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Proposed Rule2022-02343

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

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Published

February 9, 2022

Issuing agencies

Environmental Protection Agency

Abstract

The EPA is proposing to revoke 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 to reaffirm the Agency's April 25, 2016 finding that it remains appropriate and necessary to regulate hazardous air pollutant (HAP) emissions from EGUs after considering cost. The Agency is also reviewing another part of the May 22, 2020 action, a residual risk and technology review (RTR) of Mercury and Air Toxics Standards (MATS). Accordingly, in addition to soliciting comments on all aspects of this proposal, the EPA is soliciting information on the performance and cost of new or improved technologies that control HAP emissions, improved methods of operation, and risk-related information to further inform the Agency's review of the MATS RTR as directed by Executive Order 13990.

Full Text

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<title>Federal Register, Volume 87 Issue 27 (Wednesday, February 9, 2022)</title>
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[Federal Register Volume 87, Number 27 (Wednesday, February 9, 2022)]
[Proposed Rules]
[Pages 7624-7673]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2022-02343]

[[Page 7623]]

Vol. 87

Wednesday,

No. 27

February 9, 2022

Part III

Environmental Protection Agency

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40 CFR Part 63

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; Proposed Rule

Federal Register / Vol. 87 , No. 27 / Wednesday, February 9, 2022 /
Proposed Rules

[[Page 7624]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2018-0794; FRL-6716.2-01-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; Notice of Proposed Rulemaking

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The EPA is proposing to revoke 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 to reaffirm the Agency's April 25, 2016 finding
that it remains appropriate and necessary to regulate hazardous air
pollutant (HAP) emissions from EGUs after considering cost. The Agency
is also reviewing another part of the May 22, 2020 action, a residual
risk and technology review (RTR) of Mercury and Air Toxics Standards
(MATS). Accordingly, in addition to soliciting comments on all aspects
of this proposal, the EPA is soliciting information on the performance
and cost of new or improved technologies that control HAP emissions,
improved methods of operation, and risk-related information to further
inform the Agency's review of the MATS RTR as directed by Executive
Order 13990.

DATES: Comments must be received on or before April 11, 2022.
Public hearing: The EPA will hold a virtual public hearing on
February 24, 2022. See SUPPLEMENTARY INFORMATION for information on the
hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2018-0794, by any of the following methods:
<bullet> Federal eRulemaking Portal: <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>
(our preferred method). Follow the online instructions for submitting
comments.
<bullet> Email: <a href="/cdn-cgi/l/email-protection#3d5c105c5359104f1059525e5658497d584d5c135a524b">[email&#160;protected]</a>. Include Docket ID No. EPA-
HQ-OAR-2018-0794 in the subject line of the message.
<bullet> Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2018-0794.
<bullet> Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2018-0794, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
<bullet> Hand/Courier Delivery: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except Federal holidays).
Instructions: All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the SUPPLEMENTARY
INFORMATION section of this document. Out of an abundance of caution
for members of the public and our staff, the EPA Docket Center and
Reading Room are closed to the public, with limited exceptions, to
reduce the risk of transmitting COVID-19. Our Docket Center staff will
continue to provide remote customer service via email, phone, and
webform. We encourage the public to submit comments via <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> or email, as there may be a delay in processing
mail and faxes. Hand deliveries and couriers may be received by
scheduled appointment only. For further information on EPA Docket
Center services and the current status, please visit us online at
<a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
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#42292b2c256c2f272e232c2b27022732236c252d34">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION: The EPA is proposing to revoke a May 22,
2020 finding that it is not appropriate and necessary to regulate coal-
and oil-fired EGUs under CAA section 112, and to reaffirm the Agency's
April 25, 2016 finding 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 Agency had erred by not
taking cost into consideration when taking action on February 16, 2012,
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.
Based on a re-evaluation of the administrative record and the
statute, the EPA proposes to conclude that the framework applied in the
May 22, 2020 finding was ill-suited to assessing and comparing the full
range of benefits to costs, and the EPA concludes that, after applying
a more suitable framework, the 2020 determination should be withdrawn.
For reasons explained in this notice, the EPA further proposes to
reaffirm that it is appropriate and necessary to regulate HAP emissions
from 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 EGU industry and its ability to provide reliable
and affordable electricity. This notice also presents information and
analysis that has become available since the 2016 finding, pertaining
to the health risks of mercury emissions and the costs of reducing HAP
emissions, that lend further support for this determination.
The review that led to this proposal is consistent with the
direction in Executive Order 13990, ``Protecting Public Health and the
Environment and Restoring Science to Tackle the Climate Crisis,''
signed by President Biden on January 20, 2021. In response to the
Executive Order, the Agency is also reviewing another part of the May
22, 2020 action, a RTR of MATS. Accordingly, in addition to soliciting
comments on all aspects of this proposal, the EPA is soliciting
information on the performance and cost of new or improved technologies
that control HAP emissions, improved methods of operation, and risk-
related information to further inform the Agency's review of the MATS
RTR as directed by the Executive Order. Results of the EPA's review of
the RTR will be presented in a separate action.
Participation in virtual public hearing. Please note that the EPA
is deviating from its typical approach for public hearings because the
President has declared a national emergency. Due to the current Centers
for Disease Control and Prevention (CDC) recommendations, as well as
state and local orders for social distancing to limit the spread of
COVID-19, the EPA

[[Page 7625]]

cannot hold in-person public meetings at this time.
The virtual public hearing will be held via teleconference on
February 24, 2022 and will convene at 10:00 a.m. Eastern Time (ET) and
will conclude at 7:00 p.m. ET. The EPA may close a session 15 minutes
after the last pre-registered speaker has testified if there are no
additional speakers. For information or questions about the public
hearing, please contact the public hearing team at (888) 372-8699 or by
email at <a href="/cdn-cgi/l/email-protection#d685868692a6a3b4babfb5beb3b7a4bfb8b196b3a6b7f8b1b9a0">[email&#160;protected]</a>. The EPA will announce further
details 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>.
The EPA will begin pre-registering speakers for the hearing no
later than 1 business day following publication of this document in the
Federal Register. The EPA will accept registrations on an individual
basis. To register to speak at the virtual hearing, please use the
online registration form available 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> or contact the
public hearing team at (888) 372-8699 or by email at
<a href="/cdn-cgi/l/email-protection#f8aba8a8bc888d9a94919b909d998a91969fb89d8899d69f978e">[email&#160;protected]</a>. The last day to pre-register to speak at the
hearing will be February 18, 2022. Prior to the hearing, the EPA will
post a general agenda that will list pre-registered speakers in
approximate order 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>.
The EPA will make every effort to follow the schedule as closely as
possible on the day of the hearing; however, please plan for the
hearings to run either ahead of schedule or behind schedule.
Each commenter will have 5 minutes to provide oral testimony. The
EPA encourages commenters to provide the EPA with a copy of their oral
testimony electronically (via email) by emailing it to
<a href="/cdn-cgi/l/email-protection#e18a888f86cf8c848d808f8884a1849180cf868e97">[email&#160;protected]</a>. The EPA also recommends submitting the text of
your oral testimony as written comments to the rulemaking docket.
The EPA may ask clarifying questions during the oral presentations
but will not respond to the presentations at that time. Written
statements and supporting information submitted during the comment
period will be considered with the same weight as oral testimony and
supporting information presented at the public hearing.
Please note that any updates made to any aspect of the hearing will
be posted online 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>. While the EPA expects the
hearing to go forward as set forth above, please monitor our website or
contact the public hearing team at (888) 372-8699 or by email at
<a href="/cdn-cgi/l/email-protection#3c6f6c6c784c495e50555f54595d4e55525b7c594c5d125b534a">[email&#160;protected]</a> to determine if there are any updates. The
EPA does not intend to publish a document in the Federal Register
announcing updates.
If you require the services of a translator or a special
accommodation such as audio description, please pre-register for the
hearing with the public hearing team and describe your needs by
February 16, 2022. The EPA may not be able to arrange accommodations
without advanced notice.
Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2018-0794.\1\ 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>.
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\1\ 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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Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2018-0794. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit electronically any information that you consider
to be CBI or other information whose disclosure is restricted by
statute. This type of information should be submitted by mail as
discussed below.
The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
The <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
<a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, your email address will be automatically
captured and included as part of the comment that is placed in the
public docket and made available on the internet. If you submit an
electronic comment, the EPA recommends that you include your name and
other contact information in the body of your comment and with any
digital storage media you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should not include special characters or any form of encryption and be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at <a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.
The EPA is temporarily suspending its Docket Center and Reading
Room for public visitors, with limited exceptions, to reduce the risk
of transmitting COVID-19. Our Docket Center staff will continue to
provide remote customer service via email, phone, and webform. We
encourage the public to submit comments via <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> as there may be a delay in processing mail and
faxes. Hand deliveries or couriers will be received by scheduled
appointment only. For further information and updates on EPA Docket
Center services, please visit us online at <a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.
The EPA continues to carefully and continuously monitor information
from the CDC, local area health departments, and our Federal partners
so that we can respond rapidly as conditions change regarding COVID-19.
Submitting CBI. Do not submit information containing CBI to the EPA

[[Page 7626]]

through <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> or email. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information on
any digital storage media that you mail to the EPA, mark the outside of
the digital storage media as CBI and then identify electronically
within the digital storage media the specific information that is
claimed as CBI. In addition to one complete version of the comments
that includes information claimed as CBI, you must submit a copy of the
comments that does not contain the information claimed as CBI directly
to the public docket through the procedures outlined in Instructions
above. If you submit any digital storage media that does not contain
CBI, mark the outside of the digital storage media clearly that it does
not contain CBI. Information not marked as CBI will be included in the
public docket and the EPA's electronic public docket without prior
notice. Information marked as CBI will not be disclosed except in
accordance with procedures set forth in title 40 of the Code of Federal
Regulations (CFR) part 2. Send or deliver information identified as CBI
only to the following address: OAQPS Document Control Officer (C404-
02), OAQPS, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2018-
0794. Note that written comments containing CBI and submitted by mail
may be delayed and no hand deliveries will be accepted.
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:

ACI activated carbon injection
ATSDR Agency for Toxic Substances and Disease Registry
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
CFR Code of Federal Regulations
CVD cardiovascular disease
DSI dry sorbent injection
EGU electric utility steam generating unit
EIA Energy Information Administration
EPA Environmental Protection Agency
ESP electrostatic precipitator
EURAMIC European Multicenter Case-Control Study on Antioxidants,
Myocardial Infarction, and Cancer of the Breast Study
FF fabric filter
FGD flue gas desulfurization
FR Federal Register
GW gigawatt
HAP hazardous air pollutant(s)
HCl hydrogen chloride
HF hydrogen fluoride
IHD ischemic heart disease
IPM Integrated Planning Model
IRIS Integrated Risk Information System
KIHD Kuopio Ischaemic Heart Disease Risk Factor Study
kW kilowatt
MACT maximum achievable control technology
MATS Mercury and Air Toxics Standards
MI myocardial infarction
MIR maximum individual risk
MW megawatt
NAS National Academy of Sciences
NESHAP national emission standards for hazardous air pollutants
OMB Office of Management and Budget
O&M operation and maintenance
PM particulate matter
PUFA polyunsaturated fatty acid
RfD reference dose
RIA regulatory impact analysis
RTR residual risk and technology review
SCR selective catalytic reduction
SO2 sulfur dioxide
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?
II. Background
A. Regulatory History
B. Statutory Background
III. Proposed Determination Under CAA Section 112(n)(1)(A)
A. Public Health Hazards Associated With Emissions From EGUs
B. Consideration of Cost of Regulating EGUs for HAP
C. Revocation of the 2020 Final Action
D. The Administrator's Proposed Preferred Framework and Proposed
Conclusion
E. The Administrator's Proposed Benefit-Cost Analysis Approach
and Proposed Conclusion
IV. Summary of Cost, Environmental, and Economic Impacts
V. Request for Comments and for Information To Assist With Review of
the 2020 RTR
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

I. General Information

A. Executive Summary

On January 20, 2021, President Biden 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, instructs 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
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, the Agency proposes to find 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. Therefore, we propose to revoke the May 2020 determination
that it is not appropriate and necessary to regulate HAP emissions from
coal- and oil-fired EGUs under section 112 of the CAA. We further
propose 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.
In 1990, frustrated with the EPA's pace in identifying and
regulating HAP, Congress radically transformed its treatment of that
pollution. It rewrote section 112 of the CAA to require the EPA to
swiftly regulate 187 HAP with technology-based standards that would
require all major sources (defined by the quantity of pollution a
facility has the potential to emit) to meet the levels of reduction
achieved in practice by the best-performing similar sources. EGUs were
the one major source category excluded from automatic application of
these new standards. EGUs were treated differently primarily because
the 1990

[[Page 7627]]

Amendments to the CAA (1990 Amendments) included the Acid Rain Program
(ARP), which imposed criteria pollution reduction requirements on EGUs.
Congress recognized that the controls necessary to comply with this and
other requirements of the 1990 Amendments might reduce HAP emissions
from EGUs as well. Therefore, under CAA section 112(n)(1)(A), Congress
directed the EPA to regulate EGUs if, after considering a study of
``the hazards to public health reasonably anticipated to occur as a
result of [HAP] emissions by [EGUs] . . . after imposition of the [Acid
Rain Program and other] requirements of this chapter,'' the EPA
concluded that it ``is appropriate and necessary'' to do so. See CAA
section 112(n)(1)(A).
The EPA completed that study in 1998 and, in 2000, concluded that
it is appropriate and necessary to regulate HAP emissions from coal-
and oil-fired EGUs. See 65 FR 79825 (December 20, 2000). The EPA
reaffirmed that conclusion in 2012, explaining that the other
requirements of the CAA, in particular the ARP, did not lead to the HAP
emission reductions that had been anticipated because many EGUs
switched to lower-sulfur coal rather than deploy pollution controls
that may have also reduced emissions of HAP. Indeed, the statute
contemplated that the EPA would be conducting the required study within
3 years of the 1990 Amendments; but when the EPA re-examined public
health hazards remaining after imposition of the Act's requirements in
2012, the Agency accounted for over 20 years of CAA regulation, and
EGUs still remained one of the largest sources of HAP pollution.
Specifically, in 2012, the EPA concluded that EGUs were the largest
domestic source of emissions of mercury, hydrogen fluoride (HF),
hydrogen chloride (HCl), and selenium; and among the largest domestic
contributors of emissions of arsenic, chromium, cobalt, nickel,
hydrogen cyanide, beryllium, and cadmium. The EPA further found that a
significant majority of EGUs were located at facilities that emitted
above the statutory threshold set for major sources (e.g., 10 tons per
year (tpy) of any one HAP or 25 tpy or more of any combination of HAP).
See 77 FR 9304 (February 16, 2012). In 2012, the EPA also established
limits for emissions of HAP from coal- and oil-fired EGUs. Id.
Many aspects of the EPA's appropriate and necessary determination
and the CAA section 112 regulations were challenged in the U.S. Court
of Appeals for the District of Columbia Circuit (D.C. Circuit), and all
challenges were denied and the finding and standards upheld in full in
White Stallion Energy Center v. EPA, 748 F.3d 1222 (2014). The Supreme
Court granted review on a single issue and, in Michigan v. EPA, 576
U.S. 743 (2015), the Court held that the EPA erred when it failed to
consider the costs of its regulation in determining that it is
appropriate and necessary to regulate HAP emissions from EGUs, and
remanded that determination to the D.C. Circuit for further
proceedings. Following Michigan, in 2016 the EPA issued a Supplemental
Finding that it is appropriate and necessary to regulate EGU HAP after
considering the costs of such regulation. See 81 FR 24420 (April 25,
2016). In 2020, the Agency reversed that determination.\2\ 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, including many
adverse health and environmental effects of EGU HAP emissions that
cannot be quantified or monetized. We propose, therefore, to revoke the
2020 Final Action.
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\2\ 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 Agency's prior
determination that it was necessary to regulate. See 84 FR 2674
(February 7, 2019). Instead, the 2020 rulemaking stated that its
rescission was based on the appropriate prong alone: ``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.''
Id.
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We further propose to affirm, once again, that it is appropriate
and necessary to regulate coal- and oil-fired EGUs under CAA section
112. We first examine the benefits or advantages of regulation,
including new information on the risks posed by EGU HAP. We then
examine the costs or 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 benefits and costs to reach the conclusion that it is
appropriate and necessary to regulate using two alternative
methodologies.
Our preferred methodology, as it was in the 2016 Supplemental
Finding, is to consider all of the impacts of the regulation--both
costs and benefits to society--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 all-encompassing term that naturally includes consideration of
all 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 be quantified or monetized,
and we explain why almost none of those advantages can be monetized.
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 required swift reduction of the volume of HAP emissions based on
an assumption of risk, we conclude that we should place substantial
weight on reducing the large volume of HAP emissions from EGUs--both in
absolute terms and relative to other source categories--that, absent
MATS, was entering our air, water, and land, thus 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 those
benefits, 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 communities that are reliant on local
fish for their survival, and developing fetuses. We think it is highly
relevant that while EGUs generate power for all, and EGU HAP pollution
poses risks to all Americans exposed to such HAP, a smaller set of
Americans 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

[[Page 7628]]

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. 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, 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 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 thrive and to provide reliable, affordable electricity to
the benefit of all Americans. 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). Per CAA section
112(n)(1)(B), we further consider the availability and cost of control
technologies, including the relationship of that factor to controls
installed under the ARP.
As explained in detail in this document, we ultimately propose to
conclude that, weighing the risks posed by HAP emissions from EGUs
against the costs of reducing that pollution on the industry and
society as a whole, it is worthwhile (i.e., ``appropriate'') to
regulate those emissions to protect all Americans, and in particular
the most vulnerable populations, from the inherent risks posed by
exposure to HAP emitted by coal- and oil-fired EGUs. We propose to find
that this is true whether we are looking at the record in 2016 (i.e.,
information available as of the time of the 2012 threshold finding and
rulemaking) or at the updated record in 2021, in which we quantify
additional risks posed by HAP emissions from EGUs and conclude that the
actual cost of complying with MATS was almost certainly significantly
less than the EPA's projected estimate in the 2011 RIA, primarily
because fewer pollution controls were installed than projected and
because the unexpected increases in natural gas supply led to a
dramatic decrease in the price of natural gas.
In the 2016 Supplemental Finding we did not consider non-HAP health
benefits that occur by virtue of controlling HAP from EGUs as a
relevant factor for our consideration under the preferred approach.
However, because the Supreme Court in Michigan directed us to consider
health and environmental effects beyond those posed by HAP,
``including, for instance, harms that regulation might do to human
health or the environment,'' and stressed that ``[n]o regulation is
`appropriate' if it does significantly more harm than good,'' 576 U.S.
at 752, we take comment on whether it is reasonable to also consider
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, we found that
regulating EGUs for HAP resulted in substantial health benefits
accruing from coincidental reductions in particulate matter (PM)
pollution and its precursors. We also projected that regulating EGUs
for HAP would similarly result in an improvement in ozone pollution.
While we propose to reach the conclusion that HAP regulation is
appropriate even absent consideration of these additional benefits,
adding these advantages to the weighing inquiry would provide further
support for our proposed 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 in 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 we think it is a
reasonable approach where the factors the statute identifies as
important to consider cannot be quantified or monetized.
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
Regulatory Impacts Analysis (2011 RIA) \3\ performed as part of the
2012 MATS Final Rule, the total net benefits of MATS were overwhelming
even though the EPA was only able to monetize one of the many 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 the actual costs of implementing
MATS, which almost certainly were significantly lower than estimated in
the 2011 RIA.
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\3\ 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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Our proposal is organized as follows. In section II.A of this
preamble, we provide as background the regulatory and procedural
history leading up to this proposal. 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 of HAP emissions from stationary sources as much as possible and
quickly, 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.
Against this backdrop, we propose to revoke the 2020 Final Action
and reaffirm the 2016 determination that it remains appropriate to
regulate HAP emissions from EGUs after a consideration of cost.
Specifically, in section III.A of this preamble, we review the long-
standing and extensive body of evidence, as well as new mercury-related
risk analyses performed since 2016, identifying substantial risks to
human health and the environment from HAP emissions from coal- and oil-
fired EGUs that support a conclusion that regulating HAP emissions from
EGUs is appropriate. In preamble section III.B, we analyze information
regarding how the power sector elected to comply with MATS, and how our
2012 projections for the cost of regulation almost certainly
overestimated the actual costs of the regulation by a significant
amount. In preamble section III.C, we explain our reasons for revoking
the 2020 Final Action, which applied an ill-suited framework for
evaluating cost because it gave little to no weight to the statutory
concern with reducing the volume of and risks from HAP emissions to
protect even the most exposed and most vulnerable members of the
public. In section III.D of this preamble, we describe and apply our
preferred, totality-of-the-circumstances approach, giving particular
weight to the factors identified in CAA section 112(n)(1) and 112 more
generally. We propose to conclude that after considering all of the

[[Page 7629]]

relevant factors and weighing the advantages of regulation against the
cost of doing so, it is appropriate and necessary to regulate EGUs
under CAA section 112. In section III.E of this preamble, we propose an
alternative formal benefit-cost approach for making the appropriate and
necessary determination. Under this approach, we propose to conclude
that it remains appropriate to regulate HAP emissions from EGUs after
considering cost because the BCA issued with the MATS rule indicated
that the total net benefits of MATS were overwhelming even though the
EPA was only able to monetize one of many statutorily identified
benefits of regulating HAP emissions from EGUs. The new information
examined by the EPA with respect to updated science and cost
information only strengthens our conclusions under either of these
methodologies. Section IV of this preamble notes that because this
proposal reaffirms prior determinations and does not impact
implementation of MATS, this action, if finalized, would not change
those standards.
Finally, in preamble section V, in addition to soliciting comments
on all aspects of this proposed action, we separately seek comment on
any data or information that will assist in the EPA's ongoing review of
the RTR that the Agency completed for MATS in 2020.

B. Does this action apply to me?

The source category that is the subject of this proposal is Coal-
and Oil-Fired EGUs regulated by NESHAP under 40 CFR 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 proposed 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 proposed 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 proposal and key
technical documents at this same website.

II. Background

A. Regulatory History

In the 1990 Amendments, Congress substantially modified CAA section
112 to address hazardous air pollutant 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 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.\4\ 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 every
source category on the CAA section 112(c)(1) list.
---------------------------------------------------------------------------

\4\ The statute includes a separate definition of ``EGU'' that
includes both major and area source power plant facilities. CAA
section 112(a)(8).
---------------------------------------------------------------------------

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 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),
therefore, sets a unique process by which the Administrator is to
determine 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 the Study of Hazardous Air Pollutant Emissions from
Electric Utility Steam Generating Units-Final Report to Congress
(Utility Study).\5\ 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. The
second study commissioned by Congress under CAA section 112(n)(1)(B),
the Mercury Study Report to Congress (Mercury Study),\6\ was released
in 1997. Under this provision, the statute tasked the EPA with focusing
exclusively on mercury, but directed the Agency to look at other
stationary sources of mercury emission 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),

[[Page 7630]]

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. NIEHS submitted the required study to Congress in
1995.\7\ See 76 FR 24982 (May 3, 2011). 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),\8\ and it presented
a rigorous peer-review of the EPA's RfD for methylmercury. 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).\9\
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\5\ 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.
\6\ U.S. EPA. 1997. Mercury Study Report to Congress. EPA-452/R-
97-003 December 1997.
\7\ National Institute of Environmental Health Sciences (NIEHS)
Report on Mercury; available in the rulemaking docket at EPA-HQ-OAR-
2009-0234-3053.
\8\ 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.
\9\ 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 D.C. Circuit in 2008. New Jersey v. EPA, 517 F.3d
574 (DC Cir. 2008). The D.C. Circuit 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
health effects associated with mercury (2011 Final Mercury TSD) \10\
and non-mercury metal HAP emissions from EGUs (2011 Non-Hg HAP
Assessment).\11\ 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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\10\ 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).
\11\ 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.\12\ 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.
---------------------------------------------------------------------------

\12\ 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>.
---------------------------------------------------------------------------

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 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 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

[[Page 7631]]

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 63, subpart UUUUU.\13\ 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.
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\13\ Available at <a href="http://www.ecfr.gov/cgi-bin/text-idx?node=sp40.15.63.uuuuu">www.ecfr.gov/cgi-bin/text-idx?node=sp40.15.63.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. In White Stallion Energy Center v. EPA, the D.C.
Circuit unanimously denied all challenges to MATS, with one exception
discussed below in which the court was not unanimous. 748 F.3d 1222
(D.C. Cir. 2014). As part of its decision, the D.C. Circuit 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.\14\ While joining the D.C. Circuit's conclusions as to the
adequacy of the EPA's identification of public health hazards, one
judge dissented on the issue of whether the EPA erred by not
considering costs together with the harms of HAP pollution 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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\14\ 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 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 U.S. Supreme 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 U.S. Supreme 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 D.C. Circuit
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).
In response to the U.S. Supreme 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 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. The evaluation of
cost metrics that the EPA applied was consistent with approaches
commonly used to evaluate environmental policy cost impacts.\15\ 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. Using a totality-of-the-circumstances approach, the EPA weighed
these supplemental findings as to 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 remains 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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\15\ 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>).
---------------------------------------------------------------------------

In a second alternative and independent approach (referred to as
the alternative approach), the EPA considered the BCA 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 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. 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 D.C. Circuit 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 D.C. Circuit ordered that the
consolidated challenges to the 2016

[[Page 7632]]

Supplemental Finding be held in abeyance (i.e., temporarily on
hold).\16\
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\16\ 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.
---------------------------------------------------------------------------

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 one post control HAP emission
reduction benefit 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 Agency'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 Agency 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
finalizing the action would reverse the 2016 Supplemental Finding, it
would 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.\17\ See 85 FR 31312 (May 22, 2020).
---------------------------------------------------------------------------

\17\ 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.\18\ 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).
---------------------------------------------------------------------------

\18\ 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.
---------------------------------------------------------------------------

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 D.C. Circuit 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).\19\
---------------------------------------------------------------------------

\19\ Order, Westmoreland Mining Holdings LLC v. EPA, No. 20-1160
(D.C. Cir. September 28, 2020), ECF No. 1863712.
---------------------------------------------------------------------------

On January 20, 2021, President Biden 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 D.C.
Circuit to hold American Academy of Pediatrics and consolidated cases
in abeyance, pending the Agency's review of the 2020 Final Action as
prompted in Executive Order 13990, and on February 16, 2021, the D.C.
Circuit granted the Agency's motion.\20\
---------------------------------------------------------------------------

\20\ Order, American Academy of Pediatrics v. Regan, No. 20-1221
(D.C. Cir. February 16, 2021), ECF No. 1885509.
---------------------------------------------------------------------------

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. The EPA had
projected that annual EGU mercury emissions would be reduced by 75
percent with MATS implementation. In fact, EGU emission reductions have
been far more substantial (down 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 have similarly been reduced--by 96 percent and 81
percent, respectively--as compared to 2010 levels. Id. MATS is the only
Federal requirement that guarantees this level of HAP control from
EGUs.
The EPA is now proposing to revoke the 2020 reconsideration of the
2016 Supplemental Finding and to reaffirm 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

[[Page 7633]]

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 D.C. Circuit 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.\21\ 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.\22\
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\21\ 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).
\22\ ``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
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 seven 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
Agency to list all major sources and many area sources of the listed
pollutants (CAA section 112(c)), the new CAA section 112 required the
Agency 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 Agency 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 Agency 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.\23\
---------------------------------------------------------------------------

\23\ 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).
---------------------------------------------------------------------------

Further, after determining the minimum stringency level of control,
or MACT floor, CAA section 112(d)(2) requires the Agency to determine
whether more stringent standards 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

[[Page 7634]]

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
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 avoided the need 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 evaluate standards to
determine if additional reductions can be obtained, without
consideration of the specific risk associated with the HAP 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 Agency has conducted the 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 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 the risk review
provision if the CAA section 112(d) 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. Thus, even after the application of MACT standards, the
statute directs the EPA to conduct a rulemaking if even one person 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 rulemaking approach set forth in the
Benzene NESHAP for determining whether HAP emissions from stationary
sources pose an unacceptable risk and 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). That 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 our 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, 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. 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.''); 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

[[Page 7635]]

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 7412(c)(9)(B)(i) (prohibiting
the EPA from delisting a source category unless the Agency 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); 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).
The deadlines for action included in the 1990 Amendments indicate
that Congress wanted HAP pollution 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 Agency to collect the information
necessary to make the listing decision for many area source categories
and requires the Agency 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 seven 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).
As the preceding 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 inherent in 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 an assessment of risk in the first
instance with one that assumed that risk and directed swift and
substantial reductions. 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 after a consideration of cost.

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

In this action, the EPA is proposing to revoke the 2020 Final
Action and to reaffirm the appropriate and necessary determination made
in 2000, and reaffirmed in 2012 and 2016.\24\ We propose to find that,
under either our preferred totality-of-the-circumstances framework or
our alternative formal BCA framework, the information that would have
been available to the Agency 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 2016
Supplemental Finding, 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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\24\ Our proposal focuses on an analysis of the ``appropriate''
prong of the CAA section 112(n)(1)(A). The Michigan decision and
subsequent EPA actions addressing that decision have been centered
on supplementing the Agency'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 Agency'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 the hazards
posed to human health and the environment by HAP emissions from EGUs
would not be addressed 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 proposal on
reinstating the ``appropriate'' prong of the determination, leaving
undisturbed the Agency'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 Agency 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, the Agency 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).\25\ Similarly, we think
that it is reasonable to consider new information in the context of
this proposal, given that almost a decade has passed since we last
considered updated information. In this proposed reconsideration of the

[[Page 7636]]

determination per 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 benefits 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 propose
conclusions here based on analyses limited to this earlier record. But
we also believe it is reasonable to consider new data, and propose to
find that the new information regarding both public health risks and
costs bolsters the finding and supports a determination that it is
appropriate and necessary to regulate EGUs for HAP.
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\25\ The EPA was not challenged on this interpretation in White
Stallion.
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In section III.A of this preamble, we first describe the advantages
of regulation--the reduction in emissions of HAP and attendant
reduction of risks to human health and the environment, including the
distribution of these health benefits. We carefully document 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 health and
environmental impacts from HAP that are emitted by EGUs, as well as
additional risk analyses supported by new scientific studies.
Specifically, new risk screening analyses on the connection between
mercury and heart disease as well as IQ loss in children across the
U.S. further supports the conclusion that HAP emissions from EGUs pose
hazards to public health and the environment warranting regulating
under CAA section 112. The EPA also discusses the challenges associated
with fully quantifying and monetizing the human health and
environmental effects associated with HAP emissions. Finally, we note
that in addition to reducing the identified risks posed by HAP
emissions from EGUs, regulation of such HAP emissions results in
significant health and environmental co-benefits.
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. With the benefit of hindsight, we first consider whether MATS
actually cost what we projected in the 2011 RIA and conclude that the
projection in the 2011 RIA was almost certainly a significant
overestimate of the actual costs. We then evaluate the costs estimated
in the 2011 RIA against several metrics relevant to the impacts those
costs have on the EGU sector and American 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, based on data available in 2012 and
based on updated 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 because it gave virtually no
weight to the volume of HAP that would be reduced, and the vast
majority of the benefits of reducing EGU HAP, including the reduction
of risk to sensitive populations, based on the Agency's inability to
quantify or monetize post-control benefits of HAP regulations.
In preamble section III.D, we explain our preferred totality-of-
the-circumstances methodology that we propose to 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 expending money to achieve those benefits--i.e., the
effects on the electric generating industry and its ability to provide
reliable and affordable electricity. We ultimately propose to 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 costs projected in the 2011 RIA were almost certainly
significantly overestimated. 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 and ozone 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.
Finally, in section III.E, we consider an alternative methodology
to make the appropriate determination, using a formal BCA of MATS that
was conducted consistent with economic principles. This methodology is
not our preferred way to consider advantages and disadvantages for the
CAA section 112(n)(1)(A) determination, because the EPA's inability to
generate a monetized estimate of the full benefits of HAP reductions
can lead to an underestimate of the monetary value of the net benefits
of regulation. To the extent that a formal BCA is appropriate for
making the CAA section 112(n)(1)(A) determination, however, that
approach demonstrates that the monetized benefits of MATS outweigh the
monetized costs by a considerable margin, whether we look at the 2012
record or our updated record. We therefore propose that it is
appropriate to regulate EGUs for HAP applying a BCA approach as well.
In sum, the EPA proposes to conclude 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, and
whether we are considering only the administrative record as of the
original EPA response on remand to Michigan in 2016 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 costs. The EPA requests comment on this
proposed finding and on the supporting information presented in this
proposal, including information related to the risks associated with
HAP emissions from U.S. EGUs and the actual costs incurred by the power
sector due to MATS, as well as on the

[[Page 7637]]

preferred and alternative methodologies for reaching the proposed
conclusion.

A. Public Health 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 and among the
largest domestic contributors of arsenic, chromium, cobalt, nickel,
hydrogen cyanide, beryllium, and cadmium, and that a significant
majority of EGU facilities emitted above the major source thresholds
for HAP emissions.
Further, the EPA noted that the totality of risks that accrue from
these emissions were significant. These hazards include potential
neurodevelopmental impairment, increased cancer risks, 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) \26\ 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 \27\ 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.\28\ These technical
analyses were all challenged in the White Stallion case, and the D.C.
Circuit 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 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 the American public and in
particular, to vulnerable, exposed populations.
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\26\ 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.
\27\ 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)).
\28\ 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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This section of the preamble starts by briefly reviewing the long-
standing and extensive body of evidence, including new scientific
information made available since the 2016 Supplemental Finding, which
demonstrates that HAP emissions from oil- and coal-fired EGUs present
hazards to public health and the environment warranting regulation
under CAA section 112 (section III.A.2). This is followed by an
expanded discussion of the health risks associated with domestic EGU
mercury emissions based on additional evidence regarding cardiovascular
effects that has become available since the 2016 Supplemental Finding
(section III.A.3). In section III.A.4, 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). Next, the section provides an expanded discussion of some
identified environmental justice (EJ) issues associated with these
emissions (section III.A.5). Section III.A.6 identifies health effects
associated with other, non-HAP emissions from EGUs such as
SO<INF>2</INF>, direct PM<INF>2.5</INF> and other PM<INF>2.5</INF> and
ozone precursors. Because these pollutants are co-emitted with HAP, the
controls necessary to reduce HAP emissions from EGUs often reduce these
pollutants as well. After assessing all the evidence, the EPA concludes
again (section III.A.7) that regulation of HAP emissions from EGUs
under CAA section 112 greatly improves public health for Americans 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 American
population that are especially vulnerable (e.g., subsistence fishers
\29\ and their children) to impacts from EGU HAP emissions. In
addition, the concomitant reductions in co-emitted pollutants will also
provide substantial public health and environmental benefits.
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\29\ 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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2. Overview of Health Effects Associated With Mercury and Non-Mercury
HAP
In calling for the Agency to consider the regulation of HAP from
EGUs, the

[[Page 7638]]

CAA stipulated that the EPA complete three 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.
a. Review of Health Effects and Previous Risk Analyses for
Methylmercury
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, which can then
be consumed by humans.\30\ As documented in both the NAS Study and the
Mercury Study, fish and seafood consumption is the primary route of
human exposure to methylmercury, with populations engaged in
subsistence-levels of consumption being of particular concern.\31\ 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, 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.\32\ Below we review the broad range of
public health hazards associated with methylmercury exposure.
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\30\ We recognize that mercury deposition over land with
subsequent impacts to agricultural-sourced food may also represent a
public health concern, however as noted below, primary exposure to
the U.S. population is through fish consumption.
\31\ 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.
\32\ 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>.
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Neurodevelopmental Effects of Exposure to Methylmercury.
Methylmercury is a powerful neurotoxin. Because the impacts of the
neurodevelopmental effects of methylmercury are greatest during periods
of rapid brain development, developing fetuses 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 (e.g., people with iron or vitamin C
deficiencies) are especially vulnerable to adverse neurodevelopmental
outcomes. These dietary and nutritional vulnerabilities are often
particularly pronounced in underserved communities with minority
populations and low-income populations that have historically faced
economic and environmental injustice and are overburdened by cumulative
levels of pollution.\33\
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\33\ 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.
---------------------------------------------------------------------------

Infants in the womb can be exposed to methylmercury when their
mothers eat fish and shellfish that contain methylmercury. This
exposure can adversely affect unborn infants' growing brains and
nervous systems. Children exposed to methylmercury while they are in
the womb can have impacts to their cognitive thinking, memory,
attention, language, fine motor skills, and visual spatial skills.
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.\34\ 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).\35\
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\34\ U.S. EPA. 2001. IRIS Summary for Methylmercury. U.S.
Environmental Protection Agency, Washington, DC. (USEPA, 2001).
\35\ 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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Prenatal exposure to methylmercury from maternal consumption of
fish has been associated with several adverse neurodevelopmental
outcomes in various fish consuming populations. Although data are
limited, the EPA has focused on several subpopulations likely to be at
higher risk from methylmercury exposure associated with EGU HAP due to
fish consumption. As part of the 2011 Final Mercury TSD, the EPA
completed a national-scale risk assessment focused on mercury emissions
from domestic EGUs. Specifically, we examined risk associated with
mercury released from U.S. EGUs that deposits to watersheds within the
continental U.S., bioaccumulates in fish as methylmercury, and is
consumed when fish are eaten by female subsistence fishers of child-
bearing age and other freshwater self-caught fish consumers. There is
increased risk for in utero exposure and adverse outcomes in children
born to female subsistence fishers with elevated exposure to
methylmercury. The risk assessment modeled scenarios representing high-
end self-caught fish consumers active at inland freshwater lakes and
streams. The analysis estimated that 29 percent of the watersheds
studied would lead to

[[Page 7639]]

female subsistence fishers having exposures which exceeded the
methylmercury RfD, based on in utero effects, due in whole or in part
to the contribution of domestic EGU emissions of mercury. This included
up to 10 percent of modeled watersheds where deposition from U.S. EGUs
alone leads to potential exposures that exceed the RfD.\36\
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\36\ The EPA chose this risk metric in part because CAA section
112(n)(1)(C) directed the NIEHS to develop a threshold for mercury
concentration in fish tissue that can be consumed by even sensitive
populations without adverse effect and because CAA section 112(c)(6)
demonstrates a special interest in protecting the public from
exposure to mercury.
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In addition to the 2011 Final Mercury TSD focusing on subsistence
fishers referenced above, the EPA also completed a RIA in 2011
including the characterization of benefits associated with the
prospective reduction of U.S. EGU mercury emissions under MATS.\37\
However, due to limitations on the available data with regard to the
extent of subsistence fishing activity in the U.S., which prevented the
enumeration of subsistence fisher populations, the EPA was unable to
develop a quantitative estimate of the reduction in population-level
risk or associated dollar benefits for children of female subsistence
fishers. Instead, in the 2011 MATS RIA, the EPA focused on a different
population of self-caught fish consumers that could be enumerated.
Specifically, we quantitatively estimated the amount and value of IQ
loss associated with prenatal methylmercury exposure among the children
of recreational anglers consuming self-caught fish from inland
freshwater lakes, streams and rivers (unlike subsistence fishers,
available data allow the characterization of recreational fishing
activity across the U.S. including enumeration of these populations).
Although the EPA acknowledged uncertainty about the size of the
affected population and acknowledged that it could be underestimated,
these unborn children associated with recreational anglers represented
precisely the type of sensitive population most at risk from mercury
exposure that CAA section 112 is designed to protect. The results
generated in the 2011 RIA for recreational anglers suggested that by
reducing methylmercury exposure, MATS was estimated to yield an
additional 511 IQ points among the affected population of children,
which would increase their future lifetime earnings. The EPA noted at
the time that the analysis likely underestimated potential benefits for
children of recreational anglers since, due to data limitations, it did
not cover consumption of recreationally caught seafood from estuaries,
coastal waters, and the deep ocean which was expected to contribute
significantly to overall exposure. Nevertheless, this single endpoint
alone, evaluated solely for the recreational angler, provides evidence
of potentially significant health harm from methylmercury exposure.
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\37\ The 2011 MATS RfD-based risk assessment focusing on the
subsistence fisher population was designed as a screening-level
analysis to inform consideration for whether U.S. EGU-sourced
mercury represented a public health hazard. As such, the most
appropriate risk metric was modeled exposure (for highly-exposed
subsistence fishers) compared to the RfD for methylmercury. By
contrast, the 2011 RIA was focused on estimating the dollar benefits
associated with MATS and as such focused on a health endpoint which
could be readily enumerated and then monetized, which at the time
was IQ for infants born to recreational anglers.
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In 2011 we noted that other, more difficult to quantify endpoints
may also contribute to the overall burden across a broader range of
subgroups. The metrics studied in addition to IQ include those measured
by performance on neurobehavioral tests, particularly on tests of
attention, fine motor-function, language, and visual spatial ability
(USEPA, 2001; Agency for Toxic Substances and Disease Registry (ATSDR),
1999).\38\ Such adverse neurodevelopmental effects are well documented
in cohorts of subsistence fisher populations (i.e., Faroe Islands and
the Nunavik region of Arctic Canada).
---------------------------------------------------------------------------

\38\ Agency for Toxic Substances and Disease Registry (ATSDR).
1999. Toxicological profile for mercury. Atlanta, GA: U.S.
Department of Health and Human Services, Public Health Service.
---------------------------------------------------------------------------

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.\39\ The update to the methylmercury IRIS assessment will
focus on updating the quantitative aspects of neurodevelopmental
outcomes associated with methylmercury exposure. As noted in these
early 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);
\40\ 85 FR 32037 (May 8, 2020)).\41\
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\39\ <a href="https://iris.epa.gov/ChemicalLanding/&substance_nmbr=73">https://iris.epa.gov/ChemicalLanding/&substance_nmbr=73</a>.
\40\ Availability of the IRIS Assessment Plan for Methylmercury.
84 FR 13286 (April 4, 2019).
\41\ Availability of the Systematic Review Protocol for the
Methylmercury Integrated Risk Information System (IRIS) Assessment.
85 FR 32037 (May 28, 2020).
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Cardiovascular Impacts of Exposure to Methylmercury. 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. Infant exposure in the womb to
methylmercury has been associated with altered blood-pressure and
heart-rate variability in children. In adults, dietary exposure to
methylmercury has been linked to a higher risk of acute myocardial
infarction (MI), coronary heart disease, or cardiovascular heart
disease. To date, the EPA has not attempted to utilize a quantitative
dose-response assessment for cardiovascular effects associated with
methylmercury exposures because of a lack of consensus among scientists
on the dose-response functions for these effects and inconsistency
among available studies as to the association between methylmercury
exposure and various cardiovascular system effects.
However, additional studies have become available that have
increased the EPA's confidence in characterizing the dose-response
relationship between methylmercury and adverse cardiovascular outcomes.
These new studies were leveraged to inform new quantitative screening
analyses (described in section III.A.3, below) to estimate one
cardiovascular endpoint--incidence of MI mortality--that may
potentially be linked to U.S. EGU mercury emissions as well as the
number of U.S. EGU impacted watersheds. In addition to a new meta-
analysis (Hu et al., 2021) \42\ on the association of methylmercury
generally with cardiovascular disease (CVD), stroke, and ischemic heart
disease (IHD), there is a limited body of existing literature that has
examined associations between mercury and various cardiovascular
outcomes. These include acute MI, hypertension, atherosclerosis, and
heart rate variability (Roman et al., 2011).\43\
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\42\ Hu, X. F., Lowe, M., Chan, H.M., Mercury exposure,
cardiovascular disease, and mortality: A systematic review and dose-
response meta-analysis. Environmental Research 193 (2021),110538.
\43\ Roman HA, Walsh TL, Coull BA, Dewailly [Eacute], Guallar E,
Hattis D, Mari[euml]n K, Schwartz J, Stern AH, Virtanen JK, Rice G.
Evaluation of the cardiovascular effects of methylmercury exposures:
Current evidence supports development of a dose-response function
for regulatory benefits analysis. Environ Health Perspect. 2011
May;119(5):607-14. doi: 10.1289/ehp.1003012. Epub 2011 Jan 10.

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[[Page 7640]]

Immunotoxic Effects of Exposure to Methylmercury. Although exposure
to some forms of mercury can result in a decrease in immune activity or
an autoimmune response (ATSDR, 1999), evidence for immunotoxic effects
of methylmercury is limited (NAS Study).
Other Mercury-Related Human Toxicity Data Including Potential
Carcinogenicity. The Mercury Study noted that methylmercury is not a
potent mutagen but is capable of causing chromosomal damage in a number
of experimental systems. The NAS Study indicated that the evidence that
human exposure to methylmercury causes genetic damage is inconclusive;
it noted that some earlier studies showing chromosomal damage in
lymphocytes may not have controlled sufficiently for potential
confounders. One study of adults living in the Tapajos River region in
Brazil (Amorim et al., 2000) \44\ reported a relationship between
methylmercury concentration in hair and DNA damage in lymphocytes, as
well as effects on chromosomes. Long-term methylmercury exposures in
this population were believed to occur through consumption of fish,
suggesting that genotoxic effects (largely chromosomal aberrations) may
result from dietary, chronic methylmercury exposures similar to and
above those seen in the populations studied in the Faroe Islands and
Republic of Seychelles. Since 2000, more recent studies have evaluated
methylmercury genotoxicity in vitro in human and animal cell lines and
in vivo in rats.
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\44\ Amorim MI, Mergler D, Bahia MO, Dubeau H, Miranda D, Lebel
J, Burbano RR, Lucotte M. Cytogenetic damage related to low levels
of methyl mercury contamination in the Brazilian Amazon. An Acad
Bras Cienc. 2000 Dec;72(4):497-507. doi: 10.1590/s0001-
37652000000400004.
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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) \45\ 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) (NAS Study).
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\45\ 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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Some evidence of reproductive and renal toxicity in humans from
methylmercury exposure exists. However, overall, human data regarding
reproductive, renal, and hematological toxicity from methylmercury are
very limited and are based on studies of the two 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.
b. Review of Health Effects for Non-Mercury HAP
As noted earlier, EGUs are 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., irritation
of the lung, skin, and mucus membranes; 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, three of the key metal HAP emitted by EGUs (arsenic,
chromium, and nickel) have been classified as human carcinogens, while
three others (cadmium, selenium, and lead) are classified as probable
human carcinogens. Overall (metal and non-metal), the EPA has
classified four of the HAP emitted by EGUs as human carcinogens and
five as probable human carcinogens. See 76 FR 25003-25005 (May 3, 2011)
for a fuller discussion of the health effects associated with these
pollutants.
As summarized in the 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 (2011 Non-Hg
HAP Assessment),\46\ the EPA previously completed a refined chronic
inhalation risk assessment for 16 EGU case studies in order to assess
potential public health risk associated with non-mercury HAP. The 16
case studies included one unit that used oil and 15 that used coal. As
noted in the 2015 Proposal, this set of case studies was designed to
include those facilities with potentially elevated cancer and non-
cancer risk based on an initial risk screening of prospective EGU units
completed utilizing the Human Exposure Model paired with HAP emissions
data obtained from the 2005 National Emissions Inventory. For each of
the 16 case study facilities, we conducted refined dispersion modeling
with the EPA's AERMOD (American Meteorological Society/Environmental
Protection Agency Regulatory Model) system to calculate annual ambient
concentrations (see 2011 Non-Hg HAP Assessment). Average annual
concentrations were calculated at census block centroids. We calculated
the MIR for each facility as the cancer risk associated with a
continuous lifetime (24 hours per day, 7 days per week, and 52 weeks
per year for a 70-year period) exposure to the maximum concentration at
the centroid of an inhabited census block, based on application of the
unit risk estimate from the EPA's IRIS program. Based on estimated
actual emissions, the highest estimated individual lifetime cancer risk
from any of the 16 case study facilities was 20-in-1 million, driven by
nickel emissions from the one case study facility with oil-fired EGUs.
Of the facilities with coal-fired EGUs, five facilities had MIR greater
than 1-in-1 million (the highest was 5-in-1 million), with the risk
from four due to emissions of chromium VI and the risk from one due to
emissions of nickel. There were also two facilities with coal-fired
EGUs that had MIR equal to 1-in-1 million. Based on this analysis, the
EPA concludes that cancer risks associated with these HAP emissions
supports a finding that it is appropriate to regulate HAP emissions
from EGUs.
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\46\ 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. EPA-452/R-
11-013. Docket ID Item No. EPA-HQ-OAR-2009-0234-19912.
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c. Review of Other Adverse Environmental Effects Associated With EGU
HAP Emissions
Ecological Effects of Methylmercury. 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

[[Page 7641]]

for numerous avian species and mammals including polar bears, river
otters, and panthers. These adverse effects can propagate into impacts
on human welfare to the extent they influence economies that depend on
robust ecosystems (e.g., tourism).
Ecological Effects of Acid Gas HAP. Even after the ARP was largely
implemented in 2005, EGU sources comprised 82 percent of all
anthropogenic HCl (a useful surrogate for all acid gas HAP) emissions
in the U.S. When HCl dissolves in water, hydrochloric acid is formed.
When hydrochloric acid is deposited by rainfall into terrestrial and
aquatic ecosystems, it results in acidification of those systems. The
MATS rule was expected to result in an 88 percent reduction in HCl
emissions. As part of a recent Integrated Science Assessment (EPA,
2020),\47\ the EPA concluded that the body of evidence is sufficient to
infer a causal relationship between acidifying deposition and adverse
changes in freshwater biota. Affected biota from acidification of
freshwater include plankton, invertebrates, fish, and other organisms.
Adverse effects can include physiological impairment, as well as
alteration of species richness, community composition, and biodiversity
in freshwater ecosystems. This evidence is consistent and coherent
across multiple species. More species are lost with greater
acidification.
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\47\ U.S. EPA. Integrated Science Assessment (ISA) for Oxides of
Nitrogen, Oxides of Sulfur and Particulate Matter Ecological
Criteria (Final Report). U.S. Environmental Protection Agency,
Washington, DC, EPA/600/R-20/278, 2020.
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3. Post-2016 Screening-Level Risk Assessments of Methylmercury Impacts
This section of the preamble describes three screening-level risk
assessments completed since the 2016 Supplemental Finding that further
strengthen the conclusion that U.S. EGU-sourced mercury represents a
hazard to public health. These ``screening-level'' assessments are
designed as broad bounding exercises intended to illustrate the
potential scope and public health importance of methylmercury risks
associated with U.S. EGU emissions. In some cases, they incorporate
newer peer-reviewed literature that was not available to the Agency
previously. Remaining uncertainties, however, prohibit the EPA from
generating a more precise estimate at this time. Two of the three risk
assessments focus on the potential for methylmercury exposure to
increase the risk of MI-related mortality in adults and for that
reason, section III.A.3.a begins by describing the methodology used in
the analyses, including discussion of the concentration response (CR)
function \48\ for MI-related mortality and the incorporation of
confidence cutpoints designed to address uncertainty. Then, the EPA
describes an extension of the original watershed-level subsistence
fisher methylmercury risk assessment to evaluate the potential for
elevated MI-mortality risk among subsistence fishers (section
III.A.3.b). In addition, a separate risk assessment is presented for
elevated MI mortality among all adults utilizing a bounding approach
that explores potential risks associated with exposure of the general
U.S. population to methylmercury (sourced from U.S. EGUs) through fish
consumption (section III.A.3.c). Finally, focusing on
neurodevelopmental outcomes, another bounding analysis is presented
that focuses on the risk of IQ points loss in children exposed in utero
through maternal fish consumption by the population of general U.S.
fish consumers (section III.A.3.d). Each of these analyses quantify
potential impacts on incidence of adverse health effects. Section
III.A.4 provides illustrative examples of how these incidence estimates
translate to monetized benefits.
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\48\ Concentration-response functions relate levels of exposure
for the chemical of interest to the probability or rate of response
for the adverse health outcome in the exposed individual or
population. Typically these mathematical relationships are based on
data obtained either from human epidemiology studies, clinical
studies, or toxicological (animal) studies. In this case, CR
functions for MI-related mortality are based on epidemiology studies
as discussed further below.
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a. Methodology for Estimating MI-Mortality
This section describes the methodology used in the new screening-
level risk assessments related to mortality, including the EPA's
application of a CR function characterizing the relationship between
increased MI-mortality and methylmercury exposure. As discussed further
in the 2021 Risk TSD,\49\ which is contained in the docket for this
action, the approach draws on recommendations provided by an expert
panel convened by the EPA in 2010 to evaluate the cardiovascular
effects associated with methylmercury exposure (the findings of the
expert panel were summarized as a peer-reviewed paper, Roman et al.,
2011). The panel ``found the body of evidence exploring the link
between [methylmercury] and acute myocardial infarction (MI) to be
sufficiently strong to support its inclusion in future benefits
analyses, based both on direct epidemiological evidence of [a
methylmercury]-MI link and on [methylmercury's] association with
intermediary impacts that contribute to MI risk.'' Given the likely
mechanism of action associated with MI, the panel further recommended
that either hair-mercury or toenail-mercury be used as an exposure
metric because both reflect a longer-term pattern of exposure.
Regarding the shape of the CR function, the panel noted that the
EURAMIC study (Guallar et al., 2002) \50\ had identified a log-linear
model form with log-of exposure providing the best fit using toenail
mercury as the biomarker of exposure. The panel also discussed the
issue of potential effect modification by cardioprotective compounds
including polyunsaturated fatty acids (PUFA).\51\ Kuopio Ischaemic
Heart Disease Risk Factor Study (KIHD) and European Multicenter Case-
Control Study on Antioxidants, Myocardial Infarction, and Cancer of the
Breast Study (EURAMIC) datasets ``provide the strongest and most useful
data sets for quantifying methylmercury-related incidence of MI.''
However, the panel did note the disconnect between typical levels of
exposure to methylmercury in the U.S. population and the relatively
higher levels of exposure reflected in the two recommended epidemiology
studies (KIHD and EURAMIC). Therefore, the panel suggested that
consideration be given to restricting modeling MI mortality to those
with higher concentrations reflecting the levels of exposure found in
the two key epidemiology studies (corresponding to roughly 75th to 95th
percentile hair-mercury levels for U.S. women of child-bearing age, as
characterized in National Health and Nutrition Examination

[[Page 7642]]

Survey (NHANES) data and referenced by the panel).
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\49\ U.S. EPA. 2021. 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.
\50\ Guallar E, Sanz-Gallardo MI, van't Veer P, Bode P, Aro A,
G[oacute]mez-Aracena J, Kark JD, Riemersma RA, Mart[iacute]n-Moreno
JM, Kok FJ; Heavy Metals and Myocardial Infarction Study Group.
Mercury, fish oils, and the risk of myocardial infarction. N Engl J
Med. 2002 Nov 28;347(22):1747-54. doi: 10.1056/NEJMoa020157.
\51\ Virtanen JK, Voutilainen S, Rissanen TH, Mursu J, Tuomainen
TP, Korhonen MJ, Valkonen VP, Sepp[auml]nen K, Laukkanen JA, Salonen
JT. Mercury, fish oils, and risk of acute coronary events and
cardiovascular disease, coronary heart disease, and all-cause
mortality in men in eastern Finland. Arterioscler Thromb Vasc Biol.
2005 Jan;25(1):228-33. doi: 10.1161/01.ATV.0000150040.20950.61. Epub
2004 Nov 11.
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In the intervening period since the release of the expert panel's
findings in 2011 (Roman et al., 2011), the EPA has continued to review
literature characterizing the relationship between methylmercury
exposure and cardiovascular effects. While the EPA has not yet
conducted a systematic review, two recent studies are of particular
interest for quantifying the potential relationship between U.S. EGU
mercury emissions and acute MI that informed a modeling approach. Giang
and Selin (2016) \52\ presented an approach for modeling MI mortality
reflecting a number of the recommendations presented in Roman et al.,
2011 including the use of the KIHD and EURAMIC studies as the basis for
a CR function including both the log-linear functional form and the
effect estimate derived from the KIHD study results. A second study, Hu
et al. 2021,\53\ presented a meta-analysis looking at the relationship
between methylmercury exposure and mortality. That paper utilized eight
studies each determined to be of good quality and reflecting at a
minimum, adjustments for age, sex, and n-3 PUFA in specifying dose-
response relationships. Historically, studies which account for n-3
PUFA have assumed a linear relationship between PUFAs and risk of MI
(Roman et al., 2011). However, the association between PUFA intake and
cardiovascular risk may not be linear (Mozaffarian and Rimm, 2006).\54\
The potential for confounding and effect modification by PUFA and
selenium makes it difficult to interpret the relationship between
methylmercury and MI, particularly at lower doses where there is
potential for masking of methylmercury toxicity. The results of the
meta-analysis by Hu et al., 2021 illustrated this phenomenon with their
J-shaped functions for both IHD and CVD, both of which showed an
initial region of negative slope (diminishing net risk with
methylmercury exposure) before reaching an inflection point (between 1
and 2 microgram per gram ([micro]g/g) hair-mercury depending on the
endpoint) where the function turns positive (increasing risk).
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\52\ Giang A, Selin NE. Benefits of mercury controls for the
United States. Proc Natl Acad Sci U S A. 2016 Jan 12;113(2):286-91.
doi: 10.1073/pnas.1514395113. Epub 2015 Dec 28.
\53\ Hu XF, Lowe M, Chan HM. Mercury exposure, cardiovascular
disease, and mortality: A systematic review and dose-response meta-
analysis. Environ Res. 2021 Feb;193:110538. doi: 10.1016/
j.envres.2020.110538. Epub 2020 Dec 5.
\54\ Mozaffarian D, Rimm EB. Fish intake, contaminants, and
human health: Evaluating the risks and the benefits. JAMA. 2006 Oct
18;296(15):1885-99. doi: 10.1001/jama.296.15.1885. Erratum in: JAMA.
2007 Feb 14;297(6):590.
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For the EPA's new screening-level assessment, we have considered
the recommendations presented in Roman et al., 2011, as well as the J-
shaped functions presented in Hu et al., 2021, and their implications
for considering overall confidence in specifying the relationship
between cardiovascular-related mortality and methylmercury exposure. In
particular, the EPA has higher confidence in the log-linear
relationship at levels of hair-mercury exposure above the selected
confidence cutpoints. In specifying these confidence cutpoints (for
modeling MI mortality) we have looked to recommendations presented in
Roman et al., 2011, specifically that we consider modeling risk for
levels of exposure reflected in the EURAMIC and KIHD studies (with
these equating to roughly 0.66 and 1.9 [micro]g/g hair-mercury,
respectively, or approximately the 75th-95th percentile of hair-mercury
levels seen in women of childbearing age in available 1999-2000 NHANES
survey data \55\). Further, we note that these confidence cutpoints
roughly match the inflection point for IHD and CVD seen in the J-shaped
plot presented in Hu et al., 2021, which further supports their use in
defining regions of methylmercury exposure above which we have
increased confidence in modeling MI mortality. However, as noted
earlier, we are not concluding here that there is an absence of risk
below these cutpoints, as such conclusions would require a weight of
the evidence analysis and subsequent independent peer review. Rather,
we are less confident in our ability to specify the nature of the CR
function in those lower exposure regions due to possible effect
modification and/or confounding by PUFA and/or selenium. Therefore, in
applying the CR function in modeling MI mortality, we included a set of
three functions-two including the cutpoints described above and a third
no-cutpoint version of the function reflecting the assumption that risk
extends across the entire range of methylmercury exposure. In terms of
the other elements of the CR function (shape and effect estimate), we
have also followed the advice presented in Roman et al., 2011, as
further illustrated through the analysis published by Giang and Selin
2016, and utilized a log-linear form and an effect estimate of 0.10 for
MI mortality obtained from the KIHD study (see 2021 Risk TSD). As with
the other risk estimates presented for methylmercury, these estimates
reflect the baseline for U.S. EGUs prior to implementation of MATS
(i.e., 29 tons).
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\55\ NHANES has not continued to collect hair-mercury data in
subsequent years since the NHANES dataset referenced here. While
NHANES has continued with total blood-mercury monitoring, hair
mercury is a better biomarker for characterizing methylmercury
exposure over time. Given that the CR functions based on the KIHD
study (as well as observations presented in Roman et al. 2011
regarding cardio-modeling) were all based on hair-mercury, this was
chosen as the anchoring analytical biometric. The potential for bias
due to the use of the 1999-2000 NHANES data is further discussed in
the 2021 Risk TSD.
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b. Increased MI-Mortality Risk in Subsistence Fishers Exposed to
Methylmercury
This screening-level analysis of MI-mortality risk is an extension
of the female subsistence-fisher-based at-risk watershed analysis
originally completed as part of the 2011 risk assessment supporting the
appropriate and necessary determination (USEPA, 2011) and documented in
the 2011 Final Mercury TSD. In that original analysis, a series of
female subsistence fisher risk scenarios was evaluated for a subset of
3,141 watersheds within the continental U.S. for which there were
sampled methylmercury fish tissue data (that fish tissue data allowing
a higher-confidence empirically-based assessment of methylmercury risk
to be generated for those watersheds). For each watershed, we used the
fish tissue methylmercury data to characterize total mercury-related
risk and then we estimated the portion of that total risk attributable
to U.S. EGUs (based on the fraction of total mercury deposition to
those watersheds associated with U.S. EGU emissions as supported by the
Mercury Maps approach, USEPA, 2011).\56\
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\56\ A detailed discussion of the Mercury Maps approach
(establishing a proportional relationship between mercury deposition
and methylmercury concentrations in fish at the watershed level) is
presented in section 1.4.6.1 of the 2011 Final Mercury TSD which in
turn references: Mercury Maps--A Quantitative Spatial Link Between
Air Deposition and Fish Tissue Peer Reviewed Final Report. U.S. EPA,
Office of Water, EPA-823-R-01-009, September, 2001.
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We have now extended the at-risk watershed analysis completed in
2011 for the subsistence fisher scenarios to include an assessment of
the potential for increased MI mortality risk.\57\ Specifically, we
have utilized the U.S. EGU-attributable methylmercury exposure
estimates ([micro]g/kg-day methylmercury intake) generated for the
subsistence fisher scenario in each

[[Page 7643]]

watershed to generate equivalent hair-mercury exposure estimates for
that subsistence fisher scenario in each watershed (see 2021 Risk TSD
for additional detail on the conversion of daily methylmercury intake
rates into hair-mercury levels). We then compare those hair-mercury
levels to the confidence cutpoints developed for the MI mortality
screening-level risk assessment described above in section III.A.3.a.
If the hair-mercury level for a particular watershed is above either
the EURAMIC or KIHD confidence cutpoint (i.e., above 0.66 and 1.9
[micro]g/g hair-mercury, respectively), then we consider that watershed
to be at increased risk for MI mortality exclusively due to that U.S.
EGU-attributable methylmercury exposure.\58\ Note, that this is not to
suggest that exposures at watersheds where U.S. EGU-attributable
contributions are below these cutpoints are without risk, but rather
that when exposure levels exceed these cutpoints, we have increased
confidence in concluding there is an increased risk of MI mortality for
subsistence fishers active within that watershed. It is also important
to note that in many cases, total methylmercury exposure (i.e., EGU
contribution plus contributions from other sources) may exceed these
confidence cutpoints such that subsistence fishers active at those
watersheds would be at increased risk of MI mortality at least in part
due to EGU emissions. See White Stallion, 748 F.3d at 1242-43 (finding
reasonable the EPA's decision to consider cumulative impacts of HAP
from EGUs and other sources in determining whether HAP emissions from
EGUs pose a hazard to public health under CAA section 112(n)(1)(A));
see also CAA section 112(n)(1)(B) (directing the EPA to study the
cumulative impacts of mercury emissions from EGUs and other domestic
stationary sources of mercury).
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\57\ Note that while the 2011 Final Mercury TSD, in utilizing an
RfD-based approach reflecting neurodevelopmental effects, focused on
female subsistence fishers; the analysis focused on MI-mortality
risk covers all adult subsistence fishers, and we use our cutpoint
bounding analysis because there is not an RfD focused specifically
on cardiovascular effects for methylmercury.
\58\ Although we have used the MI-mortality CR function
described in section III.A.3.a of this preamble to generate
mortality incidence estimates for the general fish consuming
population (see section III.A.3.c), this is not possible for
subsistence fishers since we are not able at this point to enumerate
them. Consequently, we use the confidence cutpoints associated with
that CR function to identify exposures associated with MI mortality
risk as described here.
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Table 3 of the 2021 Risk TSD presents the results of the analysis
of risk for MI-mortality for the subsistence fisher scenarios. As with
the original RfD-based risk estimates, these results are dimensioned on
two key parameters (self-caught fish consumption rate and the watershed
percentile exposure level--hair-mercury [micro]g/g). Those watershed
percentile hair-mercury values that exceed the EURAMIC-based MI
mortality confidence cutpoints (0.66 [micro]g/g hair-mercury) are
shaded in the table and those cells that also exceed the KIHD-based MI
mortality confidence cutpoint (1.9 [micro]g/g hair-mercury) are bolded.
Once again, these thresholds identify levels of methylmercury exposure
(hair-mercury) associated with a clear association with MI-related
health effects (i.e., increased risk). Unlike the RfD-based risk
estimates, for MI-mortality estimates we only focus on U.S. EGU-
attributable methylmercury (i.e., whether U.S. EGU-attributable hair-
mercury exceeds the cutpoints of interest).
Results for the typical subsistence fisher, representing high-end
self-caught fish consumption in the U.S. population, suggest that up to
10 percent of the watersheds modeled are associated with hair-mercury
levels (due to U.S. EGU mercury emissions alone) that exceed the lower
EURAMIC cutpoint for MI-mortality risk, with 1 percent of modeled
watersheds also exceeding the KIHD cutpoint (due to U.S. EGU-mercury
emissions alone). For low-income Black subsistence fishers active in
the Southeast, up to 25 percent of the watersheds exceed the lower
EURAMIC confidence threshold (assuming the highest rate of fish
consumption), with only the upper 1 percent of watersheds exceeding the
KIHD threshold (again based only on U.S. EGU-sourced mercury exposure).
c. Characterization of MI-Mortality Risk for the General U.S.
Population Resulting From the Consumption of Commercially-Sourced Fish
The second of the three new screening-level risk analyses estimates
the incidence of MI mortality in the general U.S. population resulting
from consumption of commercially-sourced fish containing methylmercury
emitted from U.S. EGUs.\59\ This is accomplished by first estimating
the total burden of methylmercury-related MI mortality in the U.S.
population and then estimating the fraction of that total increment
attributable to U.S. EGUs. The task of modeling this health endpoint
can involve complex mechanistic modeling of the multi-step process
leading from U.S. EGU mercury emissions to mercury deposition over
global/regional fisheries to bioaccumulation of methylmercury in
fisheries stocks to exposure of U.S. fish consumers through consumption
of those commercially-sourced fish (e.g., Giang and Selin, 2016).
However, in recognition of the uncertainty associated with attempting
to model this more complex multi-step process, we have instead
developed a simpler screening analysis approach intended to generate a
range of risk estimates that reflects the impact of critical sources of
uncertainty associated with this exposure scenario. Rather than
attempting to generate a single high-confidence estimate of risk, which
in our estimation is challenging given overall uncertainty associated
with this exposure pathway, the goal with the bounding approach is
simply to generate a range of risk estimates for MI mortality that
furthers our understanding of the significant public health burden
associated with EGU HAP emissions.
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\59\ Although the analysis presented here focuses on
methylmercury exposure associated with fish consumption which, as
noted earlier, is the primary source of methylmercury exposure for
the U.S. population, EGU mercury deposited to land can also impact
other food sources including those associated with agricultural
production (e.g., rice). In the context of fish consumption,
commercially-sourced fish refers to fish consumed in restaurants or
from food stores.
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The bounding approach developed for this particular scenario is
based on the assumption that fish sourced from global commercial
fisheries are loaded by mercury deposited to those fisheries and that
the fraction of that deposited mercury originating from U.S. EGUs will
eventually be reflected as a fraction of methylmercury in those fish
and subsequently as a fraction of MI mortality risk associated with
those U.S. EGUs. One of the challenges associated with this screening
analysis is how to attribute domestic EGU contributions to global
fisheries and how that might vary from location to location. For
simplicity, the bounding analysis includes two assumptions: (1) A
potential lower-bound reflecting the assumption that U.S. fish
consumption is largely sourced from global fisheries and consequently
the U.S. EGU contribution to total global mercury emissions
(anthropogenic and natural) can be used to approximate the U.S. EGU
fractional contribution to MI mortality and (2) a potential upper-bound
where we assume that fisheries closer to U.S. EGUs (e.g., within the
continental U.S. or just offshore and/or along the U.S. Atlantic and
Pacific coastlines) supply most of the fish and seafood consumed within
the U.S., and therefore U.S. EGU average deposition over the U.S. (as a
fraction of total mercury deposition) can be used to approximate the
U.S. EGU fractional contribution to MI mortality (see 2021 Risk TSD for
more detail).\60\ The EPA is

[[Page 7644]]

continuing to review the literature (including consideration of
research by FDA) to better define the relative contributions for
sources of fish consumed within the U.S. Note that the bounding
analysis also includes consideration for another key source of
uncertainty, namely, the specification of the CR function linking
methylmercury exposure to increased MI mortality and, in particular,
efforts to account for increased confidence in specifying the CR
function for higher levels of methylmercury exposure through the use of
confidence cutpoints (section III.A.3.a). Additional detail on the
stepwise process used to first generate the total U.S. burden of MI-
mortality related to total methylmercury exposure and then apportion
that total risk estimate to the fraction contributed by U.S. EGUs is
presented the 2021 Risk TSD. Based on the 29 tons of mercury emitted by
U.S. EGUs prior to implementation of MATS, the bounding estimates from
the fraction of total mercury deposition attributable to U.S. EGUs at
the global scale is 0.48 percent (lower bound) and 1.8 percent (upper
bound). These estimated bounding percentages are important since they
have a significant impact on the overall incidence of MI mortality
ultimately attributable to U.S. EGU-sourced mercury.
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\60\ Another way of stating this is that the lower-bound
estimate reflects an assumption that U.S. EGU mercury is diluted as
part of a global pool and impacts commercial fish sourced from
across the globe (with lower levels of methylmercury contribution)
while the upper-bound estimate reflects a focus on more near-field
regional impacts by U.S. EGU mercury to fish sourced either within
the continental U.S. or along its coastline (with greater relative
contribution to methylmercury levels).
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Reflecting both the spread in the apportionment of U.S. EGU-sourced
mercury (as described above) and application of the three possible
applications of the CR function for MI mortality (no confidence-
cutpoint, KIHD cutpoint, EURAMIC cutpoint), the estimated MI-mortality
attributable to U.S. EGU-sourced mercury for the general U.S.
population associated primarily with consumption of commercially-
sourced fish ranges from 5 to 91 excess deaths each year.\61\ For those
Americans 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.
Based on this screening analysis, even after imposition of the ARP and
other CAA criteria pollutant requirements that also reduce HAP
emissions from domestic EGU sources, we find that mercury emissions
from EGUs pose a risk of premature mortality due to MI.
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\61\ 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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d. Characterization of IQ Loss for Children Born to Mothers in the
General U.S. Population Resulting From the Consumption of Commercially
Sourced Fish (and Other Food Items Containing Methylmercury)
The third new screening-level risk analysis estimates the incidence
of IQ loss in children in the general U.S. population resulting from
maternal consumption of commercially sourced fish containing
methylmercury attributable to U.S. EGUs (resulting in subsequent
prenatal exposure to methylmercury). The approach used in estimating
incidence of this adverse health effect shares several elements with
the approach described above for modeling MI mortality in the general
U.S. population, including in particular, the method used to apportion
the total methylmercury-related health burden to the fraction
associated with U.S. EGU mercury emissions (e.g., use of lower and
upper bound estimates of the fractional contribution of domestic EGU
sources). Other elements of the modeling approach, including the
specification of the number of children born annually in the U.S., the
specification of maternal baseline hair-mercury levels (utilizing
NHANES data) and the characterization of the linkage between
methylmercury exposure (in utero) and IQ loss, are based on methods
used in the original 2011 benefits analysis completed for MATS (USEPA,
2011) and are documented in the 2021 Risk TSD.
As with the MI-mortality estimates described earlier, the two
bounding estimates for the fraction of total mercury deposition
attributable to U.S. EGUs at the global and regional scales (0.48
percent and 1.8 percent, respectively) have a significant impact on the
overall magnitude of IQ points lost (for children born to the general
U.S. population) which are ultimately attributable to U.S. EGUs.
However, the EPA has relatively high confidence in modeling this
endpoint due to greater confidence in the IQ loss CR function. The
range in IQ points lost annually due to U.S. EGU-sourced mercury is
estimated at 1,600 to 6,000 points, which is distributed across the
population of U.S. children covered by this analysis.\62\ Given
variation in key factors related to maternal methylmercury exposure, it
is likely that modeled IQ loss will not be uniformly distributed across
the population of exposed children and may instead, display
considerable heterogeneity.\63\ The bounding analysis described here
was not designed to characterize these complex patterns of
heterogeneity in IQ loss across the population of children simulated
and we note that such efforts would be subject to considerable
uncertainty. However, it does provide evidence of specific adverse
outcomes with real implications to those affected. Even small
degradations in IQ in the early stages of life are associated with
diminished future outcomes in education and earnings potential.
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\62\ 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).
\63\ Maternal exposure (and hence IQ impacts to children) from
U.S. EGU-sourced mercury can display considerable variation due to
(a) spatial patterns of U.S. EGU mercury fate and transport
(including deposition and methylation) which affects impacts on fish
methylmercury and (b) variations in fish consumption by mothers
(including differences in daily intake, types of fish consumed and
geographical origins of that fish).
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4. Most HAP Benefits Cannot 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, as the above discussion demonstrates, it can be
technically challenging to estimate the extent to which EGU HAP
emissions will result in adverse effects quantitively across the U.S.
population absent regulation. In fact, the vast majority of the post-
control benefits of reducing HAP cannot be quantified or monetized with
sufficient quality to inform regulatory decisions due to data gaps,
particularly with respect to sensitive populations. 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 EJ subpopulations
that face disproportionally high exposure to EGU HAP.
Congress well understood the challenges in monetizing risks. 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
assumed and

[[Page 7645]]

identified 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 welfare. The statute also clearly places great value
on protecting even 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 (MIR) 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 inherent 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, this does not mean that these
effects do not exist or that society would not highly value these
reductions, despite the fact that the post-control effects of the
reductions generally cannot be quantified. The EPA has long
acknowledged the difficulty of quantifying and monetizing HAP benefits.
In March 2011, the EPA issued a report on the post-control benefits and
costs of the CAA. This Second Prospective Report \64\ is the latest in
a series of EPA studies that estimate and compare the post-control
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 Agency's ability to quantify
post-control HAP impacts and estimate the monetary benefits of HAP
reductions.
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\64\ 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>.
---------------------------------------------------------------------------

In preparing the benzene case study for inclusion in the Second
Prospective Report, the Agency 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,\65\
the Council noted that ``Benzene . . . has a large epidemiological
database which OAR 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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\65\ 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
post-control 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 supporting 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; for starters, the small population size means such studies
often lack sufficient statistical power to detect effects. For example,
in the case of mercury, the most exposed and most sensitive members of
the population

[[Page 7646]]

may be both small and highly concentrated, such as the subsistence
fishers that the EPA has identified as 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 post-control quantitative population-level impact
estimates for the reasons described above.
Further, for many HAP-related health endpoints, the Agency lacks
economic data that would support monetizing HAP impacts, such as
willingness to pay studies that can be used to estimate the social
value of avoided outcomes like 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 ability to quantify and
monetize post-control 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 post-
control 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
were to be quantified 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
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 significant and substantial, as supported by the
health evidence. The EPA's new screening-level analyses laid out in the
Risk TSD for this proposal 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 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 benefits of reducing HAP. There are
many other unquantified effects of reducing EGU HAP that would also
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 EPA
were able to account for all of these post-control 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 post-control impacts of reducing HAP
emissions from U.S. EGUs and a monetization of these impacts.
There are other aspects of social willingness to pay that are not
accounted for in the EPA's quantitative estimate of benefits either.
For example, in previous MATS-related rulemakings and analysis, the EPA
has not estimated what individuals would be willing to pay in order to
reduce the exposure of others who are exposed (even if they are not
experiencing high levels of HAP exposure themselves). These may be
considered and quantified as benefits depending on whether it is the
health risks to others in particular that is motivating them.\66\ For
example, Cropper et al. (2016) found that focus group participants
indicated a preference for more equitable distribution of health risks
than for income, which indicates that it is specifically the risks
others face that was important to the participants.\67\ This result is
particularly important as exposure to HAP is often disproportionately
borne by underserved and underrepresented communities (Bell and Ebisu,
2012).\68\ Unfortunately, studies to quantify the willingness to pay
for a more equitable distribution of HAP exposures are limited, so
quantification of this benefit likely cannot be performed until new
research is conducted.
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\66\ Jones-Lee, M.W. Paternalistic Altruism and the Value of
Statistical Life. The Economic Journal, vol. 102, no. 410, 1992, pp.
80-90.
\67\ Cropper M., Krupnick A., and W. Raich, Preferences for
Equality in Environmental Outcomes, Working Paper 22644 <a href="http://www.nber.org/papers/w22644">http://www.nber.org/papers/w22644</a> National Bureau of Economic Research,
September 2016.
\68\ Bell, Michelle L., and Keita Ebisu. Environmental
inequality in exposures to airborne particulate matter components in
the United States. Environmental Health Perspectives 120.12 (2012):
1699-1704.
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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) (estimating the total annual cost of CAA section 112 to be
between $6 billion and $10 billion per year and the estimated annual
benefits to be between $0 and $4 billion per year); id. at 1372-73
(estimating the total annual cost of CAA section 112 to be between $14
billion and $62 billion per year and the estimated annual benefits to
be between $0 and $4 billion per year). Despite the apparent disparity
of estimated costs and monetized benefits, Congress still enacted the
revisions to CAA section 112. 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 post-control 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.
5. Characterization of HAP Risk Relevant to Consideration of
Environmental Justice
In assessing the adverse human health effects of HAP pollution 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 minority and/or low-income populations.
Executive Order 12898 (59 FR 7629;

[[Page 7647]]

February 16, 1994) establishes Federal executive policy on EJ issues.
That Executive Order's main provision directs Federal agencies, to the
greatest extent practicable and permitted by law, to make EJ part of
their mission by identifying and addressing, as appropriate,
disproportionately high and adverse human health or environmental
effects of their programs, policies, and activities on minority
populations and low-income populations. Executive Order 14008 (86 FR
7619; February 1, 2021) also calls on Federal agencies to make
achieving EJ part of their missions ``by developing programs, policies,
and activities to address the disproportionately high and adverse human
health, environmental, climate-related and other cumulative impacts on
disadvantaged communities, as well as the accompanying economic
challenges of such impacts.'' That Executive Order also declares a
policy ``to secure environmental justice and spur economic opportunity
for disadvantaged communities that have been historically marginalized
and overburdened by pollution and under-investment in housing,
transportation, water and wastewater infrastructure, and health care.''
Under Executive Order 13563, Federal agencies may consider equity,
human dignity, fairness, and distributional considerations, where
appropriate and permitted by law.
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. In the context
of MATS, we completed watershed-level assessments of risks for a broad
set of subsistence fisher populations covering two 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 (section III.A.3.b above).
The general subsistence fisher population that was evaluated
nationally for both analyses was not subdivided by socioeconomic
status, race, or cultural practices.\69\ 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 earlier in section III.A.3.b.
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\69\ 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 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, two sub-
populations were shown to be even further disadvantaged. Low-income
Black and white populations in the Southeast and tribal fishers active
near the Great Lakes had the potential for increased risk in 25 percent
of the watersheds modeled.\70\ 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
these results are relevant in considering the benefits of regulating
EGU HAP.
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\70\ Recognizing challenges in obtaining high-end consumption
rates for tribal populations active in areas of high U.S. EGU impact
(e.g., Ohio River valley, areas of the central Southeast such as
northern Georgia, northern South Carolina, North Carolina and
Tennessee) there is the potential for our analysis of tribal-
associated risk to have missed areas of elevated U.S. EGU-sourced
mercury exposure and risk. In that case, estimates simulated for
other subsistence populations active in those areas (e.g., low-
income whites and Blacks in the Southeast as reported here and in
Table 3 of the 2021 Risk TSD) could be representative of the ranges
of risk experienced by tribal populations to the extent that
cultural practices result in similar levels of increased fish
consumption.
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6. 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).\71\ 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 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

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