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Rule2023-03574

National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units-Revocation of the 2020 Reconsideration and Affirmation of the Appropriate and Necessary Supplemental Finding

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Published

March 6, 2023

Effective

March 6, 2023

Issuing agencies

Environmental Protection Agency

Abstract

After consideration of public comments, the EPA is revoking a May 22, 2020 finding that it is not appropriate and necessary to regulate coal- and oil-fired electric utility steam generating units (EGUs) under Clean Air Act (CAA) section 112, and concluding, as it did in its April 25, 2016 finding, that it remains appropriate and necessary to regulate hazardous air pollutant (HAP) emissions from EGUs after considering cost.

Full Text

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[Federal Register Volume 88, Number 43 (Monday, March 6, 2023)]
[Rules and Regulations]
[Pages 13956-14011]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-03574]

[[Page 13955]]

Vol. 88

Monday,

No. 43

March 6, 2023

Part III

Environmental Protection Agency

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40 CFR Part 63

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National Emission Standards for Hazardous Air Pollutants: Coal- and
Oil-Fired Electric Utility Steam Generating Units--Revocation of the
2020 Reconsideration and Affirmation of the Appropriate and Necessary
Supplemental Finding; Final Rule

Federal Register / Vol. 88 , No. 43 / Monday, March 6, 2023 / Rules
and Regulations

[[Page 13956]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2018-0794; FRL-6716.2-02-OAR]
RIN 2060-AV12

National Emission Standards for Hazardous Air Pollutants: Coal-
and Oil-Fired Electric Utility Steam Generating Units--Revocation of
the 2020 Reconsideration and Affirmation of the Appropriate and
Necessary Supplemental Finding

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final action.

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SUMMARY: After consideration of public comments, the EPA is revoking a
May 22, 2020 finding that it is not appropriate and necessary to
regulate coal- and oil-fired electric utility steam generating units
(EGUs) under Clean Air Act (CAA) section 112, and concluding, as it did
in its April 25, 2016 finding, that it remains appropriate and
necessary to regulate hazardous air pollutant (HAP) emissions from EGUs
after considering cost.

DATES: This final agency action is effective March 6, 2023.

ADDRESSES: The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2018-0794. All documents in the docket are
listed in <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>. Although listed, some
information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the internet and will be publicly available only in hard
copy. With the exception of such material, publicly available docket
materials are available electronically in <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>
or in hard copy at the EPA Docket Center, Room 3334, WJC West Building,
1301 Constitution Avenue NW, Washington, DC. The Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Public Reading Room is
(202) 566-1744, and the telephone number for the EPA Docket Center is
(202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For questions about this action,
contact Melanie King, Sector Policies and Programs Division (D243-01),
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina 27711;
telephone number: (919) 541-2469; and email address:
<a href="/cdn-cgi/l/email-protection#cda6a4a3aae3a0a8a1aca3a4a88da8bdace3aaa2bb"><span class="__cf_email__" data-cfemail="a7cccec9c089cac2cbc6c9cec2e7c2d7c689c0c8d1">[email&#160;protected]</span></a>.

SUPPLEMENTARY INFORMATION: The EPA is revoking a May 22, 2020 (85 FR
31286) finding that it is not appropriate and necessary to regulate
coal- and oil-fired EGUs under CAA section 112 (2020 Final Action), and
concluding, as it did in the EPA's April 25, 2016 finding (81 FR
24420), that it remains appropriate and necessary to regulate HAP
emissions from EGUs after considering cost. The 2016 finding was made
in response to the U.S. Supreme Court's 2015 Michigan v. EPA decision,
where the Court held that the EPA had erred by not taking cost into
consideration when taking action on February 16, 2012 (77 FR 9304), to
affirm a 2000 EPA determination that it was appropriate and necessary
to regulate HAP emissions from EGUs. In the same 2012 action, the EPA
also promulgated National Emission Standards for Hazardous Air
Pollutants (NESHAP) for coal- and oil-fired EGUs, commonly known as the
Mercury and Air Toxics Standards or MATS. The EPA is taking this action
after a review of the public comments on our proposed revocation of the
2020 Final Action and our conclusion that it is appropriate and
necessary to regulate coal- and oil-fired EGUs under CAA section 112
(2022 Proposal), based, in part, on ``screening-level'' analyses
contained in the 2021 Risk Technical Support Document (TSD) \1\ and a
reassessment of the actual costs of MATS implementation in the Cost
TSD.\2\ See 87 FR 7624 (February 9, 2022). A summary of the public
comments and the EPA's responses to the comments, and the TSDs are
available in the docket for this action, Docket ID No. EPA-HQ-OAR-2018-
0794.\3\
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\1\ National-Scale Mercury Risk Estimates for Cardiovascular and
Neurodevelopmental Outcomes for the National Emission Standards for
Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam
Generating Units--Revocation of the 2020 Reconsideration, and
Affirmation of the Appropriate and Necessary Supplemental Finding;
Notice of Proposed Rulemaking. Available in the rulemaking docket,
Docket ID No. EPA-HQ-OAR-2018-0794-4605.
\2\ Supplemental Data and Analysis for the National Emission
Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric
Utility Steam Generating Units--Revocation of the 2020
Reconsideration, and Affirmation of the Appropriate and Necessary
Supplemental Finding; Notice of Proposed Rulemaking. Available in
the rulemaking docket, Docket ID No. EPA-HQ-OAR-2018-0794-4586.
\3\ As explained in a memorandum to the docket, the docket for
this action includes the documents and information, in whatever
form, in Docket ID Nos. EPA-HQ-OAR-2009-0234 (National Emission
Standards for Hazardous Air Pollutants for Coal- and Oil-fired
Electric Utility Steam Generating Units), EPA-HQ-OAR-2002-0056
(National Emission Standards for Hazardous Air Pollutants for
Utility Air Toxics; Clean Air Mercury Rule (CAMR)), and Legacy
Docket ID No. A-92-55 (Electric Utility Hazardous Air Pollutant
Emission Study). See memorandum titled Incorporation by reference of
Docket Number EPA-HQ-OAR-2009-0234, Docket Number EPA-HQ-OAR-2002-
0056, and Docket Number A-92-55 into Docket Number EPA-HQ-OAR-2018-
0794 (Docket ID Item No. EPA-HQ-OAR-2018-0794-0005).
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Based on a re-evaluation of the administrative record and the
statute, and after considering public comments, the EPA concludes that
the framework applied in the May 22, 2020 finding was ill-suited to
assessing and comparing the full range of advantages and disadvantages,
and after applying a more suitable framework, the 2020 determination is
revoked. Additionally, the EPA is reaffirming that it is appropriate
and necessary to regulate HAP emissions from coal- and oil-fired EGUs
after weighing the volume of pollution that would be reduced through
regulation, the public health risks and harms posed by these emissions,
the impacts of this pollution on particularly exposed and sensitive
populations, the availability of effective controls, and the costs of
reducing this harmful pollution, including the effects of control costs
on the electricity generation industry and its ability to provide
reliable and affordable electricity.
Preamble acronyms and abbreviations. We use multiple acronyms and
terms in this preamble. While this list may not be exhaustive, to ease
the reading of this preamble and for reference purposes, the EPA
defines the following terms and acronyms here:

ARP Acid Rain Program
BCA benefit-cost analysis
CAA Clean Air Act
CAAA Clean Air Act Amendments of 1990
CAMR Clean Air Mercury Rule
CBI Confidential Business Information
CDC Centers for Disease Control and Prevention
CFR Code of Federal Regulations
C-R concentration response
DSI dry sorbent injection
EGU electric utility steam generating unit
EIA Energy Information Administration
EJ environmental justice
EPA Environmental Protection Agency
ESP electrostatic precipitator
FGD flue gas desulfurization
FR Federal Register
HAP hazardous air pollutant(s)
HCl hydrogen chloride
HF hydrogen fluoride
IHD ischemic heart disease
IPM Integrated Planning Model
IRIS Integrated Risk Information System
MACT maximum achievable control technology
MATS Mercury and Air Toxics Standards
MI myocardial infarction

[[Page 13957]]

MW megawatt
NAS National Academy of Sciences
NESHAP national emission standards for hazardous air pollutants
NHANES National Health and Nutrition Examination Survey
OMB Office of Management and Budget
PM particulate matter
RfD reference dose
RIA regulatory impact analysis
RTR residual risk and technology review
SCR selective catalytic reduction
SO<INF>2</INF> sulfur dioxide
the Court U.S. Supreme Court
the court D.C. Circuit Court
TSD technical support document
tpy tons per year

Organization of this document. The information in this preamble is
organized as follows:

I. General Information
A. Executive Summary
B. Does this action apply to me?
C. Where can I get a copy of this document and other related
information?
D. Judicial Review and Administrative Reconsideration
II. Background
A. Regulatory History
B. Statutory Background
III. Final Determination Under CAA Section 112(n)(1)(A)
A. Public Health and Environmental Hazards Associated With
Emissions From EGUs
B. Cost Associated With Regulating EGUs for HAP
C. Revocation of the 2020 Final Action
D. The Administrator's Preferred Framework and Conclusion
E. The Administrator's Benefit-Cost Analysis Approach and
Conclusion
F. The Administrator's Final Determination
IV. Public Comments and Responses
A. Comments on the Public Health and Environmental Hazards
Associated With Emissions From EGUs
B. Comments on Consideration of Cost of Regulating EGUs for HAP
C. Comments on Revocation of the 2020 Final Action
D. Comments on the Administrator's Preferred Framework and
Conclusion
E. Comments on the Administrator's Benefit-Cost Analysis
Approach and Conclusion
V. Summary of Cost, Environmental, and Economic Impacts
VI. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
B. Paperwork Reduction Act (PRA)
C. Regulatory Flexibility Act (RFA)
D. Unfunded Mandates Reform Act (UMRA)
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act (NTTAA)
J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
K. Congressional Review Act

I. General Information

A. Executive Summary

On January 20, 2021, the President signed Executive Order 13990,
``Protecting Public Health and the Environment and Restoring Science to
Tackle the Climate Crisis'' (86 FR 7037, January 25, 2021). The
Executive order, among other things, instructed the EPA to review the
2020 final action titled ``National Emission Standards for Hazardous
Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating
Units--Reconsideration of Supplemental Finding and Residual Risk and
Technology Review'' (85 FR 31286; May 22, 2020) (2020 Final Action) and
to consider publishing a notice of proposed rulemaking suspending,
revising, or rescinding that action. Consistent with the Executive
order, the EPA has undertaken a careful review of the 2020 Final
Action, in which the EPA reconsidered its April 25, 2016 supplemental
finding (81 FR 24420) (2016 Supplemental Finding). Based on that
review, on February 9, 2022, the EPA issued a proposed action finding
that the decisional framework for making the appropriate and necessary
determination under CAA section 112(n)(1)(A) that was applied in the
2020 Final Action was unsuitable because it failed to adequately
account for statutorily relevant factors (87 FR 7624). The EPA proposed
to revoke the 2020 Final Action's determination that it is not
appropriate and necessary to regulate HAP emissions from coal- and oil-
fired EGUs under section 112 of the CAA and to reaffirm our earlier
determinations--made in 2000 (65 FR 79825; December 20, 2000) (2000
Determination), 2012 (77 FR 9304; February 16, 2012) (2012 MATS Final
Rule), and 2016--that it is appropriate and necessary to regulate coal-
and oil-fired EGUs under section 112 of the CAA. After considering the
public comments on the 2022 Proposal, the EPA is finalizing its
revocation of the 2020 Final Action and its reaffirmation of the
earlier determinations that it is appropriate and necessary to regulate
coal- and oil-fired EGUs under section 112 of the CAA.
In this action, we conclude that the methodology we applied in 2020
is ill-suited to the appropriate and necessary determination because,
among other reasons, it did not give adequate weight to the significant
volume of HAP emissions from EGUs and the attendant risks remaining
after imposition of the other requirements of the CAA, which includes
risks of many adverse health and environmental effects of EGU HAP
emissions that currently cannot be quantified or monetized. We
therefore revoke the 2020 Final Action.
We further conclude, once again, that it is appropriate and
necessary to regulate coal- and oil-fired EGUs under CAA section 112.
We come to this conclusion by first examining the advantages of
regulation, including new information on the risks posed by EGU HAP
emissions. We then examine the disadvantages of regulation, including
both the costs of compliance (which we explain we significantly
overestimated in 2012) and how those costs affect the industry and the
public. We then weigh these advantages and disadvantages to reach the
conclusion that it is appropriate and necessary to regulate, using two
separate methodologies.
Our preferred methodology is to consider all of the impacts of the
regulation using a totality-of the-circumstances approach rooted in the
Michigan court's direction to ``pay[] attention to the advantages and
disadvantages of [our] decision[].'' 576 U.S. at 753; see id. at 752
(``In particular, `appropriate' is `the classic broad and all-
encompassing term that naturally and traditionally includes
consideration of all the relevant factors.''). To help determine the
relevant factors to weigh, we look to CAA section 112(n)(1)(A), the
other provisions of CAA section 112(n)(1), and to the statutory design
of CAA section 112.
Initially, we consider the human health advantages of reducing HAP
emissions from EGUs because, in CAA section 112(n)(1)(A), Congress
directed the EPA to make the appropriate and necessary determination
after considering the results of a ``study of the hazards to public
health reasonably anticipated to occur as a result of [HAP] emissions''
from EGUs. See CAA section 112(n)(1)(A). We consider all of the
advantages of reducing emissions of HAP (i.e., the risks posed by HAP)
regardless of whether those advantages can currently be quantified or
monetized in a way that allows the benefits of such action to be
directly compared to the costs of reducing those emissions. Consistent
with CAA section 112(n)(1)(B)'s direction to examine the rate and mass
of mercury emissions, and the design of CAA section 112, which requires
swift reduction of the volume of HAP emissions from stationary

[[Page 13958]]

sources based on the risk such emissions pose, we conclude that we
should place substantial weight on reducing the large volume of HAP
emissions from EGUs, thereby reducing the risk of grave harms that can
occur as a result of exposure to HAP. Also consistent with the
statutory design of CAA section 112, in considering the advantages of
HAP reductions, we consider the distribution of risk reductions, and
the statute's clear goal in CAA section 112(n)(1)(C) and other
provisions of CAA section 112 to protect the most exposed and
susceptible populations, such as developing fetuses and communities
that are reliant on local fish for their survival. We think it is
highly relevant that, while EGUs generate power for all, and EGU HAP
emissions pose risks to anyone exposed to such HAP, a smaller set of
the population who live near EGUs face a disproportionate risk of being
significantly harmed by toxic pollution. Finally, we also consider the
identified risks to the environment posed by mercury and acid-gas HAP,
consistent with CAA section 112(n)(1)(B) and the general goal of CAA
section 112 to reduce risks posed by HAP to the environment.
We next weigh those advantages against the disadvantages of
regulation, principally in the form of the costs incurred to control
HAP before they are emitted into the environment. In evaluating the
disadvantages of MATS, we begin with the costs to the power industry of
complying with MATS. This assessment uses a sector-level (or system-
level) accounting perspective to estimate the cost of MATS, looking
beyond just pollution control costs for directly affected EGUs to
include incremental costs associated with changes in fuel supply,
construction of new capacity, and costs to non-MATS units that were
also projected to adjust operating decisions as the power system
adjusted to meet MATS requirements. Consistent with the statutory
design, we consider those costs comprehensively, examining them in the
context of the effect of those expenditures on the economics of power
generation more broadly, the reliability of electricity, the cost of
electricity to consumers, and employment effects. These metrics are
relevant to our weighing exercise because they give us a more complete
picture of the disadvantages to producers and consumers of electricity
imposed by this regulation and because our conclusion might change
depending on how this burden affects the ability of the industry to
provide reliable, affordable electricity. These metrics are relevant
measures for evaluating costs to the utility sector in part because
they are the types of metrics considered by the owners and operators of
EGUs themselves. See 81 FR 24428 (April 25, 2016).
As explained in detail in this final action, after weighing the
risks posed by HAP emissions from EGUs against the costs of reducing
that pollution on the industry and society as a whole, we conclude that
it is appropriate to regulate those emissions to protect against
adverse health and environmental impacts posed by exposure to HAP
emitted by coal- and oil-fired EGUs. We note it is particularly
important to regulate because of the risks of adverse health impacts on
the populations most vulnerable to such risks. We find that this is
true whether we are looking at the information available as of the time
of the 2012 threshold finding (as reflected in the rulemaking record
for the 2016 Supplemental Finding) or as of the time of the updated
record in 2022, in which we quantify additional risks posed by HAP
emissions from EGUs and determine, based on newer post-MATS
implementation analyses, that the actual cost of complying with MATS
was likely significantly less than the EPA's projected estimate in the
2011 Regulatory Impacts Analysis (2011 RIA).\4\ We find the actual cost
of complying with MATS was likely significantly less than the EPA's
projected estimate in the 2011 RIA primarily because fewer pollution
controls were installed than projected, and the controls that were used
were less expensive than projected.
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\4\ U.S. EPA. 2011. Regulatory Impact Analysis for the Final
Mercury and Air Toxics Standards. EPA-452/R-11-011. Available at:
<a href="https://www3.epa.gov/ttn/ecas/docs/ria/utilities_ria_final-mats_2011-12.pdf">https://www3.epa.gov/ttn/ecas/docs/ria/utilities_ria_final-mats_2011-12.pdf</a>.
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We conclude that regulation is appropriate under our preferred
totality-of-the-circumstances approach when we consider the advantages
and disadvantages associated with reducing HAP emissions alone, even
when excluding consideration of the many advantages arising from
reductions in non-HAP emissions which occur when reducing HAP
emissions. However, a true examination of all of the ``advantages and
disadvantages of [our] decision[],'' 576 U.S. at 753 (emphasis in
original), would include such non-HAP beneficial impacts. Therefore,
while we would find MATS regulation appropriate and necessary when
focusing solely on HAP, in this rulemaking, we also considered the
advantages associated with non-HAP emission reductions that result from
the application of HAP controls as part of our totality-of-the-
circumstances approach. In the 2012 MATS Final Rule, our projections
found that regulating EGUs for HAP would result in substantial health
benefits from coincidental reductions in ambient concentrations of
particulate matter (PM). We also projected that regulating EGUs for HAP
would similarly result in an improvement in ambient concentrations of
ozone. While we reach the conclusion that regulating HAP emissions from
coal- and oil-fired EGUs is appropriate even absent consideration of
these additional benefits, adding these advantages to the weighing
inquiry provides further support for our conclusion that the advantages
of regulation outweigh the disadvantages.
We recognize, as we did in 2016, that our preferred, totality-of-
the-circumstances approach to making the appropriate and necessary
determination is an exercise of judgment, and that ``[r]easonable
people, and different decision-makers, can arrive at different
conclusions under the same statutory provision.'' 81 FR 24431; April
25, 2016. However, this type of weighing of factors and circumstances
is an inherent part of regulatory decision-making, and the EPA finds it
is a reasonable approach in this case.
Next, we turn to our alternative approach of a formal benefit-cost
analysis (BCA). This approach independently supports the determination
that it is appropriate to regulate EGU HAP. Based on the 2011 RIA
performed as part of the 2012 MATS Final Rule, the total net benefits
of MATS were overwhelmingly positive even though the EPA was only able
to quantify and monetize a subset of the many societal benefits of
reducing HAP emissions from EGUs. Like the preferred approach, this
conclusion is further supported by newer information on the risks posed
by HAP emissions from EGUs as well as new information on the actual
costs of implementing MATS, which likely were significantly
overestimated in the 2011 RIA.
This final action is organized as follows. In section II.A of this
preamble, we provide as background the regulatory and procedural
history leading to this action. We also detail, in preamble section
II.B, the statutory design of HAP regulation that Congress added to the
CAA in 1990 in the face of the EPA's failure to make meaningful
progress in regulating HAP emissions from stationary sources. In
particular, we point out that many provisions of CAA section 112
demonstrate the value Congress placed on reducing the volume

[[Page 13959]]

of HAP emissions from stationary sources as much and as quickly as
possible, with a particular focus on reducing HAP related risks to the
most exposed and most sensitive members of the public. This background
assists in identifying the relevant statutory factors to weigh in
considering the advantages and disadvantages of HAP regulation.
Section III of the preamble provides a brief summary of the 2022
Proposal's findings. In section III.A, we review the public health and
environmental burden associated with EGU HAP emissions by summarizing
information previously recognized and documented in the statutorily
mandated CAA section 112(n)(1) studies, as well as additional risk
analyses supported by new scientific studies introduced in the 2022
Proposal. Section III.B considers the costs of the MATS regulation and
describes the basis for the EPA's conclusion that the original cost
projection in the 2011 RIA was likely a significant overestimate of the
actual cost. These two sections establish the foundation for the EPA's
rationale for both revoking the 2020 Final Action and affirming our
determination that regulation of HAP emissions from coal-and oil-fired
EGUs is appropriate and necessary in light of advantages and
disadvantages using our preferred totality-of-the-circumstances
approach. The revocation of the 2020 Final Action is discussed in
section III.C, and the Administrator's preferred totality-of-the-
circumstances approach is presented in section III.D. In section III.E,
we describe our alternative approach to the appropriate and necessary
determination which applies a formal BCA and that independently
supports the appropriate and necessary determination. Finally, in
section III.F, we present the Administrator's final determination that
it is appropriate and necessary to regulate HAP emissions from coal-
and oil-fired EGUs after considering cost.
The EPA provided opportunities for public comment on our proposed
revocation of the 2020 Final Action and our affirmation that it is
appropriate and necessary to regulate coal- and oil-fired EGUs under
CAA section 112. See 87 FR 7624 (February 9, 2022). Section IV of this
preamble describes some of the most pertinent public comments received
on the 2022 Proposal and provides the EPA's responses. (All of the
comments are addressed in the EPA's 2023 Response to Comments (RTC)
Document.\5\) This section follows the same order as the preceding
section with individual sections for comment responses for health
hazards (IV.A), costs (IV.B), revocation (IV.C), the preferred approach
(i.e., totality of the circumstances) (IV.D), and the alternative
approach (i.e., formal BCA) (IV.E).
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\5\ Mercury and Air Toxics Standards for Power Plants 2022
Proposed Revocation of the 2020 Reconsideration and Affirmation of
the Appropriate and Necessary Supplemental Finding. Response to
Comments. Available in the rulemaking docket, Docket ID No. EPA-HQ-
OAR-2018-0794.
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Finally, section V of this document notes that because this action
reaffirms prior determinations and does not impact implementation of
MATS, the action does not result in any cost, environmental, or
economic impacts.\6\
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\6\ However, finalizing this affirmative threshold determination
provides important certainty about the future of MATS for regulated
industry, states, other stakeholders, and the public.
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B. Does this action apply to me?

The source category that is the subject of this action is coal- and
oil-fired EGUs regulated by NESHAP under 40 CFR part 63, subpart UUUUU,
commonly known as MATS. The North American Industry Classification
System (NAICS) codes for the coal- and oil-fired EGU source category
are 221112, 221122, and 921150. This list of NAICS codes is not
intended to be exhaustive, but rather provides a guide for readers
regarding the entities that this action is likely to affect.

C. Where can I get a copy of this document and other related
information?

In addition to being available in the docket, an electronic copy of
this action is available on the internet. Following signature by the
EPA Administrator, the EPA will post a copy of this action at <a href="https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards">https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards</a>. Following publication in the Federal Register, the EPA will
post the Federal Register version of the final action and key technical
documents at this same website.

D. Judicial Review and Administrative Reconsideration

Under CAA section 307(b)(1), judicial review of this final action
is available only by filing a petition for review in the United States
Court of Appeals for the District of Columbia Circuit by May 5, 2023.
Under CAA section 307(b)(2), the requirements established by this final
action may not be challenged separately in any civil or criminal
proceedings brought by the EPA to enforce the requirements.
Section 307(d)(7)(B) of the CAA further provides that only an
objection to a rule or procedure which was raised with reasonable
specificity during the period for public comment (including any public
hearing) may be raised during judicial review. That section of the CAA
also provides a mechanism for the EPA to reconsider the rule if the
person raising an objection can demonstrate to the Administrator that
it was impracticable to raise such objection within the period for
public comment or if the grounds for such objection arose after the
period for public comment (but within the time specified for judicial
review) and if such objection is of central relevance to the outcome of
the rule. Any person seeking to make such a demonstration should submit
a Petition for Reconsideration to the Office of the Administrator, U.S.
EPA, Room 3000, WJC South Building, 1200 Pennsylvania Ave. NW,
Washington, DC 20460, with a copy to both the person(s) listed in the
preceding FOR FURTHER INFORMATION CONTACT section, and the Associate
General Counsel for the Air and Radiation Law Office, Office of General
Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW,
Washington, DC 20460.

II. Background

A. Regulatory History

In the 1990 Amendments, Congress substantially modified CAA section
112 to address HAP emissions from stationary sources. CAA section
112(b)(1) sets forth a list of 187 identified HAP, and CAA sections
112(b)(2) and (3) give the EPA the authority to add or remove
pollutants from the list. CAA section 112(a)(1) and (2) specify the two
types of sources to be addressed: major sources and area sources. A
major source is any stationary source or group of stationary sources at
a single location and under common control that emits or has the
potential to emit, considering controls, 10 tons per year (tpy) or more
of any HAP or 25 tpy or more of any combination of HAP. CAA section
112(a)(1). Any stationary source of HAP that is not a major source is
an area source.\7\ CAA section 112(a)(2). All major source categories,
besides EGUs, and certain area source categories, were required to be
included on an initial published list of sources subject to regulation
under CAA section 112. See CAA sections 112(a)(1) and (c)(1). The EPA
is required to promulgate emission standards under CAA section 112(d)
for

[[Page 13960]]

every source category on the CAA section 112(c)(1) list.
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\7\ The statute includes a separate definition of ``EGU'' that
includes both major and area source power plant facilities. CAA
section 112(a)(8).
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The general CAA section 112(c) process for listing source
categories does not apply to EGUs. Instead, Congress enacted a special
provision, CAA section 112(n)(1)(A), which establishes a separate
process by which the EPA determines whether to add EGUs to the CAA
section 112(c) list of source categories that must be regulated under
CAA section 112. Because EGUs were subject to other CAA requirements
under the 1990 Amendments, most importantly the Acid Rain Program
(ARP), CAA section 112(n)(1)(A) directs the EPA to conduct a study to
evaluate the hazards to public health that are reasonably anticipated
to occur as a result of the HAP emissions from EGUs ``after imposition
of the requirements of this chapter.'' See CAA section 112(n)(1)(A);
see also Michigan v. EPA, 576 U.S. at 748 (``Quite apart from the
hazardous-air-pollutants program, the Clean Air Act Amendments of 1990
subjected power plants to various regulatory requirements. The parties
agree that these requirements were expected to have the collateral
effect of reducing power plants' emissions of hazardous air pollutants,
although the extent of the reduction was unclear.''). The provision
directs that the EPA shall regulate EGUs under CAA section 112 if the
Administrator determines, after considering the results of the study,
that such regulation is ``appropriate and necessary.'' CAA section
112(n)(1)(A), as enacted in 1990, therefore sets a unique process by
which the Administrator was to make a one-time determination whether to
add EGUs to the CAA section 112(c) list of sources that must be subject
to regulation under CAA section 112.
The study required under CAA section 112(n)(1)(A) is one of three
studies commissioned by Congress under CAA section 112(n)(1), a
subsection entitled ``Electric utility steam generating units.'' The
first, which, as noted, the EPA was required to consider before making
the appropriate and necessary determination, was completed in 1998 and
was entitled ``Study of Hazardous Air Pollutant Emissions from Electric
Utility Steam Generating Units-Final Report to Congress'' (Utility
Study).\8\ The Utility Study contained an analysis of HAP emissions
from EGUs, an assessment of the hazards and risks due to inhalation
exposures to these emitted pollutants, and a multipathway (inhalation
plus non-inhalation exposures) risk assessment for mercury and a subset
of other relevant HAP. The study indicated that mercury was the HAP of
greatest concern to public health from coal- and oil-fired EGUs. The
study also concluded that numerous control strategies were available to
reduce HAP emissions from this source category.
---------------------------------------------------------------------------

\8\ U.S. EPA. Study of Hazardous Air Pollutant Emissions from
Electric Utility Steam Generating Units--Final Report to Congress.
EPA-453/R-98-004a. February 1998.
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The second study commissioned by Congress under CAA section
112(n)(1)(B), the ``Mercury Study Report to Congress'' (Mercury
Study),\9\ was released in 1997. Under this provision, the statute
tasked the EPA with focusing exclusively on mercury, but directed the
EPA to look at other stationary sources in addition to EGUs, the rate
and mass of emissions coming from those sources, available technologies
for controlling mercury and the costs of such technologies, and a
broader scope of impacts including environmental effects. As in the
Utility Study, the EPA confirmed that mercury is highly toxic,
persistent, and bioaccumulates in food chains. Fish consumption is the
primary pathway for human exposure to mercury, which can lead to higher
risks in certain populations. The third study, required under CAA
section 112(n)(1)(C), directed the National Institute of Environmental
Health Sciences (NIEHS) to conduct a study to determine the threshold
level of mercury exposure below which adverse human health effects were
not expected to occur (NIEHS Study). The statute required that the
study include a threshold for mercury concentrations in the tissue of
fish that could be consumed, even by sensitive populations, without
adverse effects to public health. The NIEHS submitted the required
study to Congress in 1995.\10\ See 76 FR 24982 (May 3, 2011).
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\9\ U.S. EPA. 1997. Mercury Study Report to Congress. EPA-452/R-
97-003 December 1997.
\10\ National Institute of Environmental Health Sciences (NIEHS)
Report on Mercury; available in the rulemaking docket at EPA-HQ-OAR-
2009-0234-3053.
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Later, after submission of the CAA section 112(n)(1) reports and as
part of the fiscal year 1999 appropriations, Congress further directed
the EPA to fund the National Academy of Sciences (NAS) to perform an
independent evaluation of the data related to the health impacts of
methylmercury, and, similar to the CAA section 112(n)(1)(C) inquiry,
specifically to advise the EPA as to the appropriate reference dose
(RfD) for methylmercury. Congress also indicated in the 1999 conference
report directing the EPA to fund the NAS Study, that the EPA should not
make the appropriate and necessary regulatory determination until the
EPA had reviewed the results of the NAS Study. See H.R. Conf. Rep. No.
105-769, at 281-282 (1998). This last study, completed by the NAS in
2000, was entitled ``Toxicological Effects of Methylmercury'' (NAS
Study),\11\ and it presented a rigorous peer-review of the EPA's RfD
for methylmercury.
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\11\ National Research Council (NAS). 2000. Toxicological
Effects of Methylmercury. Committee on the Toxicological Effects of
Methylmercury, Board on Environmental Studies and Toxicology,
National Research Council. Many of the peer-reviewed articles cited
in this section are publications originally cited in the NAS report.
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Based on the results of these studies and other available
information, the EPA determined on December 20, 2000, pursuant to CAA
section 112(n)(1)(A), that it is appropriate and necessary to regulate
HAP emissions from coal- and oil-fired EGUs and added such units to the
CAA section 112(c) list of source categories that must be regulated
under CAA section 112. See 65 FR 79825 (December 20, 2000) (2000
Determination).\12\
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\12\ In the same 2000 action, the EPA Administrator found that
regulation of HAP emissions from natural gas-fired EGUs is not
appropriate or necessary because the impacts due to HAP emissions
from such units are negligible. See 65 FR 79831 (December 20, 2000).
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In 2005, the EPA revised the original 2000 Determination and
concluded that it was neither appropriate nor necessary to regulate
EGUs under CAA section 112 in part because the EPA concluded it could
address risks from EGU HAP emissions under a different provision of the
statute. See 70 FR 15994 (March 29, 2005) (2005 Revision). Based on
that determination, the EPA removed coal- and oil-fired EGUs from the
CAA section 112(c) list of source categories to be regulated under CAA
section 112. In a separate but related 2005 action, the EPA also
promulgated the Clean Air Mercury Rule (CAMR), which established CAA
section 111 standards of performance for mercury emissions from EGUs.
See 70 FR 28605 (May 18, 2005). Both the 2005 Revision and the CAMR
were vacated by the U.S. Court of Appeals for the District of Columbia
Circuit (the court) in 2008. New Jersey v. EPA, 517 F.3d 574 (D.C. Cir.
2008). The court held that the EPA failed to comply with the
requirements of CAA section 112(c)(9) for delisting source categories,
and consequently also vacated the CAA section 111 performance standards
promulgated in CAMR, without addressing the merits of those standards.
Id. at 582-84.
Subsequent to the New Jersey decision, the EPA conducted additional
technical analyses, including peer-reviewed risk assessments on human

[[Page 13961]]

health effects associated with mercury (2011 Final Mercury TSD) \13\
and non-mercury metal HAP emissions from EGUs (2011 Non-Hg HAP
Assessment).\14\ Those analyses, which focused on populations with
higher fish consumption (e.g., subsistence fishers) and residents
living near the facilities who experienced increased exposure to HAP
through inhalation, found that mercury and non-mercury HAP emissions
from EGUs remain a public health hazard and that EGUs were the largest
anthropogenic source of mercury emissions to the atmosphere in the U.S.
Based on these findings, and other relevant information regarding the
volume of HAP, environmental effects, and availability of controls, in
2012, the EPA affirmed the original 2000 Determination that it is
appropriate and necessary to regulate EGUs under CAA section 112. See
77 FR 9304 (February 16, 2012).
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\13\ U.S. EPA. 2011. Revised Technical Support Document:
National-Scale Assessment of Mercury Risk to Populations with High
Consumption of Self-caught Freshwater Fish in Support of the
Appropriate and Necessary Finding for Coal- and Oil-Fired Electric
Generating Units. Office of Air Quality Planning and Standards.
December 2011. EPA-452/R-11-009. Docket ID Item No. EPA-HQ-OAR-2009-
0234-19913 (2011 Final Mercury TSD).
\14\ U.S. EPA. 2011. Supplement to the Non-Hg Case Study Chronic
Inhalation Risk Assessment In Support of the Appropriate and
Necessary Finding for Coal- and Oil-Fired Electric Generating Units.
Office of Air Quality Planning and Standards. November 2011. EPA-
452/R-11-013. Docket ID Item No. EPA-HQ-OAR-2009-0234-19912 (2011
Non-Hg HAP Assessment).
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In the same 2012 action, the EPA established a NESHAP, commonly
referred to as MATS, that required coal- and oil-fired EGUs to meet HAP
emission standards reflecting the application of the maximum achievable
control technology (MACT) for all HAP emissions from EGUs.\15\ MATS
applies to existing and new coal- and oil-fired EGUs located at both
major and area sources of HAP emissions. An EGU is a fossil fuel-fired
steam generating combustion unit of more than 25 megawatts (MW) that
serves a generator that produces electricity for sale. See CAA section
112(a)(8) (defining EGU). A unit that cogenerates steam and electricity
and supplies more than one-third of its potential electric output
capacity and more than 25 MW electric output to any utility power
distribution system for sale is also an EGU. Id.
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\15\ Although the 2012 MATS Final Rule has been amended several
times, the amendments are not a result of actions regarding the
appropriate and necessary determination and, therefore, are not
discussed in this preamble. Detail regarding those amendatory
actions can be found at <a href="https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards">https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards</a>.
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For coal-fired EGUs, MATS includes standards to limit emissions of
mercury, acid gas HAP, non-mercury HAP metals (e.g., nickel, lead,
chromium), and organic HAP (e.g., formaldehyde, dioxin/furan).
Standards for hydrogen chloride (HCl) serve as a surrogate for the acid
gas HAP, with an alternate standard for sulfur dioxide (SO<INF>2</INF>)
that may be used as a surrogate for acid gas HAP for those coal-fired
EGUs with flue gas desulfurization (FGD) systems and SO<INF>2</INF>
continuous emissions monitoring systems that are installed and
operational. Standards for filterable PM serve as a surrogate for the
non-mercury HAP metals, with standards for total non-mercury HAP metals
and individual non-mercury HAP metals provided as alternative
equivalent standards. Work practice standards that require periodic
combustion process tune-ups were established to limit formation and
emissions of the organic HAP.
For oil-fired EGUs, MATS includes standards to limit emissions of
HCl and hydrogen fluoride (HF), total HAP metals (e.g., mercury,
nickel, lead), and organic HAP (e.g., formaldehyde, dioxin/furan).
Standards for filterable PM serve as a surrogate for total HAP metals,
with standards for total HAP metals and individual HAP metals provided
as alternative equivalent standards. Periodic combustion process tune-
up work practice standards were established to limit formation and
emissions of the organic HAP.
Additional detail regarding the types of units regulated under MATS
and the regulatory requirements that they are subject to can be found
in 40 CFR part 63, subpart UUUUU.\16\ The existing source compliance
date was April 16, 2015, but many existing sources were granted an
additional 1-year extension of the compliance date for the installation
of controls. Currently all affected sources (i.e., all coal- and oil-
fired EGUs that meet the definition of an Electric Utility Steam
Generating Unit in CAA section 112(a)(8)) are subject to the
requirements in MATS.
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\16\ Available at <a href="https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-63/subpart-UUUUU">https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-63/subpart-UUUUU</a>.
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After MATS was promulgated, both the rule itself and many aspects
of the EPA's appropriate and necessary determination were challenged in
the D.C. Circuit court (the court). In White Stallion Energy Center v.
EPA, 748 F.3d 1222 (2014), the court unanimously denied all challenges
to MATS, with one exception discussed below in which the court denied
the challenge in an opinion that was not unanimous. As part of its
decision, the court concluded that the ``EPA's `appropriate and
necessary' determination in 2000, and the reaffirmation of that
determination in 2012, are amply supported by EPA's findings regarding
the health effects of mercury exposure.'' Id. at 1245.\17\ While
joining the majority's conclusions as to the adequacy of the EPA's
identification of public health hazards, then-judge Kavanaugh dissented
on the issue of whether the EPA erred by not considering costs together
with the harms of HAP emissions when making the ``appropriate and
necessary'' determination, finding that cost was a required
consideration under that determination. Id. at 1258-59 (Kavanaugh, J.,
dissenting).
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\17\ In discussing the 2011 Final Mercury TSD, the D.C. Circuit
concluded that the EPA considered the available scientific
information in a rational manner, and stated:
As explained in the technical support document (TSD)
accompanying the Final Rule, EPA determined that mercury emissions
posed a significant threat to public health based on an analysis of
women of child-bearing age who consumed large amounts of freshwater
fish. See [2011 Final] Mercury TSD . . . . The design of EPA's TSD
was neither arbitrary nor capricious; the study was reviewed by
EPA's independent Science Advisory Board, stated that it
``support[ed] the overall design of and approach to the risk
assessment'' and found ``that it should provide an objective,
reasonable, and credible determination of potential for a public
health hazard from mercury emissions emitted from U.S. EGUs.'' . . .
In addition, EPA revised the final TSD to address SAB's remaining
concerns regarding EPA's data collection practices.
Id. at 1245-46.
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The U.S. Supreme Court (the Court) subsequently granted certiorari,
directing the parties to address a single question posed by the Court
itself: ``Whether the Environmental Protection Agency unreasonably
refused to consider cost in determining whether it is appropriate to
regulate hazardous air pollutants emitted by electric utilities.''
Michigan v. EPA, 135 S. Ct. 702 (Mem.) (2014). In 2015, the Court held
that ``EPA interpreted [CAA section 112(n)(1)(A)] unreasonably when it
deemed cost irrelevant to the decision to regulate power plants.''
Michigan, 576 U.S. at 760. In so holding, the Court found that the EPA
``must consider cost--including, most importantly, cost of compliance--
before deciding whether regulation is appropriate and necessary.'' Id.
at 2711. It is ``up to the Agency,'' the Court added, ``to decide (as
always, within the limits of reasonable interpretation) how to account
for cost.'' Id. The rule was ultimately remanded back to the EPA to
complete the required cost analysis, and the court left the MATS rule
in place pending the completion of that analysis. White Stallion Energy
Center v. EPA, No. 12-1100, ECF No. 1588459 (D.C. Cir. December 15,
2015).

[[Page 13962]]

In response to the Court's direction, the EPA finalized a
supplemental finding on April 25, 2016, that evaluated the costs of
complying with MATS and concluded that the appropriate and necessary
determination was still valid. The 2016 Supplemental Finding
promulgated two different approaches to incorporate cost into the
decision-making process for the appropriate and necessary
determination. See 81 FR 24420 (April 25, 2016). The EPA determined
that both approaches independently supported the conclusion that
regulation of HAP emissions from EGUs is appropriate and necessary.
The EPA's preferred approach to incorporating cost in 2016
evaluated estimated costs of compliance with MATS against several cost
metrics relevant to the EGU sector (e.g., historical annual revenues,
annual capital expenditures, and impacts on retail electricity prices)
and found that the projected costs of MATS were reasonable for the
sector in comparison with historical data on those metrics. These
metrics are relevant measures for evaluating costs to the utility
sector in part because they are the types of metrics considered by the
owners and operators of EGUs themselves.\18\ The evaluation of cost
metrics that the EPA applied was consistent with approaches commonly
used to evaluate environmental policy cost impacts.\19\ The EPA also
examined as part of its cost analysis what the impact of MATS would be
on retail electricity prices and the reliability of the power grid. The
EPA then weighed these supplemental findings regarding cost against the
existing administrative record detailing the identified hazards to
public health and the environment from mercury, non-mercury metal HAP,
and acid gas HAP that are listed under CAA section 112, and the other
advantages to regulation. Based on that balancing, the EPA concluded
under the preferred approach that it remained appropriate to regulate
HAP emissions from EGUs after considering cost. See 81 FR 24420 (April
25, 2016) (``After evaluating cost reasonableness using several
different metrics, the Administrator has, in accordance with her
statutory duty under CAA section 112(n)(1)(A), weighed cost against the
previously identified advantages of regulating HAP emissions from
EGUs--including the agency's prior conclusions about the significant
hazards to public health and the environment associated with such
emissions and the volume of HAP that would be reduced by regulation of
EGUs under CAA section 112.'').
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\18\ 81 FR 24428 (April 25, 2016).
\19\ For example, see ``Economic Impact and Small Business
Analysis-Mineral Wool and Wool
Fiberglass RTRs and Wool Fiberglass Area Source NESHAP'' (U.S.
EPA, 2015; <a href="https://www.epa.gov/sites/default/files/2020-07/documents/mwwf_eia_neshap_final_07-2015.pdf">https://www.epa.gov/sites/default/files/2020-07/documents/mwwf_eia_neshap_final_07-2015.pdf</a>) or ``Economic Impact
Analysis of Final Coke Ovens NESHAP'' (U.S. EPA, 2002; <a href="https://www.epa.gov/sites/default/files/2020-07/documents/coke-ovens_eia_neshap_final_08-2002.pdf">https://www.epa.gov/sites/default/files/2020-07/documents/coke-ovens_eia_neshap_final_08-2002.pdf</a>).
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In a second alternative and independent approach (referred to as
the alternative approach), in 2016 the EPA considered a formal BCA and
applied the formal BCA that was available in the 2011 RIA for the 2012
MATS Final Rule. Id. at 24421. In that analysis, even though the EPA
was only able to monetize one HAP-specific endpoint, the EPA estimated
that in 2015 the final MATS rule would yield annual monetized net
benefits (in 2007 dollars) of between $37 billion to $90 billion using
a 3-percent discount rate and between $33 billion to $81 billion using
a 7-percent discount rate, in comparison to the projected $9.6 billion
in annual compliance costs. The vast majority of these monetized social
benefits were the result of non-HAP emission reductions due to the MATS
requirements. See id. at 24425. The EPA therefore determined that the
alternative approach also independently supported the conclusion that
regulation of HAP emissions from EGUs remains appropriate after
considering cost. Id.
Several state and industry groups petitioned for review of the 2016
Supplemental Finding in the D.C. Circuit. Murray Energy Corp. v. EPA,
No. 16-1127 (D.C. Cir. filed April 25, 2016). In April 2017, the EPA
moved the court to continue oral argument and hold the case in abeyance
in order to give the then-new Administration an opportunity to review
the 2016 action, and the court ordered that the consolidated challenges
to the 2016 Supplemental Finding be held in abeyance (i.e., temporarily
on hold).\20\
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\20\ Order, Murray Energy Corp. v. EPA, No. 16-1127 (D.C. Cir.
April 27, 2017), ECF No. 1672987. In response to a joint motion from
the parties to govern future proceedings, the D.C. Circuit issued an
order in February 2021 to continue to hold the consolidated cases in
Murray Energy Corp. v. EPA in abeyance. Order, Murray Energy Corp.
v. EPA, No. 16-1127 (D.C. Cir. February 25, 2021), ECF No. 1887125.
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Accordingly, the EPA reviewed the 2016 action, and on May 22, 2020,
finalized a revised response to the Michigan decision. See 85 FR 31286
(May 22, 2020). In the 2020 Final Action, after primarily comparing the
projected costs of compliance to the single HAP emission reduction
impact that could be monetized, the EPA reconsidered its previous
determination and found that it is not appropriate to regulate HAP
emissions from coal- and oil-fired EGUs after a consideration of cost,
thereby reversing the EPA's conclusion under CAA section 112(n)(1)(A),
first made in 2000 and later affirmed in 2012 and 2016. Specifically,
in its reconsideration, the EPA asserted that the 2016 Supplemental
Finding considering the cost of MATS was flawed based on its assessment
that neither of the two approaches to considering cost in the 2016
Supplemental Finding satisfied the EPA's obligation under CAA section
112(n)(1)(A), as that provision was interpreted by the U.S. Supreme
Court in Michigan. Additionally, the EPA determined that, while the
2020 Final Action reversed the 2016 Supplemental Finding, it did not
remove the coal- and oil-fired EGU source category from the CAA section
112(c)(1) list, nor would it affect the existing CAA section 112(d)
emissions standards regulating HAP emissions from coal- and oil-fired
EGUs that were promulgated in the 2012 MATS Final Rule.\21\ See 85 FR
31312 (May 22, 2020).
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\21\ This finding was based on New Jersey v. EPA, 517 F.3d 574
(D.C. Cir. 2008), which held that the EPA is not permitted to remove
source categories from the CAA section 112(c)(1) list unless the CAA
section 112(c)(9) criteria for delisting have been met.
---------------------------------------------------------------------------

In the 2020 Final Action, the EPA also finalized the risk review
required by CAA section 112(f)(2) and the first technology review
required by CAA section 112(d)(6) for the coal- and oil-fired EGU
source category regulated under MATS.\22\ The EPA determined that
residual risks due to emissions of air toxics from the coal- and oil-
fired EGU source category are acceptable and that the current NESHAP
provides an ample margin of safety to protect public health and to
prevent an adverse environmental effect. In the technology review, the
EPA did not identify any new developments in HAP emission controls to
achieve further cost-effective emissions reductions. Based on the
results of these reviews, the EPA found that no revisions to MATS were
warranted. See 85 FR 31314 (May 22, 2020).
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\22\ CAA section 112(f)(2) requires the EPA to conduct a one-
time review of the risks remaining after imposition of MACT
standards under CAA section 112(d)(2) within 8 years of the
effective date of those standards (risk review). CAA section
112(d)(6) requires the EPA to conduct a review of all CAA section
112(d) standards at least every 8 years to determine whether it is
necessary to establish more stringent standards after considering,
among other things, advances in technology and costs of additional
control (technology review). The EPA has always conducted the first
technology review at the same time it conducts the risk review and
collectively the actions are known at RTRs.

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[[Page 13963]]

Several states, industry, public health, environmental, and civil
rights groups petitioned for review of the 2020 Final Action in the
D.C. Circuit. American Academy of Pediatrics v. Regan, No. 20-1221 and
consolidated cases (D.C. Cir. filed June 19, 2020). On September 28,
2020, the court granted the EPA's unopposed motion to sever from the
lead case and hold in abeyance two of the petitions for review:
Westmoreland Mining Holdings LLC v. EPA, No. 20-1160 (D.C. Cir. filed
May 22, 2020) (challenging the 2020 Final Action as well as prior EPA
actions related to MATS, including a challenge to the MATS CAA section
112(d) standards on the basis that the 2020 Final Action's reversal of
the appropriate and necessary determination provided a ``grounds
arising after'' for filing a petition outside the 60-day window for
judicial review of MATS), and Air Alliance Houston v. EPA, No. 20-1268
(D.C. Cir. filed July 21, 2020) (challenging only the RTR portion of
the 2020 Final Action).\23\
---------------------------------------------------------------------------

\23\ Order, Westmoreland Mining Holdings LLC v. EPA, No. 20-1160
(D.C. Cir. September 28, 2020), ECF No. 1863712.
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On January 20, 2021, the President signed Executive Order 13990,
``Protecting Public Health and the Environment and Restoring Science to
Tackle the Climate Crisis.'' The Executive order, among other things,
instructs the EPA to review the 2020 Final Action and consider
publishing a notice of proposed rulemaking suspending, revising, or
rescinding that action. In February 2021, the EPA moved the court to
hold American Academy of Pediatrics and consolidated cases in abeyance,
pending the EPA's review of the 2020 Final Action as prompted in
Executive Order 13990, and on February 16, 2021, the D.C. Circuit
granted the EPA's motion.\24\ On February 9, 2022, the EPA proposed to
revoke the 2020 Final Action's determination that it is not appropriate
and necessary to regulate HAP emissions from coal- and oil-fired EGUs
under section 112 of the CAA and to reaffirm our earlier
determinations--made in 2000 (65 FR 79825; December 20, 2000) (2000
Determination), 2012 (77 FR 9304; February 16, 2012) (2012 MATS Final
Rule), and 2016--that it is appropriate and necessary to regulate coal-
and oil-fired EGUs under section 112 of the CAA.
---------------------------------------------------------------------------

\24\ Order, American Academy of Pediatrics v. Regan, No. 20-1221
(D.C. Cir. February 16, 2021), ECF No. 1885509.
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In the meantime, the requirements of MATS have been fully
implemented, resulting in significant reductions in HAP emissions from
EGUs and the risks associated with those emissions. When the final rule
was promulgated, the EPA projected that annual EGU mercury emissions
would be reduced by 75 percent with MATS implementation. In fact,
considering MATS and other market conditions, EGU mercury emission
reductions have been far more substantial and have decreased to
approximately 4 tons in 2017, which represents an 86 percent reduction
compared to 2010 (pre-MATS) levels. See Table 4 at 84 FR 2689 (February
7, 2019). Acid gas HAP and non-mercury metal HAP emissions have
similarly been reduced--by 96 percent and 81 percent, respectively--as
compared to 2010 levels. Id. MATS is the only Federal requirement that
requires HAP control from EGUs.
After considering public comment on the 2022 Proposal, the EPA is
finalizing a revocation of the 2020 reconsideration of the 2016
Supplemental Finding and reaffirming once again that it is appropriate
and necessary to regulate emissions of HAP from coal- and oil-fired
EGUs. We will provide notice of the results of our review of the 2020
RTR in a separate future action.

B. Statutory Background

Additional statutory context is useful to help identify the
relevant factors that the Administrator should weigh when making the
appropriate and necessary determination.
1. Pre-1990 History of HAP Regulation
In 1970, Congress enacted CAA section 112 to address the millions
of pounds of HAP emissions that were estimated to be emitted from
stationary sources in the country. At that time, the CAA defined HAP as
``an air pollutant to which no ambient air quality standard is
applicable and which, in the judgment of the Administrator may cause,
or contribute to, an increase in mortality or an increase in serious
irreversible, or incapacitating reversible, illness,'' but the statute
left it to the EPA to identify and list pollutants that were HAP. Once
a HAP was listed, the statute required the EPA to regulate sources of
that identified HAP ``at the level which in [the Administrator's]
judgment provides an ample margin of safety to protect the public
health from such hazardous air pollutants.'' CAA section 112(b)(1)(B)
(pre-1990 amendments); Legislative History of the CAA Amendments of
1990 (``Legislative History''), at 3174-75, 3346 (Comm. Print 1993).
The statute did not define the term ``ample margin of safety'' or
provide a risk metric on which the EPA was to establish standards, and
initially the EPA endeavored to account for costs and technological
feasibility in every regulatory decision. In Natural Resources Defense
Council (NRDC) v. EPA, 824 F.2d 1146 (D.C. Cir. 1987), the court
concluded that the CAA required that in interpreting what constitutes
``safe,'' the EPA was prohibited from considering cost and
technological feasibility. Id. at 1166.
The EPA subsequently issued the NESHAP for benzene in accordance
with the NRDC holding.\25\ Among other things, the Benzene NESHAP
concluded that there is a rebuttable presumption that any cancer risk
greater than 100-in-1 million to the most exposed individual is
unacceptable, and per NRDC, must be addressed without consideration of
cost or technological feasibility. The Benzene NESHAP further provided
that, after evaluating the acceptability of cancer risks, the EPA must
evaluate whether the current level of control provides an ample margin
of safety for any risk greater than 1-in-1 million and, if not, the EPA
will establish more stringent standards as necessary after considering
cost and technological feasibility.\26\
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\25\ National Emissions Standards for Hazardous Air Pollutants:
Benzene Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene
Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke
By-Product Recovery Plants (Benzene NESHAP). 54 FR 38044 (September
14, 1989).
\26\ ``In protecting public health with an ample margin of
safety under section 112, EPA strives to provide maximum feasible
protection against risks to health from hazardous air pollutants by
(1) protecting the greatest number of persons possible to an
individual lifetime risk level no higher than approximately 1 in 1
million and (2) limiting to no higher than approximately 1 in 10
thousand the estimated risk that a person living near a plant would
have if he or she were exposed to the maximum pollutant
concentrations for 70 years.'' Benzene NESHAP, 54 FR 38044-5,
September 14, 1989.
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2. Clean Air Act 1990 Amendments to Section 112
As the following discussion demonstrates, throughout CAA section
112 and its legislative history, Congress made clear its intent to
quickly secure large reductions in the volume of HAP emissions from
stationary sources because of its recognition of the hazards to public
health and the environment that result from exposure to such emissions.
CAA section 112 and its legislative history also reveal Congress'
understanding that fully characterizing the risks posed by HAP
emissions was exceedingly difficult; thus, Congress purposefully
replaced a regime that required the EPA to make an assessment of risk
in the first instance, with one in which Congress determined risk
existed and directed the EPA to make swift and substantial reductions
based upon the

[[Page 13964]]

most stringent standards technology could achieve. The statutory design
and direction also repeatedly emphasize that the EPA should regulate
with the most exposed and most sensitive members of the population in
mind in order to achieve an acceptable level of HAP emissions with an
ample margin of safety. As explained further below, this statutory
context informs the EPA's judgment as to the relevant factors to weigh
in the analysis of whether regulation remains appropriate along with a
consideration of cost.
In 1990, Congress radically transformed section 112 of the CAA and
its treatment of hazardous air pollution. The legislative history of
the amendments indicates Congress' dissatisfaction with the EPA's slow
pace addressing these pollutants under the 1970 CAA: ``In theory,
[hazardous air pollutants] were to be stringently controlled under the
existing Clean Air Act section 112. However, . . . only 7 of the
hundreds of potentially hazardous air pollutants have been regulated by
EPA since section 112 was enacted in 1970.'' H.R. Rep. No. 101-490, at
315 (1990); see also id. at 151 (noting that in 20 years, the EPA's
establishment of standards for only seven HAP covered ``a small
fraction of the many substances associated . . . with cancer, birth
defects, neurological damage, or other serious health impacts.'').
Congress was concerned with how few sources had been addressed during
this time. Id. (``[The EPA's] regulations sometimes apply only to
limited sources of the relevant pollutant. For example, the original
benzene standard covered just one category of sources (equipment
leaks). Of the 50 toxic substances emitted by industry in the greatest
volume in 1987, only one--benzene--has been regulated even partially by
EPA.''). Congress noted that state and local regulatory efforts to act
in the face of ``the absence of Federal regulations'' had ``produced a
patchwork of differing standards,'' and that ``[m]ost states . . .
limit the scope of their program by addressing a limited number of
existing sources or source categories, or by addressing existing
sources only on a case-by-case basis as problem sources are
identified'' and that ``[o]ne state exempts all existing sources from
review.'' Id.
In enacting the 1990 Amendments with respect to the control of
hazardous air pollution, Congress noted that ``[p]ollutants controlled
under [section 112] tend to be less widespread than those regulated
[under other sections of the CAA], but are often associated with more
serious health impacts, such as cancer, neurological disorders, and
reproductive dysfunctions.'' Id. at 315. In its substantial 1990
Amendments, Congress itself listed 189 HAP (CAA section 112(b)) and set
forth a statutory structure that would ensure swift regulation of a
significant majority of these HAP emissions from stationary sources.
Specifically, after defining major and area sources and requiring the
EPA to list all major sources and many area sources of the listed
pollutants (CAA section 112(c)), the new CAA section 112 required the
EPA to establish technology-based emission standards for listed source
categories on a prompt schedule and to revisit those technology-based
standards every 8 years (CAA section 112(d) (emission standards); CAA
section 112(e) (schedule for standards and review)). The 1990
Amendments also obligated the EPA to evaluate the residual risk within
8 years of promulgation of technology-based standards. CAA section
112(f)(2).
In setting the standards, CAA section 112(d) requires the EPA to
establish technology-based standards that achieve the ``maximum degree
of reduction,'' ``including a prohibition on such emissions where
achievable.'' CAA section 112(d)(2). Congress specified that the
maximum degree of reduction must be at least as stringent as the
average level of control achieved in practice by the best performing
sources in the category or subcategory based on emissions data
available to the EPA at the time of promulgation. This technology-based
approach permitted the EPA to swiftly set standards for source
categories without determining the risk or cost in each specific case,
as the EPA had done prior to the 1990 Amendments. In other words, this
approach to regulation quickly required that all major sources and many
area sources of HAP install control technologies consistent with the
top performers in each category, which had the effect of obtaining
immediate reductions in the volume of HAP emissions from stationary
sources. The statutory requirement that sources obtain levels of
emission limitation that have actually been achieved by existing
sources, instead of levels that could theoretically be achieved,
inherently reflects a built-in cost consideration.\27\
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\27\ Congress recognized as much:
``The Administrator may take the cost of achieving the maximum
emission reduction and any non-air quality health and environmental
impacts and energy requirements into account when determining the
emissions limitation which is achievable for the sources in the
category or subcategory. Cost considerations are reflected in the
selection of emissions limitations which have been achieved in
practice (rather than those which are merely theoretical) by sources
of a similar type or character.''
A Legislative History of the Clean Air Act Amendments of 1990
(CAA Legislative History), Vol 5, pp. 8508 -8509 (CAA Amendments of
1989; p. 168-169; Report of the Committee on Environment and Public
Works S. 1630).
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Further, after determining the minimum stringency level of control,
or MACT floor, CAA section 112(d)(2) directs the EPA to ``require the
maximum degree of reduction in emissions of the hazardous air
pollutants subject to this section (including a prohibition on such
emissions, where achievable)'' that the EPA determines are achievable
after considering the cost of achieving such standards and any non-air-
quality health and environmental impacts and energy requirements of
additional control. In doing so, the statute further specifies in CAA
section 112(d)(2) that the EPA should consider requiring sources to
apply measures that, among other things, ``reduce the volume of, or
eliminate emissions of, such pollutants . . . '' (CAA section
112(d)(2)(A)), ``enclose systems or processes to eliminate emissions''
(CAA section 112(d)(2)(B)), and ``collect, capture, or treat such
pollutants when released . . .'' (CAA section 112(d)(2)(C)). The 1990
Amendments also built in a regular review of new technologies and a
one-time review of risks that remain after imposition of MACT
standards. CAA section 112(d)(6) requires the EPA to evaluate every
NESHAP no less often than every 8 years to determine whether additional
control is necessary after taking into consideration ``developments in
practices, processes, and control technologies,'' without regard to
risk. CAA section 112(f) requires the EPA to ensure within 8 years of
promulgating a NESHAP that the risks are acceptable and that the MACT
standards provide an ample margin of safety.
The statutory requirement to establish technology-based standards
under CAA section 112 eliminated the requirement for the EPA to
identify hazards to public health and the environment in order to
justify regulation of HAP emissions from stationary sources, reflecting
Congress' judgment that such emissions are inherently dangerous. See S.
Rep. No. 101-228, at 148 (``The MACT standards are based on the
performance of technology, and not on the health and environmental
effects of the [HAP].''). The technology review required in CAA section
112(d)(6) further mandates that the EPA continually reassess standards
to determine if additional reductions can be obtained, without
evaluating the specific risk associated with the HAP

[[Page 13965]]

emissions that would be reduced. Notably, the CAA section 112(d)(6)
review of what additional reductions may be obtained based on new
technology is required even after the EPA has conducted the one-time
CAA section 112(f)(2) review and determined that the existing standard
will protect the public with an ample margin of safety.
The statutory structure and legislative history also demonstrate
Congress' concern with the many ways that HAP can harm human health and
Congress' goal of protecting the most exposed and vulnerable members of
society. The committee report accompanying the 1990 Amendments
discussed the scientific understanding regarding HAP risk at the time,
including the 1989 report on benzene performed by the EPA noted above.
H.R. Rep. No. 101-490, at 315. Specifically, Congress highlighted the
EPA's findings as to cancer incidence, and importantly, lifetime
individual risk to the most exposed individuals. Id. The report also
notes the limitations of the EPA's assessment: ``The EPA estimates
evaluated the risks caused by emissions of a single toxic air pollutant
from each plant. But many facilities emit numerous toxic pollutants.
The agency's risk assessments did not consider the combined or
synergistic effects of exposure to multiple toxics, or the effect of
exposure through indirect pathways.'' Id. Congress also noted the EPA's
use of the maximum exposed individual (MEI) tool to assess risks faced
by heavily exposed citizens. Id. The report cited particular scientific
studies demonstrating that some populations are more affected than
others--for example, it pointed out that ``[b]ecause of their small
body weight, young children and fetuses are especially vulnerable to
exposure to PCB-contaminated fish. One study has found long-term
learning disabilities in children who had eaten high-levels of Great
Lakes fish.'' Id.
The statutory structure confirms Congress' approach to risk and
sensitive populations. As noted, the CAA section 112(f)(2) residual
risk review requires the EPA--8 years after promulgating the original
MACT standard--to consider whether, after imposition of the CAA section
112(d)(2) MACT standard, there are remaining risks from HAP emissions
that warrant more stringent standards to provide an ample margin of
safety to protect public health or to prevent an adverse environmental
effect. See CAA section 112(f)(2)(A). Specifically, the statute
requires the EPA to promulgate standards under this risk review
provision if the CAA section 112(d) MACT standard does not ``reduce
lifetime excess cancer risks to the individual most exposed to
emissions from a source in the category or subcategory to less than one
in one million.'' Id. (emphasis added). Thus, even after the
application of MACT standards, the statute directs the EPA to conduct a
rulemaking if even one person (i.e., ``the individual most exposed to
emissions'') has a risk, not a guarantee, of getting cancer. This
demonstrates the statutory intent to protect even the most exposed
member of the population from the harms attendant to exposure to HAP
emissions.
If a residual risk rulemaking is required, as noted above, the
statute incorporates the detailed two-step rulemaking approach set
forth in the Benzene NESHAP for determining (1) whether HAP emissions
from stationary sources pose an unacceptable risk and (2) whether
standards provide an ample margin of safety. See CAA section
112(f)(2)(B) (preserving the prior interpretation of ``ample margin of
safety'' set forth in the Benzene NESHAP). The first step of this
approach includes a rebuttable presumption that any cancer risk greater
than 100-in-1 million to the most exposed person is per se
unacceptable. For non-cancer chronic and acute risks, the EPA has more
discretion to determine what is acceptable, but even then, the statute
requires the EPA to evaluate the risks to the most exposed individual
and EPA RfDs are developed with the goal of being protective of even
sensitive members of the population. See, e.g., CAA section
112(n)(1)(C) (requiring, in part, the development of ``a threshold for
mercury concentration in the tissue of fish which may be consumed
(including consumption by sensitive populations) without adverse
effects to public health''). If risks are found to be unacceptable, the
EPA must impose additional control requirements to ensure that post CAA
section 112(f) risks from HAP emissions are at an acceptable level,
regardless of cost and technological feasibility.
After determining whether the risks are acceptable and developing
standards to achieve an acceptable level of risk if necessary, under
the second step the EPA must then determine whether more stringent
standards are necessary to provide an ample margin of safety to protect
public health, and at this stage we must take into consideration cost,
technological feasibility, uncertainties, and other relevant factors.
As stated in the Benzene NESHAP, ``In protecting public health with an
ample margin of safety under section 112, EPA strives to provide
maximum feasible protection against risks to health from hazardous air
pollutants by . . . protecting the greatest number of persons possible
to an individual lifetime risk level no higher than approximately 1-in-
1 million.'' See 54 FR 38044-45 (September 14, 1989); see also NRDC v.
EPA, 529 F.3d 1077, 1082 (D.C. Cir. 2008) (finding that ``the Benzene
NESHAP standard established a maximum excess risk of 100-in-one
million, while adopting the one-in-one million standard as an
aspirational goal.'').
The various listing and delisting provisions of CAA section 112
further demonstrate a statutory intent to reduce risk and protect the
most exposed members of the population from HAP emissions. Because the
listing and delisting provisions focus on ``any'' potential adverse
health effects from HAP emissions and ``the individual in the
population who is most exposed,'' the EPA must necessarily consider
effects to those most exposed to such emissions. See, e.g., CAA section
112(b)(2) (requiring the EPA to add pollutants to the HAP list if the
EPA determines the HAP ``presents, or may present'' adverse human
health or adverse environmental effects); id. at CAA section
112(b)(3)(B) (requiring the EPA to add a pollutant to the list if a
petitioner shows that a substance is known to cause or ``may reasonably
be anticipated to cause adverse effects to human health or adverse
environmental effects''); id. at CAA section 112(b)(3) (authorizing the
EPA to delete a substance only on a showing that ``the substance may
not reasonably be anticipated to cause any adverse effects to human
health or adverse environmental effects.'') (emphasis added); id. at
CAA section 112(c)(9)(B)(i) (prohibiting the EPA from delisting a
source category if even one source in the category causes a lifetime
cancer risk greater than 1-in-1 million to ``the individual in the
population who is most exposed to emissions of such pollutants from the
source.''); id. at CAA section 112(c)(9)(B)(ii) (prohibiting the EPA
from delisting a source category unless the EPA determines that the
non-cancer causing HAP emitted from the source category do not ``exceed
a level which is adequate to protect public health with an ample margin
of safety and no adverse environmental effect will result from
emissions of any source'' in the category); see also id. at CAA section
112(n)(1)(C) (requiring a study to determine the level of mercury in
fish tissue that can be consumed by even ``sensitive populations''
without adverse effect to public health).

[[Page 13966]]

The deadlines for action included in the 1990 Amendments indicate
that Congress wanted HAP emissions addressed quickly. The statute
requires the EPA to list all major source categories within 1 year of
the 1990 Amendments and to regulate those listed categories on a strict
schedule that prioritizes the source categories that are known or
suspected to pose the greatest risks to the public. See CAA sections
112(c)(1), 112(e)(1) and 112(e)(2). For area sources, where the statute
provides the EPA with greater discretion to determine the sources to
regulate, it also directs the EPA to collect the information necessary
to make the listing decision for many area source categories and
requires the EPA to act on that information by a date certain.
For example, CAA section 112(k) establishes an area source program
designed to identify and list at least 30 HAP that pose the greatest
threat to public health in the largest number of urban areas (urban
HAP) and to list for regulation area sources that account for at least
90 percent of the area source emissions of the 30 urban HAP. See CAA
sections 112(k) and 112(c)(3). In addition to the urban air toxics
program, CAA section 112(c)(6) directs the EPA to identify and list
sufficient source categories to ensure that at least 90 percent of the
aggregate emissions of 7 bioaccumulative and persistent HAP, including
mercury, are subject to standards pursuant to CAA sections 112(d)(2) or
(d)(4). See CAA section 112(c)(6). Notably, these requirements were in
addition to any controls on mercury and other CAA section 112(c)(6) HAP
that would be imposed if the EPA determined it was appropriate and
necessary to regulate EGUs under CAA section 112. This was despite the
fact that it was known at the time of enactment that other categories
with much lower emissions of mercury would have to be subject to MACT
standards because of the exclusion of EGUs from CAA section 112(c)(6).

III. Final Determination Under CAA Section 112(n)(1)(A)

In this final action, the EPA is revoking the 2020 Final Action and
concluding, as it did in 2000, 2012, and 2016, that it is appropriate
and necessary to regulate HAP emissions from EGUs.\28\ We find that,
under either our preferred totality-of-the-circumstances framework or
our alternative formal BCA framework, the information that was
available to the EPA as of the time of the 2012 rulemaking supports a
determination that it is appropriate and necessary to regulate HAP from
EGUs. We also consider new information regarding the hazards to public
health and the environment and the costs of compliance with MATS that
has become available since the 2012 rulemaking and find that the
updated information strengthens the EPA's conclusion that it is
appropriate and necessary to regulate HAP from coal- and oil-fired
EGUs.
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\28\ This action focuses on an analysis of the ``appropriate''
prong of CAA section 112(n)(1)(A). The Michigan decision and
subsequent EPA actions addressing that decision have been centered
on supplementing the EPA's record with a consideration of the cost
of regulation as part of the ``appropriate'' aspect of the overall
determination. As noted, the 2020 Final Action, while reversing the
2016 Supplemental Finding as to the EPA's determination that it was
``appropriate'' to regulate HAP from EGUs, did not rescind the EPA's
prior determination that it was necessary to regulate. See 84 FR
2674 (February 7, 2019) (``CAA section 112(n)(1)(A) requires the EPA
to determine that both the appropriate and necessary prongs are met.
Therefore, if the EPA finds that either prong is not satisfied, it
cannot make an affirmative appropriate and necessary finding. The
EPA's reexamination of its determination . . . focuses on the first
prong of that analysis.''). The ``necessary'' determination rested
on two primary bases: (1) in 2012, the EPA determined that hazards
to human health and the environment from HAP emissions from EGUs
remained that would not be addressed by other CAA requirements in
its future year modeling, which accounted for all CAA requirements
to that point; and (2) our conclusion that the only way to ensure
permanent reductions in U.S. EGU emissions of HAP and the associated
risks to public health and the environment was through standards set
under CAA section 112. See 76 FR 25017 (May 23, 2011). We therefore
continue our focus in this action on reinstating the ``appropriate''
prong of the determination, leaving undisturbed the EPA's prior
conclusions that regulation of HAP from EGUs is ``necessary.'' See
65 FR 79830 (December 20, 2000); 76 FR 25017 (May 3, 2011); 77 FR
9363 (February 16, 2012).
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At the outset, we note that CAA section 112(n)(1)(A) is silent as
to whether the EPA may consider updated information when acting on a
remand of the appropriate and necessary determination. CAA section
112(n)(1)(A) directs the EPA to conduct the Utility Study within 3
years, and requires the EPA to regulate EGUs if the Administrator makes
a finding that it is appropriate and necessary to do so ``after''
considering the results of the Utility Study. Consistent with the EPA's
interpretation in 2005, 2012, 2016, and 2020, we do not read this
language to require the EPA to consider the most-up-to-date information
where the EPA is compelled to revisit the determination, but nor do we
interpret the provision to preclude consideration of new information
where reasonable. See 70 FR 16002 (March 29, 2005); 77 FR 9310
(February 16, 2012); 81 FR 24432 (April 25, 2016); 85 FR 31306 (May 22,
2020). As such, in light of CAA section 112(n)(1)(A)'s silence on this
question, the EPA has applied its discretion in determining when to
consider new information under this provision based on the
circumstances. For example, when the EPA was revisiting the
determination in 2012, we noted that ``[b]ecause several years had
passed since the 2000 finding, the EPA performed additional technical
analyses for the proposed rule, even though those analyses were not
required.'' 77 FR 9310 (February 16, 2012).\29\ Similarly, we think
that it is reasonable to consider new information in the context of
this action, given that more than a decade has passed since we last
considered updated information. In this reconsideration of the
determination, consistent with the President's Executive Order, both
the growing scientific understanding of public health risks associated
with HAP emissions and a clearer picture of the cost of control
technologies and the make-up of power sector generation over the last
decade may inform the question of whether it is appropriate to
regulate, and, in particular, help address the inquiry that the Supreme
Court directed us to undertake in Michigan. We believe the evolving
scientific information with regard to health risks of HAP emissions
from EGUs and the advantage of hindsight with regard to costs warrant
considering currently available information in making this
determination. To the extent that our determination should flow from
information that would have been available at the ``initial decision to
regulate,'' Michigan, 576 U.S. at 754, we conclude that even if we
limit ourselves to the prior record the data still support the
determination. But we also believe it is reasonable to consider new
data, and find that the new information regarding both public health
risks and costs bolsters the finding and further supports a
determination that it is appropriate and necessary to regulate EGUs for
HAP.
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\29\ The EPA was not challenged on this interpretation in White
Stallion.
---------------------------------------------------------------------------

In section III.A of this preamble, we describe the advantages of
regulation--the reduction in emissions of HAP and attendant reduction
in risks to human health and the environment, as well as the
distribution of these health benefits. We restate the numerous risks to
public health and the environment posed by HAP emissions from EGUs.
This includes information previously recognized and documented in the
statutorily mandated CAA section 112(n)(1) studies, the 2000
Determination, the 2012 MATS Final Rule, and the 2016 Supplemental
Finding about the nature and extent of

[[Page 13967]]

health and environmental impacts from HAP that are emitted by EGUs, as
well as additional risk analyses supported by new scientific studies as
summarized in the 2022 Proposal. The additional risk screening analyses
introduced in the 2022 Proposal on the connection between mercury and
heart disease as well as IQ loss in children across the U.S. further
support the conclusion that HAP emissions from EGUs pose hazards to
public health and the environment warranting regulating under CAA
section 112. This section also notes that these effects are not borne
equally across the population and that some historically disadvantaged
groups are disproportionally affected by EGU HAP emissions. The EPA
also discusses the challenges associated with fully quantifying and
monetizing the human health and environmental effects associated with
HAP emissions. Finally, although under its preferred approach, the EPA
finds regulating EGU HAP emissions is appropriate without consideration
of non-HAP emissions reductions, the significant health and
environmental benefits from such reductions further support the EPA's
conclusion.
We then turn in preamble section III.B. to the disadvantages of
regulation--the costs associated with reducing EGU HAP emissions and
other potential impacts to the sector and the economy associated with
MATS. We first consider the compliance costs. We consider whether the
actual compliance costs of MATS are consistent with those projected in
the 2011 RIA and conclude that the originally projected costs were
likely a significant overestimate. We then evaluate the estimated costs
in the 2011 RIA against several metrics relevant to the impacts those
costs have on the power sector and on electricity consumers (e.g.,
historical annual revenues, annual capital and production expenditures,
impacts on retail electricity prices, and impacts on resource adequacy
and reliability). These analyses, whether based on data available in
2012 or based on updated post-promulgation data, all show that the
costs of MATS were within the bounds of typical historical fluctuations
and that the industry would be able to comply with MATS and continue to
provide a reliable source of electricity without price increases that
were outside the range of historical variability.
In section III.C of this preamble, we explain why the methodology
used in our 2020 Finding was ill-suited to determining whether EGU HAP
regulation is appropriate and necessary. The methodology used in our
2020 Finding gave little weight to the volume of HAP that would be
reduced. The methodology also gave little weight to the vast majority
of the advantages of reducing EGU HAP, including the reduction of risk
to sensitive populations, that are extremely difficult or not currently
possible to quantify or monetize.
In preamble section III.D, we explain our preferred totality-of-
the-circumstances methodology that we use to make the appropriate
determination and our application of that methodology. This approach
looks to the statute, and particularly CAA section 112(n)(1)(A) and the
other provisions in CAA section 112(n)(1), to help identify the
relevant factors to weigh and what weight to afford those factors.
Under that methodology we weigh the significant health and
environmental advantages of reducing EGU HAP, and in particular the
benefits to the most exposed and sensitive individuals, against the
disadvantages of using productive resources to achieve those benefits--
i.e., the effects on the electric generating industry and its ability
to provide reliable and affordable electricity. We ultimately conclude
that the advantages outweigh the disadvantages whether we look at the
record from 2012 or at our new record, which includes an expanded
understanding of the health risks associated with HAP emissions and
finds that the MATS compliance costs projected in the 2011 RIA were
likely significantly overestimated. While we conclude that regulation
is appropriate considering the health and environmental impacts posed
by HAP emissions alone, we further consider that, if we also account
for the non-HAP benefits in our preferred totality-of-the-circumstances
approach, such as the benefits (including reduced mortality) of
coincidental reductions in PM, NO<INF>2</INF>, SO<INF>2</INF>, and
ozone concentrations that flow from the application of controls on HAP,
the balance weighs even more heavily in favor of regulating HAP
emissions from coal- and oil-fired EGUs.
In section III.E, we consider an alternative methodology to make
the appropriate determination. This alternative methodology draws upon
the formal BCA that was included in the 2011 RIA for the 2012 MATS
Final Rule.\30\ This formal BCA was conducted in a consistent manner
with economic principles and governmental guidance documents for
economic analysis (e.g., OMB Circular A-4 and EPA's Guidelines for
Preparing Economic Analyses) and summarized monetized costs and
benefits in its presentation of net benefits.
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\30\ We use the term ``formal benefit-cost analysis'' to refer
to an economic analysis that attempts to the extent practicable to
quantify all significant consequences of an action in monetary terms
in order to determine whether an action increases economic
efficiency. Assuming that all consequences can be monetized, actions
with positive net benefits (i.e., benefits exceed costs) improve
economic efficiency. In other words, it is a determination of
whether the willingness to pay for an action by those advantaged by
it exceeds the willingness to pay to avoid the action by those
disadvantaged by it. Measuring willingness to pay in a common metric
of economic value, like dollars, is called monetization, and it
allows for such comparisons across individuals. When there are
technical limitations that prevent certain benefits or costs that
may be of significant magnitude from being quantified or monetized,
then information is provided describing those potentially important
non-monetized benefits or costs. This usage is consistent with the
definition of a BCA used in the economics literature and the EPA's
Guidelines for Preparing Economic Analyses. Note that regulatory
impact analyses more broadly can give appropriate attention to both
unquantified and distributional effects, as OMB's Circular A-4
recommends.
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The formal BCA approach is not our preferred way to consider
advantages and disadvantages for the CAA section 112(n)(1)(A)
determination because the EPA's current inability to generate a
monetized estimate of the full benefits of HAP reductions can lead to
an underestimate of the full monetary value of the net benefits of
regulation. As discussed below, the EPA has long acknowledged the
extreme difficulty of quantifying and monetizing benefits of many HAP
emission reductions, a limitation which hinders a formal BCA designed
to capture total social benefits and costs; notably, the 2011 RIA
discussed unquantified effects in a qualitative way and noted how these
benefits and costs would influence the net benefits. A further
limitation of a formal BCA in this context is that they may not always
account for important distributional effects, such as impacts to the
most exposed and most sensitive individuals in a population, and in
this instance did not. To the extent that a formal BCA is appropriate
for making the CAA section 112(n)(1)(A) determination, however, the
formal BCA approach reported in the 2011 RIA and presented here as
alternative methodology demonstrates that--even though many of the
benefits of HAP emission reductions currently cannot be fully
quantified or monetized--the monetized benefits of MATS still outweigh
the monetized costs by a considerable margin, whether we look at the
2012 record or at our updated record. We therefore determine that a
formal BCA approach also supports a determination that it is
appropriate to regulate EGUs for HAP emissions.

[[Page 13968]]

In section III.F, we present the Administrator's conclusion that it
remains appropriate and necessary to regulate HAP emissions from coal-
and oil-fired EGUs. In sum, the EPA concludes that it is appropriate
and necessary to regulate HAP emissions from coal- and oil-fired EGUs,
whether we are applying the preferred totality-of-the-circumstances
methodology or the alternative formal benefit-cost approach as
described, and whether we are considering only the administrative
record as of the original 2012 MATS Final Rule or based on new
information made available since that time. The information and data
amassed by the EPA over the decades of administrative analysis and
rulemaking devoted to this topic overwhelmingly support the conclusion
that the advantages of regulating HAP emissions from coal- and oil-
fired EGUs outweigh the disadvantages.

A. Public Health and Environmental Hazards Associated With Emissions
From EGUs

1. Overview
The administrative record for the MATS rule detailed several
hazards to public health and the environment from HAP emitted by EGUs
that remained after imposition of the ARP and other CAA requirements.
See 80 FR 75028-29 (December 1, 2015). See also 65 FR 79825-31
(December 20, 2000); 76 FR 24976-25020 (May 3, 2011); 77 FR 9304-66
(February 16, 2012). The EPA considered all of this information again
in the 2016 Supplemental Finding, noting that this sector represented a
large fraction of U.S. emissions of mercury, non-mercury metal HAP, and
acid gases. Specifically, the EPA found that even after imposition of
the other requirements of the CAA, but absent MATS, EGUs remained the
largest domestic source of mercury, HF, HCl, and selenium emissions and
among the largest domestic contributors of arsenic, chromium, cobalt,
nickel, hydrogen cyanide, beryllium, and cadmium emissions, and that a
significant majority of EGU facilities emitted above the major source
thresholds for HAP emissions.
Further, the EPA noted that the risks that accrue from these
emissions were significant. These hazards include potential
neurodevelopmental impairment, increased cancer risks, and contribution
to chronic and acute health disorders, as well as adverse impacts on
the environment. Specifically, the EPA pointed to results from its
revised nationwide Mercury Risk Assessment (contained in the 2011 Final
Mercury TSD) \31\ as well as an inhalation risk assessment (2011 Non-Hg
HAP Assessment) for non-mercury HAP (i.e., arsenic, nickel, chromium,
selenium, cadmium, HCl, HF, hydrogen cyanide, formaldehyde, benzene,
acetaldehyde, manganese, and lead). The EPA estimated lifetime cancer
risks for inhabitants near some coal- and oil-fired EGUs to exceed 1-
in-1 million \32\ and noted that this case-study-based estimate likely
underestimated the true maximum risks for the EGU source category. See
77 FR 9319 (February 16, 2012). The EPA also found that mercury
emissions pose a hazard to wildlife, adversely affecting fish-eating
birds and mammals, and that the large volume of acid gas HAP associated
with EGUs also pose a hazard to the environment.\33\ These technical
analyses were all challenged in the White Stallion case, and the court
found that the EPA's risk finding as to mercury alone--that is, before
reaching any other risk finding--established a significant public
health concern. The court stated that ``EPA's `appropriate and
necessary' determination in 2000, and its reaffirmation of that
determination in 2012, are amply supported by EPA's finding regarding
the health effects of mercury exposure.'' White Stallion Energy Center
v. EPA, 748 F.3d 1222, 1245 (D.C. Cir. 2014). Additional scientific
evidence about the human health hazards associated with exposure to EGU
HAP emissions that has been collected since the 2016 Supplemental
Finding and is discussed in this section has extended our confidence
that these emissions pose an unacceptable risk to people in the U.S.,
and in particular, to vulnerable, exposed populations.
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\31\ U.S. EPA. 2011. Revised Technical Support Document:
National-Scale Assessment of Mercury Risk to Populations with High
Consumption of Self-caught Freshwater Fish In Support of the
Appropriate and Necessary Finding for Coal- and Oil-Fired Electric
Generating Units. Office of Air Quality Planning and Standards.
November. EPA-452/R-11-009. Docket ID Item No. EPA-HQ-OAR-2009-0234-
19913.
\32\ The EPA determined the 1-in-1 million standard was the
correct metric in part because CAA section 112(c)(9)(B)(1) prohibits
the EPA from removing a source category from the list if even one
person is exposed to a lifetime cancer risk greater than 1-in-1
million, and CAA section 112(f)(2)(A) directs the EPA to conduct a
residual risk rulemaking if even one person is exposed to a lifetime
excess cancer risk greater than 1-in-1 million. See White Stallion
at 1235-36 (agreeing it was reasonable for the EPA to consider the
1-in-1 million delisting criteria in defining ``hazard to public
health'' under CAA section 112(n)(1)(A)).
\33\ The EPA had determined it was reasonable to consider
environmental impacts of HAP emissions from EGUs in the appropriate
determination because CAA section 112 directs the EPA to consider
impacts of HAP emissions on the environment, including in the CAA
section 112(n)(1)(B) Mercury Study. See White Stallion at 1235-36
(agreeing it was reasonable for the EPA to consider the
environmental harms when making the appropriate and necessary
determination).
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The 2022 Proposal reviewed the long-standing and extensive body of
evidence and presented new scientific information made available since
the 2016 Supplemental Finding, which further demonstrated that HAP
emissions from coal- and oil-fired EGUs present hazards to public
health and the environment and warranted regulation under CAA section
112. In this section of the preamble, the EPA briefly describes the
body of evidence related to the public health burden associated with
EGU HAP emissions. The EPA describes the reasons why it is extremely
difficult to estimate the full health and environmental impacts
associated with exposure to HAP. We note the longstanding challenges
associated with quantifying and monetizing these effects, which may be
permanent and life-threatening and are often distributed unevenly
(i.e., concentrated among highly exposed individuals). Despite these
challenges, after assessing all the evidence, the EPA concludes again
that regulation of HAP emissions from EGUs under CAA section 112
greatly improves public health by reducing the risks of premature
mortality from heart attacks, cancer, and neurodevelopmental delays in
children, and by helping to restore economically vital ecosystems used
for recreational and commercial purposes. Further, we conclude that
these public health improvements will be particularly pronounced for
certain segments of the population that are especially vulnerable
(e.g., subsistence fishers \34\ and their children) to impacts from EGU
HAP emissions. In addition, the concomitant reductions in co-emitted
pollutants will also provide

[[Page 13969]]

substantial public health and environmental benefits.
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\34\ Subsistence fishers, who by definition obtain a substantial
portion of their dietary needs from self-caught fish consumption,
can experience elevated levels of exposure to chemicals that
bioaccumulate in fish including, in particular, methylmercury.
Subsistence fishing activity can be related to a number of factors
including socio-economic status (poverty) and/or cultural practices,
with ethnic minorities and tribal populations often displaying
increased levels of self-caught fish consumption (Burger et al.,
2002, Shilling et al., 2010, Dellinger 2004).
Burger J, (2002). Daily consumption of wild fish and game:
exposures of high-end recreationalists. International Journal of
Environmental Health Research 12:4, p. 343-354.
Shilling F, White A, Lippert L, Lubell M, (2010). Contaminated
fish consumption in California's Central Valley Delta. Environmental
Research 110, p. 334-344.
Dellinger J, (2004). Exposure assessment and initial
intervention regarding fish consumption of tribal members in the
Upper Great Lakes Region in the United States. Environmental
Research 95, p. 325-340.
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We received numerous public comments on the health hazards
associated with EGU HAP emissions, and our detailed responses to these
comments are presented in section IV.A below and in the 2023 RTC
Document. No information received during the comment period has
provided data or methods to cause us to change our approach to the
consideration of the advantages of the MATS regulation presented in the
2022 Proposal. As a result, this final action will rely upon the same
suite of qualitative and quantitative evidence presented in the 2022
Proposal. While the reader is directed to the 2022 Proposal and the
supporting 2021 Risk TSD for the complete analyses, we summarize the
analyses in subsequent sections of this preamble.
2. Overview of Health Effects Associated With Mercury and Non-Mercury
HAP
In calling for the EPA to consider the regulation of HAP from EGUs,
the CAA stipulated that the EPA complete 3 studies (all of which were
extensively peer-reviewed) exploring various aspects of risk posed to
human health and the environment by HAP released from EGUs. The first
of these studies, the Utility Study, published in 1998, focused on the
hazards to public health specifically associated with EGU-sourced HAP
including, but not limited to, mercury. See CAA section 112(n)(1)(A). A
second study, the Mercury Study, released in 1997, while focusing
exclusively on mercury, was broader in scope including not only human
health, but also environmental impacts, and specifically addressed the
potential for mercury released from multiple emissions sources (in
addition to EGUs) to affect human health and the environment. See CAA
section 112(n)(1)(B). The third study, required under CAA section
112(n)(1)(C), the NIEHS Study, submitted to Congress in 1995,
considered the threshold level of mercury exposure below which adverse
human health effects were not expected to occur. An additional fourth
study, the NAS Study, directed by Congress in 1999 and completed in
2000, focused on determining whether a threshold for mercury health
effects could be identified for sensitive populations and, as such,
presented a rigorous peer review of the EPA's RfD for methylmercury.
The aggregate results of these peer-reviewed studies commissioned by
Congress as part of CAA section 112(n)(1) supported the determination
that HAP emissions from EGUs represented a hazard to public health and
the environment that would not be addressed through imposition of the
other requirements of the CAA. In the 2 decades that followed, the EPA
has continued to conduct additional research and risk assessments and
has surveyed the latest science related to the risk posed to human
health and the environment by HAP released from EGUs.
Mercury is a persistent and bioaccumulative toxic metal that, once
released from power plants into the ambient air, can be readily
transported and deposited to soil and aquatic environments where it is
transformed by microbial action into methylmercury. See Mercury Study;
76 FR 24976 (May 3, 2011) (2011 NESHAP Proposal); 80 FR 75029 (December
1, 2015) (2015 Proposal). Methylmercury bioaccumulates in the aquatic
food web eventually resulting in highly concentrated levels of
methylmercury within the larger and longer-living fish (e.g., carp,
catfish, trout, and perch), which can then be consumed by humans (NAS
Study). As documented in both the NAS Study and the Mercury Study, fish
and seafood consumption is the primary route of human exposure to
methylmercury,\35\ with populations engaged in subsistence-levels of
consumption being of particular concern. The NAS Study reviewed the
effects of methylmercury on human health, concluding that it is highly
toxic to multiple human and animal organ systems. Of particular concern
is chronic prenatal exposure via maternal consumption of foods
containing methylmercury. Elevated exposure has been associated with
developmental neurotoxicity and manifests as poor performance on
neurobehavioral tests, particularly on tests of attention, fine motor
function, language, verbal memory, and visual-spatial ability. Evidence
also suggests potential for adverse effects on the cardiovascular
system, adult nervous system, and immune system, as well as potential
for causing cancer.\36\ Because the impacts of the neurodevelopmental
effects of methylmercury are greatest during periods of rapid brain
development, developing fetuses, infants, and young children are
particularly vulnerable. Children born to populations with high fish
consumption (e.g., people consuming fish as a dietary staple) or
impaired nutritional status may be especially susceptible to adverse
neurodevelopmental outcomes.\37\ These dietary and nutritional risk
factors are often particularly pronounced in vulnerable communities
with people of color and low-income populations that have historically
faced economic and environmental injustice and are overburdened by
cumulative levels of pollution.
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\35\ In light of the methylmercury impacts, the EPA and the Food
and Drug Administration have collaborated to provide advice on
eating fish and shellfish as part of a healthy eating pattern
(<a href="https://www.fda.gov/food/consumers/advice-about-eating-fish">https://www.fda.gov/food/consumers/advice-about-eating-fish</a>). In
addition, states provide fish consumption advisories designed to
protect the public from eating fish from waterbodies within the
state that could harm their health based on local fish tissue
sampling.
\36\ National Research Council. 2000. Toxicological Effects of
Methylmercury. Washington, DC: The National Academies Press. <a href="https://doi.org/10.17226/9899">https://doi.org/10.17226/9899</a>.
\37\ U.S. EPA. 1997. Mercury Study Report to Congress. EPA-452/
R-97-003 December 1997.
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Infants in the womb can be exposed to methylmercury when their
mothers eat fish and shellfish that contain methylmercury. This
exposure can adversely affect developing fetuses' growing brains and
nervous systems. Based on scientific evidence reflecting concern about
a range of neurodevelopmental effects seen in children exposed in utero
to methylmercury, the EPA defined an RfD of 0.0001 mg/kg-day for
methylmercury.<SUP>38 39</SUP> An RfD is defined as an estimate (with
uncertainty spanning perhaps an order of magnitude) of a daily exposure
to the human population (including sensitive subgroups) that is likely
to be without an appreciable risk of deleterious effects during a
lifetime (EPA, 2002).\40\
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\38\ U.S. EPA. 2001. IRIS Summary for Methylmercury. U.S.
Environmental Protection Agency, Washington, DC. (USEPA, 2001).
\39\ At this time, the EPA is conducting an updated
methylmercury IRIS assessment and recently released preliminary
assessment materials, an IRIS Assessment Plan (IAP) and Systematic
Review Protocol for methylmercury. The update to the methylmercury
IRIS assessment will focus on updating the quantitative relationship
of neurodevelopmental outcomes with methylmercury exposure. As noted
in these preliminary assessment materials, new studies are
available, since 2001, assessing the effects of methylmercury
exposure on cognitive function, motor function, behavioral,
structural, and electrophysiological outcomes at various ages
following prenatal or postnatal exposure to methylmercury (USEPA,
2001; NAS Study; 84 FR 13286 (April 4, 2019); 85 FR 32037 (May 8,
2020)).
\40\ U.S. EPA. 2002. A Review of the Reference Dose and
Reference Concentration Processes. EPA/630/P-02/002F, December 2002.
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In addition to the adverse neurodevelopmental effects, the NAS
Study indicated that there was evidence that exposure to methylmercury
in humans and animals can have adverse effects on both the developing
and adult cardiovascular system. Fetal exposure in the womb to
methylmercury has been associated with altered blood-pressure and
heart-rate variability in children. In adults, dietary exposure to

[[Page 13970]]

methylmercury has been linked to a higher risk of acute myocardial
infarction (MI), coronary heart disease, or cardiovascular heart
disease. The Mercury Study noted that while methylmercury is not a
potent mutagen, it is capable of causing chromosomal damage in a number
of experimental systems. Based on limited human and animal data,
methylmercury is classified as a ``possible human carcinogen'' by the
International Agency for Research on Cancer (IARC, 1993) \41\ and in
IRIS (USEPA, 2001). However, a quantitative estimate of the
carcinogenic risk of methylmercury has not been assessed under the IRIS
program at this time. Multiple human epidemiological studies have found
no significant association between methylmercury exposure and overall
cancer incidence, although a few studies have shown an association
between methylmercury exposure and specific types of cancer incidence
(e.g., acute leukemia and liver cancer). Finally, some studies have
also indicated reproductive and renal toxicity in humans from
methylmercury exposure (NAS Study). However, overall, human data
regarding reproductive, renal, and hematological toxicity from
methylmercury are very limited and are based on studies of the 2 high-
dose poisoning episodes in Iraq and Japan or animal data, rather than
epidemiological studies of chronic exposures at the levels of interest
in this analysis (i.e., in the range of exposure stemming from U.S. EGU
mercury emissions).
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\41\ International Agency for Research on Cancer (IARC) Working
Group on the Evaluation of Carcinogenic Risks to Humans. Beryllium,
Cadmium, Mercury, and Exposures in the Glass Manufacturing Industry.
Lyon (FR): International Agency for Research on Cancer; 1993. (IARC
Monographs on the Evaluation of Carcinogenic Risks to Humans, No.
58.) Mercury and Mercury Compounds. Available from: <a href="https://www.ncbi.nlm.nih.gov/books/NBK499780">https://www.ncbi.nlm.nih.gov/books/NBK499780</a>.
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Along with the human health hazards associated with methylmercury,
it is well-established that birds and mammals are also exposed to
methylmercury through fish consumption (Mercury Study). At higher
levels of exposure, the harmful effects of methylmercury include slower
growth and development, reduced reproduction, and premature mortality.
The effects of methylmercury on wildlife are variable across species
but have been observed in the environment for numerous avian species
and mammals including polar bears, river otters, and panthers.
As noted earlier, EGUs are also the largest source of HCl, HF, and
selenium emissions, and are a major source of metallic HAP emissions
including arsenic, chromium, nickel, cobalt, and others. Exposure to
these HAP, depending on exposure duration and levels of exposures, is
associated with a variety of adverse health effects. These adverse
health effects may include chronic health disorders (e.g., pneumonitis,
decreased pulmonary function, pneumonia, or lung damage; detrimental
effects on the central nervous system; damage to the kidneys) and
alimentary effects (such as nausea and vomiting). As of 2021, 3 of the
key metal HAP emitted by EGUs (arsenic, chromium, and nickel) have been
classified as human carcinogens, while 3 others (cadmium, selenium, and
lead) are classified as probable human carcinogens. Overall (metal and
non-metal), the EPA has classified 4 of the HAP emitted by EGUs as
human carcinogens and 5 as probable human carcinogens.
In the 2022 Proposal, the EPA also described 3 new screening-level
risk assessments completed since the 2016 Supplemental Finding that
further strengthened the conclusion that U.S. EGU-sourced mercury
represents a hazard to public health. These screening-level assessments
were designed as broad bounding exercises intended to illustrate the
potential scope and public health importance of methylmercury risks
associated with U.S. EGU emissions. The first assessment focused on
neurodevelopmental outcomes and estimated the risk of IQ points loss in
children exposed in utero through maternal fish consumption by the
population of general U.S. fish consumers. The range in IQ points lost
annually due to U.S. EGU-sourced mercury was estimated at 1,600 to
6,000 points, which is distributed across the population of U.S.
children associated with mothers who consume commercially-sourced fish
(i.e., bought in a restaurant or food store) or self-caught fish.\42\
The other 2 risk assessments focused on the potential for methylmercury
exposure to increase the risk of MI mortality in adults (among
subsistence fishers and for the general U.S. population). The new
assessment estimated that the MI-mortality attributable to U.S. EGU-
sourced mercury for the general U.S. population ranges from 5 to 91
excess deaths each year.\43\ For those individuals with high levels of
methylmercury in their body (i.e., above certain cutpoints), the
science suggests that any additional increase in methylmercury exposure
will raise the risk of fatal heart attacks.
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\42\ Inclusion of 95th percentile confidence intervals for the
effect estimate used in modeling this endpoint extends this range to
from 80 to 12,600 IQ points lost (reflecting the 5th and 95th
percentiles).
\43\ Inclusion of 95th percentile confidence intervals for the
effect estimate used in modeling MI mortality extends this range to
from 3 to 143 deaths (reflecting the 5th percentile associated with
the 5 lower bound estimate to the 95th percentile for the upper
bound estimate of 91).
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3. Most Benefits From HAP Reductions Cannot Currently Be Quantified or
Monetized
Despite the array of adverse health and environmental risks
associated with HAP emissions from U.S. coal- and oil-fired EGUs
documented above, it is technically challenging to quantitatively
estimate the extent to which EGU HAP emissions will result in adverse
effects across the U.S. population absent regulation. In fact, the vast
majority of the benefits of reducing HAP currently cannot be quantified
or monetized due to data gaps, as discussed more fully below. But that
does not mean that these benefits are small, insignificant, or
nonexistent. There are numerous unmonetized effects that contribute to
additional benefits realized from emissions reductions. These include
additional reductions in neurodevelopmental and cardiovascular effects
from exposure to methylmercury, adverse ecosystem effects including
mercury-related impacts on recreational and commercial fishing, health
risks from exposure to non-mercury HAP, and health risks in
environmental justice (EJ) subpopulations that face disproportionally
high exposure to EGU HAP.
While the EPA was able to partially quantify IQ loss and fatal MI
incidence for methylmercury through bounding analyses in the 2021 Risk
TSD, there are additional neurodevelopmental and cardiovascular
benefits that lacked the necessary data to quantify their incidence.
Another challenge was the lack of data required to quantify the number
of people impacted. While it is reasonable to assume that some degree
of subsistence fishing activity does occur at methylmercury impacted
waterbodies, we were unable to quantify the number of impacted
subsistence fishers and their children.
There are several challenges to quantifying HAP benefits.
Quantifying HAP benefits requires data to characterize the risk and
quantify the magnitude of expected (cancer and non-cancer) health
outcomes. Unlike criteria pollutants, for which risk is generally more
ubiquitous and there is more available data because a greater number of
people are impacted, significant HAP impacts are often localized in

[[Page 13971]]

communities near sources of HAP where the affected population and data
can be more limited. Generally, robust data needed to quantify the
magnitude of expected adverse noncancer impacts are lacking, and full
quantification of these benefits is made even more challenging by the
wide array of HAP and possible HAP effects.
Unlike HAP, criteria pollutants are some of the most studied
pollutants in the country with nearly the entire U.S. population
exposed to such pollutants. This has resulted in significant data for
criteria pollutants thanks to an extensive monitoring network to assess
exposure within the population. These data support quantitative
estimates of risk (incidence) and allow for greater statistical power
to identify effects from criteria pollutants with greater precision
through hundreds of epidemiological studies which have been conducted
over the past 30 years. Furthermore, those observed effect associations
have been corroborated through various experimental animal studies and
controlled exposure clinical studies. Monetization of those endpoints
characterized in epidemiological studies allows for quantification of
benefits.
In contrast to criteria pollutants, HAP are not as well studied,
which minimizes our ability to quantify risks and monetize benefits.
HAP exposures tend to be more localized. Multiple types of HAP may be
emitted from a single source, and individual communities can be
impacted by multiple sources with varying HAP emissions from each, such
that combinations of individual HAP to which people are exposed across
communities tend to be highly varied. Additionally, there are a limited
number of monitoring sites across the country for HAP, many of which
focus on only a small subset of HAP, which limits the ability to assess
exposure in epidemiological studies. Given the general lack of
sufficient quality epidemiological studies, the EPA tends to rely on
experimental animal studies to identify the range of effects which may
be associated with a particular HAP exposure.\44\ Human controlled
clinical studies are often limited due to ethical barriers (e.g.,
knowingly exposing someone to a carcinogen). As a result, there is
insufficient ability to quantify the actual (incidence of) impacts
associated with HAP exposures, which is necessary to provide a
foundation for benefits.
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\44\ For many HAP, while available toxicological and
epidemiological data allow the estimation of risks, often the types
of representative population level epidemiological data needed to
estimate incidence in the exposed populations are lacking.
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Without the estimation of specific incidence of effects there is
limited ability to monetize benefits from reducing HAP emissions,
because doing so requires first quantifying risk. Further, there is a
lack of scientific data available to support estimating the economic
value of reducing health and environmental impacts that are not
otherwise easily valued. While the EPA can quantify mortality resulting
from cancer, it is difficult to monetize the value of reducing an
individual's potential cancer risk attributable to a lifetime of HAP
exposure. An alternative approach of conducting willingness to pay
studies specifically on risk reduction may be possible, but such
studies have not yet been pursued.
Congress well understood the challenges in quantifying HAP risks.
That is why it fundamentally transformed regulation of HAP in the 1990
CAA Amendments to replace a risk-based approach to establishing
standards with a technology-based approach. As discussed in section
II.B above, the statutory language in CAA section 112 clearly supports
a conclusion that the intended benefit of HAP regulation is a reduction
in the volume of HAP emissions to reduce risks from HAP with the goal
of protecting even the most exposed and most sensitive members of the
population. The statute requires the EPA to move aggressively to
quickly reduce and eliminate HAP, placing high value on doing so in the
face of uncertainty regarding the full extent of harm posed by
hazardous pollutants on human health and the environment. The statute
also clearly places great value on protecting the most vulnerable
members of the population by instructing the EPA, when evaluating risk
in the context of a determination of whether regulation is warranted,
to focus on risk to the most exposed and most sensitive members of the
population. See, e.g., CAA sections 112(c)(9)(B), 112(f)(2)(B), and
112(n)(1)(C). For example, in evaluating the potential for cancer
effects associated with emissions from a particular source category
under CAA section 112(f)(2), the EPA is directed by Congress to base
its determinations on the maximum individual risk to the most highly
exposed individual living near a source. Similarly, in calculating the
potential for non-cancer effects to occur, the EPA evaluates the impact
of HAP to the most exposed individual and accounts for sensitive
subpopulations.
Notably, Congress in CAA section 112 did not require the EPA to
quantify risk across the entire population, or to calculate average or
``typical'' risks. The statutory design focusing on maximum risk to
individuals living near sources acknowledges the difficulty in
enumerating HAP effects, given the large number of pollutants and the
uncertainties associated with those pollutants, as well as the large
number of sources emitting HAP. However, the fact that many effects
cannot currently be quantified does not mean that these effects do not
exist or that society would not highly value HAP emission reductions.
The EPA has long acknowledged the difficulty of quantifying and
monetizing HAP benefits. In March 2011, the EPA issued a report on the
benefits and costs of the CAA. This Second Prospective Report \45\ is
the latest in a series of EPA studies that estimate and compare the
benefits and costs of the CAA and related programs over time. Notably,
it was the first of these reports to include any attempt to quantify
and monetize the impacts of reductions in HAP, and it concentrated on a
small case study for a single pollutant, entitled ``Air Toxics Case
Study--Health Benefits of Benzene Reductions in Houston, 1990-2020.''
As the EPA summarized in the Second Prospective Report, ``[t]he purpose
of the case study was to demonstrate a methodology that could be used
to generate human health benefits from CAAA controls on a single HAP in
an urban setting, while highlighting key limitations and uncertainties
in the process. . . . Benzene was selected for the case study due to
the availability of human epidemiological studies linking its exposure
with adverse health effects'' (pg. 5-29). In describing the approach,
the EPA noted: ``[b]oth the Retrospective analysis and the First
Prospective analysis omitted a quantitative estimation of the benefits
of reduced concentrations of air toxics, citing gaps in the
toxicological database, difficulty in designing population-based
epidemiological studies with sufficient power to detect health effects,
limited ambient and personal exposure monitoring data, limited data to
estimate exposures in some critical microenvironments, and insufficient
economic research to support valuation of the types of health impacts
often associated with exposure to individual air toxics'' (pg. 5-29).
These difficulties have long hindered the EPA's ability to quantify the
impacts of HAP controls

[[Page 13972]]

and estimate the monetary benefits of HAP reductions.
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\45\ U.S. EPA Office of Air and Radiation, April 2011. The
Benefits and Costs of the Clean Air Act from 1990 to 2020, Final
Report--Rev. A. Available at <a href="https://www.epa.gov/sites/production/files/2015-07/documents/fullreport_rev_a.pdf">https://www.epa.gov/sites/production/files/2015-07/documents/fullreport_rev_a.pdf</a>.
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In preparing the benzene case study for inclusion in the Second
Prospective Report, the EPA asked the Advisory Council on Clean Air
Compliance Analysis (the Council) to review the approach. In its 2008
consensus advice to the EPA after reviewing the benzene case study,\46\
the Council noted that ``Benzene . . . has a large epidemiological
database which OAR [the EPA's Office of Air and Radiation] used to
estimate the health benefits of benzene reductions due to CAAA
controls. The Council was asked to consider whether this case study
provides a basis for determining the value of such an exercise for HAP
benefits characterization nationwide.'' They concluded:
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\46\ U.S. EPA Advisory Council on Clean Air Act Compliance
Analysis, Review of the Benzene Air Toxics Health Benefits Case
Study. July 11, 2008. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P1000ZYP.PDF?Dockey=P1000ZYP.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P1000ZYP.PDF?Dockey=P1000ZYP.PDF</a>.

As recognized by OAR, the challenges for assessing progress in
health improvement as a result of reductions in emissions of
hazardous air pollutants (HAPs) are daunting. Accordingly, EPA has
been unable to adequately assess the economic benefits associated
with health improvements from HAP reductions due to a lack of
exposure-response functions, uncertainties in emissions inventories
and background levels, the difficulty of extrapolating risk
estimates to low doses and the challenges of tracking health
progress for diseases, such as cancer, that have long latency
periods. . . .
The benzene case study successfully synthesized best practices
and implemented the standard damage function approach to estimating
the benefits of reduced benzene, however the Council is not
optimistic that the approach can be repeated on a national scale or
extended to many of the other 187 air toxics due to insufficient
epidemiological data. With some exceptions, it is not likely that
the other 187 HAPs will have the quantitative exposure-response data
needed for such analysis. Given EPA's limited resources to evaluate
a large number of HAPs individually, the Council urges EPA to
consider alternative approaches to estimate the benefits of air
toxics regulations.

In addition to the difficulties noted by the Council, there are
other challenges that affect the EPA's ability to fully characterize
impacts of HAP on populations of concern, including sensitive groups
such as children or those who may have underlying conditions that
increase their risk of adverse effects following exposure to HAP.
Unlike for criteria pollutants such as ozone and PM, the EPA lacks
information from controlled human exposure studies conducted in
clinical settings which enable us to better characterize dose-response
relationships and identify subclinical outcomes. Also, as noted by the
Council and by the EPA itself in preparing the benzene case study, the
almost universal lack of HAP-focused epidemiological studies is a
significant limitation. Estimated risks reported in epidemiologic
studies of fine PM (PM<INF>2.5</INF>) and ozone enable the EPA to
estimate health impacts across large segments of the U.S. population
and quantify the economic value of these impacts. Epidemiologic studies
are particularly well suited to informing air pollution health impact
assessments because they report measures of population-level risk that
can be readily used in a risk assessment.
However, such studies are infrequently performed for HAP. Exposure
to HAP is typically more uneven and more highly concentrated among a
smaller number of individuals than exposure to criteria pollutants.
Hence, conducting an epidemiologic study for HAP is inherently more
challenging. A comparatively small number of people are exposed to HAP,
which means an epidemiologic study will frequently lack sufficient
statistical power to detect an adverse effect. For example, in the case
of mercury, the most exposed and most sensitive members of the
population may be both small in number and highly concentrated, such as
the subsistence fishers that the EPA has identified as most likely to
suffer deleterious effects from U.S. EGU HAP emissions. While it is
possible to estimate the potential risks confronting this population in
a case-study approach (an analysis that plays an important role in
supporting the public health hazard determination for mercury as
discussed above in sections III.A.2 and III.A.3), it is not possible to
translate these risk estimates into quantitative population-level
impact estimates for the reasons described above.
Expressing the economic value of avoided HAP-related cases of
morbidity effects is also challenging. The EPA lacks willingness-to-pay
information that would support estimating the economic value of avoided
HAP impacts for outcomes including heart attacks, IQ loss, and renal or
reproductive failure. In addition, the absence of socio-demographic
data, such as the number of affected individuals comprising sensitive
subgroups further limits the ability to monetize HAP-impacted effects.
All of these deficiencies impede the EPA's current ability to quantify
and monetize HAP-related impacts, even though those impacts may be
severe and/or impact significant numbers of people.
Though it may be difficult to quantify and monetize most HAP-
related health and environmental benefits, this does not mean such
benefits are small. The nature and severity of effects associated with
HAP exposure, ranging from lifelong cognitive impairment to cancer to
adverse reproductive effects, implies that the economic value of
reducing these impacts would be substantial if they could be quantified
and monetized completely. By extension, it is reasonable to expect both
that reducing HAP-related incidence affecting individual endpoints
would yield substantial benefits if fully quantified and monetized, and
moreover that the total societal impact of reducing HAP would be quite
large when evaluated across the full range of endpoints. In judging it
appropriate to regulate based on the risks associated with HAP
emissions from U.S. EGUs, the EPA is placing weight on the likelihood
that these effects are substantial, as supported by the health
evidence. The EPA's new screening-level analyses presented in the 2021
Risk TSD for this action illustrate this point. Specifically, in
exploring the potential for MI-related mortality risk attributable to
mercury emissions from U.S. EGUs, the EPA's upper bound estimate is
that these emissions (i.e., counterfactual EGU emissions in 2016
without MATS) may contribute to as many as 91 additional premature
deaths each year. The value society places on avoiding such severe
effects is very high; as the EPA illustrates in the valuation
discussion in the 2021 Risk TSD, the benefit of avoiding such effects
could approach $720 million per year. Similarly, for IQ loss in
children exposed in utero to U.S. EGU-sourced mercury, our upper bound
estimate approaches 6,000 IQ points lost which could translate into a
benefit approaching $50 million per year.
These estimates are intended to illustrate the point that the HAP
impacts are large and societally meaningful, but not to suggest that
they are even close to the full monetized benefits of reducing HAP.
There are many other unquantified effects of reducing mercury (e.g., EJ
impacts, subsistence fisher impacts, and ecological impacts, among
others) and non-mercury HAP (e.g., reduced cancer risks, environmental
impacts, and disproportionate exposures) that have substantial value to
society. As described above, mercury alone is associated with a host of
adverse health and environmental effects. The statute clearly
identifies this basket of effects as a significant concern in directing
the EPA to study them specifically. If the

[[Page 13973]]

EPA were able to account for all of these effects in our quantitative
estimates, the true benefits of MATS would be far clearer. However,
available data and methods currently preclude a full quantitative
accounting of the impacts of reducing HAP emissions from U.S. EGUs and
a monetization of these impacts.
The HAP-related legislative history for the 1990 Amendments
includes little discussion of the monetized benefits of HAP, perhaps
due to these attendant difficulties. When such monetized benefits were
estimated in several outside reports submitted to Congress before
passage of the 1990 Amendments, the estimates were based on reduced
cancer deaths and the value of the benefits that are quantified were
estimated to be small as compared to the estimated costs of regulating
HAP emissions under CAA section 112. See, e.g., A Legislative History
of the Clean Air Act Amendments of 1990, Vol. I at 1366-67 (November
1993) and id. at 1372-73. Despite the apparent disparity between
benefits that could be monetized and estimated costs, Congress still
enacted the revisions to CAA section 112, requiring regulation of HAP
in most instances based on Congress' determination of risk and without
first requiring the EPA to assess risk. Thus, it is reasonable to
conclude that Congress found HAP emissions to be worth regulating even
without evidence that the monetized benefits of doing so were greater
than the costs. The EPA believes this stems from the value that the
statute places on reducing HAP regardless of whether the benefits of
doing so can be quantified or monetized, and the statute's purpose of
protecting even the most exposed and most sensitive members of the
population.
4. Characterization of HAP Risk Relevant to Consideration of EJ
In assessing the adverse human health effects of HAP emissions from
EGUs, we note that these effects are not borne equally across the
population, and that some of the most exposed individuals and
subpopulations--protection of whom is, as noted, of particular concern
under CAA section 112--are people of color and/or low-income
populations. The EPA defines EJ as the fair treatment and meaningful
involvement of all people regardless of race, color, national origin,
or income with respect to the development, implementation, and
enforcement of environmental laws, regulations, and policies. See
<a href="https://www.epa.gov/environmentaljustice/learn-about-environmental-justice">https://www.epa.gov/environmentaljustice/learn-about-environmental-justice</a>. The EPA further defines the term fair treatment to mean that
no group of people should bear a disproportionate burden of
environmental harms and risks, including those resulting from the
negative environmental consequences of industrial, governmental, and
commercial operations or programs and policies. Id.
In the context of MATS, exposure scenarios of clear relevance from
an EJ perspective include the full set of subsistence fisher scenarios
included in the watershed-level risk assessments completed for the
rule. Subsistence fisher populations are potentially exposed to
elevated levels of methylmercury due to their elevated levels of self-
caught fish consumption which, in turn, are often driven either by
economic need (i.e., poverty) and/or cultural practices (i.e.,
longstanding traditions of fishing and fish consumption are central to
many Tribes' cultural identity). In the context of MATS, we completed
watershed-level assessments of risks for a broad set of subsistence
fisher populations covering 2 health endpoints of clear public health
significance including: (a) neurodevelopmental effects in children
exposed prenatally to methylmercury (the methylmercury-based RfD
analysis described in the 2011 Final Mercury TSD), and (b) potential
for increased MI-mortality risk in adults due to methylmercury exposure
(see section III.A.3.b in the 2022 Proposal).
The general subsistence fisher population that was evaluated
nationally for both analyses was not subdivided by socioeconomic
status, race, or cultural practices.\47\ Therefore, the risk estimates
derived do not fully inform our consideration of EJ impacts, although
the significantly elevated risks generated for this general population
are clearly relevant from a public health standpoint. However, the
other, more differentiated subsistence fisher populations, which are
subdivided into smaller targeted communities, are relevant in the EJ
context and in some instances were shown to have experienced levels of
risk significantly exceeding those of the general subsistence fisher
population, as noted in section III.A.3.b in the 2022 Proposal.
---------------------------------------------------------------------------

\47\ Note that the RfD-based analysis described in the 2011
Final Mercury TSD and referenced here addressed the potential for
neurodevelopmental effects in children and therefore focused on the
ingestion of methylmercury by female subsistence fishers. By
contrast, the analysis focusing on increased MI-mortality risk for
subsistence fishers described in the 2021 Risk TSD and referenced
here was broader in scope and encompassed all adult subsistence
fishers.
---------------------------------------------------------------------------

In particular, for the watershed analysis focusing on the
methylmercury RfD-based analysis (i.e., neurodevelopmental risk for
children exposed prenatally), while the general female fisher scenario
suggested that modeled exposures (from U.S. EGU-sourced mercury alone)
exceeded the methylmercury RfD in approximately 10 percent of the
watersheds modeled (2011 Final Mercury TSD, Table 2-6), for low-income
Black subsistence fisher females in the Southeast, modeled exposures
exceeded the RfD in approximately greater than 25 percent of the
watersheds. These results suggest a greater potential for adverse
effects in low-income Black populations in the Southeast. Similarly,
while the general subsistence fisher had exposure levels suggesting an
increased risk for MI-mortality risk in 10 percent of the watersheds
modeled, 3 sub-populations were shown to be even further disadvantaged
(low-income White and Black populations in the southeast and tribal
populations near the Great Lakes). Both of these results (the
neurodevelopmental RfD-based analysis and the analysis of increased MI-
mortality risk) suggest that subsistence fisher populations that are
racially or culturally, geographically, and income-differentiated could
experience elevated risks relative to not only the general population
but also the population of subsistence fishers generally. We think that
opportunities to remove systemic barriers to underserved communities
are relevant considerations in determining the benefits of regulating
EGU HAP.
5. Overview of Health and Environmental Effects Associated With Non-HAP
Emissions From EGUs
Alongside the HAP emissions enumerated above, U.S. EGUs also emit a
substantial quantity of criteria pollutants, including direct
PM<INF>2.5</INF>, nitrogen oxides (NO<INF>X</INF>) (including
NO<INF>2</INF>), and SO<INF>2</INF>, even after implementation of the
ARP and numerous other CAA requirements designed to control criteria
pollutants. In the 2011 RIA, for example, the EPA estimated that U.S.
EGUs would emit 3.4 million tons of SO<INF>2</INF> and 1.9 million tons
of NO<INF>X</INF> in 2015 prior to implementation of any controls under
MATS (see Table ES-2). These EGU SO<INF>2</INF> emissions were
approximately twice as much as all other sectors combined (EPA
SO<INF>2</INF> Integrated Science Assessment, 2017).\48\ These
pollutants contribute to the formation of PM<INF>2.5</INF> and ozone
criteria pollutants in the atmosphere, the exposure to which is
causally linked with a range of adverse

[[Page 13974]]

public health effects. SO<INF>2</INF> both directly affects human
health and is a precursor to PM<INF>2.5</INF>. Short-term exposure to
SO<INF>2</INF> causes respiratory effects, particularly among adults
with asthma. SO<INF>2</INF> serves as a precursor to PM<INF>2.5</INF>,
the exposure to which increases the risk of premature mortality among
adults, lung cancer, new onset asthma, exacerbated asthma, and other
respiratory and cardiovascular diseases. Likewise, EGU-related
emissions of NO<INF>X</INF> will adversely affect human health in the
form of respiratory effects including exacerbated asthma.
NO<INF>X</INF> is a precursor pollutant to both PM<INF>2.5</INF> and
ground-level ozone. Exposure to ozone increases the risk of
respiratory-related premature death, new onset asthma, exacerbated
asthma, and other outcomes. Fully accounting for the human health
impacts of reduced EGU emissions under MATS entails quantifying both
the direct impacts of HAP as well as the avoided premature deaths and
illnesses associated with reducing these co-emitted criteria
pollutants. Similarly, U.S. EGUs emit substantial quantities of
CO<INF>2</INF>, a powerful greenhouse gas (GHG): the EPA estimated
these emissions at 2.23 million metric tpy in 2015 (2011 RIA, Table ES-
2). The environmental impacts of GHG emissions are accounted for
through the social cost of carbon, which can be used to estimate the
benefits of emissions reductions projected in the 2011 RIA to occur
under MATS.
---------------------------------------------------------------------------

\48\ U.S. EPA. Integrated Science Assessment for Sulfur Oxides--
Health Criteria (Final Report). U.S. Environmental Protection
Agency, Washington, DC, EPA/600/R-17-451, December 2017.
---------------------------------------------------------------------------

Not all of the non-HAP benefits of MATS were quantified or
monetized in the 2011 RIA. However, the EPA thoroughly documented these
potential effects and identified those for which quantification and/or
monetization was possible. Specifically, the EPA calculated the number
and value of avoided PM<INF>2.5</INF>-related impacts, including 4,200
to 11,000 premature deaths, 4,700 nonfatal heart attacks, 2,600
hospitalizations for respiratory and cardiovascular diseases, 540,000
lost work days, and 3.2 million days when adults restrict normal
activities because of respiratory symptoms exacerbated by
PM<INF>2.5</INF> (2011 RIA, p. ES-3). We also estimated substantial
additional health improvements for children from reductions in upper
and lower respiratory illnesses, acute bronchitis, and asthma attacks.
In addition, we included in our monetized benefits estimates the effect
from the reduction in CO<INF>2</INF> emissions resulting from this
final action, based on the interagency SC-CO<INF>2</INF> estimates.
These benefits stemmed from imposition of MATS and would be
coincidentally realized alongside the HAP benefits.
6. Summary of Public Health and Environmental Hazards Associated With
Emissions From EGUs
The EPA finds that the evidence provided in this section of the
preamble, informed where possible with new scientific evidence
available since the publication of the 2016 Supplemental Finding, once
again demonstrates that HAP released from U.S. EGUs represent a
significant public health hazard absent regulation under CAA section
112. As noted earlier, the EPA found that even after imposition of the
other requirements of the CAA, EGUs were the largest domestic source of
mercury, HF, HCl, and selenium and among the largest domestic
contributors of arsenic, chromium, cobalt, nickel, hydrogen cyanide,
beryllium, and cadmium. The EPA has documented a wide range of adverse
health effects in children and adults associated with mercury
including, in particular, neurodevelopmental effects in children
exposed prenatally (e.g., IQ, attention, fine motor-function, language,
and visual spatial ability) and a range of cardiovascular effects in
adults including fatal MI and non-fatal IHD. Non-mercury HAP have also
been associated with a wide range of chronic health disorders (e.g.,
decreased pulmonary function, pneumonia, or lung damage; detrimental
effects on the central nervous system; and damage to the kidneys).
Furthermore, 3 of the key metal HAP emitted by EGUs (arsenic, chromium,
and nickel) have been classified as human carcinogens and there is
evidence to suggest that, prior to MATS, emissions from these sources
had the potential to result in cancer risks greater than 1-in-1
million.
Further, this section briefly describes the results from several
new screening-level risk assessments considering mercury from domestic
EGU sources. These risk assessments focused on 2 broad populations of
exposure: (a) subsistence fishers exposed to mercury through self-
caught fish consumption within the continental U.S. and (b) the general
U.S. population exposed to mercury through the consumption of
commercially-sourced fish (i.e., purchased from restaurants and food
stores). The results of these screening-level risk assessments are
useful for informing our understanding about the potential scope and
public health importance of these impacts, but remaining uncertainties
prohibit precise estimates of the size of these impacts currently. For
example, numerous studies considering multiple, large cohorts have
shown that people exposed to high amounts of mercury are at higher risk
of fatal and non-fatal cardiovascular disease. While U.S. EGUs are only
one of multiple global sources that contribute to this mercury
exposure, the EPA's screening analysis suggests the potential for U.S.
EGU emissions of mercury to contribute to premature mortality in the
general U.S. population.
Furthermore, as part of the subsistence fisher analyses, we
included scenario modeling for a number of EJ-relevant populations
showing that several populations (including low-income Blacks and
Whites in the Southeast and tribal populations near the Great Lakes)
had risk levels that were significantly above the general subsistence
fisher population modeled for the entire U.S. As noted earlier, the EPA
believes that Congress intended in CAA section 112 to address risks to
the most exposed and most sensitive members of the public. These
additional risk assessments suggest that there are populations that are
particularly vulnerable to EGU HAP emissions, including populations of
concern from an EJ standpoint.
MATS has played a critical role in reducing the significant volume
and risks associated with EGU HAP emissions discussed above. Mercury
emissions declined by 86 percent, acid gas HAP by 96 percent, and non-
mercury metal HAP by 81 percent between 2010 (pre-MATS and certain
market conditions) and 2017. See Table 4 at 84 FR 2689 (February 7,
2019). MATS is the only Federal requirement that guarantees a level of
HAP control from EGUs. At the same time, the concomitant reductions in
CO<INF>2</INF>, NO<INF>X</INF>, and SO<INF>2</INF>, also provide
substantial public health and environmental benefits. Given the
numerous and important public health and environmental risks associated
with EGU emissions, the EPA again concludes that the advantages of
regulating HAP emissions from this sector are significant, and that is
true whether we look at the HAP emissions reductions alone or the
concomitant reduction in non-HAP emissions.

B. Cost Associated With Regulating EGUs for HAP

1. Introduction
In this action, the EPA considers the 2011 projected costs
comprehensively, examining them in the context of the effect of those
expenditures on the economics of power generation more broadly, the
reliability of electricity, and the cost of electricity to consumers.
These metrics are relevant to our weighing exercise because they give
us a more complete picture of the

[[Page 13975]]

disadvantages to producers and consumers of electricity imposed by this
regulation.
Similar to the EPA's consideration of benefits of regulation, our
consideration of costs and disadvantages is specific to the unique
charge in section 112(n)(1)(A) to determine whether EGU HAP regulation
is appropriate and necessary, and the Supreme Court's direction in
Michigan v. EPA. As the Court recognized, the EPA has discretion ``to
decide (as always within the limits of reasonable interpretation) how
to account for cost.'' Michigan, 135 S. Ct. at 2711. To reasonably
exercise this discretion, the EPA considered the language and context
of CAA section 112(n)(1) as well as the general goals of section 112 of
the CAA. We note as well that the EPA routinely uses other methods to
consider costs under other provisions of the statute, and that we are
not in this action suggesting that the analysis appropriate to
112(n)(1)(A) finding is appropriate for any other statutory provisions.
As discussed in more detail below, the 2022 Proposal analyzed new
cost information indicating that the cost projection used in the 2011
RIA and the 2016 Supplemental Finding likely significantly
overestimated the actual costs of compliance of MATS by an amount in
the billions of dollars. Specifically, with the benefit of hindsight,
we now know that the EGU sector installed far fewer controls to comply
with the HAP emissions standards than projected; certain modeling
assumptions, if updated with newer information, would have resulted in
a lower cost estimate; unexpected advancements in technology occurred;
and the country experienced a dramatic increase in the availability of
comparatively inexpensive natural gas. All of these factors likely
resulted in a significantly lower actual cost of compliance than the
EPA's projected estimates in 2011.
The EPA received numerous public comments on these analyses, and
our detailed responses to these comments are presented in section IV.B
below and in the 2023 RTC Document. No information received during the
comment period has provided new data or methods to cause us to change
the analytical approaches used in the 2022 Proposal to consider the
costs of the MATS regulation. As a result, this final action will rely
upon the same suite of qualitative and quantitative evidence presented
in the 2022 Proposal. While the reader is directed to the 2022 Proposal
and the supporting Cost TSD for the complete analyses, the EPA
summarizes the analyses in subsequent sections of this preamble.
Additionally, in response to several commenters' suggestion for the
EPA to consider employment impacts from EGU HAP regulation, the EPA
notes that the 2011 RIA did consider employment impacts. As explained
in further detail in section IV.B.2 below, the 2011 RIA projected both
employment gains and losses as a result of the regulation but that the
net projected change in employment due to MATS was ambiguous.
Nonetheless, the EPA has taken such employment impacts into
consideration in this final action and finds that they do not play a
significant role in the EPA's decision making.
2. Compliance Cost Projections in the 2011 RIA Were Likely
Significantly Overestimated
In evaluating the costs and disadvantages of MATS, the EPA begins
with the costs to the power industry of complying with MATS. This
assessment uses a sector-level (or system-level) accounting perspective
to estimate the cost of MATS, looking beyond just pollution control
costs for directly affected EGUs to include incremental costs
associated with changes in fuel supply, construction of new capacity,
and costs to non-MATS units that were also projected to adjust
operating decisions as the power system adjusted to meet MATS
requirements. Such an approach is warranted due to the nature of the
power sector, which is a large, complex, and interconnected industry.
Using this broad view, the 2011 RIA projected that the compliance
cost of MATS would be $9.6 billion per year in 2015.\49\ However, there
are inherent limits to what can be predicted ex ante. The cost estimate
was made 5 years prior to full compliance with MATS, and stakeholders,
including a leading power sector trade association, have indicated that
our initial cost projection significantly overestimated actual costs
expended by industry. Independent analyses provided to the EPA
indicated that we may have overestimated the cost of MATS by billions
of dollars per year. Moreover, there have been significant changes in
the power sector in the time since MATS was promulgated that were not
anticipated in either EPA or U.S. Energy Information Administration
(EIA) projections at the time.\50\ Entirely outside of the realm of EPA
regulation, there were dramatic shifts in the cost of natural gas and
renewables, as well as the implementation of new state policies and
Federal tax incentives, which have also further encouraged construction
of new renewable units. These have led to significantly faster and
greater than anticipated retirements of coal-fired generating units.
---------------------------------------------------------------------------

\49\ All costs were reported in 2007 dollars.
\50\ In 2009, coal-fired generation was by far the largest
source of utility scale generation, providing more power than the
next two sources (natural gas and nuclear) combined. By 2016,
natural gas had passed coal-fired generation as the leading source
of generation in the U.S. While natural gas-fired generation,
nuclear generation and renewable generation have all increased since
2009, coal-fired generation has significantly declined.
---------------------------------------------------------------------------

While there are significant challenges to producing an ex post cost
estimate that provides an apples-to-apples comparison to our 2011 cost
projections, due to the complex and interconnected nature of the
industry and the related difficulty of attributing costs to MATS or
other factors, we approximated the extent of our overestimate in the
2022 Proposal. In the proposed rule, we reviewed a suite of
quantitative and qualitative updates and considered studies that were
performed by outside entities and concluded that the available ex post
evidence points to significantly lower costs of compliance for the
power sector under MATS than suggested by the ex ante projections in
the 2011 RIA. The proposal explained that there are numerous reasons
for this, and chief among them is the fact that the natural gas
industry has undergone profound change in recent years.
As detailed in the 2022 Proposal and supporting Cost TSD, following
the promulgation of MATS, natural gas supply increased substantially,
leading to dramatic price decreases that resulted in major shifts in
the economics of fossil fuel-fired electric generating technologies.
The 2011 RIA modeling did not fully anticipate this historic change in
natural gas supply and the related decrease in natural gas prices. As a
result of this and other fundamental changes in the industry, we see a
very different pattern of control installations than was projected:
\51\
---------------------------------------------------------------------------

\51\ As discussed in the proposal, although we assumed that all
pollution controls of these types that were installed between 2013
and 2016 were singularly attributable to MATS requirements and we
therefore attributed all costs associated with controls of these
types to MATS in this analysis, this is a conservative assumptions
given that some of the observed installations likely occurred in
response to other regulations to control criteria air pollutants.
---------------------------------------------------------------------------

<bullet> 21 percent less capacity of dry FGD than projected;
<bullet> 64 percent less capacity of dry sorbent injection (DSI)
than projected;
<bullet> 3 percent less capacity of activated carbon injection than
projected;
<bullet> 69 percent less capacity of fabric filters than projected;
and

[[Page 13976]]

<bullet> Likely fewer electrostatic precipitator (ESP) and scrubber
control upgrades than projected.
Installation and operation of these controls together were
responsible for approximately 70 percent of the projected annual
compliance costs in the 2011 RIA. Because so many projected controls
were not installed, we know that the control-related costs were likely
significantly overestimated. By simply comparing between projected and
installed controls, we found in the 2022 Proposal that the projected
control-related costs for 2015 of about $7 billion were likely
overestimated by $2.2 to $4.4 billion, and possibly more.
In addition, since promulgation of MATS, the EPA has found it
necessary to update some of the assumptions used in the modeling that
informed the RIA cost estimate, in order to capture the most recently
available information and best reflect the current state of the power
sector.
Specifically:
<bullet> HCl emissions for EGUs burning subbituminous and lignite
coals are much lower than assumed in 2011, reducing the number of
controls necessary for compliance than was projected in 2011;
<bullet> DSI controls require less sorbent than assumed in 2011,
lowering the operating cost of these controls, and other lower-cost
sorbents are likely available; and
<bullet> The assumed cost of ESP upgrades in the 2011 analysis was
likely much higher than the actual cost of these upgrades.
While not quantified here, the reductions in cost and advances in
performance of control technology between the time of the EPA's 2011
modeling and implementation of the rule would, if quantified, likely
add to the $2.2 to $4.4 billion overestimate for pollution control
costs.
Three studies submitted to the EPA during earlier rulemakings
support this finding that the 2011 RIA cost projection was
significantly overestimated:
<bullet> Andover Technology Partners estimated that the actual
annual costs of compliance with MATS were approximately $2 billion and
stated that the 2011 RIA may have overestimated annual compliance costs
by approximately $7 billion.
<bullet> M.J. Bradley & Associates used information from the EIA to
estimate that owners and operators of coal-fired EGUs incurred total
capital expenditures on environmental retrofits of $4.45 billion from
December 2014 to April 2016. For comparison, the estimated total
upfront (not annualized) capital expenditures underpinning the 2011 RIA
annual compliance cost estimate is about $36.5 billion, which is more
than eight times higher than the M.J. Bradley & Associates estimate of
actual total capital expenditures.
<bullet> Edison Electric Institute, the association that represents
U.S. investor-owned electric companies, estimated cumulative costs
incurred by the industry in response to MATS of $18 billion over a 7-
year period, suggesting an annual amount of about $2.6 billion (or, as
the EPA notes in the 2022 Proposal, is about $7 billion less than the
2011 RIA projected).
The EPA received no data or analysis during the public comment
period that alters the conclusions made in the 2022 Proposal based on
the evidence presented in the proposed rule and summarized here. We
thus finalize here our conclusion that the available ex post evidence
points to a power sector that incurred significantly lower costs of
compliance obligations under MATS than anticipated based on the ex ante
projections when the rule was finalized in 2012. This overestimate was
significant--for just one part of the original compliance cost
estimate, the EPA was able to quantify a range of at least $2.2 to $4.4
billion in projected costs related to the installation, operation, and
maintenance of controls which were not expended by industry. This
projected overestimation is limited to these costs; it does not account
for other ways in which the rule's costs were likely overestimated,
such as advances in control technologies that made control applications
less expensive or more efficient at reducing emissions. The other
studies conducted by stakeholders asserted there were even greater
differences between projected and actual costs of MATS, and further
support the EPA's conclusions that the 2011 cost projections were
likely significantly overestimated.
3. Evaluation of Metrics Related to MATS Compliance
The EPA next examines the projected cost of MATS--both total cost
and specific types of costs--and we use sector-level metrics that put
those cost estimates in context with the economics of the power sector.
The reason we examine these metrics is to better understand the
disadvantages that expending these costs had on the electricity
generating industry and the public more broadly, and to understand
these costs in the context of the sector that incurred them.
Additionally, these metrics are relevant measures for evaluating costs
to the utility sector in part because they are the types of metrics
used in regulatory analysis as well as considered by the owners and
operators of EGUs themselves.
For purposes of these analyses, the EPA uses the 2011 RIA ex ante
projections, keeping in mind conclusions derived from newer ex post
analyses which indicate the 2011 RIA cost projections were likely
significantly overestimated. Specific to the power sector, we evaluate
the projected costs of the rule relative to revenues from electricity
sales across nearly 20 years. We compare the projected expenditures
required under the rule with historic expenditures by the industry over
the same time period. We also look at the projected effects of MATS on
retail electricity prices and power sector generating capacity.
Specifically, we examined the 2011 projected cost in the context of the
following four metrics: compliance costs as a percent of power sector
sales, compliance expenditures compared to the power sector's annual
expenditures, impact on retail price of electricity, and impact on
power sector generating capacity.
As discussed in the 2022 Proposal and presented in the Cost TSD,
based on the 2011 RIA, the total projected cost of the MATS rule to the
power sector in 2015 represented between 2.7 and 3.0 percent of annual
electricity sales when compared to years from 2000 to 2019, a small
fraction of the value of overall sales (and even smaller when one takes
into account that the 2011 RIA projections were likely significantly
overestimated). Looking at capital expenditures, the EPA demonstrated
that the projected MATS capital expenditures in 2015 represented
between 3.6 and 10.4 percent of total annual power sector capital
expenditures when compared to years surrounding the finalization of the
MATS rule. Such an investment by the power sector would comprise a
small percentage of the sector's historical annual capital expenditures
on an absolute basis and also would fall within the range of historical
variability in such capital expenditures. Using data from U.S. Census
Bureau, for example, the year-to-year variability in annual power
sector capital expenditures ranged from a decrease in capital
expenditures of $19.5 billion to an increase of $23.4 billion over this
time (see Table A-5 of the Cost TSD). Similarly, the EPA demonstrated
that the projected capital and operating expenditures in 2015
represented between 4.3 and 6.2 percent of total annual power sector
capital and operating expenditures over 2000 to 2019 and is well within
the substantial range of annual variability. Using

[[Page 13977]]

capital expenditure data from U.S. Census Bureau and production
expenditure data from Hitachi Powergrids Velocity Suite, for example,
the year-to-year variability in annual power sector capital and
operating expenditures ranged from a decrease of $32.8 billion to an
increase of $27.5 billion over this time (see Table A-6 of the Cost
TSD). This action's analysis indicating that far fewer controls were
installed than the EPA had projected is particularly relevant to
considering our findings as to this metric; with the overestimation of
capital expenditures in mind, actual investments by the power sector to
comply with MATS would have comprised an even smaller percentage of
historical annual capital expenditures.
With respect to impacts on the wider public, the EPA examined the
projected impacts on average retail electricity prices and found the
modest increases--which, like overall compliance costs, are also likely
to have been significantly overestimated--to be within the range of
historical variability. Additionally, these small retail price impacts
would have occurred during a period in which national average retail
electricity prices had fallen from 9.10 cents per kilowatt-hour in 2012
to 8.68 cents per kilowatt-hour in 2019 (see Table A-7 of the Cost
TSD). Finally, previous analysis indicated that the vast majority of
the generation capacity in the power sector would remain operational
and that the power sector would be able to comply with the MATS
requirements while maintaining its ability to generate, transmit, and
distribute reliable electricity at reasonable cost to consumers. We
have seen no evidence to contradict those findings.
The EPA is finalizing the determination that each of these analyses
are appropriate bases for evaluating the costs conferred by the MATS-
related projected compliance expenditures. As we note above, even
though the projected costs we use in this analysis are likely
significantly overestimated, we find that they are still relatively
small when placed in the context of the economics of the industry, and
well within historical variations. Again, we received no data or
analysis during the public comment period that alters the conclusions
made in the 2022 Proposal based on the evidence just presented.
4. Other Cost Considerations
We also reaffirm our previous findings regarding the costs of
mercury controls, consistent with the instruction from the statute to
study the availability and cost of such controls in CAA section
112(n)(1)(B). 80 FR 75036-37 (December 1, 2015). We similarly reaffirm
our previous records and findings regarding the cost of controls for
other HAP emissions from EGUs, and the cost of implementing the
utility-specific ARP, which Congress wrote into the 1990 CAA Amendments
and implementation of which Congress anticipated could result in
reductions in HAP emissions. Id. With respect to the costs of
technology for control of mercury and non-mercury HAP, the record
evidence shows that in 2012 controls were available and routinely used
and that control costs had declined considerably over time. Id. at
75037-38. With regard to the ARP, industry largely complied with that
rule by switching to lower-sulfur coal rather than installing more
costly pollution controls, and subsequently the actual costs of
compliance were substantially lower than projected. Though the reasons
for discrepancies between projected and actual costs are different for
MATS than they were for the ARP, as discussed in section III.B.2 above,
the newer information examined as part of this action demonstrates that
the projected cost estimates for MATS were also likely significantly
overestimated.
5. Conclusion
Section III.B.2 summarizes our finding that the 2011 RIA costs were
likely significantly overestimated. Section III.B.3 summarizes our
evaluation of the cost metrics related to MATS compliance, and
concludes that even though the cost estimates we used in this analysis
were likely significantly overestimated, they were relatively small
when placed in the context of the industry's revenues and expenditures,
and well within historical variations. Similarly, we conclude that the
projected impact on average retail electricity price was within the
range of historical variability. We also note in section III.B.3 that
previous analysis indicated that the vast majority of the generation
capacity in the power sector would remain operational and that the
power sector would be able to comply with the MATS requirements while
maintaining its ability to generate, transmit, and distribute reliable
electricity at reasonable cost to consumers. We have seen no evidence
to contradict those findings. In section III.B.4, we reaffirm
additional cost considerations regarding the availability and cost of
control technologies discussed in earlier rulemakings.

C. Revocation of the 2020 Final Action

We are revoking the 2020 Final Action because we find that the
framework used to consider cost in 2020 was ill-suited to making the
appropriate and necessary determination in the context of CAA section
112(n)(1)(A) specifically and the CAA section 112 program generally.
The 2020 Final Action focused on a comparison of costs to monetized HAP
benefits, which was not required nor supported by the statutory text of
CAA section 112(n)(1)(A) and legislative history. Accordingly, we
exercise our discretion to adopt a different approach. We also disagree
with the conclusions presented in the 2020 Final Action as to the 2016
Supplemental Finding's two approaches.
The 2020 Final Action established a three-step framework for making
the appropriate and necessary determination, which it deemed at the
time as the appropriate method for the EPA to determine whether it was
appropriate and necessary to regulate EGUs under CAA section
112(n)(1)(A). Under this framework, the EPA first ``compare[d] the
monetized costs of regulation against the subset of HAP benefits that
could be monetized''; second, it ``consider[d] whether unquantified HAP
benefits may alter that outcome''; and third ``the EPA consider[d]
whether it is appropriate, notwithstanding the above, to determine that
it is `appropriate and necessary' to regulate EGUs under CAA section
112(n)(1)(A) out of consideration for the PM co-benefits that result
from such regulation.'' 85 FR 31302 (May 22, 2020).
Applying the first part of the framework, the EPA noted that the
costs of regulation estimated in the 2011 RIA were disproportionately
higher--by three orders of magnitude--than the monetized HAP benefits,
and concluded ``[t]hat does not demonstrate `appropriate and
necessary.' '' Id. Under the framework's second inquiry, the EPA
determined that the unquantified HAP benefits, even if monetized, were
unlikely to alter its conclusion under the first part of the framework.
Id.; see also 85 FR 31304 (noting that ``valuing HAP-related morbidity
outcomes would not likely result in estimated economic values similar
to those attributed to avoiding premature deaths''). Finally, applying
the third part of its framework, the EPA noted that nearly all of the
monetized benefits of MATS as reflected in the 2011 RIA were derived
from PM benefits. See 85 FR 31302-03 (May 22, 2020). The EPA then
posited that, ``[h]ad the HAP-specific benefits of MATS been closer to
the costs of regulation, a different question might have arisen as to
whether the Administrator could find that co-

[[Page 13978]]

benefits legally form part of the justification for determination that
regulation of EGUs under CAA section 112(d) is appropriate and
necessary.'' See 85 FR 31303 (May 22, 2020). However, because of the
factual scenario presented in the record, the EPA in the 2020 Final
Action stated that ``[t]he EPA does not need to, and does not,
determine whether that additional step would be appropriate . . . given
that the monetized and unquantified HAP-specific benefits do not come
close to a level that would support the prior determination.'' Id. In
conclusion, the EPA stated that ``[u]nder the interpretation of CAA
section 112(n)(1)(A) that the EPA adopts in this action, HAP benefits,
as compared to costs, must be the primary question in making the
`appropriate and necessary' determination.'' Id.
We find that this three-step framework is an unsuitable approach to
making the appropriate and necessary determination under CAA section
112(n)(1)(A) because it places undue primacy on those HAP benefits that
have been monetized, and fails to consider critical aspects of the
inquiry posed to the EPA by Congress in CAA section 112(n)(1). While
the 2020 Final Action purported to consider unquantified HAP benefits
at step 2, it failed to square that consideration with the difficulty
of monetizing and the potential magnitude of these benefits, as
discussed in section III.A.3 above, and with the statutory structure.
Moreover, the 2020 three-step framework also did not in any meaningful
way grapple with the bases upon which the EPA had relied to design the
2016 preferred approach, as discussed above, including the broad
statutory purpose of CAA section 112 to reduce the volume of HAP
emissions with the goal of reducing the risk from HAP emissions to a
level that is protective of even the most exposed and most sensitive
subpopulations; the fact that we rarely can fully characterize or
quantify risks at a nationwide level; the fact that except for one of
the many health endpoints for only one of the many HAP emitted from
EGUs, the EPA lacked the information necessary to monetize any benefit
of reductions in HAP emissions; and the fact that health endpoints and
other key benefits may be highly significant even if they cannot
currently be fully quantified or monetized. The sole rationale provided
in the 2020 Final Action for rejecting the relevance of the statute's
clear purpose as evinced in the broader CAA section 112 program and
reflected in the provisions of CAA section 112(n)(1) was that CAA
section 112(n)(1)(A) is a separate provision and threshold
determination. See 85 FR 31293-94 (May 22, 2020). But we do not think
it is sensible to view the statute's direction to the EPA to make a
separate determination as to EGUs as an invitation to disregard the
statutory factors of CAA section 112(n)(1),the greater statutory
context in which that determination exists, and the urgency with which
Congress directed the EPA to regulate HAP emissions in the 1990
amendments, and we do not think that the 2020 Final Action provided an
adequately reasoned basis for abandoning the interpretation and
assessment provided in the 2016 Supplemental Finding. And in any event,
we believe the methodology we are finalizing in this action is better
suited to making the statutory finding than the 2020 framework.
In the 2020 rulemaking, the EPA did not explain its rationale for
its decision to anchor the appropriate and necessary determination at
step one as a comparison between the monetized costs of regulation and
monetized HAP-specific benefits. Rather, the proposed and final rules
repeatedly state that the ``primary'' inquiry in the determination
should be a comparison of costs and HAP benefits, but did not explain
why only monetized HAP benefits should be given primacy. See, e.g., 85
FR 31286, 31288, 31303 (May 22, 2020). Given the EPA's recognition of
the broad grant of discretion inherent in the phrase ``appropriate and
necessary,'' see 81 FR 24430-31 (April 25, 2016), its acknowledgement
of Congress' ``particularized focus on reducing HAP emissions and
addressing public health and environmental risks from those emissions''
in CAA section 112, see 85 FR 31299 (May 22, 2020), and its knowledge
and recognition that the monetized value of one of its points of
comparison represented but a small subset of the advantages of
regulation, see 85 FR 31302 (May 22, 2020), we now believe it was
inappropriate to adopt a framework that first and foremost compared
monetized value to monetized value alone. Nothing in the CAA or the
Supreme Court's decision in Michigan v. EPA required the EPA's decision
in 2020 to hinge its framework on monetized HAP benefits.
The EPA's consideration of the non-monetized benefits of MATS in
2020 (i.e., the various endpoints discussed in section III.A, including
virtually all of the HAP benefits associated with this final action)
occurred only at step two, where the EPA considered whether the
unquantified benefits, if monetized, were ``likely to overcome the
imbalance between the monetized HAP benefits and compliance costs in
the record.'' See 85 FR 31296 (May 22, 2020). This approach undervalues
the vast array of adverse health and environmental impacts associated
with HAP emissions from coal- and oil-fired EGUs that have been
enumerated by the EPA \52\ and the social value (benefit) of avoiding
those impacts through regulation by considering them at a second-step
of the framework and summarily dismissing such impacts and benefits as
unlikely to overcome costs without sufficient analysis. Indeed, while
the 2020 Final Action claimed that unquantified HAP benefits associated
with regulating EGUs were significant, as discussed further below, it
disregarded certain health and welfare risks associated with HAP
emissions and gave incomplete consideration to others.
---------------------------------------------------------------------------

\52\ See, e.g., 65 FR 79829-30 (December 20, 2000); 76 FR 24983-
85, 24993-97, 24999-25001, 25003-14, 25015-19 (May 3, 2011).
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Further, the three-step framework gave no consideration to the
important statutory objective of protecting the most at-risk
subpopulations. As noted above, throughout CAA section 112, Congress
placed special emphasis on regulating HAP from sources to levels that
would be protective of those individuals most exposed to HAP emissions
and most sensitive to those exposures as discussed in section II.B.2
above. The rigid and narrow approach to making the appropriate and
necessary determination in the 2020 Final Action is at odds with the
text and purpose of CAA section 112, and is certainly not required
under the express terms of CAA section 112 or CAA section 112(n)(1)(A).
We note as well that the three-step framework employed by the 2020
Final Action is not a formal BCA conforming to recognized principles
(see, e.g., OMB Circular A-4,\53\ EPA Guidelines for Preparing Economic
Analyses \54\). BCA is a specific tool developed by economists to
assess total society-wide benefits and costs, to determine the economic
efficiency of a given action. Instead of conforming to this
comprehensive approach, the first step--and, as applied in the 2020
Final Action, the most important step--of the three-step framework
focused primarily

[[Page 13979]]

on comparing the rule's total costs to a very small subset of HAP
benefits that could be monetized. The EPA largely dismissed and at most
gave only secondary weight to the vast majority of the benefits of
regulating HAP emissions from stationary sources that cannot currently
be quantified, and completely ignored the non-HAP monetized benefits
directly attributable to the MATS rule which was contrary to both
economic principles for cost-benefit analysis and the Supreme Court's
direction to consider ``all the relevant factors'' in making the
appropriate and necessary finding. Michigan v. EPA, 576 U.S. at 752.
---------------------------------------------------------------------------

\53\ U.S. OMB. 2003. Circular A-4 Guidance to Federal Agencies
on Preparation of Regulatory Analysis. Available at <a href="https://www.whitehouse.gov/wp-content/uploads/legacy_drupal_files/omb/circulars/A4/a-4.pdf">https://www.whitehouse.gov/wp-content/uploads/legacy_drupal_files/omb/circulars/A4/a-4.pdf</a>, accessed September 2, 2022.
\54\ U.S. EPA. 2014. Guidelines for Preparing Economic Analyses.
EPA-240-R-10-001. National Center for Environmental Economics,
Office of Policy. Washington, DC. December. Available at <a href="https://www.epa.gov/environmental-economics/guidelines-preparing-economic-analyses">https://www.epa.gov/environmental-economics/guidelines-preparing-economic-analyses</a>, accessed July 23, 2021.
---------------------------------------------------------------------------

Commenters on the 2019 Proposal (84 FR 2670 (February 7, 2019))
objected strenuously to the EPA's revised framework for making the
appropriate and necessary determination, arguing that the 2019
Proposal's interpretation ``fails to meaningfully address factors that
are `centrally relevant' to the inquiry of whether it is appropriate
and necessary to regulate HAP from EGUs,'' and that the EPA's new
interpretation must fall because the EPA failed to provide a reasoned
explanation for its change in policy, as required by Motor Vehicle
Mfrs. Ass'n of United States, Inc. v. State Farm Mut. Automobile Ins.
Co., 463 U.S. 29 (1983), and FCC v. Fox Television Stations, Inc., 556
U.S. 502 (2009). See 85 FR 31294 (May 22, 2020). Among the factors that
commenters argued had been inadequately addressed under the new
framework were the ``hazards to public health reasonably anticipated to
occur'' that had not been monetized; the non-monetizable benefits of
HAP regulation such as the latency, persistence in the environment, and
toxicity of HAP as recognized by Congress; the distributional impacts
on particular communities and individuals most impacted by HAP emitted
from power plants; and preservation of tribal social practices. In
responses to these comments, the EPA claimed that it was not
``disregarding'' or ``dismissing'' the concerns raised by the
commenters, but rather simply weighing them differently, and explained
that the Administration's changed priorities provided the ``reasoned
basis'' for its changed interpretation. See 85 FR 31296-97 (May 22,
2020).
Agencies do have broad discretion to re-evaluate policies and
change their ``view of what is in the public interest,'' State Farm,
463 U.S. at 57, but such re-evaluations must still adhere to principles
of reasoned decision-making. The 2020 Final Action did not aver that
the statute prohibited the EPA from considering the factors commenters
identified in making its appropriate and necessary determination, e.g.,
non-monetized benefits. Instead, the EPA stated that it was permitted
to pick its decisional framework and admitted that its decisional
framework might undervalue certain factors. For example, with respect
to commenters' concerns that the revised appropriate and necessary
framework did not adequately account for adverse impacts on tribal
culture or undue concentration of public health risks on certain
population subgroups or individuals, the EPA stated: ``In a cost-
benefit comparison, the overall amount of the benefits stays the same
no matter what the distribution of those benefits is.'' 85 FR 31297
(May 22, 2020). There, the EPA found it ``reasonable to conclude that
those factors to which the EPA previously gave significant weight-
including qualitative benefits, and distributional concerns and impacts
on minorities-will not be given the same weight in a comparison of
benefits and costs for this action under CAA section 112(n)(1)(A).''
The decisional framework in the 2020 Final Action, however, did not
give ``less weight'' to these factors--it effectively gave them none.
In both the selection and application of its framework, the EPA in the
2020 Final Action effectively ignored these factors altogether, and we
do not agree that the inability to monetize a factor should render it
unimportant. Cf. Am. Trucking Ass'ns, Inc. v. EPA, 175 F.3d 1027, 1052-
53 (D.C. Cir. 1999), reversed in part on other grounds in Whitman v.
Am. Trucking Ass'ns, 531 U.S. 457 (2001) (holding that the EPA was not
permitted to ignore information ``because the . . . benefits are
difficult, if not impossible, to quantify reliably and because there is
`no convincing basis for concluding that any such effects . . . would
be significant' ''); Pub. Citizen v. Fed. Motor Carrier Safety Admin.,
374 F.3d 1209, 1219 (D.C. Cir. 2004) (``The mere fact that the
magnitude of . . . effects is uncertain is no justification for
disregarding the effect entirely.'') (emphasis in original). The mere
mention and summary dismissal of factors does not constitute meaningful
consideration of those factors.
In the 2020 Final Action, like the 2016 Supplemental Finding before
it, the EPA maintained that there is more than one permissible way to
interpret the EPA's obligation to consider cost in the appropriate and
necessary determination. Given the EPA's knowledge of the significant
risks and often irreversible impacts of HAP exposure on vulnerable
populations like developing fetuses, the disproportionate impact of EGU
HAP emissions on communities who subsist on freshwater fish due to
cultural practices and/or economic necessity, and the record of data
demonstrating risks to public health amassed over decades, and, perhaps
more importantly, the overwhelming quantity of advantages to regulation
that could not be monetized, we do not think that selecting a framework
that compared first and foremost monetized HAP benefits alone with
costs was appropriate. And even if the framework ultimately addressed
the statutorily relevant factors because at the second step the EPA
``acknowledged'' these benefits and claimed they were ``relevant,'' we
think that the application of that second step fell short, and that the
framework we propose in this document is a more appropriate framework
for making the determination of appropriateness.
The secondary consideration of non-monetized HAP benefits in the
three-step framework only considered HAP-related impacts of regulation
insofar as the EPA speculated about what the monetized value of those
benefits might be. See 85 FR 31296 (May 22, 2020) (asserting that
monetized value of avoiding morbidity effects such as neurobehavioral
impacts is ``small'' compared to monetized value associated with
avoided deaths). The EPA did not, at this second step, grapple with the
existing risk analyses, including those stemming from the statutorily
mandated studies in CAA section 112(n)(1). Those analyses demonstrated
substantial public health and environmental hazards, even if the
hazards were not translated into monetized benefits. See White
Stallion, 748 F.3d at 1245. While the EPA alluded to some of these
risks, the EPA in 2020 ignored important health and welfare hazards
documented in the record. For example, endpoints such as delayed infant
brain development, increased potential for acute and chronic lung and
kidney disorders, as well as adverse effects on wildlife and essential
ecosystem services were not acknowledged in the 2020 second step
determination. And even for those risks it did consider, that
consideration was incomplete. For example, the 2020 Final Action
concluded that any benefits accruing to a reduction in premature
mortality as a result of reduced HAP emissions was unlikely to be
significant. As discussed in section III.A.3 above, and in more detail
in the 2021 Risk TSD, recent analyses performed by the EPA conclude
that the benefit of avoiding such effects for a single endpoint
(avoided MI deaths for the general U.S.

[[Page 13980]]

population from mercury exposure through fish consumption) could be as
high as $720 million per year.
The EPA also did not explain why other attributes of risk--such as
impacts on vulnerable populations, which the EPA is considering in this
rulemaking as discussed in section III.A, and the reality that HAP
emissions from EGUs are not distributed equally across the population
but disproportionately impacts some individuals and communities far
more than others--were unimportant, stating only that the selected
framework did not accommodate consideration of those factors. The EPA
did not acknowledge in any way the importance the statute places on
these effects, which is discussed in section II.B.2 above.
As noted, the EPA did not point to anything in the CAA as
supporting the use of its three-step framework. This is in stark
contrast to the 2016 Supplemental Finding rulemaking, in which the EPA
examined CAA section 112(n)(1)(A) and the other section 112(n)(1)
provisions, and the rest of CAA section 112 generally, and D.C. Circuit
case law on CAA cost considerations to inform the EPA's interpretation
of CAA section 112(n)(1)(A). See 80 FR 75030 (December 1, 2015); 2015
Legal Memorandum. In the 2020 Final Action, the EPA merely asserted
that a comparison of benefits to costs is ``a traditional and
commonplace way to assess costs'' and claimed that the Supreme Court's
holding in Entergy Corp. v. Riverkeeper, 556 U.S. 208 (2009) supported
the EPA's 2020 position that, absent an unambiguous prohibition to use
a BCA, an agency may generally rely on a BCA as a reasonable way to
consider cost. See 85 FR 31293 (May 22, 2020). The 2020 Final Action
also pointed out ``many references comparing'' costs and benefits from
the Michigan decision, including: ``EPA refused to consider whether the
costs of its decision outweighed the benefits'' (576 U.S. at 743);
``[o]ne would not say that it is rational, never mind `appropriate,' to
impose billions of dollars in economic costs in return for a few
dollars in health or environmental benefits'' (Id. at 752); and ``[n]o
regulation is `appropriate' if it does more harm than good'' (Id.).
But while we agree that a comparison of benefits to costs is a
traditional way to assess costs, the 2020 framework was not a BCA as
understood in the economics literature and in OMB and EPA guidance.
There is no economic theory or guidance of which we are aware that
endorses the approach to comparing certain benefits to costs presented
in the 2020 Final Action, in which the first--and, as applied, most
important--step entails comparing total costs with a small subset of
total benefits. See section III.E for further discussion. Moreover,
general support for weighing costs and benefits does not justify
placing undue weight on monetized HAP benefits, with secondary
consideration for all other benefits for which monetary values cannot
be calculated. As noted in Justice Breyer's concurrence in Entergy
Corp., the EPA has the ability ``to describe environmental benefits in
non-monetized terms and to evaluate both costs and benefits in
accordance with its expert judgment and scientific knowledge,'' and to
engage in this balancing out

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