.4. and III.I.2., EPA may adjust the level of refinement for
a particular exposure assessment by conducting a ``fit-for-purpose''
assessment. While EPA will always apply the scientific standards
required under TSCA, the depth or extent of analysis will be
commensurate with the nature and significance of the decision. For
example, EPA may find that the types of exposures described in this
paragraph warrant consideration as part of an exposure assessment,
either in a qualitative or a quantitative exposure assessment.
Additionally, the Agency will decide the level of analysis warranted
based on a number of factors, including but not limited to: the
substance's physical-chemical properties; environmental fate and
transport properties; the likely duration, intensity, frequency, and
number of exposures under the condition of use; reasonably available
information about the release; and other relevant considerations.

    Even where a condition of use is not expected to be a significant
contributor to risk from a particular chemical, TSCA nonetheless
requires EPA to include it in the scope of the risk evaluation.
However, and as described in Unit III.E.4., EPA has discretion to
conduct its evaluations in a fit-for-purpose manner, which may justify
tailoring the level of analyses to focus more detailed--and therefore
more time and resource intensive--quantitative efforts on the
conditions of use that pose the greatest potential for exposure and
therefore risk.
3. Inclusion of All Exposure Pathways
    In carrying out the first ten risk evaluations under TSCA, EPA
narrowed the scope of those evaluations by excluding analysis of
certain exposures to the general population from releases to air, water
and land. The approach, which was not contemplated in the procedural
framework rule but was first articulated in ``Problem Formulation''
documents published in 2018 (after the Final Scope documents) for each
of the first ten chemicals undergoing risk evaluation, was premised on
an argument that those pathways were already adequately assessed and
managed--or could theoretically in the future be assessed and managed--
under other EPA statutes and regulatory programs (Ref. 12). EPA further
stated at that time that its intention was to use Agency resources
efficiently under the TSCA program, avoid duplicating efforts taken
pursuant to other Agency programs, maximize scientific and analytical
efforts, and meet TSCA's statutory deadline for completing risk
evaluations. In the final risk evaluations for the first ten chemicals,
EPA excluded exposure pathways that could be covered by regulatory
programs under the Clean Air Act (CAA), Clean Water Act (CWA), Safe
Drinking Water Act (SDWA), Resource Conservation and Recovery Act
(RCRA), and Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA) (e.g., drinking water pathways covered under the
SDWA due to the existence of National Primary Drinking Water
Regulations (NPDWRs) with chemical-specific, enforceable Maximum
Contaminant Levels (MCL), or the inclusion of the chemical as an
unregulated chemical on the Candidate Contaminant List (CCL)). EPA
further asserted that this approach was supported by several TSCA
authorities, including TSCA section 6(b)(4)(D), which gives the Agency
authority to include the conditions of use that the Administrator
``expects to consider'' and section 9(b)(1), which allows Administrator
to use other EPA administered statutes, if the Administrator determines
there is risk to health or the environment (Ref. 13).
    This approach was criticized by the Science Advisory Committee on
Chemicals (SACC), public commenters, and others (Ref. 14, 15, 16). As
announced on June 30, 2021, EPA will no longer follow the approach and
no longer intends to apply it to risk evaluations. Additionally, the
Agency applied the Draft TSCA Screening Level Approach for Assessing
Ambient Air and Water Exposures to Fenceline Communities Version 1.0
(Ref. 17) and additional feedback from peer review and public comment
in order to consider whether its past failure to have assessed the
risks associated with these exposures--along with its application of
other past policies and interpretations--may have resulted in
unaccounted potential risks. 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's prior interpretation in support
of that approach was premised in large part on the Agency's
interpretation of TSCA section 6(b)(4)(D) as providing the
discretionary authority to tailor the scope of exposures evaluated in
TSCA risk evaluations. See, e.g., Risk Evaluation for Methylene
Chloride, sec. 1.4.2 (Ref. 13). For the reasons explained in Unit
III.B., EPA no longer interprets TSCA section 6(b)(4)(D) to provide
broad discretionary authority to exclude conditions of use or exposure
pathways from the scope of TSCA risk evaluations.
    EPA also cited TSCA section 9(b)(1) as support for its approach,
asserting that the instruction in that provision for the Administrator
to ``coordinate actions taken under [TSCA] with actions taken under
other Federal laws administered [by EPA]'' provided a broad,
freestanding authority to exclude from the scope of TSCA risk
evaluations exposure pathways that are addressed or could in the future
be addressed by other EPA-administered statutes and regulatory
programs. See, e.g., Risk Evaluation for Methylene Chloride, section
1.4.2 (Ref. 13). EPA asserted that such exclusions from TSCA risk
evaluations were also permitted under the remaining text of TSCA
section 9(b)(1), which establishes a process for determining whether to
use EPA-administered authorities other than TSCA to protect against a
risk ``[i]f the Administrator determines that a risk to health or the
environment associated with a chemical substance or mixture could be
eliminated or reduced to a sufficient extent by actions taken under the
authorities contained in such other Federal laws.'' But upon
reconsideration, neither provision in TSCA section 9(b)(1) is properly
interpreted as authorizing exposure pathways to be excluded from TSCA
risk evaluations.
    Intra-agency coordination is integral to ensuring that EPA actions
are well-informed, effective, and efficient, but a general requirement
under TSCA section 9(b)(1) to ``coordinate actions'' cannot be read to
displace the more specific requirements under TSCA section 6(b)(4)(F)
to conduct a risk evaluation that shall ``integrate and assess
available information on hazards and exposures for the conditions of
use of the chemical substance,'' and ``take into account . . . the
likely duration, intensity, frequency, and number of exposures under
the conditions of use of the chemical substance.'' And the remaining
text of TSCA section 9(b) is directed at risk management action, which
cannot logically take place until after EPA has conducted an evaluation
and determined that a risk is presented. If exposure pathways covered
by other laws are not assessed in TSCA risk evaluations, it is unclear
how the Administrator would have sufficient information to determine
under TSCA section 9(b) that a risk to health or the environment
associated with a chemical substance could be eliminated or reduced to
a sufficient extent under another Federal law, or whether it is in the
public interest to protect against such risk by actions taken under
TSCA--a finding that must, pursuant to TSCA section 9(b)(2), consider
``all relevant aspects of the risk.'' Legislative history from TSCA's
original 1976 enactment supports this understanding that TSCA section
9(b)--the text of which was at that time split between TSCA section
9(b) and TSCA section 6(c) (pertaining to risk management rulemaking
procedures)--is properly interpreted in the context of risk management
action rather than any preceding evaluation of risk (Ref. 18). As
explained in the Conference Committee's 1976 report (Ref. 18) ``the
requirement to examine other EPA laws and to make determinations
applies only when the Administrator takes regulatory action to protect
against an unreasonable risk under this Act.''
    EPA recognizes that there may be exposure-reducing impacts from
existing regulations and intends to

consider reasonably available information when estimating exposures,
including available monitoring data. There may also be circumstances
where an unreasonable risk identified in the risk evaluation may be
eliminated or reduced to a sufficient extent under the authorities
contained in other Federal laws, such that a referral under TSCA
section 9 might be appropriate. However, the mere existence of
authority to assess or regulate a chemical, exposure pathway, or use
under a statute other than TSCA does not equate to effective risk
management of that chemical, exposure pathway or use, and an assumption
that risk will--or could be--managed in the future cannot be used to
satisfy the Agency's statutory obligations to evaluate existing
chemical substances under TSCA and manage identified risks. Wholesale
exclusion of identified exposure pathways for a chemical substance from
the scope of the TSCA risk evaluation for that substance is
inconsistent with EPA's obligations under TSCA section 6(b)(4)(F), as
noted, as well as with requirements under TSCA section 26(h), (i) and
(k) to make decisions based on science that are consistent with the
best available science and are based on the weight of the scientific
evidence, and to take into consideration reasonably available
information relating to a chemical substance, ``including . . .
exposure information,'' under the conditions of use. Furthermore, TSCA
section 9 already contemplates a time and place for determination of
whether EPA or another Federal agency can adequately address chemical
risks under the authority of another Federal law: during the risk
management rulemaking process after the risk has been identified in a
risk evaluation.
    Accordingly, EPA is proposing changes in the rule to ensure that
risk evaluations include all relevant exposure pathways, thereby
providing the basis for development of strong, scientifically and
legally defensible regulatory protections. Specifically, EPA is
proposing to explicitly require that each risk evaluation 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.
4. Comprehensive But Fit-For-Purpose
    While the changes described in Unit III.E.1. through 3. could all
lead to future TSCA risk evaluations that are more comprehensive in
scope, EPA recognizes the enormity of the challenge to complete these
responsibilities within the timeframes set forth by Congress. The law
provides the Agency with only 3 to 3.5 years to finalize a TSCA risk
evaluation. The primary purpose of a TSCA risk evaluation is to support
regulatory decision making--either to form the basis of a subsequent
rulemaking to eliminate identified unreasonable risk under TSCA section
6(a), or to determine that the chemical does not present unreasonable
risk and therefore rulemaking is not necessary. Given the tens of
thousands of existing chemicals, Congress further mandated that risk
evaluations be completed on an ongoing basis and within specified
timeframes.
    Risk evaluations under TSCA should not be so complex or
procedurally cumbersome that they cannot reliably be completed within
the timeframes required by the statute. At the same time, EPA cannot
produce partial or incomplete TSCA risk evaluations or otherwise pursue
risk evaluations in a manner that is incompatible with the statutory
framework. Although EPA must balance resource expenditure and
manageability, it must do so within the confines of its statutory
mandate. As such, EPA is proposing some changes to the rule to ensure
consistency with TSCA's text, structure, and purpose, while also
clarifying where the statute provides flexibilities in how EPA conducts
TSCA risk evaluations. For example, 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.
    In order 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. (15 U.S.C. 2605(b)(4)). For example, while risk evaluations
must consider the full spectrum of the chemical's conditions of use,
not all of those conditions of use will warrant the same level of
evaluation. As described in the 2017 final rule, EPA expects it may be
able to complete its analysis on certain conditions of use and/or
exposure pathways without extensive or quantitative evaluations of
exposure. For example, lower-volume or less dispersive uses could
receive less quantitative evaluations than uses with more extensive or
complicated exposure patterns. In addition, not all identified
toxicological endpoints may need the same level of analysis and
consideration. Efficiencies may be gained in similarly tailoring
approaches to peer review and/or systematic review. EPA can make
scientifically sound risk determinations, considering reasonably
available information, consistent with the best available science, and
based on the weight of scientific evidence, through a combination of
different types of information and risk assessment approaches.
Ultimately, the proposed changes--TSCA risk evaluations that are both
more comprehensive (e.g., that consider all exposure pathways) and
better incorporate fit-for-purpose approaches that ensure EPA is
meeting its statutory deadlines--will lead to more scientifically sound
and legally defensible risk evaluations that support robust TSCA
section 6(a) risk management rules that address any unreasonable risks
of injury to human health or the environment.
5. Additional Efficiencies
    Based on the Agency's early implementation efforts and experience
using the data gathering authorities afforded under the amended
statute, it has become clear that EPA should identify, obtain, review,
and synthesize data and information for risk evaluations much earlier
in the TSCA existing chemical risk assessment and risk management
process. Doing so will enable the Agency to finalize risk evaluations
in the aggressive timeframes provided by the law, and as necessary,
initiate risk management actions in a timely manner. EPA believes a
more sustainable process would involve--either during prioritization or
before--review of reasonably available information, identification of
data needs and gaps, and preliminary efforts to scope the potential
risk evaluation. Prioritization is the statutorily required initiating
step in the TSCA existing chemical risk evaluation and risk management
process. (15 U.S.C. 2605(b)). This 9- to 12-month process includes a
risk-based screening to ultimately designate a chemical substance as a
high-priority substance for risk evaluations or low-priority substance
for which a risk evaluation is not warranted at the time. In the
interest of creating additional efficiencies, EPA 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, which may result in the publication of the
``draft scope'' before the initiation of the subsequent risk
evaluation.
    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. Publishing this information early will
allow the Agency to give an early indication as to the conditions of
use, hazards, exposures and potentially exposed or susceptible
subpopulations that the Agency expects to consider and may provide
early indications as to how the Agency expects to conduct a fit-for-
purpose risk evaluation. This information will accompany the
prioritization screening review criteria, and EPA will look to public
comment and submission of available relevant data to inform both the
final priority designation but also, if the chemical is then designated
as a high priority, the information to inform the scope.
    As the first statutorily required step of the risk evaluation
process, TSCA requires the Agency to publish the scope of the risk
evaluation no later than 6 months after initiating the risk evaluation.
(15 U.S.C. 2605(b)(4)(D)). This scope must include the hazards,
exposures, conditions of use, and the potentially exposed or
susceptible subpopulations the Administrator expects to consider. Under
the 2017 final rule, however, EPA must publish the scope in a ``draft''
form, followed by no less than a 45-day public comment period. The 2017
final rule states that the Agency generally expects to publish this
draft no later than 3 months after initiation of the risk evaluation.
Stakeholders supported this provision during the development of the
2017 proposed rule; due to the gravity of the ``final'' scope on the
risk evaluation process and possible state preemption, it was important
for stakeholders to have the ability to comment on the draft scope. The
proposed rule would 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 the Agency more time to review and
effectively use the public input in the development of the risk
evaluation's scope. EPA requests comment on this 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.

F. Risk Determinations

1. 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. As described earlier, EPA believes, as supported by
the plain language in the law, that the chemical's full spectrum of
conditions of use must be included and assessed in the risk evaluation.
EPA fully intends to continue to consider exposures associated with
each condition of use. However, following that analysis, and for the
reasons described in this Unit, the Agency no longer intends to make
separate risk determinations for individual conditions of use. Instead,
EPA is proposing changes to the regulations to clarify and codify the
approach that the Agency originally proposed in the 2017 proposed rule
(i.e., to make a single risk determination on the whole chemical
substance). EPA believes that this approach is consistent with the
statutory text and structure, as well as Congressional intent, and will
enable the Agency's risk determinations to better reflect the potential
for combined exposures across multiple conditions of use.
    In the 2017 proposed rule, EPA proposed that risk determinations be
made on the ``chemical substance,'' consistent with the plain language
of the law and Agency's interpretation of the new requirements in TSCA
at that time. (Ref. 9 at pp. 7572, 7565 through 7566, and 7580). As
described in the preamble, ``TSCA section 6(b)(4)(A) specifies that a
risk evaluation must determine whether `a chemical substance' presents
an unreasonable risk of injury to health or the environment `under the
conditions of use.' The evaluation is on the chemical substance--not
individual conditions of use--and it must be based on `the conditions
of use.' ''. Thus, in the 2017 proposed regulatory text, EPA proposed
to determine whether the chemical substance presents an unreasonable
risk of injury to health or the environment under the conditions of
use. (Ref. 9 at p. 7480).
    The 2017 proposed rule provided an exception that would allow EPA
to make an ``early determination'' for a specific use that was deemed
to present unreasonable risk. Where such an early determination was
made, the risk management efforts to address that specific use could
begin more expeditiously and not wait until the end of the 3 to 3.5
year risk evaluation process (Ref. 8 at pp. 7568 and 7578). EPA did not
propose a similar process for use-specific early determinations of no
unreasonable risk. This exception made logical sense, in that, if a
specific use of a chemical--in isolation--presented an unreasonable
risk under TSCA, that chemical itself would necessarily present an
unreasonable risk irrespective of risks posed by other uses. The
converse may not be true. Where a specific use might not present an
``unreasonable risk'' on its own, it may nonetheless contribute to an
unreasonable risk determination when considered together with other
uses of the chemical (e.g., when considering it in an aggregate
exposure scenario).
    EPA received comment on the 2017 proposed rule that limiting
``early determinations'' only to uses that present unreasonable risk
was unfair, and encouraged the Agency to extend this concept of early,
use-specific risk determinations to those uses determined not to
present unreasonable risk. The 2017 final rule stated that ``EPA will
determine whether the chemical substance presents an unreasonable risk
of injury to health or the environment under each condition of uses
[sic] within the scope of the risk evaluation, either in a single
decision document or in multiple decision documents'' (Ref. 1). There
was one particular passage in the preamble to the 2017 final rule which
stated that EPA would make individual risk determinations for all
conditions of use identified in the scope. (Ref. 1 at p. 33744).
    Concerns about a use-specific approach to risk determinations were
raised as part of litigation on the final rule in Safer Chemicals v.
EPA (Ref. 2 at p. 413), including that such an approach ignores the
potential risks when the same individuals are exposed to the same
chemical through multiple conditions of use (e.g., in the workplace and
in the home). Those exposures, when combined, may present unreasonable
risk, whereas, when viewed in isolation, may not. A panel of the Ninth
Circuit Court of Appeals recognized the ambiguity of the regulation on
this point, and ultimately held that a challenge regarding ``use-by-use
risk evaluations [was] not justiciable because it is not clear, due to
the ambiguous text of the Risk Evaluation Rule, whether the Agency will
actually conduct risk evaluations in the manner Petitioners fear''
(Ref. 2 at p. 413). Subsequent to the Ninth Circuit's decision, EPA
made individual risk determinations for each condition of use evaluated
in the first ten risk evaluations (i.e., the condition of use-specific
approach to risk determinations). That approach was

based on the particular passage in the preamble to the 2017 final rule
stating that EPA would make individual risk determinations for all
conditions of use identified in the scope. (Ref. 1 at p. 33744). The
approach resulted in a mix of findings that certain conditions of use
for a chemical ``present unreasonable risk'' while others ``do not
present unreasonable risk.''
    As announced in June 2021 as the path forward for the first ten
risk evaluations, EPA has revisited this decision and determined to
revise the use-specific risk determinations for most of the first ten
chemicals to reflect a single determination on the chemical substance
itself (Ref. 7). These revisions did not require the Agency to change
any of its underlying analyses in the risk evaluations. In the case of
many of these first 10 chemicals, EPA had already determined that many
or most of the individual conditions of use presented an unreasonable
risk.
    In revising the risk determinations for the first 10 chemicals, EPA
noted that in contrast to the portion of the preamble of the 2017 final
rule that discusses the intent of the Agency to make multiple risk
determinations, the regulatory text itself and other statements in the
preamble reference a risk determination for the chemical substance
under its conditions of use, rather than separate risk determinations
for each of the conditions of use of a chemical substance. See for
example, the revised risk determination for Methylene Chloride (Ref.
13). Notwithstanding the one preambular statement about condition of
use-specific risk determinations, the preamble to the 2017 final rule
also contains support for a risk determination on the chemical
substance as a whole.
    Although the Agency indicated in its June 2021 announcement that it
would make a single risk determination on a chemical when it was
``clear that majority of conditions of use warrant one determination,''
EPA now believes a better understanding of the statute is that a single
determination on the chemical substance is required in every instance,
and is proposing to make this clear in this procedural rule. TSCA
section 6(b)(4)(A) specifies that in a risk evaluation, EPA must
determine whether ``a chemical substance'' presents an unreasonable
risk of injury to health or the environment ``under the conditions of
use.'' This language clarifies that the risk determination is on the
chemical substance--not individual conditions of use--and it must be
based on ``the conditions of use.''
    Although EPA previously found ambiguity in TSCA section 6(b)(4)(A),
it now believes that a better reading of the statute in light of its
content and structure (and other reasons described in this paragraph)
is that it requires EPA to simultaneously evaluate all conditions of
use of a chemical substance. TSCA section 6(a) requires EPA to apply
risk-management requirements ``to the extent necessary so that the
chemical substance or mixture no longer presents such risk.'' This
phrasing suggests that the chemical substance presents the unreasonable
risk, and not specific conditions of use. Further, TSCA section 6(i)(1)
explains that ``a determination by the Administrator under subsection
(b)(4)(A) that a chemical substance does not present an unreasonable
risk of injury to health or the environment shall be issued by order
and considered to be a final agency action, effective beginning on the
date of issuance of the order.'' Similarly, TSCA section 6(i)(2)
explains that ``a final rule promulgated under subsection (a),
including the associated determination by the Administrator under
subsection (b)(4)(A) that a chemical substance presents an unreasonable
risk of injury to health or the environment, shall be . . . a final
agency action, effective beginning on the date of promulgation of the
final rule.'' Both of these provisions speak in terms of whether the
chemical substance presents unreasonable risk. Neither provision
mentions the conditions of use. The structure of TSCA section 6(i) also
implies a binary decision by not addressing a scenario in which a
chemical substance would be subject to TSCA section 6(i)(1) and (2).
    EPA's view that there should be one determination on the chemical
substance is further bolstered by TSCA's preemption provisions at
Section 18, and its numerous references to ``chemical substance.'' In
TSCA section 18(a)(1)(B)--titled ``Chemical substances found not to
present an unreasonable risk or restricted''--the law states that
preemption applies, for example, when EPA issues ``the determination''
in TSCA section 6(i)(1) (i.e., a determination that the chemical
substance does not present an unreasonable risk). EPA notes in
particular that the word ``determination'' in this provision is
singular, suggesting Congress did not envision multiple determinations
under TSCA section 6(i)(1). Additionally, TSCA section 18(a)(1)(B)(ii)
states that permanent preemption is triggered by a final TSCA section
6(a) risk management rule for ``the chemical substance,'' suggesting
again that Congress did not envision that TSCA section 6(a) risk
management rules would address only risks presented by individual uses
or some subset of a chemical's uses, but rather unreasonable risk
presented by the chemical as a whole.
    Based on its text and structure, EPA now reads TSCA as requiring
the Agency, in each risk evaluation, to make a single risk
determination of the chemical substance. EPA does not believe that the
statutory text and structure permit the Agency to make separate risk
determinations for each condition of use. The legislative history also
tends to favor this reading, including Congressional floor statements
made on the day of passage supporting the risk determination being for
the chemical substance. ``. . . EPA's understanding of a chemical's
conditions of use . . . will be critical to EPA's final determination
of whether a chemical is safe or presents an unreasonable risk that
must be controlled'' and S3520 ``A Section 6(i) order, determining that
a chemical substance does not present an unreasonable risk under
conditions of use, is similarly final Agency action applicable to all
those conditions of use that were identified in the scope of EPA's risk
evaluation on the chemical substance'').'' (Ref. 11).
    Although the Agency has 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. 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. Rather, EPA may
determine that a chemical substance presents an unreasonable risk based
on risk associated with even a single condition of use.
    Some have criticized this approach in public comments on the
revised risk determinations. They have noted, for example, that a
singular risk determination could create confusion as to whether all
uses or only certain uses of a chemical pose unreasonable risk.
Fundamentally, EPA believes these concerns are risk communication
issues that the Agency can and intends to continue to improve on. EPA
will in every risk evaluation provide a rationale and explanation as to
which conditions

of use or exposure pathways are significant contributors to risk. The
Agency is committed to clearly communicating on the Agency's analysis
of particular uses within the risk evaluation and will not make
statements about the risk associated with the chemical substance absent
such explanation. Rather, as indicated in the proposed regulatory text
at 40 CFR 702.37(a)(5), and in order to inform risk management
requirements, EPA generally expects every risk determination to
identify which conditions of use are--or are not--significant
contributors to EPA's determination that the risk presented is
unreasonable. That said, for those chemical substances that EPA
determines present unreasonable risk, the risk evaluation is not the
end of the TSCA process. The primary purpose of a risk evaluation is
not to provide the public with guidance or suggested actions with
respect to particular chemical uses. Risk evaluations are scientific
documents intended to inform EPA decisions as to whether regulatory
action is needed to address unreasonable risks to human health or the
environment. Ultimately, when the TSCA existing chemicals review
process--including any TSCA section 6(a) rulemaking to manage risk--is
complete, the public should have full confidence that the chemical can
only be manufactured, processed, distributed in commerce, used and
disposed of in accordance with the associated risk management
requirements, and that the chemical substance no longer presents an
unreasonable risk.
    Likewise, others have expressed concern that EPA will use a
singular risk determination to regulate in an overly broad manner. A
determination of unreasonable risk for a chemical substance does not
mean that EPA will, by default, propose or finalize a section 6(a) risk
management rule requiring all manufacture or use of the chemical
substance to be banned. EPA's statutory authority to regulate chemicals
under TSCA section 6 is available only ``to the extent necessary so
that the chemical substance or mixture no longer presents
[unreasonable] risk.'' (15 U.S.C. 2605(a)). EPA has a range of
authorities available under TSCA section 6(a) to address unreasonable
risk, including--but not limited to--requiring additional occupational
safety measures, product labels, or concentration limits. Where such
measures can eliminate unreasonable risk, EPA may propose them as part
of the risk management rulemaking process. EPA's determination of
appropriate regulatory requirements will be on a case-by-case basis,
and will not regulate chemical substances in a manner that is
inconsistent with the requirements of TSCA sections 6(a) and (c)(2).
For example, EPA may derive an exposure limit in the risk evaluation.
Such a limit would necessarily be based solely on risk-related
information, adhering to the statutory directive not to consider costs
or other non-risk factors during the risk evaluation. However, because
EPA is required to consider costs and other non-risk factors during the
risk management phase, including whether uses of a substance are
critical to Federal mission needs, or whether alternatives for a use of
a substance exist, the exposure limit presented in a risk evaluation
may not always or automatically signal the manner in which EPA will
regulate occupational risks during the risk management phase.
    It is important to note, however, in exercising EPA's authority
under TSCA section 6(a) to ensure that ``the chemical substance . . .
no longer presents such risk,'' EPA may regulate conditions of use that
do not themselves contribute to unreasonable risk for a given chemical.
For example, where a risk evaluation's underlying analysis suggests
that particular use downstream in the supply chain is significantly
contributing to unreasonable risk determination for the chemical
substance, EPA's risk management actions need not apply only to the
downstream use. EPA may, for example, determine that elimination of the
unreasonable risk requires regulation of the chemical's upstream
manufacture, processing or distribution in commerce--even where the
upstream activity itself does not directly result in the exposures that
present the unreasonable risk.
    EPA considered whether to re-propose a process for making use-
specific early determinations of unreasonable risk prior to completing
the risk evaluation for the remaining conditions of use, as
contemplated in the original 2017 proposed rule. However, based on
experience in conducting risk evaluations on the first 10 chemicals and
implementing the new requirements in TSCA section 6, the notion of
early, use-specific risk determinations is not practical or realistic
within the statutory deadlines. The theoretical benefit of such an
approach--enabling the early start of risk management efforts for the
subset of uses that are clearly of highest risk--is outweighed by the
burdens of managing the completion of multiple risk evaluation
processes on a single chemical followed by potentially multiple
rulemakings, each of which must comply with statutory deadlines. In the
event that there is a known, imminent and unreasonable risk of serious
or widespread injury to health or the environment (i.e., imminent
hazard) associated with a use or chemical that the Agency needs to
address immediately, TSCA section 7 provides EPA the authority to take
such immediate action.
    EPA believes the approach, consistent with the 2017 proposed rule,
(i.e., to make a single risk determination on the chemical substance)
is aligned with the statutory text and structure, and will ensure that
the Agency is best positioned to incorporate reasonably available
information, make determinations consistent with the best available
science and based on the weight of scientific evidence, including,
where appropriate, risk determinations that consider aggregate exposure
resulting from multiple conditions of use. (15 U.S.C. 2625(h), (i), and
(k)). As such, EPA is proposing that risk evaluations will always
culminate in a single risk determination on the ``chemical substance''
instead of individual risk determinations on individual conditions of
use. EPA is proposing related conforming changes throughout the
regulatory text, including the proposed addition of 702.37(a)(5) and
the explicit mention of a single determination in 702.39(f)(1).
2. ``Unreasonable Risk'' Considerations
    TSCA requires that a risk evaluation include a determination of
whether or not a chemical presents unreasonable risk, and further
requires that this determination be independent of cost or other non-
risk factors. (15 U.S.C. 2506(b)(4)(A) and (F)(iii)). Neither TSCA nor
the 2017 final rule define ``unreasonable risk'' given the inherently
unique nature of each risk evaluation and the need for EPA to make this
determination on a case-by-case basis. As described in the preamble to
the 2017 final rule (Ref. 1 at p. 33735), EPA may weigh a variety of
factors in determining unreasonable risk. The Administrator will
consider relevant factors including, but not limited to: The effects of
the chemical substance on health and human exposure to such substance
under the conditions of use (including cancer and non-cancer risks);
the effects of the chemical substance on the environment and
environmental exposure under the conditions of use; the population
exposed (including any susceptible subpopulations), the severity of
hazard (the nature of the hazard, the irreversibility of hazard), and
uncertainties.

    The 2016 amendments also required that EPA's determination of
unreasonable risk consider the risks to potentially exposed or
susceptible subpopulations. Where EPA identifies risks as part of the
risk evaluation, the risks to a potentially exposed or susceptible
population may be more significant or severe than the risks to the
general population. EPA would more explicitly reflect this statutory
requirement in proposed Sec.  702.39(f), as the 2017 final rule did not
explicitly reference the statutory requirement to consider the risk to
potentially exposed or susceptible subpopulations when making the final
risk determination. Additionally, as discussed more fully in Unit
III.G.4., 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.
``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. The proposed change clarifies that EPA will consider
the risk to potentially exposed or susceptible subpopulations as part
of its determination of whether or not the chemical presents
unreasonable risk.
    Likewise, and as discussed further in Units III.G.2. and 3., EPA's
determination of unreasonable risk from the chemical substance will
also consider, where relevant, the Agency's analyses on aggregate
exposures and cumulative risk. For example, where a single population
is exposed to a chemical through multiple routes or pathways, EPA's
assessment of those aggregate exposures may inform the determination of
whether that chemical presents an unreasonable risk. Similarly, a
cumulative risk assessment may be conducted on a category of chemicals,
where the science supports this type of assessment, and the findings
may inform the unreasonable risk determination for the category.

G. Risk Evaluation Considerations

1. Occupational Exposure Assumptions
    EPA is proposing some clarifications to the assumptions that it
will and will not apply in risk evaluations related to worker exposure.
    In carrying out the first ten TSCA chemical risk evaluations, as
part of the unreasonable risk determinations, EPA assumed that workers
were provided and always used personal protective equipment (PPE) in a
manner that achieves the stated assigned protection factor (APF) for
respiratory protection, or used impervious gloves for dermal
protection. In support of this assumption, EPA relied on public
comments indicating that some employers, particularly in the industrial
setting, provide PPE to their employees and follow established worker
protection standards (e.g., OSHA requirements for protection of
workers). As EPA noted in prior risk evaluations (e.g., Risk Evaluation
for Methylene Chloride (Dichloromethane, DCM), 126 (Ref. 13 at p. 126),
the consideration of assumed use of PPE in a risk determination could
lead to an underestimation of the risk to workers. Further, parties in
litigation as well as public commenters on several TSCA risk
evaluations argued that making risk determinations based on assumptions
of PPE conflates the risk evaluation and risk management phases. In
June 2021, the Agency announced it would be revisiting the risk
determinations that were based on these assumptions and noted its plans
to consider information on use of PPE and other ways industry protects
its workers during the risk management process (Ref. 7).
    TSCA requires that EPA evaluate the chemical substance under the
intended, known, or reasonably foreseen circumstances associated with
the chemical's manufacture, processing, distribution in commerce, use
and disposal. EPA believes that the blanket occupational exposure
assumptions on PPE do not reflect the known or reasonably foreseen
chemical exposures that impact workers, and their continued application
in TSCA risk evaluations would result in underestimates of risk. For
example, workers may be highly exposed because they are not covered by
Occupational Safety and Health Administration (OSHA) standards, their
employers are out of compliance with OSHA standards, or because the PPE
is not sufficient to address the risk or their PPE does not fit or
function properly. Further, many of OSHA's chemical-specific
permissible exposure limits were largely adopted in the 1970s and have
not been updated since they were established (Ref. 19). Additionally,
TSCA risk evaluations are subject to statutory science standards, an
explicit requirement to consider risks to potentially exposed or
susceptible subpopulations, and a prohibition on considering costs and
other non-risk factors when determining whether a chemical presents an
unreasonable risk that warrants regulatory actions--all requirements
that do not apply to development of OSHA regulations. As such, EPA may
find unreasonable risk for purposes of TSCA notwithstanding OSHA
requirements. Where risk evaluations assume fully protective PPE use,
and therefore little or no exposures for workers, the risk evaluations
may underestimate and/or fail to identify unreasonable risk. EPA is
requesting 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.
    EPA is not suggesting that there is widespread non-compliance with
applicable OSHA standards. In fact, EPA has received public comments
from industry in response to various EPA documents associated with TSCA
risk evaluations about occupational safety practices currently in use
at their facilities, including adherence to OSHA standards and non-OSHA
industry guidelines. EPA also acknowledges that other Federal agencies
and their contractors that use chemicals may similarly have well-
established occupational control measures in place. EPA will consider
comments received during the risk evaluation process, as well as other
information on use of PPE and other ways industry and Federal agencies
protect their workers, as potential ways to address unreasonable risk
during the risk management process. EPA recognizes that in some
instances and in certain workplace locations, particularly advanced
manufacturing facilities (e.g., those involved in the aerospace and
defense industrial base industrial sectors) there could be well-
established occupational safety protections in place. As EPA moves
forward with risk management rules, the Agency will strive for
consistency with existing OSHA requirements and/or best industry
practices when those measures would address the identified unreasonable
risk and would adopt a similar approach when making decisions about
managing risks for uses of chemicals that are required to meet national
security and critical infrastructure mission imperatives for other
Federal agencies. EPA will proactively communicate with Federal
agencies to identify such circumstances with an aim to propose measures
in the risk management process to address occupational risk that will
meet TSCA's statutory requirement to eliminate unreasonable risk of
injury to health and the environment, while also leveraging ongoing
interagency dialogue and striving to avoid potential

impacts to mission and infrastructure critical uses.
    EPA is proposing regulatory amendments to clarify that, in future
risk evaluations, EPA's 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. The EPA 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, the Agency will take into account known
occupational control measures in the exposure assessments. However, the
Agency 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 Sec.  702.39(f)(2),
EPA would 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. For example,
where EPA has reasonably available information that substantiates use
and effectiveness of PPE (e.g., information demonstrating that
performance of a condition of use is impossible in the absence of PPE),
EPA generally expects to take that information into account in the risk
determination. The exposure reduction information (e.g., use of PPE)
from the risk evaluation's exposure assessment would then be considered
and incorporated in a future risk management action, as appropriate and
as required pursuant to TSCA section 6(a), and we encourage commenters
with interests or concerns on this to offer comments on this point in
connection with such a future action.
2. Aggregate Exposure
    Pursuant to TSCA section 6(b)(4)(F)(ii), when conducting a risk
evaluation, EPA must ``describe whether aggregate or sentinel exposures
to a chemical substance under the conditions of use were considered,
and the basis for that consideration.'' While there is no mandate to
conduct aggregate exposure analyses, EPA may conduct aggregate exposure
analyses at its discretion. In the 2017 final rule EPA defined
aggregate exposure as ``the combined exposures to an individual from a
single chemical substance across multiple routes and across multiple
pathways.'' In this proposed rule, EPA is proposing slight revisions to
the definition. 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, which is consistent
with the definition used in General Principles for Performing Aggregate
Exposure and Risk Assessments (Ref. 20). Additionally, EPA is proposing
to strike ``single'' chemical, as TSCA allows the Agency to conduct
risk evaluations on categories of chemicals.
    The consideration of an aggregate exposure assessment may be
particularly important for assessing chemical risks to overburdened
communities. If a community is exposed to a chemical substance through
multiple routes and/or pathways (e.g., exposure via air, land, and
water or exposure via drinking water and water recreation) and/or from
multiple sources (e.g., through different conditions of use occurring
at multiple facilities), the Agency has the authority to aggregate
those exposures, subject to the best available science standard, per
TSCA section 26(h). Not only does the Agency have the authority, but in
developing a comprehensive risk estimate for a chemical substance, it
is the Agency's responsibility to consider the aggregation of what may
be lower individual exposures from individual conditions of use and
routes of exposure. EPA is committed to conducting an aggregate
assessment, as supported by the science, in future TSCA risk
evaluations. In an aggregate exposure assessment, it may be appropriate
to also consider potential background exposures from non-TSCA uses that
are not within the scope of the risk evaluation. EPA could also
consider the disproportionate impacts that background exposures may
have on overburdened communities to inform the final unreasonable risk
determination.
3. Cumulative Risk
    Advancing the science to support cumulative risk assessment is a
high priority for the Agency. Cumulative risk assessment is applicable
to all lifestages, and could inform the Agency's efforts to understand
and mitigate those risks to potentially exposed or susceptible
subpopulations, including children and overburdened communities.
Several reports from the National Research Council (NRC)--including the
1994 report Science and Judgment in Risk Assessment (Ref. 21) the 2008
report Phthalates and Cumulative Risk Assessment: The Tasks Ahead (Ref.
22), and the 2009 report Science and Decisions: Advancing Risk
Assessment (Ref. 23)--have highlighted the importance of understanding
the combined risk from multiple chemical stressors. These reports, as
well as statutory requirements such as those presented in the Food
Quality Protection Act of 1996 (Ref. 24), have helped drive EPA's
evolving work on cumulative risk assessment. Because individuals are
co-exposed to many chemicals in their daily lives, some of which may
have the same health effects, EPA believes that in some cases the best
approach to assess risk to human health may be to look at the combined
risk to health from multiple chemicals.
    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 (15 U.S.C. 2605(b)(4)(G)), consider the
reasonably available information, consistent with the best available
science, and make decisions based on the weight of the scientific
evidence (15 U.S.C. 2625(h), (i), and (k)). EPA 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. (15 U.S.C. 2625(c)).
Under TSCA section 26(c), EPA may take ``any action authorized'' under
any provision of TSCA, in accordance with that provision with respect
to a category of chemical substances or mixtures of chemical
substances. TSCA defines ``category of chemical substances'' as a group
of chemical substances the members of which are 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, or the
members of which are in some other way suitable for the classification
as such for purposes of [TSCA].'' (15 U.S.C. 2625(c)). This definition
provides EPA with the flexibility to group chemical substances for
inclusion in a risk evaluation and a cumulative risk assessment when
supported by the best available science.
    There are multiple definitions of the term ``cumulative risk
assessment.'' For TSCA risk evaluations, the Agency is

currently relying on the definition in EPA's Framework for Cumulative
Risk Assessment that defines cumulative risk assessment as ``an
analysis, characterization, and possible quantification of the combined
risks to health and/or the environment from multiple agents and/or
stressors'' (Ref. 25). This could include evaluation of multiple
chemical substances that jointly exert a common toxic effect. Exposures
to these chemicals could occur through multiple exposure pathways and
through multiple routes of exposure. EPA expects to use available EPA
(Refs. 26, 27, 28, 29), OECD (Ref. 30), and World Health Organization/
International Programme on Chemical Safety (WHO/IPCS) (Ref. 31)
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.
    A risk evaluation on a single chemical may not accurately provide a
complete understanding of the risks to an exposed population, given
simultaneous exposure to multiple chemicals. In turn, without
considering the cumulative risk of chemicals, the Agency's risk
mitigation may not fully be able to consider the public-health
implications of various risk management options for reducing exposure.
EPA is committed to considering applying cumulative risk assessment
approaches, as appropriate and where such analysis, based on reasonably
available information, represents the best available science, for
future chemicals undergoing risk evaluation. The Agency developed and
released a Draft Proposed Principles of Cumulative Risk Assessment
Under the Toxic Substances Control Act (Ref. 32) and Draft Proposed
Approach for Cumulative Risk Assessment of High-Priority Phthalates and
a Manufacturer Requested Phthalate Under the Toxic Substances Control
Act (Ref. 33) for public comment and peer review in February 2023. The
Agency is considering feedback from both stakeholders and peer
reviewers and EPA will continue to develop robust methodology for the
inclusion of cumulative risk assessment in TSCA risk evaluations. EPA
seeks comment on how the Agency could incorporate provisions for
cumulative risk assessment into our risk evaluation procedures in a way
that would accommodate future advancements in the science of cumulative
risk assessment as well as ensure that the scope and complexity of any
such assessments is consistent with that envisioned by Congress when it
established deadlines for conducting risk evaluations.
    As described in Unit III.G.4., TSCA also explicitly requires EPA's
risk evaluations to consider unreasonable risk to ``potentially exposed
or susceptible subpopulations,'' and the statute provides authority to
consider non-chemical as well as chemical stressors when identifying
these subpopulations. Non-chemical stressors are factors found in the
built, natural, and social environments including physical factors
(e.g., geographic location) and psychosocial factors (e.g., poor
nutrition) (Ref. 34). EPA's Office of Research and Development has
defined cumulative impacts as the totality of exposures to combinations
of chemical and non-chemical stressors and their effects on health,
well-being, and quality of life outcomes (Ref. 34) and may or may not
include toxicologically defined risk. EPA has not to date considered
cumulative impacts in TSCA risk evaluations, but may in the future as
appropriate data, methods, and guidance are available.
4. Potentially Exposed or Susceptible Subpopulations
    TSCA requires EPA to evaluate risk to ``potentially exposed or
susceptible subpopulation[s]'' identified as relevant to the risk
evaluation by the Administrator, under the conditions of use. (15
U.S.C. 2605(b)(4)(A)). TSCA defines the term as ``a group of
individuals within the general population identified by the EPA who,
due to either greater susceptibility or greater exposure, may be at
greater risk than the general population of adverse health effects from
exposure to a chemical substance or mixture, such as infants, children,
pregnant women, workers, or the elderly.'' (15 U.S.C. 2602(12)). TSCA
does not further define ``greater susceptibility'' or ``greater
exposure,'' giving the Agency discretion to interpret these terms.
Greater susceptibility could include increased risk of experiencing an
adverse effect due to one's lifestage or a pre-existing condition or
circumstance (e.g., immune-compromised conditions, lifestyle factors
such as smoking status or alcohol abuse, age, ethnicity, or sex). This
is consistent with EPA's Policy on Children's Health to protect
children from environmental exposures by consistently and explicitly
considering early life exposures and lifelong health in all human
health decisions. The Agency will use its discretion and interpret
``greater exposure'' to potentially include fenceline communities
(e.g., those communities in close proximity to facilities emitting air
pollutants or living near effluent releases to water) or body burden.
Additionally, Congress' inclusion of ``such as'' allows EPA to
potentially identify communities who ``may be at greater risk than the
general population.'' Thus, EPA may evaluate any subpopulation that may
be at greater risk due to greater susceptibility or exposure, and
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. The disproportionality can be as
a result of greater vulnerability to environmental hazards, lack of
opportunity for public participation, or other factors. Increased
vulnerability may be attributable to an accumulation of negative or
lack of positive environmental, health, economic, or social conditions
within these populations or places. The term describes situations where
multiple factors, including both environmental and socio-economic
stressors, may act cumulatively to impact health and the environment
and contribute to persistent environmental health disparities. These
situations may apply to communities with environmental justice
concerns.
    EPA's 2017 proposed rule proposed a definition of PESS that
included more examples of PESS than set forth by Congress in the
statutory definition. EPA did not finalize that definition as proposed.
In response to public comments, the Agency explained that ``it would be
difficult for the Agency to list all the potential subpopulations that
the Agency might have reason to include in a risk evaluation'' and that
EPA did not want to imply exclusion of other subpopulations. However,
EPA now believes that it is appropriate to propose the addition of
``overburdened communities'' to the definition of PESS because it
reflects the Agency's understanding and acknowledgment that exposure to
a chemical substance may disproportionately impact communities already
experiencing disproportionate and adverse human health or environmental
burdens. Nothing in TSCA or this proposed rule

would prevent the Agency from identifying another group or
subpopulation as a ``potentially exposed or susceptible subpopulation''
in a given TSCA risk evaluation and specifically considering those
exposures and risks within.
    To identify overburdened communities when conducting a risk
evaluation, EPA 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, and may use available
screening tools, such as EJSCREEN (Ref. 35) or EnviroAtlas (Ref. 36).
These and other tools may also allow the Agency to capture greater
susceptibility or greater exposure using the data layers for
socioeconomic factors (e.g., income/poverty, education) or location
(e.g., housing, employment, geography), and for environmental
indicators (e.g., air toxics cancer risk, respiratory hazard index,
particulate matter levels, ozone, Superfund site proximity, hazardous
waste proximity, proximity to multiple chemical manufacturing or
processing facilities), which may provide information for future
cumulative assessment. EPA also continues to develop approaches for
assessing the risk to overburdened communities. For example, in 2022
EPA submitted for peer review the Screening Level Approach for
Assessing Ambient Air and Water Exposures to Fenceline Communities (Ref
16). This proposed screening level methodology evaluated the potential
chemical exposures and associated potential risks to fenceline
communities, or communities in close proximity, and thus commonly at
greater exposure, to chemical emission sources. The Agency continues to
develop risk evaluation approaches to help determine risk from all
relevant exposure pathways with an emphasis on exposures to these
commonly overburdened communities.

H. Science Policy and Scientific Standards

1. Scientific Guidelines and Procedures
    Congress recognized the importance of Agency policies, procedures
and guidance necessary to facilitate implementation of the 2016
amendments to TSCA. (15 U.S.C. 2625(l)(1)). This proposed rule, as does
the 2017 final rule, codifies the use of appropriate Agency guidance in
the development of risk evaluations (proposed Sec.  702.37(a)(1)).
Agency guidance and methodology documents, which may include publicly
available handbooks, frameworks, protocols, or any other process
support documents have long provided process and method transparency to
Agency scientific work products. The appropriateness of the documents
relates to their application in the methods, approaches, and science
policy decisions used in TSCA risk evaluations. For example, the
Exposure Factors Handbook: 2011 Edition (Ref. 10), provides exposure
assessors inside the Agency as well as outside, with data on standard
factors to calculate human exposure to environmental agents. Other EPA
guidance and methodology documents provide background for the
development of the TSCA risk evaluations, specifically the EPA
Guidelines for Carcinogen Risk Assessment (Ref. 37), and the EPA
Supplemental Guidance for Assessing Susceptibility from Early-Life
Exposure to Carcinogens (Ref. 38). EPA will continue to use these and
other existing Agency guidances in the development of TSCA risk
evaluations. EPA may develop and use additional guidance as needed
using a transparent process.
2. Peer Review
    Science is the foundation that supports the work of EPA, and this
is equally true for TSCA risk evaluations. The quality and integrity of
the science are vital to the credibility of the Agency's decisions and
processes, including but not limited to the evaluation of risks from
chemicals, determination of whether a chemical presents an unreasonable
risk, decisions on how best to manage that risk, and ultimately the
Agency's effectiveness in pursuing its mission to protect human health
and the environment. One important element in ensuring that decisions
are consistent with the best available science and based on the weight
of scientific evidence is to have an open, transparent and independent
scientific peer review process along with opportunities for public
comment.
    EPA has a long-standing history of peer review and has shown its
commitment to peer review in the TSCA program. TSCA section 26(o)
required EPA to establish an advisory committee, known as the Science
Advisory Committee on Chemicals (SACC), to provide independent advice
and expert consultation with respect to the scientific and technical
aspects of issues relating to the implementation of TSCA. EPA expects
to continue to obtain scientific advice and peer review from the SACC.
The 2017 final rule explicitly required peer review to be conducted on
all risk evaluations, which the Agency did for each of the first ten
risk evaluations (Ref. 8). Reports from those peer review committees
proved extremely instructive and resulted in more robust and
scientifically defensible products and improvements to EPA methods used
in the risk evaluation process.
    The Agency 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. However, EPA is proposing
some modifications to the language from the 2017 final rule to provide
increased clarity on both the guidance the Agency will use to conduct
peer review and on what peer review will be conducted. First, the
Agency proposes removing the reference to specific versions of guidance
documents. The 2017 final rule names specifically the EPA Peer Review
Handbook 4th Edition 2015 (Ref. 39) and OMB's Information Quality
Bulletin for Peer Review (Ref. 40). While at the time of this proposed
rule these documents were and still are applicable, the Agency
recognizes that these documents may be updated and/or their names
modified and seeks to avoid confusion as to which guidance documents
will be used. The Agency proposes at Sec.  702.41 to refer instead to
``applicable peer review policies, procedures, guidance documents, and
methods adopted by EPA and the Office of Management and Budget (OMB) to
serve as the guidance for peer review activities. EPA interprets
``applicable'' to reference the most current versions and believes this
change will appropriately incorporate any future versions of peer
review guidance documents from both the Agency and OMB (i.e., the EPA
Peer Review Handbook and OMB Final Information Quality Bulletin for
Peer Review).
    The peer review guidance documents discussed in this Unit III.H.2.,
as well as their predecessors, provide guidance on all aspects of the
peer review process. This includes guidance on when to conduct peer
review and on what should be considered in selecting the appropriate
peer review approach, including allowable latitude for the type of peer
review that EPA can conduct. In determining the appropriate type of
peer review, EPA can consider the complexity of the information and any
prior peer review of underlying information. EPA has previously used
this flexibility in the TSCA program and sought a letter peer review,
as opposed to, for instance, a committee established under the Federal
Advisory Committee Act (FACA) (5 U.S.C. 10), to peer review new and
updated information used in

the revised draft risk evaluation for Pigment Violet 29 (Ref. 41).
    The Agency fully intends to uphold the EPA Peer Review Policy
Statement, which states in part, ``. . . For highly influential
scientific assessments, external peer review is the expected procedure.
For influential scientific information intended to support important
decisions, or for work products that have special importance in their
own right, external peer review is the approach of choice . . .''
However, as discussed in the EPA Peer Review Handbook 4th Edition,
there are circumstances when the additional peer review of influential
products that have had adequate prior peer review may not be necessary
(Ref. 39). As the Agency looks to the future of TSCA risk evaluations,
it is expected that specific approaches may be used repeatedly, after
due consideration of complexity, novelty, and prior peer review. That
is, there may be situations when repeated peer review is not warranted.
    For example, EPA did not peer review the 2020 1,4-Dioxane;
Supplemental Analysis to the Draft TSCA Risk Evaluation (Ref. 42). In
response to peer review of the draft risk evaluation for 1,4-dioxane,
published in September 2019 (Ref. 43), members of the SACC, as well as
public commenters, highlighted omissions in the draft evaluation,
specifically 1,4-dioxane exposures as a byproduct in products and
general population exposure from the surface water pathway. As a
result, those conditions of use from the presence of 1,4-dioxane as a
byproduct in consumer use were included in the scope of a supplemental
analysis to the draft risk evaluation. In that situation, because the
analytical approaches to assessing the unreasonable risk associated
with these conditions of use mirrored those approaches used for the
conditions of use evaluated in the peer reviewed September 2019 draft
risk evaluation and there was not new or novel scientific information
to consider, the Agency determined that additional peer review was not
warranted, but sought public comment on the supplemental analysis.
    EPA believes that future risk evaluations and associated analyses
may present similar circumstances for EPA's consideration. 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 (see Unit III.I.1.). EPA's Peer
Review Handbook specifically references circumstances that may not
necessitate additional peer review including ``work that has been
previously reviewed in a manner consistent with the OMB Peer Review
[Bulletin] and EPA's Peer Review Handbook'' (Ref. 39). Thus, this
portion or section of a TSCA assessment may not need additional peer
review. To this end, EPA proposes to add clarity around what will be
peer reviewed. The 2017 final rule stated that ``the risk evaluation''
will be peer reviewed. The proposed regulatory text at Sec.  702.41
provides EPA's 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. EPA requests comments on the proposed
changes with respect to peer review, including whether the proposed
addition of ``or portions thereof'' is consistent with OMB and Agency
guidance.
    Consistent with the 2017 proposed and final rules, EPA will not
seek peer review of any determination as to whether the risk is
``unreasonable,'' which is an Agency policy determination. Consistent
with OMB and EPA guidance, the purpose of peer review is the
independent review of the science underlying the TSCA risk assessment
not an evaluation of EPA's policy determinations. TSCA expressly
reserves to the Agency the final determination of whether risk posed by
a chemical substance is ``unreasonable.'' (15 U.S.C. 2605(i)). This is
consistent with the statutory purpose of the SACC, ``to provide
independent advice and expert consultation, at the request of the
Administrator, with respect to the scientific and technical aspects of
issues relating to the implementation of this title'' (15 U.S.C.
2625(o)(2)).

I. Scientific Standards

    TSCA section 6(h) and (i) require the Agency to make decisions
under TSCA section 6 in a manner that is consistent with the best
available science and based on the weight of scientific evidence.
Specifically, TSCA section 26(h) requires that in carrying out TSCA
sections 4, 5, and 6, to the extent the Agency makes decisions based on
science, the Agency shall ``use scientific information, technical
procedures, measures, methods, protocols, methodologies, or models,
employed in a manner consistent with the best available science.'' The
statute then lists considerations: (1) The extent to which the
scientific information, technical procedures, measures, methods,
protocols, methodologies, or models employed to generate the
information are reasonable for and consistent with the intended use of
the information; (2) The extent to which the information is relevant
for the Administrator's use in making a decision about a chemical
substance or mixture; (3) The degree of clarity and completeness with
which the data, assumptions, methods, quality assurance, and analyses
employed to generate the information are documented; (4) The extent to
which the variability and uncertainty in the information, or in the
procedures, measures, methods, protocols, methodologies, or models, are
evaluated and characterized; and (5) The extent of independent
verification or peer review of the information or of the procedures,
measures, methods, protocols, methodologies or models. Section 26(i)
states ``the Administrator shall make decisions under sections 4, 5,
and 6 based on the weight of scientific evidence.'' TSCA does not
define either ``best available science'' or ``weight of scientific
evidence'' and there is no requirement in the statute to define them by
rule. Codification of definitions has potentially broader impacts
beyond TSCA section 6 risk evaluations and rules, including TSCA
sections 4 and 5 actions, and potentially other applications outside of
TSCA.
    EPA received significant comment about the codification of
definitions for these terms during the development of the 2017 proposed
rule (Ref. 1 and Ref. 44). Some commenters noted that it is imperative
that the Agency have specific criteria which would allow for
consistency and transparency for how EPA will implement science. Others
argued that since interested persons may submit risk assessments to the
Agency for consideration (under TSCA section 26(l)(5)), it is necessary
for the Agency to provide a standard and expectation. Many commenters
noted that there are a number of ways the Agency could and has defined
these terms across other statutory obligations and suggested this could
be both a reason to codify TSCA-specific definitions, or to not codify
them to avoid future limitations in implementation approaches. Others
have argued that the risk evaluation rule should be reserved for
process and procedure, and that codification of

specific process definitions would limit the Agency's ability to adapt
to the changing science of risk evaluation, as well as the science that
informs risk evaluation. Further, some argued that defining the terms
would limit the flexibility afforded the Agency, and arguably the
mandate, to implement and advance novel science.
    EPA determined not to propose codifying definitions of either of
these terms in the 2017 proposed rule (Ref. 9 at p. 7572), citing the