7624 Federal Register / Vol. 87, No. 27 / Wednesday, February 9, 2022 / Proposed Rules 

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. 

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: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Email: a-and-r-docket@epa.gov. 

Include Docket ID No. EPA–HQ–OAR– 

2018–0794 in the subject line of the 

message. 

• Fax: (202) 566–9744. Attention 

Docket ID No. EPA–HQ–OAR–2018– 

0794. 

• 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. 

• 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 https://

www.regulations.gov/, 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 https://

www.regulations.gov/ 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 https:// 

www.epa.gov/dockets. 

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: king.melanie@epa.gov. 

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 


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Federal Register / Vol. 87, No. 27 / Wednesday, February 9, 2022 / Proposed Rules 7625 

1As 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 Coaland 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). 

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 preregistered 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 SPPDpublichearing@epa.gov. 

The EPA will announce further details 

at https://www.epa.gov/stationarysources-air-pollution/mercury-and-airtoxics-standards. 

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 

https://www.epa.gov/stationary-sourcesair-pollution/mercury-and-air-toxicsstandards or contact the public hearing 

team at (888) 372–8699 or by email at 

SPPDpublichearing@epa.gov. 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 preregistered speakers in approximate 

order at: https://www.epa.gov/ 

stationary-sources-air-pollution/ 

mercury-and-air-toxics-standards. 

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 king.melanie@epa.gov. 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 https://www.epa.gov/ 

stationary-sources-air-pollution/ 

mercury-and-air-toxics-standards. 

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 SPPDpublichearing@

epa.gov 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 preregister 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 

https://www.regulations.gov/. 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 https://

www.regulations.gov/. 

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 https:// 

www.regulations.gov/, 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 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. 

The https://www.regulations.gov/ 

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 https://

www.regulations.gov/, 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 https:// 

www.epa.gov/dockets. 

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 https://

www.regulations.gov/ 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 https://

www.epa.gov/dockets. 

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 


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7626 Federal Register / Vol. 87, No. 27 / Wednesday, February 9, 2022 / Proposed Rules 

through https://www.regulations.gov/ 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 CaseControl 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 BenefitCost 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 OilFired 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 coaland 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 oilfired 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 


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2The 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. 

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. 

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 thecircumstances 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 allencompassing 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 


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3U.S. EPA. 2011. Regulatory Impact Analysis for 

the Final Mercury and Air Toxics Standards. EPA– 

452/R–11–011. Available at: https://www3.epa.gov/ 

ttn/ecas/docs/ria/utilities_ria_final-mats_2011- 

12.pdf. 

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-thecircumstances 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. 

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 mercuryrelated risk analyses performed since 

2016, identifying substantial risks to 

human health and the environment 

from HAP emissions from coal- and oilfired 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 


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4The statute includes a separate definition of 

‘‘EGU’’ that includes both major and area source 

power plant facilities. CAA section 112(a)(8). 

5U.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. 6U.S. EPA. 1997. Mercury Study Report to 

Congress. EPA–452/R–97–003 December 1997. 

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 https://www.epa.gov/ 

stationary-sources-air-pollution/ 

mercury-and-air-toxics-standards. 

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. 

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), 


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7National Institute of Environmental Health 

Sciences (NIEHS) Report on Mercury; available in 

the rulemaking docket at EPA–HQ–OAR–2009– 

0234–3053. 

8National 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 peerreviewed 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). 

10U.S. EPA. 2011. Revised Technical Support 

Document: National-Scale Assessment of Mercury 

Risk to Populations with High Consumption of Selfcaught 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). 

11U.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). 

12Although 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 https://

www.epa.gov/stationary-sources-air-pollution/ 

mercury-and-air-toxics-standards. 

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

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 coaland 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 peerreviewed risk assessments on human 

health effects associated with mercury 

(2011 Final Mercury TSD) 10 and nonmercury 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). 

In the same 2012 action, the EPA 

established a NESHAP, commonly 

referred to as MATS, that required coaland 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 onethird 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. 

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 

(SO2) that may be used as a surrogate for 

acid gas HAP for those coal-fired EGUs 

with flue gas desulfurization (FGD) 

systems and SO2 continuous emissions 

monitoring systems that are installed 

and operational. Standards for filterable 

PM serve as a surrogate for the nonmercury 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 


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13Available at www.ecfr.gov/cgi-bin/textidx?node=sp40.15.63.uuuuu. 

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. 

15For example, see ‘‘Economic Impact and Small 

Business Analysis–Mineral Wool and Wool 

Fiberglass RTRs and Wool Fiberglass Area Source 

NESHAP’’ (U.S. EPA, 2015; https://www.epa.gov/ 

sites/default/files/2020-07/documents/mwwf_eia_

neshap_final_07-2015.pdf) or ‘‘Economic Impact 

Analysis of Final Coke Ovens NESHAP’’ (U.S. EPA, 

2002; https://www.epa.gov/sites/default/files/2020- 

07/documents/coke-ovens_eia_neshap_final_08- 

2002.pdf). 

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. 

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). 

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-thecircumstances 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, nonmercury 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.’’) 

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 HAPspecific 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 


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16Order, 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. 

17This 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. 

18CAA 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. 

19Order, Westmoreland Mining Holdings LLC v. 

EPA, No. 20–1160 (D.C. Cir. September 28, 2020), 

ECF No. 1863712. 

20Order, American Academy of Pediatrics v. 

Regan, No. 20–1221 (D.C. Cir. February 16, 2021), 

ECF No. 1885509. 

Supplemental Finding be held in 

abeyance (i.e., temporarily on hold).16

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). 

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 OilFired 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). 

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

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

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 


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21National 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. 

23Congress 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). 

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-in1 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

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

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 nonair-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 


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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 PCBcontaminated 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 


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24Our 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). 

25The EPA was not challenged on this 

interpretation in White Stallion. 

a lifetime cancer risk greater than 1-in1 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 noncancer 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 coaland oil-fired EGUs. 

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 mostup-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 


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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. 

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-thecircumstances 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-thecircumstances 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-thecircumstances 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 


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26U.S. EPA. 2011. Revised Technical Support 

Document: National-Scale Assessment of Mercury 

Risk to Populations with High Consumption of Selfcaught 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. 

27The 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)). 

28The 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). 

29Subsistence fishers, who by definition obtain a 

substantial portion of their dietary needs from selfcaught 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. 

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. 

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 SO2, direct PM2.5 and other 

PM2.5 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. 

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 


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30We recognize that mercury deposition over 

land with subsequent impacts to agriculturalsourced 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 (https:// 

www.fda.gov/food/consumers/advice-about-eatingfish). 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. 

32National Research Council. 2000. Toxicological 

Effects of Methylmercury. Washington, DC: The 

National Academies Press. https://doi.org/ 

10.17226/9899. 

33Burger 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. 

34U.S. EPA. 2001. IRIS Summary for 

Methylmercury. U.S. Environmental Protection 

Agency, Washington, DC. (USEPA, 2001). 

35U.S. EPA. 2002. A Review of the Reference 

Dose and Reference Concentration Processes. EPA/ 

630/P–02/002F, December 2002. 

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 EGUsourced 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 visualspatial 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. 

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

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

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 highend self-caught fish consumers active at 

inland freshwater lakes and streams. 

The analysis estimated that 29 percent 

of the watersheds studied would lead to 


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36The 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. 

37The 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. 

38Agency 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. 

39https://iris.epa.gov/ChemicalLanding/ 

&substance_nmbr=73. 

40Availability of the IRIS Assessment Plan for 

Methylmercury. 84 FR 13286 (April 4, 2019). 

41Availability of the Systematic Review Protocol 

for the Methylmercury Integrated Risk Information 

System (IRIS) Assessment. 85 FR 32037 (May 28, 

2020). 

42Hu, 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. 

43Roman HA, Walsh TL, Coull BA, Dewailly E ́, 

Guallar E, Hattis D, Marie ̈n K, Schwartz J, Stern AH, 

Virtanen JK, Rice G. Evaluation of the 

cardiovascular effects of methylmercury exposures: 

Current evidence supports development of a doseresponse function for regulatory benefits analysis. 

Continued 

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

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. 

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). 

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

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 metaanalysis (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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Environ Health Perspect. 2011 May;119(5):607–14. 

doi: 10.1289/ehp.1003012. Epub 2011 Jan 10. 

44Amorim 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. 

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: https://www.ncbi.nlm.

nih.gov/books/NBK499780. 

46U.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. 

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. 

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). 

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 NonMercury 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 nonmetal), 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. 

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 


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47U.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. 

48Concentration-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. 

49U.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, Go ́mez-Aracena J, Kark JD, Riemersma 

RA, Martı ́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, Seppa ̈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. 

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. 

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 MImortality 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. 

a. Methodology for Estimating MIMortality 

This section describes the 

methodology used in the new screeninglevel 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 peerreviewed 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 hairmercury 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 hairmercury levels for U.S. women of childbearing age, as characterized in National 

Health and Nutrition Examination 


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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. 

53Hu 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. 

54Mozaffarian 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. 

55NHANES has not continued to collect hairmercury 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 hairmercury, 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. 

56A 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. 

57Note 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 MImortality 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. 

Survey (NHANES) data and referenced 

by the panel). 

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 loglinear 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 

(mg/g) hair-mercury depending on the 

endpoint) where the function turns 

positive (increasing risk). 

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 cardiovascularrelated 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 mg/g hair-mercury, 

respectively, or approximately the 75th95th 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). 

b. Increased MI-Mortality Risk in 

Subsistence Fishers Exposed to 

Methylmercury 

This screening-level analysis of MImortality 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 mercuryrelated 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

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 (mg/kg-day 

methylmercury intake) generated for the 

subsistence fisher scenario in each 


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58Although 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. 

59Although 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, commerciallysourced fish refers to fish consumed in restaurants 

or from food stores. 

60Another way of stating this is that the lowerbound 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 

Continued 

watershed to generate equivalent hairmercury 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 mg/g hairmercury, respectively), then we 

consider that watershed to be at 

increased risk for MI mortality 

exclusively due to that U.S. EGUattributable 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). 

Table 3 of the 2021 Risk TSD presents 

the results of the analysis of risk for MImortality for the subsistence fisher 

scenarios. As with the original RfDbased risk estimates, these results are 

dimensioned on two key parameters 

(self-caught fish consumption rate and 

the watershed percentile exposure 

level—hair-mercury mg/g). Those 

watershed percentile hair-mercury 

values that exceed the EURAMIC-based 

MI mortality confidence cutpoints (0.66 

mg/g hair-mercury) are shaded in the 

table and those cells that also exceed the 

KIHD-based MI mortality confidence 

cutpoint (1.9 mg/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. 

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 lowerbound 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 upperbound 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 


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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). 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). 

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). 

63Maternal 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). 

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. 

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. 

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 hairmercury 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. 

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 oilfired 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 


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64U.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 https://www.epa.gov/sites/production/files/2015- 

07/documents/fullreport_rev_a.pdf. 

65U.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 https://nepis.epa.gov/Exe/ZyPDF.cgi/ 

P1000ZYP.PDF?Dockey=P1000ZYP.PDF. 

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. 

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: 

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 exposureresponse 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 (PM2.5) 

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 


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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. 

67Cropper M., Krupnick A., and W. Raich, 

Preferences for Equality in Environmental 

Outcomes, Working Paper 22644 http://

www.nber.org/papers/w22644 National Bureau of 

Economic Research, September 2016. 

68Bell, 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. 

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 casestudy 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 postcontrol 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 HAPimpacted 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 HAPrelated 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 postcontrol 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. 

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; 


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69Note 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. 

70Recognizing 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. 

71U.S. EPA. Integrated Science Assessment for 

Sulfur Oxides—Health Criteria (Final Report). U.S. 

Environmental Protection Agency, Washington, DC, 

EPA/600/R–17–451, December 2017. 

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 underinvestment 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 MImortality 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. 

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. EGUsourced 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 MImortality risk in 10 percent of the 

watersheds modeled, two subpopulations 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 RfDbased 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. 

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 PM2.5, 

nitrogen oxides (NOX) (including NO2), 

and SO2, 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 

SO2 and 1.9 million tons of NOX in 2015 

prior to implementation of any controls 

under MATS (see Table ES–2). These 

EGU SO2 emissions were approximately 

twice as much as all other sectors 

combined (EPA SO2 Integrated Science 

Assessment, 2017).71 These pollutants 

contribute to the formation of PM2.5 and 

ozone criteria pollutants in the 

atmosphere, the exposure to which is 

causally linked with a range of adverse 

public health effects. SO2 both directly 

affects human health and is a precursor 

to PM2.5. Short-term exposure to SO2

causes respiratory effects, particularly 

among adults with asthma. SO2 serves 

as a precursor to PM2.5, the exposure to 

which increases the risk of premature 

mortality among adults, lung cancer, 

new onset asthma, exacerbated asthma, 

and other respiratory and cardiovascular 

diseases. Likewise, EGU-related 

emissions of NOX will adversely affect 

human health in the form of respiratory 

effects including exacerbated asthma. 

NOX is a precursor pollutant to both 

PM2.5 and ground-level ozone. Exposure 

to ozone increases the risk of 

respiratory-related premature death, 

new onset asthma, exacerbated asthma, 

and other outcomes. Fully accounting 

for the human health impacts of 

reduced EGU emissions under MATS 

entails quantifying both the direct 

impacts of HAP as well as the avoided 

premature deaths and illnesses 

associated with reducing these coemitted criteria pollutants. Similarly, 


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72See https://19january2017snapshot.epa.gov/ 

climatechange/social-cost-carbon_.html: ‘‘EPA and 

other federal agencies use estimates of the social 

cost of carbon (SC–CO2) to value the climate 

impacts of rulemakings. The SC–CO2 is a measure, 

in dollars, of the long-term damage done by a ton 

of carbon dioxide (CO2) emissions in a given year. 

This dollar figure also represents the value of 

damages avoided for a small emission reduction 

(i.e., the benefit of a CO2 reduction). The SC–CO2

is meant to be a comprehensive estimate of climate 

change damages and includes changes in net 

agricultural productivity, human health, property 

damages from increased flood risk, and changes in 

energy system costs, such as reduced costs for 

heating and increased costs for air conditioning. 

However, given current modeling and data 

limitations, it does not include all important 

damages.’’ 

U.S. EGUs emit substantial quantities of 

CO2, a powerful greenhouse gas (GHG): 

The EPA estimated these emissions at 

2.23 million metric tpy in 2015 (2011 

RIA, Table ES–2). The environmental 

impacts of GHG emissions are 

accounted for through the social cost of 

carbon,72 which can be used to estimate 

the benefits of emissions reductions due 

to regulation. 

Not all of the non-HAP benefits of 

MATS were quantified or monetized in 

the 2011 RIA. However, the EPA 

thoroughly documented these potential 

effects and identified those for which 

quantification and/or monetization was 

possible. Specifically, the EPA 

calculated the number and value of 

avoided PM2.5-related impacts, 

including 4,200 to 11,000 premature 

deaths, 4,700 nonfatal heart attacks, 

2,600 hospitalizations for respiratory 

and cardiovascular diseases, 540,000 

lost work days, and 3.2 million days 

when adults restrict normal activities 

because of respiratory symptoms 

exacerbated by PM2.5 (2011 RIA, p. ES– 

3). We also estimated substantial 

additional health improvements for 

children from reductions in upper and 

lower respiratory illnesses, acute 

bronchitis, and asthma attacks. In 

addition, we included in our monetized 

co-benefits estimates the effect from the 

reduction in CO2 emissions resulting 

from this rule, based on the interagency 

SC–CO2 estimates. These benefits 

stemmed from imposition of MATS and 

would be coincidentally realized 

alongside the HAP benefits. 

7. Summary of Public Health Hazards 

Associated With Emissions From EGUs 

The EPA is proposing to find that the 

evidence provided in this section of the 

preamble, informed where possible with 

new scientific evidence available since 

the publication of the 2016 

Supplemental Finding, once again 

demonstrates that HAP released from 

U.S. EGUs represent a significant public 

health hazard absent regulation under 

CAA section 112. As noted earlier, the 

EPA found that even after imposition of 

the other requirements of the CAA, 

EGUs were the largest domestic source 

of mercury, HF, HCl, and selenium and 

among the largest domestic contributors 

of arsenic, chromium, cobalt, nickel, 

hydrogen cyanide, beryllium, and 

cadmium. The EPA has documented a 

wide range of adverse health effects in 

children and adults associated with 

mercury including, in particular, 

neurodevelopmental effects in children 

exposed prenatally (e.g., IQ, attention, 

fine motor-function, language, and 

visual spatial ability) and a range of 

cardiovascular effects in adults 

including fatal MI and non-fatal IHD. 

Non-mercury HAP have also been 

associated with a wide range of chronic 

health disorders (e.g., irritation of the 

lung; decreased pulmonary function, 

pneumonia, or lung damage; 

detrimental effects on the central 

nervous system; and damage to the 

kidneys). Furthermore, three of the key 

metal HAP emitted by EGUs (arsenic, 

chromium, and nickel) have been 

classified as human carcinogens and 

there is evidence to suggest that, prior 

to MATS, emissions from these sources 

had the potential to result in cancer 

risks greater than 1-in-1 million. 

Further, this section describes the 

results from several new screening-level 

risk assessments considering mercury 

from domestic EGU sources. These risk 

assessments focused on two broad 

populations of exposure: (a) Subsistence 

fishers exposed to mercury through selfcaught fish consumption within the 

continental U.S. and (b) the general U.S. 

population exposed to mercury through 

the consumption of commerciallysourced fish (i.e., purchased from 

restaurants and food stores). The results 

of these screening-level risk assessments 

are useful for informing our 

understanding about the potential scope 

and public health importance of these 

impacts, but remaining uncertainties 

prohibit precise estimates of the size of 

these impacts currently. For example, 

numerous studies considering multiple, 

large cohorts have shown that people 

exposed to high amounts of mercury are 

at higher risk of fatal and non-fatal CVD. 

While U.S. EGUs are only one of 

multiple global sources that contribute 

to this mercury exposure, the EPA’s 

screening analysis suggests the potential 

for U.S. EGU emissions of mercury to 

contribute to premature mortality in the 

general U.S. population. 

Furthermore, as part of the 

subsistence fisher analyses, we included 

scenario modeling for a number of EJrelevant populations showing that 

several populations (including lowincome Blacks and whites in the 

Southeast and tribal populations near 

the Great Lakes) had risk levels that 

were significantly above the general 

subsistence fisher population modeled 

for the entire U.S. As noted earlier, the 

EPA believes that Congress intended in 

CAA section 112 to address risks to the 

most exposed and most sensitive 

members of the public. These additional 

risk assessments suggest that there are 

populations that are particularly 

vulnerable to EGU HAP emissions, 

including populations of concern from 

an EJ standpoint. 

MATS plays a critical role in reducing 

the significant volume and risks 

associated with EGU HAP emissions 

discussed above. Mercury emissions 

have declined by 86 percent, acid gas 

HAP by 96 percent, and non-mercury 

metal HAP by 81 percent since 2010 

(pre-MATS). See Table 4 at 84 FR 2689 

(February 7, 2019). MATS is the only 

Federal requirement that guarantees this 

level of HAP control from EGUs. At the 

same time, the concomitant reductions 

in CO2, NOX, and SO2, also provide 

substantial public health and 

environmental benefits. Given the 

numerous and important public health 

and environmental risks associated with 

EGU emissions, the EPA again 

concludes that the advantages of 

regulating HAP emissions from this 

sector are significant. Acknowledging 

the difficulties associated with 

characterizing risks from HAP emissions 

discussed earlier in this section, we 

solicit comments about the health and 

environmental hazards of EGU HAP 

emissions discussed in this section and 

the appropriate approaches for 

quantifying such risks, as well any 

information about additional risks and 

hazards not discussed in this proposal. 

B. Consideration of Cost of Regulating 

EGUs for HAP 

1. Introduction 

In evaluating the costs and 

disadvantages of MATS, we begin with 

the costs to the power industry of 

complying with MATS. This assessment 

uses a sector-level (or system-level) 

accounting perspective to estimate the 

cost of MATS, looking beyond just 

pollution control costs for directly 

affected EGUs to include incremental 

costs associated with changes in fuel 

supply, construction of new capacity, 

and costs to non-MATS units that were 

also projected to adjust operating 

decisions as the power system adjusted 

to meet MATS requirements. Such an 

approach is warranted due to the nature 

of the power sector, which is a large, 

complex, and interconnected industry. 


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73All costs were reported in 2007 dollars. 

74 IPM, developed by ICF International, is a stateof-the-art, peer-reviewed, dynamic, deterministic 

linear programming model of the contiguous U.S. 

electric power sector. IPM provides forecasts of 

least-cost capacity expansion, electricity dispatch, 

and emission control strategies while meeting 

electricity demand and various environmental, 

transmission, dispatch, and reliability constraints. 

The EPA has used IPM for over 2 decades to 

understand power sector behavior under future 

business-as-usual conditions and to evaluate the 

economic and emission impacts of prospective 

environmental policies. 

75 In 2009, coal-fired generation was by far the 

most important source of utility scale generation, 

providing more power than the next two sources 

(natural gas and nuclear) combined. By 2016, 

natural gas had passed coal-fired generation as the 

leading source of generation in the U.S. While 

natural gas-fired generation, nuclear generation and 

renewable generation have all increased since 2009, 

coal-fired generation has significantly declined. 

This means that while the MATS 

requirements are directed at a subset of 

EGUs in the power sector, the 

compliance actions of the MATSregulated EGUs can affect production 

costs and revenues of other units due to 

generation shifting and fuel and 

electricity price changes. Thus, the 

EPA’s projected compliance cost 

estimate represents the incremental 

costs to the entire power sector to 

generate electricity, not just the 

compliance costs projected to be 

incurred by the coal- and oil-fired EGUs 

that are regulated under MATS. 

Limiting the cost estimate to only those 

expenditures incurred by EGUs directly 

regulated by MATS would provide an 

incomplete estimate of the costs of the 

rule. 

Using this broad view, in the 2011 

RIA we projected that the compliance 

cost of MATS would be $9.6 billion per 

year in 2015.73 This estimate of 

compliance cost was based on the 

change in electric power generation 

costs between a base case without 

MATS and a policy case where the 

sector complies with the HAP emissions 

limits in the final MATS. The EPA 

generated this cost estimate using the 

Integrated Planning Model (IPM).74 This 

model is designed to reflect electricity 

markets as accurately as possible using 

the best available information from 

utilities, industry experts, natural gas 

and coal market experts, financial 

institutions, and government statistics. 

Notably, the model includes cost and 

performance estimates for state-of-theart air pollution control technologies 

with respect to mercury and other HAP 

controls. But there are inherent limits to 

what can be predicted ex ante. And 

because the estimate was made 5 years 

prior to full compliance with MATS, 

stakeholders, including a leading power 

sector trade association, have indicated 

that our initial cost projection 

significantly overestimated actual costs 

expended by industry. There are 

significant challenges to producing an 

ex post cost estimate that provides an 

apples-to-apples comparison to our 

initial cost projections, due to the 

complex and interconnected nature of 

the industry. However, independent 

analyses provided to the EPA indicate 

that we may have overestimated the cost 

of MATS by billions of dollars per year. 

Moreover, there have been significant 

changes in the power sector in the time 

since MATS was promulgated that were 

not anticipated in either EPA or U.S. 

Energy Information Administration 

(EIA) projections at the time.75 Entirely 

outside of the realm of EPA regulation, 

there were dramatic shifts in the cost of 

natural gas and renewables, state 

policies, and Federal tax incentives, 

which have also further encouraged 

construction of new renewables. These 

have led to significantly faster and 

greater than anticipated retirement of 

coal capacity and coal-fired generation. 

While there are significant limitations 

to producing an ex post cost estimate, 

we have endeavored, where possible, to 

approximate the extent of our 

overestimate. The unexpected shifts in 

the power sector, including the rapid 

increase in natural gas supplies that 

occurred after promulgation of MATS, 

resulted in our projected estimates of 

natural gas prices to be approximately 

double what they were in actuality. 

Incremental natural gas expenditures 

accounted for approximately 25 percent 

of the $9.6 billion compliance cost 

estimate for 2015 in the 2011 RIA. The 

market trends of the power sector also 

had major impacts on the number of 

controls installed and operated on coalfired EGUs in the years following 

promulgation of MATS. With respect to 

just pollution control installation and 

operation, we project that we 

overestimated annual compliance costs 

by at least $2.2 to 4.4 billion per year, 

simply as a result of fewer pollution 

controls being installed than were 

estimated in the 2011 RIA. Though this 

range of an overestimate is limited to 

costs associated with pollution controls 

and operation, those costs made up 70 

percent of the projected $9.6 billion 

figure. 

We additionally find that the controls 

that were installed at MATS-regulated 

EGUs were likely both less expensive 

and more effective in reducing pollution 

than originally projected, resulting in 

our estimate likely being too high for 

these reasons as well. Lastly, since 

completing the 2011 RIA, we have 

updated several assumptions in our 

modeling that would also have resulted 

in a lower cost estimate had they been 

incorporated into our modeling at the 

time of the rule. Taking into account the 

above considerations, we believe we 

overestimated the cost of MATS by 

billions of dollars. 

We next examine the projected cost of 

MATS—both total cost and specific 

types of costs—using sector-level 

metrics that put those cost estimates in 

context with the economics of the 

power sector. The reason we examine 

these metrics is to better understand the 

disadvantages that expending these 

costs had on the EGU industry and the 

public more broadly, just as on the 

benefits side we look beyond the 

volume of pollution reductions to the 

health and environmental advantages 

conferred by the reductions. 

For purposes of these analyses, we 

use the 2011 RIA projections, keeping in 

mind our newer analyses, which 

indicated that those projections were 

almost certainly overestimated. Specific 

to the power sector, we evaluate the 

projected costs of the rule to revenues 

from electricity sales across nearly 20 

years, and we compare the projected 

expenditures required under the rule 

with historic expenditures by the 

industry over the same time period. We 

additionally evaluate broader impacts 

on the American public by looking at 

projected effects of MATS on retail 

electricity prices and our analyses of 

whether the power sector could 

continue to provide adequate and 

reliable electricity after imposition of 

the rule. We find that, when viewed in 

context, the projected costs of MATS to 

both the power sector and the public 

were small relative to these metrics and 

well within the range of historical 

variability. Moreover, experience has 

borne out our projection that the EGU 

sector could continue to provide 

adequate, reliable, and affordable 

electricity to the American public after 

the imposition of the rule. 

Section III.B.2 contains our discussion 

of the ways in which the compliance 

costs for MATS were likely 

overestimated. Section III.B.3 expands 

upon and re-evaluates the cost metrics 

used in the 2016 Supplemental Finding 

by adding post-promulgation 

information to our analysis, and we 

discuss impacts on power sector 

generating capacity. In section III.B.4, 

we propose to reaffirm additional cost 

considerations regarding the availability 

and cost of control technologies 

discussed in earlier rulemakings, and in 

section III.B.5, we provide our proposed 

conclusions regarding the costs, or 

disadvantages, of regulating HAP from 

EGUs. 


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76Affected sources were required to be in 

compliance with the requirements in MATS within 

3 years after the effective date of the rule (i.e., by 

April 2015). However, sources were allowed to 

request an additional year to comply with the rule 

and the vast majority of sources were required to 

be in compliance with the rule’s requirements by 

April 2016. We therefore think 2017 is a reasonable 

year in which to analyze installed controls on the 

EGU fleet. 

77 Kopits, E., A. McGartland, C. Morgan, C. 

Pasurka, R. Shadbegian, N. B. Simon, D. Simpson 

and A. Wolverton (2015). Retrospective cost 

analyses of EPA regulations: a case study approach. 

Journal of Benefit-Cost Analysis 5(2): 173–193. 

78Linn, J. and K. McCormack (2019). The Roles 

of Energy Markets and Environmental Regulation in 

Reducing Coal-Fired Plant Profits and Electricity 

2. Compliance Cost Projections in the 

2011 RIA Were Likely Significantly 

Overestimated 

In issuing this proposal, the EPA finds 

itself in a position Congress was not 

likely to have contemplated when it 

promulgated the 1990 Amendments. 

The statute contemplated that the EPA 

would have completed the required 

studies and presumably made its 

determination more than 20 years ago. 

Due to litigation and multiple changes 

of administration following Michigan, 

we are, at this point, nearly 10 years 

after promulgation of the regulation 

about which we are making a threshold 

determination, and 5 years after full 

implementation of that regulation. The 

vast majority of MATS-affected sources 

were required to be in compliance with 

the rule’s requirements by April 2016, 

and installation of new controls–or 

upgrades to existing controls–were in 

place by 2017.76 This means we now 

have on hand unit-level data regarding 

installations, a clearer picture about 

market trends, and updated, more 

accurate assumptions that, taken 

together, produce a very different 

picture of the actual costs of MATS than 

what we projected when we reaffirmed 

the appropriate and necessary 

determination and promulgated the rule 

in 2012. Therefore, while the Agency 

considers that the information that was 

available at the time of MATS 

promulgation provided a valid 

analytical basis for the threshold 

appropriate and necessary 

determination, because many years have 

elapsed since then, the EPA believes it 

is reasonable to examine how the power 

sector has evolved since MATS was 

finalized and, with the benefit of 

hindsight, compare important aspects of 

the 2011 RIA projections with what 

actually happened since MATS was 

promulgated. Because our obligation 

under CAA section 112(n)(1)(A) is to 

fully consider the advantages and 

disadvantages of regulating a large, 

critically important industry, whose role 

impacts the lives of every American, we 

think it is important to evaluate and 

consider the best, currently available 

information, even if, as discussed in 

sections III.B.3 and 4, the pre-existing 

record supports the same conclusion. 

This ex post examination demonstrates 

that the EPA almost certainly 

significantly overestimated compliance 

costs in the 2011 RIA, which further 

supports the determination that 

regulation is appropriate and necessary 

after considering cost. We also do not 

view this updated, post-hoc evaluation 

of what happened post-promulgation as 

undermining the record we established 

in 2012. Models are not invalidated 

‘‘solely because there might be 

discrepancies between those predictions 

and the real world. That possibility is 

inherent in the enterprise of 

prediction.’’ EME Homer City 

Generation, L.P. v. EPA, 795 F.3d 118, 

135–36 (D.C. Cir. 2015). 

In an ideal world, with perfect 

information, we would be able to 

generate an ex post analysis of 

regulatory costs that could be compared 

to our ex ante cost estimate prepared at 

the time MATS was issued. However, it 

is extremely challenging to produce 

rigorous retrospective estimates of 

regulatory costs. A literature review and 

series of case studies performed by EPA 

staff provides insights on how analysts 

can perform retrospective cost 

analysis.77 Kopits et al. (2015) identifies 

several challenges associated with ex 

post cost assessments, including data 

limitations with respect to how facilities 

chose to comply with regulations and 

comprehensive facility-level pollution 

abatement costs. A key component to a 

rigorous retrospective analysis noted by 

the authors that can be particularly 

difficult to achieve is an accurate 

definition of the counterfactual, that is, 

what would have occurred absent the 

rule. It is this counterfactual that 

provides the baseline against which the 

incremental costs of regulation are 

estimated. 

In the case of MATS, to construct an 

estimate of ex post implementation 

costs that is directly comparable to the 

ex ante 2011 RIA cost estimate, we 

would first need to accurately attribute 

changes in the power sector that were 

due to MATS requirements rather than 

to market and technological changes, 

other regulations, or, importantly, 

combinations of these factors (i.e., 

properly specify the counterfactual). 

Second, we would need actual 

information of the incremental costs 

that had been associated with facilitylevel operational changes due to MATS, 

such as observed changes in dispatch, 

actual fuel consumption, and how 

controls in MATS-affected units were 

actually operated. Even the operation of 

non-MATS affected units would be 

relevant to such an analysis, because 

operational decisions are interconnected 

on the grid via dispatch decisions as 

well as through fuel markets. While 

there may be approaches such as 

econometric analysis, simulation 

modeling, and event study analysis that 

could capture and estimate components 

of the problem identified above and 

derive an estimate of ex post MATS 

costs, the approach would very likely 

require different methods and 

assumptions than the 2011 RIA 

estimates which were based on the 

comparison of two forward-looking sets 

of projections. Even if we undertook 

such additional analysis or modeling, 

ultimately we would still only be able 

to provide a new estimate of regulatory 

costs, not an actual cost. Given how 

challenging it is to produce rigorous 

retrospective estimates of regulatory 

costs, particularly at a system-level, an 

ex post analysis is better suited to 

comparing particular aspects of the 

analysis, which can help us understand 

whether costs in the 2011 RIA were 

over- or under-estimated and can yield 

a general sense of how much reality 

diverged from the projection, than to 

attempting to generate a new and 

precise ‘‘actual’’ total compliance cost 

estimate for MATS. 

Estimating retrospective costs for a 

rule of the magnitude of MATS is an 

especially significant challenge because 

the rule regulates hundreds of units 

within a complex, interdependent, and 

dynamic economic sector. Units within 

the power sector are also subject to 

many regulatory requirements and other 

economic drivers. While we can observe 

the decisions of the sector and 

individual units in terms of decisions 

on controls, fuels, and retirement, we 

cannot pinpoint the reason(s) behind 

each unit-level decision. With respect to 

identifying the counterfactual against 

which to evaluate retrospective 

compliance costs, several unforeseen 

factors since MATS promulgation have 

driven changes in the power sector that 

have led to the composition of the 

current fleet being different than the 

fleet projected in the 2011 RIA. For 

example, dramatic increases in the 

supply of natural gas, along with 

advances in cost and performance of 

renewable generation technologies and 

low electricity demand growth, none of 

which were fully anticipated in the 

2011 RIA, have made strong 

contributions to shifts away from coalfired generation.78 79 Additionally, other 


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Sector Emissions. RAND Journal of Economics 50: 

733–767. 

79Coglianese, J., et al. (2020). The Effects of Fuel 

Prices, Environmental Regulations, and Other 

Factors on U.S. Coal Production, 2008–2016. The 

Energy Journal 41(1): 55–82. 

80 85 FR 53516 (August 28, 2020), 80 FR 67838 

(November 3, 2015), and 85 FR 64650 (October 13, 

2020), respectively. 

81 Declaration of James E. Staudt, Ph.D., CFA, at 

3, White Stallion Energy Center v. EPA, No. 12– 

1100 (DC Cir., December 24, 2015). Also available 

at Docket ID Item No. EPA–HQ–OAR–2009–0234– 

20549. 

82 In addition to the 2015 study, Andover 

Technology Partners produced two other analyses 

in 2017 and 2019, respectively, that estimated the 

ongoing costs of MATS. The 2017 report estimated 

that the total annual operating cost for MATSrelated environmental controls was about $620 

million, an estimate that does not include ongoing 

payments for installed environmental capital. The 

2019 report estimates the total annual ongoing 

incremental costs of MATS to be about $200 

million; again, this estimate does not include 

ongoing MATS-related capital payment. The 2017 

report is available in Docket ID Item No. EPA–HQ– 

OAR–2018–0794–0794. The 2019 report is available 

in Docket ID Item No. EPA–HQ–OAR–2018–0794– 

1175. 

83Available in Docket ID Item No. EPA–HQ– 

OAR–2018–0794–1145. 

84Available in Docket ID Item No. EPA–HQ– 

OAR–2018–0794–2267. 

85U.S. EPA. 2021. Supplemental Data and 

Analysis for the National Emission Standards for 

Hazardous Air Pollutants: Coal- and Oil-Fired 

Electric Utility Steam Generating Units—Revocation 

of the 2020 Reconsideration, and Affirmation of the 

Appropriate and Necessary Supplemental Finding; 

Notice of Proposed Rulemaking (‘‘Cost TSD’’). 

86We projected that regulation of coal- and oilfired EGUs under MATS would induce units to 

switch to natural gas, which in turn would increase 

the price of natural gas and the cost of those 

expenditures. 

EPA regulations such as the Disposal of 

Coal Combustion Residuals from 

Electric Utilities final rule, the Steam 

Electric Power Generating Effluent 

Guidelines—2015 Final Rule, and the 

2020 Steam Electric Reconsideration 

Rule, were promulgated after MATS.80

While the compliance periods of these 

rules all postdate the MATS compliance 

date, utilities are likely to consider 

multiple regulations simultaneously 

when making planning decisions, a 

likelihood that also complicates the 

identification of the counterfactual 

scenario of a world without MATS that 

is needed to generate an ex post 

incremental cost estimate of MATS that 

would be directly comparable to the ex 

ante 2011 RIA cost estimate. 

Even though it is extremely 

challenging to produce the type of ex 

post incremental cost estimate 

discussed above, several stakeholders 

have conducted analyses, focusing on 

different components of the regulation’s 

cost, to assess actual costs of 

compliance. While none of these 

estimates can be precisely compared 

against the EPA ex ante estimates 

because they use different methods than 

the power sector modeling the EPA used 

in the 2011 RIA, all of the independent 

analyses suggested that the actual 

compliance costs expenditures were 

significantly lower—by billions of 

dollars—than the EPA estimated in the 

2011 RIA. 

First, a 2015 analysis by Andover 

Technology Partners focused on the 

capital and operating costs associated 

with the actual installation and 

operation of pollution control 

equipment at MATS-regulated units and 

made two key findings: the number of 

installed controls was significantly 

lower than the number of controls that 

was projected in the 2011 RIA and the 

cost of the installed controls was 

generally lower than the control costs 

that the EPA assumed in the 2011 RIA 

modeling. Based on these findings, the 

study estimated that the EPA’s projected 

cost of compliance was over-estimated 

by approximately $7 billion.81 82 In other 

words, the Andover Technology 

Partners estimated that the EPA’s 

projected cost was approximately four 

times higher than their retrospective 

estimate of cost, which they estimated 

to be approximately $2 billion per year. 

Second, a 2017 study performed by 

M.J. Bradley & Associates (MJB&A) used 

information from the EIA and estimated 

that owners and operators of coal-fired 

EGUs incurred total capital 

expenditures on environmental retrofits 

of $4.45 billion from December 2014 to 

April 2016.83 To the EPA’s 

understanding, the MJB&A cost estimate 

represents total upfront capital costs 

(not ongoing operating and maintenance 

expenditures), and is not annualized as 

was the capital expenditure in the 2011 

RIA-based projected cost estimate. For 

comparison, the estimated total upfront 

(not annualized) capital expenditures 

underpinning the 2011 RIA annual 

compliance cost estimate is about $36.5 

billion, which is more than eight times 

higher than the MJB&A estimates. This 

result suggests that the capital cost 

component of the 2011 RIA cost 

projections was significantly 

overestimated, potentially by a factor of 

more than eight. 

Third, the Edison Electric Institute 

(EEI), the association that represents all 

U.S. investor-owned electric companies, 

estimated that by April 2019, owners 

and operators of coal- and oil-based 

EGUs incurred cumulative (not annual) 

compliance costs of more than $18 

billion to comply with MATS, including 

both capital and operations and 

maintenance costs since MATS became 

effective in April 2012.84 In order to 

provide a simple comparison between 

the EEI figure, which was incurred over 

7 years, and the annualized amount 

presented in the 2011 RIA ($9.6 billion), 

we can divide the EEI figure by 7 to 

estimate an average annual amount of 

approximately $2.6 billion, which is 

similar to the Andover Technology 

Partners estimate of approximately $2 

billion. Also in line with the Andover 

Technology Partners estimate, EEI’s 

estimate suggests that the annual costs 

related to MATS compliance were 

overestimated in the 2011 RIA by 

approximately $7 billion. While there is 

some uncertainty in the amount of time 

over which those costs were incurred, as 

well as the exact nature of those 

expenditures, it is clear that the 

information provided by EEI supports a 

conclusion that the costs of compliance 

with MATS were significantly lower 

than the Agency’s projections. 

In summary, it is the EPA’s 

understanding that two of these studies 

indicate that the 2011 RIA may have 

overestimated annual compliance costs 

by approximately $7 billion, and the 

third study finds that the projected total 

upfront capital costs may have been 

overestimated by a factor of more than 

eight. While each of these retrospective 

cost estimates is developed from bases 

that are dissimilar from one another 

and, in particular, from how the EPA 

developed the prospective cost 

estimates in the 2011 RIA, each of the 

independent analyses indicate that the 

costs of MATS are likely significantly 

less than the EPA estimated in the 2011 

RIA. 

For this proposal, the EPA has 

evaluated whether the ex ante estimates 

in the 2011 RIA were likely accurate, 

overestimated, or underestimated, and 

the details of the EPA’s new analysis are 

contained in the docketed TSD (referred 

to herein as the ‘‘Cost TSD’’).85

Consistent with our systems-level 

approach, we begin our analysis with an 

evaluation of natural gas expenditures 

during the relevant time period. The 

rapid decrease in the price of natural gas 

during this time period affected U.S. 

power generation profoundly, including 

U.S. EGU fuel expenditures; this has 

significant implications for our ex post 

analysis because natural gas 

expenditures constituted approximately 

25 percent of the projected 2015 

compliance costs in the 2011 RIA.86

These market shifts in the industry also 

impacted expenditures associated with 

the installation and operation of 

pollution control equipment at MATSaffected facilities. Those costs 

constituted a majority—about 70 

percent—of the projected annual 

compliance costs in 2015. The following 


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87U.S. Crude Oil and Natural Gas Proved 

Reserves, Year-end 2019 (Table 9: U.S. proved 

reserves of natural gas). EIA, January 11, 2021 

release available at https://www.eia.gov/naturalgas/ 

crudeoilreserves. Accessed July 23, 2021. 

88 Monthly Energy Review, EIA (June 24, 2021) 

and Today in Energy (‘‘U.S. total energy exports 

exceed imports in 2019 for the first time in 67 

years’’), EIA (April 20, 2020) available at https://

www.eia.gov/todayinenergy/detail.php?id=43395. 

Accessed July 23, 2021. 

89BP, Statistical Review of World Energy 2021 

available at https://www.bp.com/en/global/ 

corporate/energy-economics/statistical-review-ofworld-energy.html. Accessed July 23, 2021. 

sections closely examine these two 

components of the compliance cost and 

use available information to evaluate 

whether the projected compliance costs 

reported in the 2011 RIA were likely 

higher or lower than actual costs. We 

also review important cost assumptions 

used in the 2011 RIA. Taken together, 

this suite of quantitative and qualitative 

evaluations indicates that the projected 

costs in the 2011 RIA were almost 

certainly significantly overestimated. 

We find that the 2011 RIA’s estimate of 

the number of installations alone led to 

an overestimate of about $2.2 to $4.4 

billion, and that if recent updates to the 

cost and performance assumption for 

pollution controls had been reflected in 

the 2011 RIA modeling, the projected 

compliance costs would likely have 

been even lower (suggesting the 

overestimate could be greater than $4.4 

billion). 

a. Natural Gas Supply 

The natural gas industry has 

undergone significant change in recent 

years. Starting in the mid-2000s, 

technological changes in natural gas 

drilling and extraction initiated major 

market changes that resulted in 

significant increases to domestic 

supplies of natural gas. As these 

technologies have continued to advance, 

they have had a lasting impact on 

natural gas markets, resulting in major 

shifts in the economics of electric sector 

operations given the abundant supply of 

natural gas at relatively low costs. This 

section summarizes these changes and 

the implications for the cost projection 

presented in the 2011 RIA. 

In 2005, the EIA estimated that 

proved reserves of natural gas were 213 

trillion cubic feet (tcf).87 In 2019, the 

estimate of proved reserves was 495 tcf, 

an increase of 132 percent. The market 

effects of this major supply shift were 

profound across the economy, but 

especially for the power sector. By the 

end of 2019, aided by advances in 

drilling and hydraulic fracturing 

techniques, natural gas production from 

tight and shale gas formations was the 

major source of domestic production 

(see Table 1 below) and had increased 

three-fold from 2005 production levels. 

TABLE 1—U.S. NATURAL GAS PRODUCTION, BY SOURCE

[Trillion cubic feet] 

Year Tight/shale 

gas 

Other lower 

48 onshore 

Lower 48 

offshore Other 

2005 ................................................................................................................. 7.2 5.1 3.4 2.3 

2006 ................................................................................................................. 8.0 5.1 3.2 2.3 

2007 ................................................................................................................. 9.0 4.9 3.1 2.3 

2008 ................................................................................................................. 10.3 4.9 2.6 2.4 

2009 ................................................................................................................. 11.1 4.5 2.7 2.4 

2010 ................................................................................................................. 12.4 4.2 2.5 2.2 

2011 ................................................................................................................. 14.8 4.0 2.0 2.1 

2012 ................................................................................................................. 16.7 3.7 1.6 2.0 

2013 ................................................................................................................. 17.6 3.5 1.4 1.7 

2014 ................................................................................................................. 19.5 3.4 1.3 1.6 

2015 ................................................................................................................. 21.0 3.2 1.4 1.5 

2016 ................................................................................................................. 21.1 2.8 1.3 1.4 

2017 ................................................................................................................. 22.2 2.7 1.1 1.3 

2018 ................................................................................................................. 25.7 2.7 1.0 1.3 

2019 ................................................................................................................. 29.3 2.4 1.0 1.2 

2020 ................................................................................................................. 29.2 2.3 1.2 1.2 

Source: U.S. EIA, https://www.eia.gov/energyexplained/natural-gas/where-our-natural-gas-comes-from.php, accessed July 25, 2021. 

Note: ‘‘Other’’ includes production from 

Alaska and Coalbed Methane sources. 

As a result, the natural gas market 

underwent a long period of sustained 

low prices (see Table 2 below). These 

market shifts were not fully anticipated 

or predicted by observers, as indicated 

by natural gas futures prices at the time 

of MATS promulgation. Although these 

changes took root in the mid-2000s, the 

lasting market disruption would take 

more time to cement itself. From 2010 

through 2019, the U.S became one of the 

world’s leading producers of natural 

gas, breaking domestic production 

records year-on-year through the 

decade, while maintaining record-low 

prices. During this timeframe, the U.S. 

shifted from a total net energy importer 

to an exporter,88 while maintaining 

some of the lowest relative natural gas 

prices globally.89

TABLE 2—NATURAL GAS PRICES

Year 

NYMEX natural 

gas Henry Hub 

natural gas futures 

($/MMBtu), annual 

average, as of: 

2011–03–16 

NYMEX natural 

gas Henry Hub 

natural gas futures 

($/MMBtu), annual 

average, as of: 

2011–12–21 

Henry Hub spot 

natural gas index 

annual average 

price 

($/MMBtu) 

2005 ........................................................................................................................... .............................. .............................. 8.63 

2006 ........................................................................................................................... .............................. .............................. 6.74 

2007 ........................................................................................................................... .............................. .............................. 6.96 


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90Table 4.3, Monthly Energy Review, EIA, April 

2021, available at https://www.eia.gov/totalenergy/ 

data/monthly/archive/00352104.pdf. 

91EIA, Electricity Data Browser, Net generation, 

United States, all sectors, annual, available at 

https://www.eia.gov/electricity/data/browser/. 

TABLE 2—NATURAL GAS PRICES—Continued 

Year 

NYMEX natural 

gas Henry Hub 

natural gas futures 

($/MMBtu), annual 

average, as of: 

2011–03–16 

NYMEX natural 

gas Henry Hub 

natural gas futures 

($/MMBtu), annual 

average, as of: 

2011–12–21 

Henry Hub spot 

natural gas index 

annual average 

price 

($/MMBtu) 

2008 ........................................................................................................................... .............................. .............................. 8.90 

2009 ........................................................................................................................... .............................. .............................. 3.94 

2010 ........................................................................................................................... .............................. .............................. 4.37 

2011 ........................................................................................................................... 4.24 .............................. 4.00 

2012 ........................................................................................................................... 4.91 3.43 2.75 

2013 ........................................................................................................................... 5.31 4.07 3.73 

2014 ........................................................................................................................... 5.67 4.43 4.37 

2015 ........................................................................................................................... 6.04 4.66 2.63 

2016 ........................................................................................................................... 6.36 4.90 2.51 

2017 ........................................................................................................................... 6.67 5.16 2.98 

2018 ........................................................................................................................... 6.97 5.43 3.16 

2019 ........................................................................................................................... 7.25 5.70 2.56 

2020 ........................................................................................................................... 7.50 5.96 2.03 

2021 ........................................................................................................................... 7.76 6.23 ..............................

2022 ........................................................................................................................... 8.02 6.50 ..............................

2023 ........................................................................................................................... 8.28 6.78 ..............................

2024 ........................................................................................................................... .............................. 7.06 ..............................

Source: Annual Average Henry Hub Price, EIA. NYMEX price, from S&P Global data. 2015 data from 2011 RIA, Chapter 3. 

The EPA projected a 2015 natural gas 

price of roughly $5/MMBtu when 

MATS was finalized in December 2011, 

which was a reasonable expectation 

based on prevailing market conditions 

at that time. However, natural gas prices 

post-MATS promulgation ended up 

being considerably lower than 

anticipated, which resulted in major 

shifts in the economics of fossil fuelfired electric generating technologies 

(see Table 2 above and Chart A–1 in the 

Cost TSD). From 2005 through 2010, 

annual average natural gas prices (at 

Henry Hub) averaged about $6.60/ 

MMBtu. Several years later, as MATS 

compliance began, prices averaged 

roughly $2.75/MMBtu for the years 2015 

through 2019. This market shift greatly 

changed the economics of power plant 

operation for fossil fuel-fired facilities, 

with the electric sector surpassing the 

industrial sector to become the largest 

consumer of natural gas (38 percent of 

the total in 2020),90 and gas-fired 

generators becoming the leading source 

of electric generation in the electric 

sector, representing 40 percent of total 

generation in 2020.91

The modeling supporting the 2011 

RIA did not anticipate this major change 

in natural gas supply, which has clearly 

had a significant impact on the electric 

power sector and those sources covered 

by MATS. While we do not quantify the 

impact this change would have on the 

projected compliance costs associated 

with incremental changes in natural gas 

use and price (about 25 percent of the 

total projected compliance cost in the 

2011 RIA), we note that any closures of 

covered units that occurred as a result 

of the changed relative economics of 

fuel prices would decrease the MATSrelated compliance costs for the sector. 

These closures reduced the amount of 

control capacity necessary for 

compliance with MATS, and we 

estimate below a range of costs 

associated with the overestimation of 

control installations in the 2011 RIA. 

Several researchers have investigated 

the role of relative fuel prices as a factor 

in decisions that were made regarding 

closures of coal-fired units around 2015. 

Generally, these studies attribute 

closures primarily to the decrease in 

natural gas prices, and they also note 

smaller factors such as advances in the 

cost and performance of renewable 

generating sources, lower-thananticipated growth in electricity 

demand, and environmental regulations. 

For example, Linn and McCormack 

(2019) developed a simulation model of 

the U.S. Eastern Interconnection that 

reproduced unit operation, emissions, 

and retirements over the 2005–2015 

period. The authors use this model to 

explain the relative contributions of 

demand, natural gas prices, wind 

generation, and environmental 

regulations, including MATS, to the 

changes in the share of coal in 

electricity generation. The results 

showed that lower electricity 

consumption and natural gas prices 

account for a large majority of the 

declines in coal plant profitability and 

resulting retirements. The authors found 

that the environmental regulations they 

modeled, NOX emissions caps and 

MATS, played a relatively minor role in 

declines of coal plant profitability and 

retirements. 

Additionally, Coglianese et al. (2020) 

developed a statistical modeling 

approach to enable the decomposition 

of changes in U.S. coal production from 

2008–2016 into changes due to a variety 

of factors, including changes in 

electricity demand, natural gas prices 

relative to coal, renewable portfolio 

standards, and environmental 

regulations that affect coal-fired plants. 

The results indicated that declines in 

natural gas prices explained about 92 

percent of the decrease in coal 

production between 2008 and 2016. Air 

regulations, including MATS, explained 

about 6 percent of the drop in coal 

production. The study attributed about 

5.2 GW of coal-fired EGU retirements to 

MATS. 

These studies both demonstrate that 

the decrease in natural gas prices played 

a significant role in closures of coalfired EGUs. While we do not quantify 

the impact this change had on the 

projected costs included in the 2011 

RIA, we note that any closures of 

covered units that occurred as a result 

of the dramatically changed relative 

economics of fuel prices would decrease 

the MATS-related compliance costs for 

the sector. 


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b. Projected Versus Observed Pollution 

Control Installations 

The 2011 RIA reported a sector-level 

compliance cost of $9.6 billion annually 

in 2015. The majority of those costs— 

about 70 percent—represented the 

incremental annualized capital and 

annual operation and maintenance 

(O&M) costs associated with installation 

and operation of pollution controls for 

compliance with MATS at coal steam 

units. Given the time that has passed, 

we can now compare the incremental 

projected pollution control capacity 

reported in the 2011 RIA with available 

information regarding actual (observed) 

control installations. For this proposal, 

therefore, the EPA has compared 

observed installations and costs over 

2013–2016 to unit-level estimates of the 

control installation capacity and 

associated costs presented in the 2011 

RIA. This analysis demonstrates, subject 

to the caveats and uncertainty discussed 

below, that the 2011 RIA likely 

overestimated total pollution control 

retrofit capacity that would occur in 

response to MATS and, thus, likely 

overestimated MATS compliance costs. 

For example, the analysis that follows 

demonstrates that fabric filter (FF) 

systems—which are an expensive and 

capital-intensive control technology— 

were only installed on less than onethird of the capacity anticipated in the 

2011 RIA analysis. 

This comparison of projected to 

observed control capacity installations 

relies on the simplifying assumption 

that all dry scrubbers (e.g., dry FGD 

systems), dry sorbent injection (DSI) 

systems, activated carbon injection 

(ACI) systems, and FF systems installed 

during the 2013–2016 period were 

installed for compliance with the MATS 

emissions limits. This assumption is 

necessitated by the absence of 

comprehensive data on the specific 

reasons EGUs installed pollution control 

equipment. While assuming pollution 

controls of these types that were 

installed in this period are singularly 

attributable to MATS requirements is a 

reasonable assumption for this analysis, 

it is a highly conservative assumption 

given that some of the observed 

installations likely occurred in response 

to other regulations to control criteria 

air pollutants (e.g., Cross-State Air 

Pollution Rule, Regional Haze, Federal 

implementation plans, or state 

implementation plans) or enforcement 

actions (e.g., consent decrees). Because 

some of the observed installations in 

this analysis likely resulted from nonMATS requirements, the approach 

potentially over-attributes the amount of 

pollution controls built specifically for 

MATS compliance, thereby leading to 

an overestimate of the control costs 

associated with MATS. 

Table 3 presents the findings of this 

analysis in capacity terms. The total 

capacity projected to retrofit with each 

control in the 2011 RIA is reported for 

the base case (i.e., projected future 

conditions absent MATS) and under 

MATS. The difference is presented in 

the ‘Projected Incremental Controls’ 

column. So, for example, in the 2011 

RIA the EPA projected that there would 

be an incremental 20.3 GW of capacity 

retrofitting with dry FGD that is 

attributable to MATS. We compare the 

projected incremental controls capacity 

value to the observed installations 

capacity value. Note that we are unable 

to estimate the total capacity of 

observed upgrades to electrostatic 

precipitators (ESP) and scrubbers due to 

a lack of available data regarding such 

upgrades. For additional information, 

see the docketed Cost TSD. 

TABLE 3—PROJECTED VS. OBSERVED CAPACITY

[Gigawatts (GW)] 

Pollution control retrofit Base case MATS 

Projected 

incremental 

controls 

Observed 

installations 

(2013–2016) 

Difference: 

Observed 

minus 

projected 

(2013–2016) 

Percent 

difference: 

Observed 

minus 

projected 

(2013–2016) 

Dry FGD ................................................... 4.6 24.8 20.3 16.0 ¥4.3 ¥21 

DSI ........................................................... 8.6 52.5 43.9 15.8 ¥28.1 ¥64 

ACI ........................................................... 0 99.3 99.3 96.1 ¥3.2 ¥3 

FF ............................................................. 12.7 114.7 102 31.4 ¥70.6 ¥69 

ESP Upgrade ........................................... 0 33.9 33.9 N/A N/A N/A 

Scrubber Upgrade .................................... 0 63.1 63.1 N/A N/A N/A 

Source: Projected Controls: 2011 RIA; Observed Installations: NEEDS v.5.16. 

Note: FF installations include installations specifically related to PM control, as well as installations included with dry scrubber, DSI, and some 

ACI retrofits in the modeling. Totals may not sum due to rounding. 

This analysis demonstrates that 

projected incremental capacity of dry 

FGD, DSI, ACI, and FF was likely 

significantly overestimated in the 2011 

RIA. The capacities of actual installed 

control technologies are lower, often 

significantly lower, than projected (and 

again, this analysis attributes all control 

installations of certain types during this 

time period to MATS, even though some 

portion of those installations were likely 

made in whole or in part due to other 

regulations). For example, the installed 

DSI capacity is about two-thirds lower 

than was projected. The difference 

between observed installed control 

capacities and what we projected those 

incremental control capacities would be 

translates directly into significantly 

lower costs than estimated. Because the 

vast majority of compliance costs in the 

2011 RIA were related to the installation 

and operation of pollution controls, and 

because significant deployment of any 

higher-cost compliance strategies did 

not occur, the large differences observed 

in Table 3 suggest that the projected 

compliance costs were likely 

significantly overestimated as well. For 

example, approximately $2 billion was 

estimated to be attributable to the 

installation and operation of DSI 

controls (21 percent of the total annual 

projected costs of MATS), when in 

actuality, only one-third of those 

installations occurred (and some were 

likely attributable to regulations other 

than MATS). 

We also conduct an analysis of the 

approximate costs related to the 

overestimate of projected incremental 

pollution controls. This analysis is 

discussed in detail in the Cost TSD. 

Specifically, we compared observed 

installations over 2013–2016 to unitlevel estimates of the control 

installation capacity and associated 

costs presented in the 2011 RIA to 

develop a range of the potential 

overestimate of compliance costs related 


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92See https://www.epa.gov/airmarkets/ipmanalysis-proposed-mercury-and-air-toxicsstandards-mats. Accessed July 23, 2021. 

93See https://www.epa.gov/airmarkets/ 

documentation-supplement-base-case-v410mats. 

Accessed July 23, 2021. 

94 Id. 

95See https://www.epa.gov/sites/default/files/ 

2019-03/documents/chapter_5.pdf. Accessed July 

23, 2021. 

96While we are unable to quantify precisely the 

impact that updating this assumption would have 

on the projected compliance costs, we can observe 

that most incremental DSI capacity (about 40 GW) 

would not require DSI controls in the 2011 RIA 

modeling, holding all else constant. 

97See https://www.epa.gov/sites/production/files/ 

2015-07/documents/updates_to_epa_base_case_

v4.10_ptox.pdf. Accessed July 23, 2021. 

98See Dry Sorbent Injection Cost Development 

Methodology at https://www.epa.gov/sites/ 

production/files/2015-07/documents/append5_

4.pdf. Accessed July 23, 2021. 

99See https://www.epa.gov/airmarkets/ 

documentation-epa-platform-v6-november-2018- 

reference-case-chapter-5-emission-control. 

Accessed July 23, 2021. 

100See Dry Sorbent Injection for SO2/HCl Control 

Cost Development Methodology at https://

www.epa.gov/sites/production/files/2018-05/ 

documents/attachment_5-5_dsi_cost_development_

methodology.pdf. Accessed July 23, 2021. 

101Based on a 500 MW plant with a heat rate of 

9,500 Btu/kWh burning bituminous coal. 

102Analysis of PM and Hg Emissions and 

Controls from Coal-Fired Power Plants. Andover 

Technology Partners (August 19, 2021), available in 

the rulemaking docket. 

to projected control installations that 

did not occur. 

As result of this analysis, we find that 

based on this one variable—the number 

of control technology installations—the 

2011 RIA overestimated control costs by 

about $2.2 to $4.4 billion (or 2.7 times). 

If recent updates to the cost and 

performance assumptions for pollution 

controls had been reflected in the 2011 

RIA modeling, the projected compliance 

costs would likely have been even lower 

(suggesting the overestimate could be 

greater than $4.4 billion). The EPA did 

not quantify advances in cost and 

performance of control technology 

between the time of the EPA’s modeling 

and implementation of the rule due to 

uncertainty. We note that this may be 

one reason that the Andover Technology 

Partners’ overestimate for control costs 

of $7 billion exceeds the EPA’s range of 

overestimates ($2.2–4.4 billion) for the 

same control and operation costs. The 

next section helps explain some of the 

difference quantified above, and 

provides further qualitative evidence 

supporting the EPA’s conclusion that 

the 2011 RIA likely significantly 

overestimated the compliance costs 

associated with meeting MATS 

requirements. 

c. 2011 RIA Modeling Assumptions 

Since promulgation of MATS, the 

EPA has found it necessary to update 

some of the modeling assumptions used 

in the IPM modeling that informed the 

RIA cost estimate, in order to capture 

the most recently available information 

and best reflect the current state of the 

power sector. Several of these recent 

updates are directly related to pollution 

control retrofits that were projected to 

be installed for MATS in the 2011 RIA. 

Had these updates been reflected in our 

modeling, it likely would have projected 

fewer controls needing to be installed 

and therefore a lower cost estimate 

overall. 

The full suite of assumptions utilized 

in the IPM modeling are reported in the 

model documentation, which provides 

additional information on the 

assumptions discussed here as well as 

all other assumptions and inputs to the 

model.92 Updates specific to MATS 

modeling are also in the IPM 4.10 

Supplemental Documentation for 

MATS.93 As was included in the 2011 

RIA discussion regarding uncertainty 

and limitations of the power sector 

modeling analysis (Section 3.15), the 

cost and emissions impact projections 

did not take into account the potential 

for advances in the capabilities of 

pollution control technologies or 

reductions in their costs over time. EPA 

modeling cannot anticipate in advance 

the full spectrum of compliance 

strategies that the power sector may 

innovate to achieve required emission 

reductions, and experience has shown 

that regulated industry often is able to 

comply at lower costs through 

innovation or efficiencies. Where 

possible, the EPA designs regulations to 

assure environmental performance 

while preserving flexibility for affected 

sources to design their own solutions for 

compliance. Industry will employ an 

array of responses, some of which 

regulators may not fully anticipate and 

will generally lead to lower costs 

associated with the rule than modeled 

in ex ante analysis. See, e.g., section 

III.D of this preamble, discussing how 

the actual cost of the ARP was up to 70 

percent less than what had been 

estimated. 

A first example regards the 

assumptions of HCl removal for certain 

types of coal. When lignite and 

subbituminous coals are combusted, the 

chemistry of coal ash alkalinity removes 

HCl emissions. The 2011 RIA modeling 

assumed a 75 percent reduction of HCl 

emissions from lignite and 

subbituminous coals.94 Upon 

subsequent review of available data, the 

EPA updated this assumption to 95 

percent HCl removal.95 This revised 

assumption regarding improved HCl 

removal from coal ash alkalinity 

effectively lowers uncontrolled HCl 

emissions rates in the projections and is 

a better reflection of actual removal 

rates observed by EGUs combusting 

subbituminous and/or lignite coal. This 

updated assumption, had it been used 

in the 2011 RIA modeling, would have 

significantly decreased the incremental 

capacity of acid gas controls (e.g., DSI, 

dry FGD) that the model projected to be 

needed for compliance with the MATS 

acid gas limits.96 The lower projection 

for controls would in turn have resulted 

in a lower cost estimate. 

For a second example, the EPA 

updated the DSI retrofit cost 

methodology used in our power sector 

modeling. The 2011 RIA compliance 

cost projections assumed an SO2

removal rate of 70 percent and a 

corresponding HCl removal effect of 90 

percent 97 based on a technical report, 

developed by Sargent and Lundy in 

August 2010.98 These assumptions have 

been updated to reflect an SO2 removal 

rate of 50 percent and a corresponding 

HCl removal effect of 98 percent for 

units with FF in the EPA’s recent 

modeling,99 based on an updated 

technical report from Sargent and 

Lundy.100

These revised assumptions, which 

better reflect the actual cost and 

performance of DSI, would reduce the 

variable costs significantly, by about 

one-third at a representative plant,101

because less sorbent is required to 

achieve the same amount of HCl 

reduction. If the EPA had been able to 

use this new information in the 2011 

RIA modeling, the projected compliance 

costs would have been lower, reflecting 

the reduced sorbent necessary to 

achieve the MATS emission limits. 

Furthermore, we note that while these 

modeling assumptions are based on a 

single sorbent (trona), alternative 

sorbents are available, potentially at a 

lower cost for some units. 

A third example relates to the 

assumed cost of ESP upgrades. In the 

2011 RIA modeling, the EPA assumed 

that a range of upgrades would be 

necessary at units with existing ESP 

controls in order to meet the MATS PM 

standard. The EPA assumed the cost of 

these upgrades ranged from $55/ 

kilowatt (kW) to $100/kW (in 2009 

dollars). However, new evidence 

suggests that many ESP upgrades were 

installed and are available at less than 

$50/kW.102

These examples highlight the 

uncertainty inherent in ex ante 

compliance cost projections, and 

contribute additional evidence that the 

projected compliance costs presented in 


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103As discussed above, although we attributed all 

controls of these types to MATS in this analysis, 

even those controls that were installed were likely 

due in part or in whole for reasons other than 

MATS. 

104For example, the sales test is often used by the 

EPA when evaluating potential economic impacts 

of regulatory actions on small entities. In the 

context of a small entity analysis, an evaluation of 

the change in profits to owners is likely the best 

approach to assessing the economic burden to 

owners from a regulatory action. Data limitations 

prevent solely analyzing profit changes to EGU 

owners as a result of MATS in this proposal. 

the 2011 RIA were likely overestimated 

and that actual compliance costs for 

MATS in 2015 were likely significantly 

less than the $9.6 billion estimate. 

d. Conclusion That the 2011 RIA Costs 

Were Overestimated 

After reviewing this suite of 

quantitative and qualitative updates and 

considering studies that were performed 

by outside entities, the EPA concludes 

that the available ex post evidence 

points to significantly lower costs of 

compliance for the power sector under 

MATS than suggested by the ex ante 

projections in the 2011 RIA. There are 

numerous reasons for this, and chief 

among them is the fact that the natural 

gas industry has undergone profound 

change in recent years. Following the 

promulgation of MATS, natural gas 

supply increased substantially, leading 

to dramatic price decreases that resulted 

in major shifts in the economics of fossil 

fuel-fired electric generating 

technologies. The 2011 RIA modeling 

did not fully anticipate this historic 

change in natural gas supply and the 

related decrease in natural gas prices. 

As a result of this and other 

fundamental changes in the industry, 

we see a very different pattern of control 

installations than was projected: 103

• 21 percent less capacity of dry FGD 

than projected; 

• 64 percent less capacity of DSI than 

projected; 

• 3 percent less capacity of ACI than 

projected; 

• 69 percent less capacity of FF than 

projected; and 

• Likely fewer ESP and scrubber 

control upgrades than projected. 

These controls were responsible for 

approximately 70 percent of the 

projected annual compliance costs in 

the 2011 RIA. Because so many 

projected controls were not installed, 

we know that the control-related costs 

were almost certainly significantly 

overestimated. By simply comparing 

between projected and installed 

controls, we now find that the projected 

control-related costs for 2015 of about 

$7 billion were likely overestimated by 

$2.2 to $4.4 billion, and possibly more. 

In addition, we have updated some of 

the modeling assumptions that 

supported the 2011 RIA. Specifically: 

• HCl emissions for EGUs burning 

subbituminous and lignite coals are 

much lower than originally modeled, 

reducing the number of controls 

necessary for compliance in the model; 

• DSI controls require less sorbent 

than originally assumed, lower the 

operating cost of these controls, and 

other lower-cost sorbents are likely 

available; and 

• The assumed cost of ESP upgrades 

in the modeling was likely much higher 

than the actual cost of these upgrades. 

While not quantified here, the 

advances in cost and performance of 

control technology between the time of 

the EPA’s modeling and implementation 

of the rule would, if quantified, likely 

add to the $2.2 to $4.4 billion 

overestimate. 

Furthermore, the three studies 

submitted to the EPA during earlier 

rulemakings support this finding that 

the 2011 RIA cost projection was 

significantly overestimated: 

• Andover Technology Partners 

estimated that the actual costs of 

compliance with MATS were 

approximately $2 billion, and that the 

2011 RIA may have overestimated 

compliance costs by approximately $7 

billion. 

• MJB&A estimated that the total 

upfront capital expenditures of 

pollution controls installed for 

compliance with the rule were 

overestimated in the 2011 RIA by a 

factor of more than eight. 

• EEI, the association that represents 

all U.S. investor-owned electric 

companies, estimated cumulative costs 

incurred by the industry in response to 

MATS, and that estimate suggests an 

annual amount about $7 billion less 

than the 2011 RIA projected. 

Taken together, this information 

indicates that the projected costs in the 

2011 RIA were almost certainly 

significantly overestimated. We solicit 

comment on data resource and methods 

such as econometric, simulation, and 

event study approaches that may aid the 

EPA in better characterizing the ex post 

regulatory costs of MATS for 

consideration before we issue the final 

rule. 

3. Evaluation of Metrics Related to 

MATS Compliance 

In the next four sections, we place the 

costs that we estimated in 2011, and 

which, as just explained, were likely 

significantly overestimated, in the 

context of the EGU industry and the 

services the EGU industry provides to 

society. The purpose of these 

comparisons is to better understand the 

disadvantages conferred by expending 

this money, both in terms of their scale 

and distribution, in order to weigh cost 

as a factor in our preferred methodology 

for making the appropriate 

determination. While we recognize the 

projected cost estimate from the 2011 

RIA in absolute terms is perceived as a 

large number, our findings demonstrate 

that, for example, the (overestimated) 

projected cost estimate is less than 3 

percent of the power sector’s revenues 

from electricity sales, even when 

compared against data from 2019 

(which had the lowest electricity sale 

revenues in a nearly 20 year period). As 

we did in 2016, we first contextualize 

the costs of MATS against power sector 

data for the years 2000 to 2011, i.e., the 

information that was available to the 

Agency when we were promulgating 

MATS in 2012 and reaffirming the 

appropriate and necessary 

determination. For purposes of this 

proposal, we also expand our 

assessment to compare the 2011 cost 

estimates to the most recent years of 

data available regarding, for example, 

industry revenue and electricity prices. 

The intent of expanding the years of 

analysis is to update our assessments 

from the 2016 Supplemental Finding 

considering power sector trends with 

the newest information. We continue to 

use projections developed for the 2011 

RIA for purposes of these evaluations, 

because as discussed in section III.B.2, 

we are unable to generate new, bottomline actual cost projections. However, in 

section III.D, we consider these 

evaluations in light of the EPA’s finding 

that the projected costs were almost 

certainly significantly overestimated. 

a. Compliance Costs as a Percent of 

Power Sector Sales 

The first metric examined here (as in 

2016) is a comparison of the annual 

compliance costs of MATS to electricity 

sales at the power sector-level (i.e., 

revenues), often called a sales test. The 

sales test is a frequently used indicator 

of potential impacts from compliance 

costs on regulated industries.104

Incorporating updated information from 

the EIA, Section 2.a and Table A–4 of 

the Cost TSD present the value of retail 

electricity sales from 2000 to 2019, as 

well as net generation totals for the 

electric power sector for the same 

period. 

This information indicates that the 

$9.6 billion in annual compliance costs 

of MATS projected for 2015 would have 

represented about 2.7 percent of 2008 

power sector revenues from retail 

electricity sales, the peak year during 


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the 2000 to 2019 period. The $9.6 

billion in projected compliance costs 

would constitute about 2.9 percent of 

2019 sales, which was the lowest sales 

level observed in the post-2011 period. 

These projected compliance costs are a 

very small percentage of total EGU 

revenues from electricity sales in both 

robust or lean years, and newer data 

confirms the findings of the 2016 

record. Moreover, if we account for the 

fact that the $9.6 billion figure likely 

significantly overestimated the actual 

cost of compliance, the percentage of 

compliance costs to revenues would be 

even smaller. 

b. Compliance Expenditures Compared 

to the Power Sector’s Annual 

Expenditures 

The next metrics we examine are a 

comparison of the annual capital 

expenditures projected in the 2011 RIA 

to be needed for MATS compliance to 

historical power sector-level overall 

capital expenditures, followed by a 

comparison of projected annual capital 

and production expenditures related to 

MATS compliance to historical power 

sector-level overall capital and 

production expenditures. 

First, we evaluate capital 

expenditures. Capital costs represent 

largely irreversible investments for firms 

that must be paid off regardless of future 

economic conditions, as opposed to 

other important variable costs, such as 

fuel costs, that may vary according to 

economic conditions and generation 

needs. Section 2.b and Table A–5 of the 

Cost TSD present two sets of estimates 

for trends in annual capital 

expenditures by the electric power 

sector through 2019. The first set of 

information is based on data compiled 

by S&P Global, a private sector firm that 

provides data and analytical services. 

The second set of information is from 

the U.S. Census Bureau’s Annual 

Capital Expenditures Survey. While 

each dataset has limitations, the 

estimates from each correspond to one 

another reasonably well. 

The 2011 RIA modeling estimated the 

incremental capital expenditures 

associated with MATS compliance to be 

$4.2 billion for 2015. As discussed in 

section III.B.2, the 2011 RIA likely 

significantly overestimated compliance 

costs. This conclusion also applies to 

the capital cost component of the 

overall cost because, as detailed earlier, 

fewer pollution controls were installed 

during the 2013–2016 timeframe than 

were projected in the 2011 RIA. While 

the EPA is not able to produce an 

alternative capital cost estimate directly 

comparable to the estimates from the 

2011 RIA, the analysis discussed in 

section III.B.2 and the Cost TSD 

indicated the annualized capital 

expenditures at units that installed 

controls under MATS might be as low 

as $0.7 billion ($3.5 billion lower than 

projected in 2011 RIA, or less than onefifth). 

Even using the significantly 

overestimated figure of $4.2 billion in 

our comparison shows that the 

projected capital expenditures 

associated with MATS represent a small 

fraction of the power sector’s overall 

capital expenditures in recent years. 

Specifically, the $4.2 billion estimate 

represents about 3.6 or 3.7 percent of 

2019 (i.e., most recent) power sector 

level capital expenditures based on the 

S&P Global and U.S. Census 

information, respectively. Compared 

against 2004 power sector level capital 

expenditures (i.e., the 20-year low), the 

$4.2 billion figure represents 10.4 or 9.3 

percent of sector level capital 

expenditures (using the two respective 

data sets). Additionally, the projected 

$4.2 billion in incremental capital costs 

is well within the range of annual 

variability associated with capital 

expenditures for the sector over the 

2000–2019 period. During this period, 

based on the Census information, for 

example, the largest year-to-year 

decrease in power sector-level capital 

expenditures was $19.5 billion (from 

2001 to 2002) and the largest year-toyear increase in power sector-level 

capital expenditures was $23.4 billion 

(from 2000 to 2001). This wide range 

(¥$19.5 to +$23.4 billion) indicates 

substantial year-to-year variability in 

industry capital expenditures, and the 

projected $4.2 billion increase in capital 

expenditures in 2015 projected under 

MATS falls well within this variability. 

Similar results are found using the S&P 

Global information. If a $4.2 billion 

increase in capital expenditures in 2015 

projected under MATS falls well within 

the variability of historical trends, then 

a capital expenditure of less than $4.2 

billion would also fall within this 

variability. 

Next, in order to provide additional 

perspective to the projected cost 

information, we look at a broader set of 

costs faced by industry, including both 

capital and production expenditures 

together. Section 2.b and Table A–6 of 

the Cost TSD present two sets of 

estimates through 2019 for trends in 

annual total (capital and production) 

expenditures by the electric power 

sector using the same two data sets as 

above, which we then compare with the 

projected annual total expenditures 

required by MATS. 

We find that even the overestimated 

$9.6 billion compliance cost projection 

from the 2011 RIA represents a small 

fraction of the power sector’s annual 

capital and production expenditures 

compared to historical data, and is well 

within annual variability in total costs 

over the 2000 to 2011 and the 2012 to 

2019 periods. Compared to 2008 data 

(i.e., the historic high for total industry 

expenditures), the projected $9.6 billion 

estimate represents about 4.2 to 4.3 

percent of total expenditures. The 

MATS projected compliance cost 

represents 6.2 to 6.6 percent of total 

expenditures in 2003 (which was the 

lowest year for total industry 

expenditures during the studied time 

period). Additionally, the EPA notes 

that, similar to the capital expenditures 

analysis set forth in the 2015 Proposal, 

the projected $9.6 billion in incremental 

capital plus production costs is well 

within the range of annual variability in 

costs in general over the 2000 to 2019 

period. For example, during this period, 

the largest year-to-year decrease in 

power sector-level capital and 

production expenditures ranged from 

$30.5 billion to $32.8 billion. The 

largest year-to-year increase in power 

sector-level capital and production 

expenditures in this period ranged from 

$27.5 billion to $28.7 billion. If a $9.6 

billion increase in expenditures falls 

well within the variability of historical 

trends, then an expenditure 

substantially less than $9.6 billion 

would also fall within this variability. 

c. Impact on Retail Price of Electricity 

We are cognizant that, for an industry 

like the power sector, costs and 

disadvantages to regulation are not 

solely absorbed by regulated sources. 

Many firms in the industry are assured 

cost-recovery for expenditures, so there 

is considerable potential for EGUs to 

pass through the costs of compliance to 

consumers via increases in retail 

electricity prices. This is especially true 

given that the demand for electricity is 

not particularly price-responsive. That 

is, because people are dependent on 

electricity for daily living, they are not 

likely to reduce their consumption of 

electricity even when the price goes up 

but will instead pay the higher price, 

thus absorbing the costs of compliance 

incurred by the industry. Notably, 

average retail electricity prices have 

fallen since the promulgation of MATS. 

While we analyze these aspects of 

cost separately, control costs and 

electricity prices are not separate 

economic indicators. Electricity price 

increases are generally related to 

increases in the capital and operating 

expenditures by the power sector. 

Therefore, the electricity price impacts 

and the associated increase in electricity 


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105The EPA generally uses the term ‘‘reliability’’ 

to refer to the ability to deliver the resources to the 

projected electricity loads so the overall power grid 

remains stable, and the term ‘‘resource adequacy’’ 

generally refers to the provision of adequate 

generating resources to meet projected load and 

generating reserve requirements in each region. 

106U.S. EPA. 2011. Resource Adequacy and 

Reliability in the Integrated Planning Model 

Projections for the MATS Rule (Resource Adequacy 

and Reliability TSD), http://www3.epa.gov/ttn/atw/ 

utility/revised_resource_adequacy_tsd.pdf, Docket 

ID Item No. EPA–HQ–OAR–2009–0234–19997. 

107U.S. EPA. 2011. The Environmental Protection 

Agency’s Enforcement Response Policy For Use of 

Clean Air Act Section 113(a) Administrative Orders 

In Relation To Electric Reliability And The Mercury 

and Air Toxics Standard, https://www.epa.gov/ 

sites/default/files/documents/mats-erp.pdf, Docket 

ID Item No. EPA–HQ–OAR–2009–0234–20577. 

108https://www.epa.gov/enforcement/ 

enforcement-response-policy-mercury-and-airtoxics-standard-mats. 

bills by consumers are not costs that are 

additional to the compliance costs 

described earlier in this section. In fact, 

to the extent the compliance costs are 

passed on to electricity consumers, the 

costs to the EGU owners in the power 

sector are reduced. Therefore, in order 

to further assess the disadvantages to 

regulation, in this case to consumers of 

electricity in all sectors (residential, 

commercial, industrial, transportation, 

and other sectors), we evaluate as we 

did in 2016 the projected effect MATS 

was anticipated to have on retail 

electricity prices, as measured against 

the variations in electricity prices from 

year to year. For this proposal, we 

expanded that analysis using updated 

data from the EIA, as presented in 

section 2.c and Table A–7 of the Cost 

TSD. 

Looking at 2000–2019 data, we find 

that the projected 0.3 cents per kilowatthour projected increase in national 

average retail electricity price under 

MATS is well within the range of 

annual variability over the 2000–2019 

period. During that time period, the 

largest year-to-year decrease in national 

average retail electricity price was ¥0.2 

cents per kilowatt-hour (from 2001 to 

2002) and the largest year-to-year 

increase was 0.5 cents per kilowatt-hour 

(from 2005 to 2006). For the newer data 

analyzed, we also found that average 

retail electricity prices have generally 

decreased since 2011, from 9.33 cents 

per kilowatt-hour in 2011 to 8.68 cents 

per kilowatt-hour in 2019, or by nearly 

7 percent. 

After considering the potential 

impacts of MATS on retail electricity 

prices, the EPA concludes that the 

projected increase in electricity prices is 

within the historical range. In addition, 

any increase in electricity prices would 

not be additive to the overall 

compliance costs of MATS. Rather, such 

price impacts would in part reflect the 

ability of many EGUs to pass their costs 

on to consumers, thereby reducing the 

share of MATS compliance costs borne 

by owners of EGUs. Given the 

relationship between compliance costs 

and electricity prices, we would also 

therefore expect the significant 

overestimate of compliance costs 

reflected in the $9.6 billion figure to 

translate into overestimates in our 

projections for electricity price 

increases. Therefore, incorporating this 

newer data into our analysis, we find 

that MATS did not result in increases in 

electricity prices for American 

consumers that were outside the range 

of normal year-to-year variability, and 

during the period when MATS was 

implemented, electricity prices 

generally decreased. 

d. Impact on Power Sector Generating 

Capacity 

We recognize that the power sector 

plays a role of critical importance to the 

American public. A potential 

disadvantage to regulation that we 

consider to be a relevant factor in our 

consideration under CAA section 

112(n)(1)(A) is how such regulation 

would impact the provision of adequate 

and reliable electricity throughout the 

country.105 Therefore, we analyzed, as 

part of the 2012 record, projected net 

changes in generation capacity under 

MATS, as compared to the base case, 

that is, what expected generation 

capacity would have been absent the 

rule.106 We also conducted an analysis 

of the impacts of projected retirements 

on electric reliability. Id. And finally, in 

parallel with finalizing MATS, the 

EPA’s Office of Enforcement and 

Compliance Assurance issued a policy 

memorandum describing an approach 

for units that were reliability critical 

that could demonstrate a need to 

operate in noncompliance with MATS 

for up to a year.107

Our analysis indicated that the vast 

majority of the generation capacity in 

the power sector directly affected by the 

requirements of MATS would remain 

operational following MATS. 

Specifically, our model projected that 

operational capacity with MATS in 

place would be reduced by less than 1 

percent nationwide. See Resource 

Adequacy and Reliability TSD at 2. 

With respect to reliability, our modeling 

indicated that coal retirements would be 

distributed throughout the power grid, 

and that there would only be small 

impacts at the regional level, and that in 

those regions, we anticipated small 

decreases in overall adequacy of 

resources and robust remaining reserve 

margins. Id. These analyses therefore 

found that the power sector would be 

able to continue to provide adequate 

and reliable electricity even with 

regulation of the EGU sector for HAP. 

Additionally, since MATS was 

promulgated, the EPA has not been 

made aware of reliability or resource 

adequacy problems attributable to 

MATS. As noted, the EPA’s enforcement 

office concurrently issued a policy 

memorandum to work with sources that 

faced demonstrated reliability concerns, 

and five administrative orders were 

issued in connection with the policy.108

We think this small number of sources 

obtaining relief due to their reliability 

critical status provides some 

confirmation of the EPA’s projections 

that regulation would not cause 

widespread resource and reliability 

problems. 

4. Other Cost Considerations 

We also propose to reaffirm our 

previous findings regarding the costs of 

mercury controls, consistent with the 

instruction from the statute to study the 

availability and cost of such controls in 

CAA section 112(n)(1)(B). 80 FR 75036– 

37 (December 1, 2015). We similarly 

propose to reaffirm our previous records 

and findings regarding the cost of 

controls for other HAP emissions from 

EGUs, and the cost of implementing the 

utility-specific ARP, which Congress 

wrote into the 1990 CAA Amendments 

and implementation of which Congress 

anticipated could result in reductions in 

HAP emissions. Id. With respect to the 

costs of technology for control of 

mercury and non-mercury HAP, the 

record evidence shows that in 2012 

controls were available and routinely 

used and that control costs had declined 

considerably over time. Id. at 75037–38. 

With regard to the ARP, industry largely 

complied with that rule by switching to 

lower-sulfur coal, and subsequently the 

actual costs of compliance were 

substantially lower than projected. 

Though the reasons for discrepancies 

between projected and actual costs are 

different for MATS, as discussed in 

section III.B.2, the newer information 

examined as part of this proposal 

demonstrates that the projected cost 

estimates for MATS were also likely 

significantly overestimated. 

5. Summary of Consideration of Cost of 

Regulating EGUs for HAP 

In this section, the EPA noted several 

studies performed by outside entities 

suggesting that costs of MATS may have 

been overestimated in the 2011 RIA. We 

discussed the dramatic impacts to the 

power sector over the last 10 years due 

to increasing supplies and decreasing 

price of natural gas and renewables, and 


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we conducted a suite of quantitative and 

qualitative updates to the information 

available in the 2011 RIA. Based on this 

information, we propose to conclude 

that the available ex post evidence 

points to a power sector that incurred 

significantly lower costs of compliance 

obligations under MATS than 

anticipated based on the ex ante 

projections when the rule was finalized 

in 2012. This overestimate was 

significant—for just one part of the 

original compliance cost estimate, the 

EPA was able to quantify a range of at 

least $2.2 to $4.4 billion in projected 

costs related to the installation, 

operation, and maintenance of controls 

which were not expended by industry. 

This projected overestimation is limited 

to these costs; it does not account for 

other ways in which the rule’s costs 

were likely overestimated, such as 

advances in control technologies that 

made control applications less 

expensive or more efficient at reducing 

emissions. The other studies conducted 

by stakeholders asserted there were 

even greater differences between 

projected and actual costs of MATS. 

We next examined the 2011 projected 

costs, which were almost certainly 

significantly overestimated, in the 

context of the EGU industry and the 

services the EGU industry provides to 

society. The purpose of these 

comparisons was to better understand 

the disadvantages imposed by these 

costs, in order to weigh cost as a factor 

in our preferred methodology for 

making the appropriate determination. 

Even though the cost estimates we used 

in this analysis were almost certainly 

significantly overestimated, we noted 

they were relatively small when placed 

in the context of the industry’s revenues 

and expenditures, and well within 

historical variations. 

Based on the 2011 RIA, the total 

projected cost of the MATS rule to the 

power sector in 2015 represented 

between 2.7 and 3.0 percent of annual 

electricity sales when compared to years 

from 2000 to 2019, a small fraction of 

the value of overall sales (and even 

smaller when one takes into account 

that the 2011 RIA projections were 

likely significantly overestimated). 

Looking at capital expenditures, the 

EPA demonstrated that the projected 

MATS capital expenditures in 2015 

represented between 3.6 and 10.4 

percent of total annual power sector 

capital expenditures when compared to 

years surrounding the finalization of the 

MATS rule. Such an investment by the 

power sector would comprise a small 

percentage of the sector’s historical 

annual capital expenditures on an 

absolute basis and also would fall 

within the range of historical variability 

in such capital expenditures. Similarly, 

the EPA demonstrated that the projected 

capital and operating expenditures in 

2015 represented between 4.3 and 6.2 

percent of total annual power sector 

capital and operating expenditures over 

2000 to 2019, and is well within the 

substantial range of annual variability. 

This proposal’s analysis indicating that 

the far fewer controls were installed 

than the EPA had projected would be 

required is particularly relevant to 

considering our findings as to this 

metric; with the overestimation of 

capital expenditures in mind, actual 

investments by the power sector to 

comply with MATS would have 

comprised an even smaller percentage 

of historical annual capital 

expenditures. 

With respect to impacts on the wider 

American public, the EPA examined 

impacts on average retail electricity 

prices and found the modest increases— 

which, like overall compliance costs, 

are also likely to have been significantly 

overestimated—to be within the range of 

historical variability. Experience has 

also shown that national average retail 

electricity prices in years after MATS 

promulgation have declined. Finally, 

previous analysis indicated that the vast 

majority of the generation capacity in 

the power sector would remain 

operational and that the power sector 

would be able to continue to provide 

adequate and reliable electricity after 

implementation of the rule, and we have 

seen no evidence to contradict those 

findings. 

The EPA proposes that each of these 

analyses are appropriate bases for 

evaluating the disadvantages to society 

conferred by the MATS-related 

projected compliance expenditures. As 

we note above, even though the 

projected costs we use in this analysis 

are almost certainly significantly 

overestimated, we find that they are still 

relatively small when placed in the 

context of the economics of the 

industry, and well within historical 

variations. We solicit comments on all 

aspects of this proposed consideration 

of costs. 

C. Revocation of the 2020 Final Action 

We are proposing to revoke the 2020 

Final Action because we find that the 

framework used to consider cost in 

2020, which centered the Agency’s 

mandated determination under CAA 

section 112(n)(1)(A) on a comparison of 

costs to monetized HAP benefits, was an 

approach ill-suited to making the 

appropriate and necessary 

determination in the context of CAA 

section 112(n)(1)(A) specifically and the 

CAA section 112 program generally. 

Moreover, the statutory text and 

legislative history do not support a 

conclusion that the 2020 framework is 

required under CAA section 

112(n)(1)(A), and we exercise our 

discretion to adopt a different approach. 

We also disagree with the conclusions 

presented in the 2020 Final Action as to 

the 2016 Supplemental Finding’s two 

approaches. 

The 2020 Final Action established the 

following framework for making the 

appropriate and necessary 

determination. It stated: 

‘‘The Administrator has concluded that the 

following procedure provides the appropriate 

method under which the EPA should 

proceed to determine whether it is 

appropriate and necessary to regulate EGUs 

under CAA section 112(n)(1)(A). First, the 

EPA compares the monetized costs of 

regulation against the subset of HAP benefits 

that could be monetized. . . . Second, the 

EPA considers whether unquantified HAP 

benefits may alter that outcome. . . . Third, 

the EPA considers whether it is appropriate, 

notwithstanding the above, to determine that 

it is ‘‘appropriate and necessary’’ to regulate 

EGUs under CAA section 112(n)(1)(A) out of 

consideration for the PM co-benefits that 

result from such regulation.’’ 85 FR 31302 

(May 22, 2020). 

Applying the first part of the 

framework, the Agency noted that the 

costs of regulation estimated in the 2011 

RIA were disproportionately higher—by 

three orders of magnitude—than the 

monetized HAP benefits, and concluded 

‘‘[t]hat does not demonstrate 

‘appropriate and necessary.’ ’’ Id. Under 

the framework’s second inquiry, the 

EPA determined that the unquantified 

HAP benefits, even if monetized, were 

unlikely to alter its conclusion under 

the first part of the framework. Id.; see 

also 85 FR 31304 (noting that ‘‘valuing 

HAP-related morbidity outcomes would 

not likely result in estimated economic 

values similar to those attributed to 

avoiding premature deaths’’). Finally, 

applying the third part of its framework, 

the EPA noted that nearly all of the 

monetized benefits of MATS as reflected 

in the 2011 RIA were derived from PM 

benefits. See 85 FR 31302–03 (May 22, 

2020). The EPA then posited that, 

‘‘[h]ad the HAP-specific benefits of 

MATS been closer to the costs of 

regulation, a different question might 

have arisen as to whether the 

Administrator could find that cobenefits legally form part of the 

justification for determination that 

regulation of EGUs under CAA section 

112(d) is appropriate and necessary.’’ 

See 85 FR 31303 (May 22, 2020). 

However, because of the factual scenario 

presented in the record, the Agency in 

the 2020 Final Action stated that ‘‘[t]he 


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109See, e.g., 65 FR 79829–30 (December 20, 

2000); 76 FR 24983–85, 24993–97, 24999–25001, 

25003–14, 25015–19 (May 3, 2011). 

EPA does not need to, and does not, 

determine whether that additional step 

would be appropriate . . . given that the 

monetized and unquantified HAPspecific benefits do not come close to a 

level that would support the prior 

determination.’’ Id. In conclusion, the 

EPA stated that ‘‘[u]nder the 

interpretation of CAA section 

112(n)(1)(A) that the EPA adopts in this 

action, HAP benefits, as compared to 

costs, must be the primary question in 

making the ‘appropriate and necessary’ 

determination.’’ Id. 

We note that the three-step framework 

employed by the 2020 Final Action is 

not a BCA conforming to recognized 

principles (see, e.g., OMB Circular A–4, 

EPA Economic Guidelines). BCA is a 

specific tool developed by economists to 

assess total society-wide benefits and 

costs, to determine the economic 

efficiency of a given action. Instead of 

conforming to this comprehensive 

approach, the three-step framework 

focused primarily on comparing the 

rule’s total costs to a very small subset 

of HAP benefits that could be 

monetized. The Agency gave secondary 

weight to the vast majority of the 

benefits of regulating HAP emissions 

from stationary sources that cannot be 

quantified, and completely ignored the 

non-HAP monetized benefits directly 

attributable to the MATS rule. 

We propose to find that this three-step 

framework is an unsuitable approach to 

making the appropriate and necessary 

determination under CAA section 

112(n)(1)(A) because it places undue 

primacy on those HAP benefits that 

have been monetized, and fails to 

consider critical aspects of the inquiry 

posed to the EPA by Congress in CAA 

section 112(n)(1). The 2020 three-step 

framework also did not in any 

meaningful way grapple with the bases 

upon which the EPA had relied to 

design the 2016 preferred approach, as 

discussed above, including the broad 

statutory purpose of CAA section 112 to 

reduce the volume of HAP emissions 

with the goal of reducing the risk from 

HAP emissions to a level that is 

protective of even the most exposed and 

most sensitive subpopulations; the fact 

that we rarely can fully characterize or 

quantify risks, much less benefits, at a 

nationwide level; and the fact that 

except for one of the many health 

endpoints for only one of the many HAP 

emitted from EGUs, the EPA lacked the 

information necessary to monetize any 

post-control benefit of reductions in 

HAP emissions. The sole rationale 

provided in the 2020 Final Action for 

rejecting the relevance of the statute’s 

clear purpose as evinced in the broader 

CAA section 112 program and reflected 

in the provisions of CAA section 

112(n)(1) was that CAA section 

112(n)(1)(A) is a separate provision and 

threshold determination. See 85 FR 

31293–94 (May 22, 2020). But we do not 

think it is sensible to view the statute’s 

direction to the EPA to make a separate 

determination as to EGUs as an 

invitation to disregard the statutory 

factors of CAA section 112(n)(1) and the 

greater statutory context in which that 

determination exists, and we do not 

think that the 2020 Final Action 

provided an adequately reasoned basis 

for abandoning the interpretation and 

assessment provided in the 2016 

Supplemental Finding. And in any 

event, we believe the methodology we 

propose today is better suited to making 

the statutory finding than the 2020 

framework. 

In the 2020 rulemaking, the EPA did 

not explain its rationale for its decision 

to anchor the appropriate and necessary 

determination at step one as a 

comparison between the monetized 

costs of regulation and monetized HAP 

specific benefits. Rather, the proposed 

and final rules repeatedly state that the 

‘‘primary’’ inquiry in the determination 

should be a comparison of costs and 

HAP benefits, but did not explain why 

only monetized HAP benefits should be 

given primacy. See, e.g., 85 FR 31286, 

31288, 31303 (May 22, 2020). Given the 

Agency’s recognition of the broad grant 

of discretion inherent in the phrase 

‘‘appropriate and necessary,’’ see 81 FR 

24430–31 (April 25, 2016), its 

acknowledgement of Congress’ 

‘‘particularized focus on reducing HAP 

emissions and addressing public health 

and environmental risks from those 

emissions’’ in CAA section 112, see 85 

FR 31299 (May 22, 2020), and its 

knowledge and recognition that the 

dollar value of one of its points of 

comparison represented but a small 

subset of the advantages of regulation, 

see 85 FR 31302 (May 22, 2020), we 

now believe it was inappropriate to 

adopt a framework that first and 

foremost compared dollar value to 

dollar value. Nothing in the CAA 

required the Agency’s decision in 2020 

to hinge its framework on monetized 

HAP benefits. The consideration of the 

non-monetized benefits of MATS (i.e., 

dozens of endpoints, including virtually 

all of the HAP benefits associated with 

this rule) occurred only at step two, 

where the Agency considered whether 

the unquantified benefits, if monetized, 

were ‘‘likely to overcome the imbalance 

between the monetized HAP benefits 

and compliance costs in the record.’’ 

See 85 FR 31296 (May 22, 2020). This 

approach discounts the vast array of 

adverse health and environmental 

impacts associated with HAP emissions 

from coal- and oil-fired EGUs that have 

been enumerated by the EPA 109 and 

discounts the social value (benefit) of 

avoiding those impacts through 

regulation, simply because the Agency 

cannot assign a dollar value to those 

impacts. Further, the three-step 

framework gave no consideration to the 

important statutory objective of 

protecting the most at-risk 

subpopulations. As noted above, in 

CAA section 112(n)(1)(C) Congress 

directed the EPA to establish threshold 

levels of exposure under which no 

adverse effect to human health would be 

expected to occur, even considering 

exposures of sensitive populations, and 

throughout CAA section 112, Congress 

placed special emphasis on regulating 

HAP from sources to levels that would 

be protective of those individuals most 

exposed to HAP emissions and most 

sensitive to those exposures. The rigid 

and narrow approach to making the 

appropriate and necessary 

determination in the 2020 Final Action 

is at odds with the text and purpose of 

CAA section 112, and is certainly not 

required under the express terms of 

CAA section 112 or CAA section 

112(n)(1)(A). 

Commenters on the 2019 Proposal 

objected strenuously to the Agency’s 

revised framework for making the 

appropriate and necessary 

determination, arguing that the 2019 

Proposal’s interpretation ‘‘fails to 

meaningfully address factors that are 

‘centrally relevant’ to the inquiry of 

whether it is appropriate and necessary 

to regulate HAP from EGUs,’’ and that 

the Agency’s new interpretation must 

fall because the EPA failed to provide a 

reasoned explanation for its change in 

policy, as required by Motor Vehicle 

Mfrs. Ass’n of United States, Inc. v. 

State Farm Mut. Automobile Ins. Co., 

463 U.S. 29 (1983), and FCC v. Fox 

Television Stations, Inc., 556 U.S. 502 

(2009). See 85 FR 31294 (May 22, 2020). 

Among the factors that commenters 

argued had been inadequately addressed 

under the new framework were the 

‘‘hazards to public health reasonably 

anticipated to occur’’ that had not been 

monetized; the non-monetizable 

benefits of HAP regulation such as 

preservation of tribal social practices; 

the latency, persistence in the 

environment, and toxicity of HAP as 

recognized by Congress; and the 

distributional impacts on particular 

communities and individuals most 


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impacted by HAP emitted from power 

plants. In responses to these comments, 

the EPA claimed that it was not 

‘‘disregarding’’ or ‘‘dismissing’’ the 

concerns raised by the commenters, but 

rather simply weighing them differently, 

and explained that the Administration’s 

changed priorities provided the 

‘‘reasoned basis’’ for its changed 

interpretation. See 85 FR 31296–97 

(May 22, 2020). 

Agencies do have broad discretion to 

re-evaluate policies and change their 

‘‘view of what is in the public interest,’’ 

State Farm, 463 U.S. at 57, but such reevaluations must still adhere to 

principles of reasoned decision-making. 

The 2020 Final Action did not aver that 

the concerns identified by commenters 

were factors that the statute does not 

instruct the Agency to consider in 

making its appropriate and necessary 

determination. Instead, the EPA stated 

that it was permitted to pick its 

decisional framework and admitted that 

its decisional framework might 

undervalue certain factors. For example, 

with respect to commenters’ concerns 

that the revised appropriate and 

necessary framework did not adequately 

account for adverse impacts on tribal 

culture or undue concentration of 

public health risks on certain 

population subgroups or individuals, 

the EPA stated, 

‘‘In a cost-benefit comparison, the overall 

amount of the benefits stays the same no 

matter what the distribution of those benefits 

is. The EPA, therefore, believes it is 

reasonable to conclude that those factors to 

which the EPA previously gave significant 

weight–including qualitative benefits, and 

distributional concerns and impacts on 

minorities–will not be given the same weight 

in a comparison of benefits and costs for this 

action under CAA section 112(n)(1)(A).’’ 85 

FR 31297 (May 22, 2020). 

The decisional framework in the 2020 

Final Action, however, did not give 

‘‘less weight’’ to these factors—it gave 

them none. In both the selection and 

application of its framework, the EPA in 

the 2020 Final Action effectively 

ignored these factors altogether, and we 

do not agree that the inability to 

monetize a factor should render it 

unimportant. Cf. Am. Trucking Ass’ns, 

Inc. v. EPA, 175 F.3d 1027, 1052–53 

(D.C. Cir. 1999), reversed in part on 

other grounds in Whitman v. Am. 

Trucking Ass’ns, 531 U.S. 457 (2001) 

(holding that the EPA was not permitted 

to ignore information ‘‘because the . . . 

benefits are difficult, if not impossible, 

to quantify reliably and because there is 

‘no convincing basis for concluding that 

any such effects . . . would be 

significant’ ’’); Pub. Citizen v. Fed. Motor 

Carrier Safety Admin., 374 F.3d 1209, 

1219 (D.C. Cir. 2004) (‘‘The mere fact 

that the magnitude of . . . effects is 

uncertain is no justification for 

disregarding the effect entirely.’’) 

(emphasis in original). The mere 

mention and summary dismissal of 

factors does not constitute meaningful 

consideration of those factors. 

In the 2020 Final Action, like the 

2016 Supplemental Finding before it, 

the EPA maintained that there is more 

than one permissible way to interpret 

the Agency’s obligation to consider cost 

in the appropriate and necessary 

determination. Given the Agency’s 

knowledge of the significant risks and 

often irreversible impacts of HAP 

exposure on vulnerable populations like 

developing fetuses, the disproportionate 

impact of EGU HAP emissions on 

communities who subsist on freshwater 

fish due to cultural practices and/or 

economic necessity, and the record of 

data demonstrating risks to public 

health amassed over decades, and, 

perhaps more importantly, the 

overwhelming quantity of advantages to 

regulation that could not be monetized, 

we do not think that selecting a 

framework that compared first and 

foremost monetized HAP benefits with 

costs was appropriate. And even if the 

framework ultimately addressed the 

statutorily relevant factors because at 

the second step the EPA stated that it 

was considering non-monetized HAP 

benefits, we think that the application of 

that second step fell short. The 

secondary consideration of nonmonetized HAP benefits in the threestep framework only considered postcontrol HAP-related impacts of 

regulation insofar as the EPA speculated 

about what the monetized value of those 

benefits might be (see 85 FR 31296 (May 

22, 2020), asserting that monetized 

value of avoiding morbidity effects such 

as neurobehavioral impacts is ‘‘small’’ 

compared to monetized value associated 

with avoided deaths). The Agency did 

not, at this second step, grapple with the 

existing risk analyses, including those 

stemming from the statutorily mandated 

studies in CAA section 112(n)(1). Those 

analyses demonstrated substantial 

public health and environmental 

hazards, even if the hazards were not 

translated into post-control monetized 

benefits. See White Stallion, 748 F.3d at 

1245. The Agency also did not explain 

why other attributes of risk—such as 

impacts on vulnerable populations and 

the reality that HAP pollution from 

EGUs is not distributed equally across 

the population but disproportionately 

impacts some individuals and 

communities far more than others— 

were unimportant, stating only that the 

selected framework did not 

accommodate consideration of those 

factors. 

As noted, the Agency did not point to 

anything in the CAA as supporting the 

use of its three-step framework. This is 

in stark contrast to the 2016 

Supplemental Finding rulemaking, in 

which the EPA examined CAA section 

112(n)(1)(A) and the other section 

112(n)(1) provisions, and the rest of 

CAA section 112 generally, and D.C. 

Circuit case law on CAA cost 

considerations to inform the EPA’s 

interpretation of CAA section 

112(n)(1)(A). See 80 FR 75030 

(December 1, 2015); 2015 Legal 

Memorandum. In the 2020 Final Action, 

the EPA merely asserted that a 

comparison of benefits to costs is ‘‘a 

traditional and commonplace way to 

assess costs’’ and claimed that the 

Supreme Court’s holding in Entergy 

Corp. v. Riverkeeper, 556 U.S. 208 

(2009) supported the EPA’s 2020 

position that, absent an unambiguous 

prohibition to use a BCA, an agency 

may generally rely on a BCA as a 

reasonable way to consider cost. See 85 

FR 31293 (May 22, 2020). The 2020 

Final Action also pointed out ‘‘many 

references comparing’’ costs and 

benefits from the Michigan decision, 

including: ‘‘EPA refused to consider 

whether the costs of its decision 

outweighed the benefits’’ (576 U.S. at 

743); ‘‘[o]ne would not say that it is 

rational, never mind ‘appropriate,’ to 

impose billions of dollars in economic 

costs in return for a few dollars in 

health or environmental benefits’’ (Id. at 

752); and ‘‘[n]o regulation is 

‘appropriate’ if it does more harm than 

good’’ (Id.). 

But while we agree that a comparison 

of benefits to costs is a traditional way 

to assess costs, the 2020 framework was 

not a BCA. There is no economic theory 

or guidance of which we are aware that 

endorses the version of BCA presented 

in the 2020 Final Action, in which total 

costs are compared against a small 

subset of total benefits. See section III.E 

for further discussion. Moreover, 

general support for weighing costs and 

benefits does not justify placing undue 

weight on monetized HAP benefits, with 

secondary consideration for all other 

benefits, and only valuing those other 

benefits to the extent of their 

speculative monetized effects. As noted 

in Justice Breyer’s concurrence in 

Entergy Corp., the EPA has the ability 

‘‘to describe environmental benefits in 

non-monetized terms and to evaluate 

both costs and benefits in accordance 

with its expert judgment and scientific 

knowledge,’’ and to engage in this 

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110CAA section 112(n)(1)(B) also directs the EPA 

to study available technologies for controlling 

mercury and the cost of such controls, and we 

consider those in our assessment of cost. 

111The statute directed the EPA to complete all 

three CAA section 112(n)(1) studies within 4 years 

of the 1990 Amendments, expressing a sense of 

urgency with regard to HAP emissions from EGUs 

on par with addressing HAP emissions from other 

stationary sources. See CAA section 112(e) 

(establishing schedules for setting standards on 

listed source categories as expeditiously as 

practicable, but no later than between 2–10 years). 

benefit proceedings and futile attempts 

at comprehensive monetization.’’ 556 

U.S. at 235 (Breyer, J., concurring). 

Benefits—the advantages of regulation— 

can encompass outcomes that are not or 

cannot be expressed in terms of dollars 

and cents, just as the Court found that 

‘‘ ‘cost’ includes more than the expense 

of complying with regulations; any 

disadvantage could be termed a cost.’’ 

Michigan, 576 U.S. at 752. And the 

Court faulted the EPA’s interpretation 

for ‘‘preclud[ing] the Agency from 

considering any type of cost—including, 

for instance, harms that regulation 

might do to human health or the 

environment. . . . No regulation is 

‘appropriate’ if it does significantly 

more harm than good.’’ Id. The 

constricted view of benefits that the 

Agency adopted in 2020 was ill-suited 

to the statutory inquiry as interpreted in 

Michigan. 

The primary basis in the 2020 action 

upon which the EPA relied to find that 

the 2016 preferred approach was flawed 

was that the preferred approach failed to 

‘‘satisf[y] the Agency’s obligation under 

CAA section 112(n)(1)(A) as interpreted 

by the Supreme Court in Michigan.’’ See 

84 FR 2674 (February 7, 2019). The 2019 

Proposal claimed that the chief flaw of 

the preferred approach was the 

Agency’s failure to ‘‘meaningfully 

consider cost within the context of a 

regulation’s benefits,’’ asserting that the 

Michigan Court contemplated that a 

proper consideration of cost would be 

relative to benefits. See 84 FR 2675 

(February 7, 2019). But that is not an 

accurate characterization of the 2016 

preferred approach, wherein the Agency 

weighed the existing record from 2012 

demonstrating that HAP emissions from 

EGUs pose a number of identified 

hazards to both public health and the 

environment remaining after imposition 

of the ARP and other CAA requirements 

against the cost of MATS. 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.’’). The 2020 Final Action further 

stated that the preferred approach was 

an ‘‘unreasonable’’ interpretation of 

CAA section 112(n)(1)(A) and 

impermissibly de-emphasized the 

importance of the cost consideration in 

the appropriate and necessary 

determination. See 85 FR 31292 (May 

22, 2020). It is a decisional framework 

which rests primarily upon a 

comparison of the costs of a regulation 

and the small subset of HAP benefits 

which could be monetized that does not 

‘‘meaningfully consider[s] cost within 

the context of a regulation’s benefits,’’ 

because such a narrow approach 

relegates as secondary (and in 

application appeared to ignore 

altogether) the vast majority of that 

rule’s HAP benefits and other 

advantages. We therefore propose to 

revoke the 2020 three-step approach and 

determination because we do not think 

it is a suitable way to assess the 

advantages and disadvantages of 

regulation under CAA section 

112(n)(1)(A) and in applying it, the 

Agency failed to meaningfully address 

key facts in the existing record. Even if 

the Agency’s selection of the 2020 

framework could be considered a 

permissible interpretation of the broad 

‘‘appropriate and necessary’’ 

determination in CAA section 

112(n)(1)(A), we exercise our discretion 

under the statute and as described in 

Michigan, to approach the 

determination differently. 

D. The Administrator’s Proposed 

Preferred Framework and Proposed 

Conclusion 

The EPA is proposing a preferred, 

totality-of-the-circumstances approach 

as a reasonable way to ‘‘pay attention to 

the advantages and disadvantages of 

[our] decision,’’ Michigan, 576 U.S. at 

753, in determining whether it is 

appropriate to regulate coal- and oilfired EGUs under section 112 of the 

CAA. This approach, including which 

factors we consider and how much 

weight we give them, is informed by 

Congress’ design of CAA section 

112(n)(1) specifically, and CAA section 

112 generally. 

Specifically, under this approach we 

first consider and weigh the advantages 

of reducing EGU HAP via regulation. 

We focus on the public health 

advantages of reducing HAP emissions 

because in CAA section 112(n)(1)(A), 

Congress specifically directed the EPA 

to regulate EGUs under CAA section 112 

after considering the results of the 

‘‘study of hazards to public health 

reasonably anticipated to occur as a 

result of emissions’’ by EGUs. We also 

consider the other studies 

commissioned by Congress in CAA 

sections 112(n)(1)(B) and (C) and the 

types of information the statute directed 

the EPA to examine under those 

provisions—the rate and mass of EGU 

mercury emissions, the health and 

environmental effects of such emissions, 

and the threshold level of mercury 

concentrations in fish tissue which may 

be consumed (even by sensitive 

populations) without adverse effects to 

public health.110 We place considerable 

weight on the factors addressed in the 

studies required in the other provisions 

of CAA section 112(n)(1) because that 

provision is titled ‘‘Electric utility steam 

generating units,’’ so it is reasonable to 

conclude that the information in those 

studies is important and relevant to a 

determination of whether HAP 

emissions from EGUs should be 

regulated under CAA section 112.111

See Michigan, 576 U.S. at 753–54 (citing 

CAA sections 112(n)(1)(B) and (C), its 

caption, and the additional studies 

required under those subparagraphs as 

relevant statutory context for the 

appropriate and necessary 

determination). 

Notably, the studies of CAA section 

112(n)(1) place importance on the same 

considerations that are expressed in the 

terms and overall structure of CAA 

section 112. For example, CAA section 

112(n)(1)(A) and section 112(n)(1)(B) 

both show interest in the amount of 

HAP emissions from EGUs—section 

112(n)(1)(A) by requiring the EPA to 

estimate the risk remaining after 

imposition of the ARP and other CAA 

requirements and section 112(n)(1)(B) 

by requiring the EPA to study the rate 

and mass of mercury emissions; 

therefore, we believe it is reasonable to 

conclude that we should consider and 

weigh the volume of toxic pollution 

EGUs contributed to our air, water, and 

land absent regulation under CAA 

section 112, in total and relative to other 

domestic anthropogenic sources, and 

the potential to reduce that pollution, 

thus reducing its grave harms. In 

addition, the clear goal in CAA section 

112(n)(1)(C) and elsewhere to consider 

risks to the most exposed and 

susceptible populations supports our 

decision to place significant weight on 

reducing the risks of HAP emissions 

from EGUs to the most sensitive 

members of the population (e.g., 

developing fetuses and children), and 

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112Unquantified effects include additional 

neurodevelopmental and cardiovascular effects 

from exposure to methylmercury, ecosystem effects, 

health risks from exposure to non-mercury HAP, 

and effects in EJ relevant subpopulations that face 

disproportionally high risks. 

caught local fish for their survival. 

Finally, we also consider the identified 

risks to the environment posed by 

mercury and acid-gas HAP, consistent 

with CAA section 112(n)(1)(B) and the 

general goal of CAA section 112 to 

address adverse environmental effects 

posed by HAP emissions. See CAA 

section 112(a)(7) (defining ‘‘adverse 

environmental effect’’). 

We next examine the disadvantages of 

regulation, principally in the form of the 

costs incurred to capture HAP before 

they enter the environment. As with the 

advantages side of the equation, where 

we consider the consequences of 

reducing HAP emissions to human 

health and the environment, we 

consider the consequences of these 

expenditures for the electricity 

generating sector and society. We 

therefore consider compliance costs 

comprehensively, placing them in the 

context of the effect those expenditures 

have 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 society 

imposed by this regulation, and because 

our conclusion might change depending 

on how this burden affects the ability of 

the industry to thrive and provide 

reliable, affordable electricity to the 

benefit of all Americans. Consistent 

with CAA section 112(n)(1)(B), we 

further consider relevant control costs 

for EGUs and the relationship of control 

costs expected and experienced under 

the ARP and MATS. 

Below, consistent with this 

framework, we consider and weigh the 

advantages to regulation against the 

costs of doing so, giving particular 

weight to our examination of the public 

health hazards we reasonably anticipate 

to occur as a result of HAP emissions 

from EGUs, and the risks posed by those 

emissions to exposed and vulnerable 

populations. We note as well that had 

we found regulation under CAA section 

112 to impose significant barriers to 

provision of affordable and reliable 

electricity to the American public, this 

would have weighed heavily in our 

decision. 

We acknowledge, as we recognized in 

the 2016 preferred approach, that this 

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), but this type of 

weighing of factors and circumstances is 

an inherent part of regulatory decisionmaking. As noted in then-Judge 

Kavanaugh’s dissent in White Stallion, 

‘‘All regulations involve tradeoffs, and 

. . . Congress has assigned EPA, not the 

courts, to make many discretionary calls 

to protect both our country’s 

environment and its productive 

capacity.’’ 748 F.3d at 1266 (noting as 

well that ‘‘if EPA had decided, in an 

exercise of its judgment, that it was 

‘appropriate’ to regulate electric utilities 

under the MACT program because the 

benefits outweigh the costs, that 

decision would be reviewed under a 

deferential arbitrary and capricious 

standard of review’’). Bright-line tests 

and thresholds are not required under 

the CAA’s instruction to determine 

whether regulation is ‘‘appropriate and 

necessary,’’ nor have courts interpreted 

broad provisions similar to CAA section 

112(n)(1)(A) in such manner. In 

Catawba Cty. v. EPA, the D.C. Circuit 

held that ‘‘[a]n agency is free to adopt 

a totality-of-the-circumstances test to 

implement a statute that confers broad 

authority, even if that test lacks a 

definite ‘threshold’ or ‘clear line of 

demarcation to define an open-ended 

term.’ ’’ 571 F.3d 20, 37 (D.C. Cir. 2009). 

In undertaking this analysis, we are 

cognizant that, while the Agency has 

been studying the science underlying 

this determination for decades, the 

understanding of risks, health, and 

environmental impacts associated with 

toxic air pollution continues to evolve. 

In this notice, we explained the 

additional information that has become 

available to the Agency since we 

performed our national risk 

assessments, and explained why, 

despite the certainty of the science 

demonstrating substantial health risks, 

we are unable at this time to quantify or 

monetize many of the effects associated 

with reducing HAP emissions from 

EGUs.112 We continue to think it is 

appropriate to give substantial weight to 

these public health impacts, even where 

we lack information to precisely 

quantify or monetize those impacts. As 

the D.C. Circuit stated in Ethyl Corp. v. 

EPA, 

‘‘Where a statute is precautionary in 

nature, the evidence difficult to come by, 

uncertain, or conflicting because it is on the 

frontiers of scientific knowledge, the 

regulations designed to protect public health, 

and the decision that of an expert 

administrator, we will not demand rigorous 

step-by-step proof of cause and effect. . . . 

[I]n such cases, the Administrator may assess 

risks. . . . The Administrator may apply his 

expertise to draw conclusions from 

suspected, but not completely substantiated, 

relationships between facts, from trends 

among facts, from theoretical projections 

from imperfect data, from probative 

preliminary data not yet certifiable as ‘fact,’ 

and the like.’’ 

541 F.2d 1, 28 (D.C. Cir. 1976). See also 

Lead Industries Ass’n v. EPA, 647 F.2d 

1130, 1155 (D.C. Cir. 1980) (‘‘[R]equiring 

EPA to wait until it can conclusively 

demonstrate that a particular effect is 

adverse to health before it acts is 

inconsistent with both the [Clean Air] 

Act’s precautionary and preventive 

orientation and the nature of the 

Administrator’s statutory 

responsibilities.’’). 

The EPA is not alone in needing to 

make difficult judgments about whether 

a regulation that has a substantial 

economic impact is ‘‘worth it,’’ in the 

face of uncertainty such as when the 

advantages of the regulation are hard to 

quantify in monetary terms. The 

Transportation Security Administration 

(TSA), when determining whether to 

require Advanced Imaging Technology 

at certain domestic airports, faced 

assertions that the high cost of 

widespread deployment of this type of 

screening was ‘‘not worth the cost.’’ 

TSA acknowledged that it did not 

‘‘provide monetized benefits’’ or 

‘‘degree of benefits’’ to justify the use of 

the screening, but noted that the agency 

‘‘uses a risk-based approach . . . in 

order to try to minimize risk to 

commercial air travel.’’ See 81 FR 

11364, 11394 (March 3, 2016). The 

agency pointed out that it could not 

consider ‘‘only the most easily 

quantifiable impacts of a terrorist attack, 

such as the direct cost of an airplane 

crashing,’’ but rather that it had an 

obligation to ‘‘pursue the most effective 

security measures reasonably available 

so that the vulnerability of commercial 

air travel to terrorist attacks is reduced,’’ 

noting that some commenters were 

failing to consider the more difficult to 

quantify aspects of the benefits of 

avoiding terrorist attacks, such as 

‘‘substantial indirect effects and social 

costs (such as fear) that are harder to 

measure but which must also be 

considered by TSA when deciding 

whether an investment in security is 

cost-beneficial.’’ Id. 

In reviewing Agency decisions like 

these, courts do ‘‘not to substitute [their] 

judgment[s] for that of the agenc[ies],’’ 

State Farm, 463 U.S. at 43 (1983), and 

‘‘[t]his is especially true when the 

agency is called upon to weigh the costs 

and benefits of alternative policies,’’ 

Center for Auto Safety v. Peck, 751 F.2d 

1336, 1342 (D.C. Cir. 1985). See also 


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113The NAS Study had also highlighted this 

population as one of particular concern due to the 

regular and frequent consumption of relatively large 

quantities of fish. See 65 FR 79830 (December 20, 

2000). 

United Church of Christ v. FCC, 707 

F.2d 1413, 1440 (D.C. Cir. 1983) (‘‘[C]ost 

benefit analyses epitomize the types of 

decisions that are most appropriately 

entrusted to the expertise of an 

agency.’’). Agencies are entitled to this 

deference even where, or perhaps 

particularly where, costs or benefits can 

be difficult to quantify. For example, in 

Consumer Elecs. Ass’n v. FCC, the D.C. 

Circuit upheld the FCC’s mandate to 

require digital tuners, finding 

reasonable the Commission’s 

identification of benefits, that is, 

‘‘principally speeding the 

congressionally-mandated conversion to 

DTV and reclaiming the analog 

spectrum,’’ coupled with the FCC’s 

‘‘adequate[ ] estimate[ of] the long-range 

costs of the digital tuner mandate within 

a range sufficient for the task at hand 

. . . and [its finding of] the estimated 

costs to consumers to be ‘within an 

acceptable range.’’’ 347 F.3d 291, 303– 

04 (D.C. Cir. 2003) (‘‘We will not here 

second-guess the Commission’s 

weighing of costs and benefits.’’). 

Similarly, the Food and Drug 

Administration, in weighing the costs 

and benefits of deeming electronic 

cigarettes to be ‘‘tobacco products,’’ 

described the benefits qualitatively, 

‘‘ ‘potentially coming from’ . . . 

premarket review [i.e., the statutory 

consequence of deeming], which will 

result in fewer harmful or additive 

products from reaching the market than 

would be the case in the absence of the 

rule; youth access restrictions and 

prohibitions on free samples, which can 

be expected to constrain youth access to 

tobacco products and curb rising 

uptake; health warning statements, 

which will help consumers understand 

and appreciate the risks of using tobacco 

products; prohibitions against false or 

misleading claims and unsubstantiated 

modified risk claims; and other changes 

[such as monitoring and ingredient 

listings].’’ Nicopure Labs, LLC v. FDA, 

266 F. Supp. 3d 360, 403–404 (D.D.C. 

2017), aff’d, 944 F.3d 267 (D.C. Cir. 

2019). Plaintiffs challenging the rule 

claimed that because the FDA had not 

quantified the benefits of the rule, it 

‘‘cannot realistically determine that a 

rule’s benefits justify its costs,’’ because 

‘‘it does not have . . . a general grasp 

of the rule’s benefits.’’ Id. at 406. The 

court disagreed, finding the agency’s 

statement of benefits to have ‘‘provided 

substantial detail on the benefits of the 

rule, and the reasons why quantification 

was not possible’’ and in any case 

agreeing with the agency that there was 

no obligation to quantify benefits in any 

particular way. Id. 

We think the inquiry posed to the 

Agency by CAA section 112(n)(1)(A) has 

similarities to these other decisions, in 

which agencies tasked with protecting 

and serving the American public elected 

to take actions that would impose 

significant costs in order to achieve 

important benefits that could not be 

precisely quantified or were in some 

cases uncertain—protection from 

terrorist attacks, speeding the 

advancement of digital technology, and 

subjecting a new product to marketing 

and safety regulation. In those cases, the 

framework for decision-making was to 

make a judgment after a weighing of 

advantages against disadvantages, 

considering qualitative factors as well as 

quantified metrics. Here, we employ a 

similar totality-of-the-circumstances 

approach to the CAA section 

112(n)(1)(A) inquiry as to whether it is 

appropriate to regulate HAP emissions 

from EGUs. 

Earlier sections of this preamble 

(sections III.A. and III.B.) discuss in 

detail the EPA’s evaluation of the public 

health and environmental advantages of 

regulating HAP from U.S. EGUs and the 

reasons it is not possible to quantify or 

monetize most of those advantages, as 

well as the EPA’s comprehensive 

assessment of the costs of doing so. We 

will not in this section repeat every 

detail and data point, but we 

incorporate all of that analysis here and 

highlight only a few of the 

considerations that weighed heavily in 

our application of the preferred totalityof-the-circumstances approach. 

Under our preferred approach, we 

first consider the public health 

advantages to reducing HAP from EGUs, 

and the other focuses for study 

identified by Congress in CAA section 

112(n)(1). As noted, we give particular 

weight in our determination to the 

information related to the statutory 

factors identified for the EPA’s 

consideration by the studies—namely, 

the hazards to public health reasonably 

anticipated to occur as a result of EGU 

HAP emissions (112(n)(1)(A)), the rate 

and mass of mercury emissions from 

EGUs (112(n)(1)(B)), the health and 

environmental effects of such emissions 

(112(n)(1)(B)), and the levels of mercury 

exposure below which adverse human 

health effects are not expected to occur 

as well as the mercury concentrations in 

the tissue of fish which may be 

consumed (including by sensitive 

populations) without adverse effects to 

public health (112(n)(1)(C)). 

The statutorily mandated studies are 

the foundation for the Agency’s finding 

that HAP emissions from U.S. EGUs 

represent a clear hazard to public health 

and the environment, but as 

documented in section III.A., the EPA 

has continued to amass an extensive 

body of evidence related to the original 

study topics that only furthers the 

conclusions drawn in the earlier 

studies. As discussed in section III.A, 

the EPA completed a national-scale risk 

assessment focused on mercury 

emissions from U.S. EGUs as part of the 

2011 Final Mercury TSD. That 

assessment specifically 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. 

We focused on the female subsistence 

fisher subpopulation because there is 

increased risk for in utero exposure and 

adverse outcomes in children born to 

female subsistence fishers with elevated 

exposure to methylmercury.113 Our 

analysis estimated that 29 percent of the 

watersheds studied would lead to 

exposures exceeding the methylmercury 

RfD for this population, based on in 

utero effects, due in part to the 

contribution of domestic EGU emissions 

of mercury. We also found that 

deposition of mercury emissions from 

U.S. EGUs alone led to potential 

exposures that exceed the RfD in up to 

10 percent of modeled watersheds. 

We have also examined impacts of 

prenatal methylmercury exposure on 

unborn children of recreational anglers 

consuming self-caught fish from inland 

freshwater lakes, streams, and rivers, 

and found significant IQ loss in the 

affected population of children. Our 

analysis, which we recognized did not 

cover consumption of recreationally 

caught seafood from estuaries, coastal 

waters, and the deep ocean, 

nevertheless indicated significant health 

harm from methylmercury exposure. 

Methylmercury exposure also leads to 

adverse neurodevelopmental effects 

such as performance on neurobehavioral 

tests, particularly on tests of attention, 

fine motor function, language, and 

visual spatial ability. See section 

III.A.2.a. 

The population that has been of 

greatest concern with respect to 

methylmercury exposure is women of 

childbearing age because the developing 

fetus is the most sensitive to the effects 

of methylmercury. See 85 FR 24995 

(May 3, 2011). In the Mercury Study, the 

EPA estimated that, at the time of the 

study, 7 percent of women of 

childbearing age in the continental U.S. 


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(or about 4 million women) were 

exposed to methylmercury at levels that 

exceeded the RfD and that about 1 

percent of women of childbearing age 

(or about 580,000 women) had 

methylmercury exposures three to four 

times the RfD. See 65 FR 79827 

(December 20, 2000). We also performed 

a new bounding analysis for this 

proposal that focuses on the potential 

for IQ points lost in children exposed in 

utero through maternal fish 

consumption by the population of 

general U.S. fish consumers (section 

III.A.3.d). 

Another important human health 

impact documented by the EPA over the 

last 2 decades includes cardiovascular 

impacts of exposure to 

methylmercury—including altered 

blood-pressure and heart-rate variability 

in children as a result of infant exposure 

in the womb and higher risk of acute 

MI, coronary heart disease, and 

cardiovascular heart disease in adults, 

due to dietary exposure. Studies that 

have become available more recently led 

the EPA to perform new quantitative 

screening analyses (as described in 

section III.A.3) to estimate the incidence 

of MI (heart attack) mortality that may 

be linked to U.S. EGU mercury 

emissions. The new analyses performed 

include an extension of the original 

watershed-level subsistence fisher 

methylmercury risk assessment to 

evaluate the potential for elevated MImortality risk among subsistence fishers 

(section III.A.3.b; 2021 Risk TSD) and a 

separate risk assessment examining 

elevated MI mortality among all adults 

that explores potential risks associated 

with exposure of the general U.S. 

population to methylmercury from 

domestic EGUs through commerciallysourced fish consumption (section 

III.A.3.c; 2021 Risk TSD). The updated 

subsistence fisher analysis estimated 

that up to 10 percent of modeled 

watersheds are associated with 

exposures linked to increased risk of MI 

mortality, but for some populations 

such as low-income Black subsistence 

fishers active in the Southeast, that 

number is approximately 25 percent of 

the watersheds modeled. The bounding 

analysis results estimating MI-mortality 

attributable to U.S. EGU-sourced 

mercury for the general U.S. population 

range from 5 to 91 excess deaths 

annually. As noted, we give significant 

weight to these findings and analyses 

examining public health impacts 

associated with methylmercury, given 

the statutory focus in CAA section 

112(n)(1)(B) and 112(n)(1)(C) on adverse 

effects to public health from EGU 

mercury emissions and the directive to 

develop an RfD (‘‘threshold level of 

mercury exposure below which adverse 

human health effects are not expected to 

occur’’), and in particular one that is 

designed to assess ‘‘mercury 

concentrations in the tissue of fish 

which may be consumed (including 

consumption by sensitive 

populations).’’ See CAA section 

112(n)(1)(C). 

Because of CAA section 112(n)(1)(A)’s 

broader focus on hazards to public 

health from all HAP, not just mercury, 

we also give considerable weight to 

health effects associated with nonmercury HAP exposure (see section 

III.A.2.b for further detail), including 

chronic health disorders such as 

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). The 2011 Non-Hg HAP 

Assessment, performed as part of the 

EPA’s 2012 reaffirmation of the 

appropriate and necessary 

determination, expanded on the original 

CAA section 112(n)(1)(A) Utility Study 

by examining further public health 

hazards reasonably anticipated to occur 

from EGU HAP emissions after 

imposition of other CAA requirements. 

This study included a refined chronic 

inhalation risk assessment that was 

designed to assess how many coal- and 

oil-fired EGUs had cancer and noncancer risks associated with them, and 

indicated that absent regulation, a 

number of EGUs posed cancer risks to 

the American public (see section 

III.A.2.b). 

As discussed in section II.B, the 

statutory design of CAA section 112 

quickly secured dramatic reductions in 

the volume of HAP emissions from 

stationary sources. CAA section 

112(n)(1)(B) also directs the EPA to 

study, in the context of the Mercury 

Study, the ‘‘rate and mass’’ of mercury 

emissions. We therefore think it is 

reasonable to consider, in assessing the 

advantages to regulating HAP emissions 

from EGUs, what the volume of 

emissions was from that sector prior to 

regulation—as an absolute number and 

relative to other sources—and what the 

expected volume of emissions would be 

with CAA section 112(d) standards in 

place. Prior to the EPA’s promulgation 

of MATS in 2012, the EPA estimated 

that in 2016, without MATS, coal-fired 

U.S. EGUs above 25 MW would emit 29 

tons of mercury per year. While these 

mercury emissions from U.S. EGUs 

represented a decrease from 1990 and 

2005 levels (46 tons and 53 tons, 

respectively), they still represented 

nearly half of all anthropogenic mercury 

emissions in 2011 (29 out of 64 tons 

total). Considered on a proportional 

basis, the relative contribution of U.S. 

EGUs to all domestic anthropogenic 

mercury emissions was also stark. The 

EGU sector emitted more than six times 

as much mercury as any other sector 

(the next highest being 4.6 tons). See 

Table 3 at 76 FR 25002 (May 3, 2011). 

Prior to MATS, U.S. EGUs were 

estimated to emit the majority of HCl 

and HF nationally, and were the 

predominant source of emissions 

nationally for many metal HAP as well, 

including antimony, arsenic, chromium, 

cobalt, and selenium. Id. at 25005–06. In 

2012, the EPA projected that MATS 

would result in an 88 percent reduction 

in hydrogen chloride emissions, a 75 

percent reduction in mercury emissions, 

and a 19 percent reduction in PM 

emissions (a surrogate for non-mercury 

metal HAP) from coal-fired units greater 

than 25 MW in 2015 alone. See 77 FR 

9424 (February 16, 2012). In fact, actual 

emission reductions since MATS 

implementation have been even more 

substantial. In 2017, by which point all 

sources were required to have complied 

with MATS, the EPA estimated that acid 

gas HAP emissions from EGUs had been 

reduced by 96 percent, mercury 

emissions had been reduced by 86 

percent, and non-mercury metal HAP 

emissions had been reduced by 81 

percent compared to 2010 levels. See 84 

FR 2689 (February 7, 2019). Retaining 

the substantial reductions in the volume 

of toxic pollution entering our air, 

water, and land, from this large fleet of 

domestic sources reduces the 

substantial risk associated with this 

pollution faced by all Americans. 

Even though reducing HAP from 

EGUs would benefit all Americans by 

reducing risk and hazards associated 

with toxic air pollution, it is worth 

noting that the impacts of EGU HAP 

pollution in the U.S. have not been 

borne equally nationwide. Certain 

communities and individuals have 

historically borne greater risk from 

exposure to HAP emissions from EGUs 

prior to MATS, as demonstrated by the 

EPA’s risk analyses. The individuals 

and communities that have been most 

impacted have shouldered a 

disproportionate burden for the energy 

produced by the power sector, which in 

turn benefits everyone—i.e., these 

communities are subject to a greater 

share of the externalities of HAP 

pollution that is generated by EGUs 

producing power for everyone. A clear 

example of these disproportionately 

impacted populations are subsistence 

fishers who live near U.S. EGUs 


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experiencing increased risk due to U.S. 

EGU mercury deposition at the 

watersheds where they are active (2011 

Final Mercury TSD). CAA section 

112(n)(1)(C) directed the EPA to 

examine risks to public health 

experienced by sensitive populations as 

a result of the consumption of mercury 

concentrations in fish tissue, which we 

think includes fetuses and communities 

that are reliant on local fish for their 

survival, and CAA section 112 more 

generally is drafted in order to be 

protective of small cohorts of highly 

exposed and susceptible populations. 

We therefore weigh heavily the 

importance of reducing risks to 

particularly impacted populations, 

including those who consume large 

amounts of self-caught fish reflecting 

cultural practice and/or economic 

necessity, including tribal populations, 

specific ethnic communities and lowincome populations including Black 

persons living in the southeastern U.S. 

Consistent with CAA section 

112(n)(1)(B) and the general goal of CAA 

section 112 to reduce risks posed by 

HAP to the environment, we also 

consider the ecological effects of 

methylmercury and acid gas HAP (see 

section III.A.2.c). Scientific studies have 

consistently found evidence of adverse 

impacts of methylmercury on fish-eating 

birds and mammals, and insect-eating 

birds. These harmful effects can include 

slower growth and development, 

reduced reproduction, and premature 

mortality. Adverse environmental 

impacts of emissions of acid gas HAP, 

in particular HCl, include acidification 

of terrestrial and aquatic ecosystems. In 

the EPA’s recent Integrated Science 

Assessment for Oxides of Nitrogen, 

Oxides of Sulfur and Particulate 

Matter—Ecological Criteria (2020), we 

concluded that the body of evidence is 

sufficient to infer a causal relationship 

between acidifying deposition and 

adverse changes in freshwater biota like 

plankton, invertebrates, fish, and other 

organisms. Adverse effects on those 

animals can include physiological 

impairment, loss of species, changes in 

community composition, and 

biodiversity. Because EGUs contribute 

to mercury deposition in the U.S., we 

conclude that EGUs are contributing to 

the identified adverse environmental 

effects, and consider the beneficial 

impacts of mitigating those effects by 

regulating EGUs. 

We turn next in our application of the 

preferred approach to the consideration 

of the disadvantages of regulation, 

which in this case we measure primarily 

in terms of the costs of that regulation. 

As discussed in section III.B, for 

purposes of this preferred totality-ofthe-circumstances approach, we start 

with the sector-level estimate developed 

in the 2011 RIA. Given the complex, 

interconnected nature of the power 

sector, we think it is appropriate to 

consider this estimate, which represents 

the incremental costs to the entire 

power sector to generate electricity, not 

just the compliance costs projected to be 

borne by regulated EGUs. We explain in 

section III.B that while a precise ex post 

estimate of this sector-level figure is not 

possible, we update those aspects of the 

cost estimate where we can credibly do 

so (see section III.B.2), and our 

consideration of the cost of regulation 

therefore takes into account the fact that 

new analyses performed as part of this 

proposal demonstrate that the 2011 RIA 

cost estimate was almost certainly 

significantly overestimated. We propose 

to conclude that regulation is 

appropriate and necessary under either 

cost estimate. 

As with the benefits side of the ledger, 

where we look comprehensively at the 

effects of reducing the volume of HAP, 

we also comprehensively assess costs in 

an attempt to evaluate the economic 

impacts of the regulation as a whole. We 

situate the cost of the regulation in the 

context of the economics of power 

generation, as we did in 2016, because 

we think examining the costs of the rule 

relative to three sector-wide metrics 

provides a useful way to evaluate the 

disadvantages of expending these 

compliance costs to this sector beyond 

a single monetary value. For each of 

these metrics, we use our 2011 estimate 

of compliance costs, which, as is 

discussed in section III.B.2 and the Cost 

TSD, was likely to have been 

significantly overestimated by a figure 

in the billions of dollars. We first 

evaluate the 2011 projected annual 

compliance costs of MATS as a percent 

of annual power sector sales, also 

known as a ‘‘sales test.’’ A sales test is 

a frequently used indicator of potential 

impacts from compliance costs on 

regulated industries, and the EPA’s 

analysis showed that projected 2015 

compliance costs, based on the 2011 

estimate, represented between 2.7–3.5 

percent of power sector revenues from 

historical annual retail electricity sales. 

See section III.B.3; Cost TSD; 80 FR 

75033 (December 1, 2015). We also 

examine the annual capital 

expenditures that were expected for 

MATS compliance as compared to the 

power sector’s historical annual capital 

expenditures. We conclude that 

projected incremental annual capital 

expenditures of MATS would be a small 

percentage of 2011 power sector-level 

capital expenditures, and well within 

the range of historical year-to-year 

variability on industry capital 

expenditures. Id. Finally, we consider 

the annual operating or production 

expenses in addition to capital 

expenditures because we were 

encouraged during the 2016 rulemaking 

to use this broader metric of power 

industry costs to provide perspective on 

the cost of MATS relative to total capital 

and operational expenditures by the 

industry historically. Consistent with 

our other findings, we conclude that, 

even when using the likely 

overestimated cost of MATS based on 

the 2011 RIA, the total capital and 

operational expenditures required by 

MATS are in the range of about 5 

percent of total historical capital and 

operational expenditures by the power 

sector during the period of 2000–2011. 

See section III.B.3; Cost TSD; 81 FR 

24425 (April 25, 2016). In this proposal, 

we re-analyze all of these metrics using 

updated data to reflect more recent 

information (as of 2019), and took into 

consideration the fact that the 2011 RIA 

cost estimate was almost certainly 

significantly overestimated. All of this 

new analysis further supports our 

findings as to the cost of MATS relative 

to other power sector economics based 

on the record available to the Agency at 

the time we were making the threshold 

determination (i.e., the 2012 record). 

Consistent with the Michigan Court’s 

instruction to consider all advantages 

and disadvantages of regulation, we also 

assess, as we did in 2016, disadvantages 

to regulation that would flow to the 

greater American public. Specifically, 

we examine whether regulation of EGUs 

would adversely impact the provision of 

reliable, affordable electricity to the 

American public, because had 

regulation been anticipated to have such 

an effect, it would have weighed heavily 

on our decision as to whether it was 

appropriate to require such regulation. 

The CAA tasks the EPA with the 

purpose of protecting and enhancing air 

quality in the U.S., but directs that in 

doing so we promote public health and 

welfare and the productive capacity of 

the U.S. population. CAA section 

101(b)(1). As noted, we also think 

examining these potential impacts is 

consistent with the ‘‘broad and allencompassing’’ nature of the term 

‘‘appropriate,’’ as characterized by the 

Supreme Court. Michigan, 576 U.S. at 

752. We were particularly interested in 

examining the expected impact of 

MATS implementation on the retail 

price of electricity, because in electricity 

markets, utility expenditures can be 

fully or partially passed to consumers. 

It was therefore reasonable to assume 


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114U.S. EPA Clean Air Markets Div., 2011, 

National Acid Precipitation Assessment Program 

Report to Congress 2011: An Integrated Assessment, 

National Science and Technology Council, 

Washington, DC. 

that the cost of MATS could result in 

increased retail electricity prices for 

consumers, although we emphasize, as 

we did in 2016, that the electricity price 

impacts examined under this metric do 

not reflect additional compliance costs 

on top of the estimate produced in the 

2011 RIA but rather reflect the passing 

on of a share of those costs to consumers 

(and ultimately reducing the costs EGU 

owners would otherwise bear). 

However, even though the impacts on 

electricity prices are reflected in the 

total cost estimate to the sector as a 

whole, we think, for the reasons stated 

above, that electricity price impacts are 

worthy of special attention because of 

the potential effect on the American 

public. 

We therefore estimate the percent 

increase in retail electricity prices 

projected to result from MATS 

compared to historical levels of 

variation in electricity prices. See 

section III.B.3; 80 FR 75035 (December 

1, 2015). We estimate that retail 

electricity prices for 2015 would 

increase by about 0.3 cents per kilowatthour, or 3.1 percent with MATS in 

place. Between 2000 and 2011, the 

largest annual year-to-year decrease in 

retail electricity price was –0.2 cents per 

kilowatt-hour and the largest year-toyear increase during that period was 

+0.5 cents per kilowatt-hour. The 

projected 0.3 cents increase due to 

MATS was therefore well within normal 

historical fluctuations. Id. As with the 

other metrics examined, as the increase 

in retail electricity prices due to MATS 

was within the normal range of 

historical variability, a substantially 

lower estimate for impacts on electricity 

prices would only further support the 

EPA’s determination. We also note in 

section III.B.3 that the year-to-year retail 

electricity price changes in the new 

information we examined (i.e., years 

2011–2019) were within the same 

ranges observed during the 2000–2011 

period, and that in fact, during that 

period when MATS was implemented, 

retail electricity prices have generally 

decreased (9.3 cents per kilowatt-hour 

in 2011 to 8.7 cents per kilowatt-hour in 

2019). Consistent with these observed 

trends in retail electricity prices, as 

discussed in section III.B.2 and further 

below, our ex post analysis of MATS 

indicates that the projected compliance 

costs in the 2011 RIA—and, as a 

corollary, the projected increases in 

retail electricity prices—were likely 

significantly overestimated. Certainly, 

we have observed nothing in the data 

that suggests the regulation of HAP from 

EGUs resulted in increases in retail 

electricity prices for the American 

public that would warrant substantial 

concern in our weighing of this factor. 

Similar to our reasoning for 

examining impacts on electricity prices 

for American consumers, in assessing 

the potential disadvantages to 

regulation, we elected to also look at 

whether the power sector would be able 

to continue to provide reliable 

electricity to all Americans after the 

imposition of MATS. We think this 

examination naturally fits into our 

assessment of whether regulation is 

‘‘appropriate,’’ because had MATS 

interfered with the provision of reliable 

electricity to the American public, that 

would be a significant disadvantage to 

regulation to weigh in our analysis. In 

examining this factor, we looked at both 

resource adequacy and reliability—that 

is, the provision of generating resources 

to meet projected load and the 

maintenance of adequate reserve 

requirements for each region (resource 

adequacy) and the sector’s ability to 

deliver the resources to the projected 

electricity loads so that the overall 

power grid remains stable (reliability). 

See section III.B.3; U.S. EPA 2011, 

Resource Adequacy and Reliability TSD; 

80 FR 75036 (December 1, 2015). Our 

analysis indicated that the power sector 

would have adequate and reliable 

generating capacity, while maintaining 

reserve margins over a 3-year MATS 

compliance period. Id. We did not in 

this proposal update the Resource 

Adequacy and Reliability Study 

conducted in 2011, but we note that the 

EPA, as a primary regulator of EGUs, is 

keenly aware of adequacy and reliability 

concerns in the power sector and in 

particular the relationship of those 

concerns to environmental regulation. 

We have not seen evidence in the last 

decade to suggest that the 

implementation of MATS caused power 

sector adequacy and reliability 

problems, and only a handful of sources 

obtained administrative orders under 

the enforcement policy issued with 

MATS to provide relief to reliability 

critical units that could not comply with 

the rule by 2016. 

In addition to the cost analyses 

described above, the EPA revisited its 

prior records examining the costs of 

mercury controls consistent with the 

requirement in CAA section 

112(n)(1)(B), the cost of controls for 

other HAP emissions from EGUs, and 

the cost of implementing the utilityspecific ARP, which Congress wrote 

into the 1990 CAA Amendments and 

implementation of which Congress 

anticipated could result in reductions in 

HAP emissions. 80 FR 75036–37 

(December 1, 2015). The ARP, like 

MATS, was expected to have a 

significant financial impact on the 

power sector, with projections of its cost 

between $6 billion to $9 billion per year 

(in 2000 dollars), based on the 

expectation that many utilities would 

elect to install FGD scrubbers in order 

to comply with the ARP. Id. at 75037. 

The actual costs of compliance were 

much less (up to 70 percent lower than 

initial estimates), in large part because 

of the utilities’ choice to comply with 

the ARP by switching to low sulfur coal 

instead of installing scrubbers.114 This 

choice also resulted in far fewer 

reductions in HAP emissions than 

would have occurred if more EGUs had 

installed SO2 scrubbers. We believe the 

considerable reduction in the 

implementation cost of the ARP is 

important because of the economic 

benefit that accrued from delaying the 

large capital costs of controls by almost 

25 years. With respect to the costs of 

technology for control of mercury and 

non-mercury HAP, the record evidence 

shows that in 2012 controls were 

available and routinely used and that 

control costs had declined considerably 

over time. Id. at 75037–38. We also note 

that, as explained at length in section 

III.B.2, the actual compliance costs of 

MATS, with respect to capital and 

operating expenditures associated with 

installing and operating controls, were 

significantly lower than what we 

projected at the time of the rule. In 

addition, the newer information 

examined as part of this proposal 

demonstrates that actual control costs 

were much lower than we projected, 

which weighs further in favor of a 

conclusion that it is appropriate to 

impose those costs in order to garner the 

advantages of regulation. 

Our review of the record and 

application of the preferred totality-ofthe-circumstances approach has 

demonstrated that we have, over the last 

2 decades, amassed a voluminous and 

scientifically rigorous body of evidence 

documenting the significant hazards to 

public health associated with HAP 

emissions from EGUs, particularly to 

certain vulnerable populations that bear 

greater risk from these emissions than 

the general public. We have looked at 

the volume of emissions coming from 

these sources and what the impact of 

regulation would be on that volume. We 

examined the cost of regulation to 

industry (even using an estimate of cost 

that we know to be higher than what 

was expended), and the potential 


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115This estimate of premature mortality is for the 

EGU sector after imposition of the ARP and other 

CAA requirements, but before MATS 

implementation. 

116See, e.g., Comment Letter from Edison Electric 

Institute, Docket ID Item No. EPA–HQ–OAR–2018– 

0794–2267; Comment Letter from Edison Electric 

Institute, NRECA, American Public Power 

Association, The Clean Energy Group, Class of ’85 

Regulatory Response Group, Large Public Power 

Council, Global Energy Institute, International 

Brotherhood of Electrical Workers, International 

Brotherhood of Boilermakers, Iron Ship Builders, 

Blacksmiths, Forgers & Helpers, and the Laborers’ 

International Union of North America, Docket ID 

Item No. EPA–HQ–OAR–2018–0794–0577. 

117See, e.g., Comment Letter from Attorneys 

General of Massachusetts, California, Connecticut, 

Delaware, Illinois, Iowa, Maine, Maryland, 

Michigan, Minnesota, Nevada, New Jersey, New 

Mexico, New York, North Carolina, Oregon, Rhode 

Island, Vermont, Virginia, Washington, and the 

District of Columbia, the Maryland Department of 

the Environment, the City Solicitor of Baltimore, 

the Corporation Counsels of Chicago and New York 

City, the County Attorney of the County of Erie, NY, 

and the County Counsel for the County of Santa 

Clara, CA, Docket ID Item No. EPA–HQ–OAR– 

2018–0794–1175. 

118See, e.g., Comment Letter from ADA Carbon 

Solutions, LLC, Docket ID Item No. EPA–HQ–OAR– 

2018–0794–0794; Comment Letter from Advanced 

Emissions Solutions, Inc., Docket ID Item No. EPA– 

HQ–OAR–2018–0794–1181; Comment Letter from 

Exelon Corporation, Docket ID Item No. EPA–HQ– 

OAR–2018–0794–1158. 

adverse impacts that could be felt by the 

American public via increased 

electricity prices and access to reliable 

electricity. And, consistent with the 

statute, we have also considered adverse 

impacts of EGU pollution on the 

environment as well as availability of 

controls and the costs of those controls. 

Even based solely on the record 

available to us at the time we issued the 

regulation and made the threshold 

determination in 2012, we find that the 

benefits of regulation are manifold, and 

they address serious risks to vulnerable 

populations that remained after the 

implementation of the ARP and other 

controls imposed upon the power sector 

that were required under the CAA. We 

have placed considerable weight on 

these benefits, given the statutory 

directive to do so in CAA section 

112(n)(1)(A) and Congress’ clear 

purpose in amending CAA section 112 

in 1990. In contrast, the costs, while 

large in absolute terms, were shown in 

our analyses to be within the range of 

other expenditures and commensurate 

with revenues generated by the sector, 

and our analysis demonstrated that 

these expenditures would not and did 

not have any significant impacts on 

electricity prices or reliability. After 

considering and weighing all of these 

facts and circumstances, in an exercise 

of his discretion under the Act, the 

Administrator proposes to conclude that 

the substantial benefits of reducing HAP 

from EGUs, which accrue in particular 

to the most vulnerable members of 

society, are worth the costs. 

Consequently, we propose to find after 

weighing the totality of the 

circumstances, that regulation of HAP 

from EGUs is appropriate after 

considering cost. 

The newer information examined as 

part of this proposal regarding both 

benefits and costs is directionally 

consistent with all of the findings the 

EPA has made in the 2016 

administrative record. The robust and 

long-standing scientific foundation 

regarding the adverse health and 

environmental risks from mercury and 

other HAP is fundamentally unchanged 

since the comprehensive studies that 

Congress mandated in the CAA were 

completed decades ago. But in this 

proposal, we completed screening level 

risk assessments, informed by newer 

meta-analyses of the dose-response 

relationship between methylmercury 

and cardiovascular disease, which 

indicate that a segment of the American 

public is at increased risk of 

prematurely dying by heart attack due to 

methylmercury exposure with as many 

as 91 deaths per year (and possibly 

more) being attributable to mercury 

emissions from EGUs.115 Further, 

analyses show that some populations 

(e.g., low-income Blacks in the 

Southeast and certain tribal 

communities engaging in subsistence 

fishing activity) likely bear a 

disproportionately higher risk from EGU 

HAP emissions than the general 

populace. 

The new cost information analyzed by 

the EPA, discussed in section III.B, 

indicates that the cost projection used in 

the 2016 Supplemental Finding (i.e., the 

2011 RIA cost estimate) likely 

significantly overestimated the actual 

costs of compliance of MATS. 

Specifically, the EGU sector installed far 

fewer controls to comply with the HAP 

emissions standards than projected; 

certain modeling assumptions, if 

updated with newer information, would 

have resulted in a lower cost estimate; 

unexpected advancements in 

technology occurred; and the country 

experienced a dramatic increase in the 

availability of comparatively 

inexpensive natural gas. All of these 

factors likely resulted in a lower actual 

cost of compliance than the EPA’s 

projected estimates in 2011. We 

therefore find that when we consider 

information available to the Agency 

after implementation of the rule, our 

conclusion that it was appropriate to 

regulate this sector for HAP is further 

strengthened. The costs projected in the 

2011 RIA were almost certainly 

overestimated by an amount in the 

billions of dollars. 

We note as well that during prior 

rulemaking processes related to the 

appropriate and necessary 

determination, stakeholders suggested 

that undermining the threshold finding 

in order to pave the way to rescinding 

MATS would have grave economic and 

health consequences. Utilities reported 

that they rely upon the mandated status 

of MATS in order to recoup 

expenditures already made to comply 

with the rule before Public Utility 

Commission proceedings.116 States 

asserted that they rely upon the Federal 

protections achieved by the rule in state 

implementation planning and other 

regulatory efforts.117 And other 

industries, such as pollution control 

companies, have made business 

decisions based on the existence of 

MATS.118 We think these reliance 

interests, nearly all of which are 

aligned, also weigh in favor of retaining 

the appropriate and necessary 

determination, particularly given the 

fact that a significant portion of 

compliance costs have already been 

spent. 

Finally, while we focus on the HAP 

benefits, we note that the Michigan 

court directed that ‘‘any disadvantage 

could be termed a cost.’’ Michigan, at 

752. The corollary is that any advantage 

could be termed a benefit. And so, while 

it is not necessary to our conclusion that 

regulation is appropriate, we also 

consider, under our totality-of-thecircumstances approach, whether there 

are additional advantages or 

disadvantages to the specific controls 

imposed under MATS. Specifically, we 

note that because the controls required 

to reduce HAP from U.S. EGUs resulted 

in substantial reductions in co-emitted 

pollutants, including direct PM2.5 as 

well as SO2 and NOX, which are both 

precursors to ozone and fine particle 

formation, the Administrator’s proposed 

conclusion is further supported by the 

ramifications of the regulatory 

requirements in MATS for these 

pollutants. We propose that the benefits 

associated with such reductions may be 

appropriate to consider where the 

framework for making the CAA section 

112(n)(1)(A) determination is a totalityof-the-circumstances approach, and we 

take comment on that approach. 

Therefore, while we conclude that the 

benefits associated with regulating HAP 

alone outweigh the costs without 

consideration of non-HAP benefits, we 

also propose that, to the extent we 

consider benefits attributable to 

reductions in co-emitted pollutants as a 

concomitant advantage, these benefits 

act to confirm that regulation is 


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119We use the term ‘‘formal benefit-cost analysis’’ 

to refer to an economic analysis that attempts to 

quantify all significant consequences of an action in 

monetary terms in order to determine whether an 

action increases economic efficiency. Assuming 

that all consequences can be monetized, actions 

with positive net benefits (i.e., benefits exceed 

costs) improve economic efficiency. 

120U.S. EPA. Integrated Science Assessment (ISA) 

for Particulate Matter (Final Report, Dec 2019). U.S. 

Environmental Protection Agency, Washington, DC, 

EPA/600/R–19/188, 2019. 

121U.S. EPA. Integrated Science Assessment (ISA) 

for Ozone and Related Photochemical Oxidants 

(Final Report, Apr 2020). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R– 

20/012, 2020. 

appropriate under a totality-of-thecircumstances approach. Specifically, 

we note that reductions in co-emissions 

of direct PM2.5, SO2 and NOX will have 

substantial health benefits in the form of 

decreased risk of premature mortality 

among adults, and reduced incidence of 

lung cancer, new onset asthma, 

exacerbated asthma, and other 

respiratory and cardiovascular diseases. 

In the 2011 RIA, the EPA estimated the 

number and value of avoided PM2.5- 

related impacts, including 4,200 to 

11,000 premature deaths, 4,700 nonfatal 

heart attacks, 2,600 hospitalizations for 

respiratory and cardiovascular diseases, 

540,000 lost work days, and 3.2 million 

days when adults restrict normal 

activities because of respiratory 

symptoms exacerbated by PM2.5. We 

also estimated substantial additional 

health improvements for children from 

reductions in upper and lower 

respiratory illnesses, acute bronchitis, 

and asthma attacks. In addition, we 

estimated the benefit of reductions in 

CO2 emissions under MATS. Although 

the EPA only partially monetized the 

benefits associated with these 

reductions in co-emitted pollutants in 

the 2011 RIA, the Agency estimated 

that—due in particular to the strong 

causal relationship between PM2.5 and 

premature mortality—these reductions 

could result in as much as $90 billion 

(in 2016 dollars) in additional public 

health benefits annually. Therefore, if 

these non-HAP benefits are considered 

in the totality-of-the-circumstances 

approach, we take note of the fact that 

regulating EGUs for HAP emissions 

results in substantial other health 

benefits accruing to the American 

public by virtue of regulating HAP from 

EGUs. 

E. The Administrator’s Proposed 

Benefit-Cost Analysis Approach and 

Proposed Conclusion 

In addition to the preferred approach, 

we separately put forward an alternative 

approach, as we did in 2016, to support 

a determination that it is appropriate 

and necessary to regulate HAP from 

EGUs when looking at the results of a 

formal BCA. The formal BCA we 

conducted for purposes of meeting 

Executive Order 12866 using 

established BCA practices also 

demonstrates that the benefits estimated 

for MATS far exceed the estimated 

costs, as reported in the 2011 RIA.119 In 

its net benefits projection, the 2011 RIA 

monetized only one post control benefit 

from regulating HAP emissions from 

EGUs because the Agency did not and 

does not have the information necessary 

to monetize the many other benefits 

associated with reducing HAP 

emissions from EGUs. See section 

III.A.4. However, the 2011 RIA properly 

accounted for all benefits by discussing 

qualitatively those that could not be 

quantified and/or monetized. While 

some of the impacts on particularly 

impacted populations—such as the 

children of recreational anglers 

experiencing IQ loss—were reflected in 

the net benefits calculation, that 

accounting does not really grapple with 

the equitable question of whether a 

subset of Americans should continue to 

bear disproportionate health risks in 

order to avoid the increased cost of 

controlling HAP from EGUs. We 

continue to prefer a totality-of-thecircumstances approach to making the 

determination under CAA section 

112(n)(1)(A), but we think that if a BCA 

is to be used, it should, consistent with 

economic theory and principles, 

account for all costs and all benefits. 

BCA has been part of executive 

branch rulemaking for decades. Over the 

last 50 years, Presidents have issued 

Executive Orders directing agencies to 

conduct these analyses as part of the 

rulemaking development process. 

Executive Order 12866, currently in 

effect, requires a quantification of 

benefits and costs to the extent feasible 

for any regulatory action that is likely to 

result in a rule that may have an annual 

effect on the economy of $100 million 

or more or adversely affect in a material 

way certain facets of society. Executive 

Order 12866, at section 3(f)(1). 

The EPA performed a formal BCA to 

comport with Executive Order 12866 as 

part of the 2012 MATS rulemaking 

process (referred to herein as the 2011 

RIA). In the 2016 Supplemental 

Finding, the EPA relied on the BCA it 

had performed for Executive Order 

12866 purposes as an alternative basis 

upon which to make the appropriate 

and necessary determination. That BCA, 

which reflected in its net benefits 

calculation only certain categories of 

benefits that could be confidently 

monetized, estimated that the final 

MATS would yield annual net 

monetized benefits (in 2007 dollars) of 

between $37 billion to $90 billion using 

a 3-percent discount rate and $33 billion 

to $81 billion using a 7-percent discount 

rate. See 80 FR 75040 (December 1, 

2015). These estimates included the 

portion of the HAP benefits described in 

section III.A that could be monetized at 

the time, along with additional health 

benefits associated with the controls 

necessary to control the HAP emissions 

from U.S. EGUs. Specifically, as noted, 

the net benefits estimates included only 

one of the many HAP benefits 

associated with reduction of HAP. 

Nonetheless, the monetized benefits of 

MATS outweighed the estimated $9.6 

billion in annual monetized costs by 

between 3-to-1 or 9-to-1 depending on 

the benefit estimate and discount rate 

used. The implementation of control 

technologies to reduce HAP emissions 

from EGU sources also led to reductions 

in emissions of SO2, direct PM2.5, as 

well as other precursors to PM2.5 and 

ozone. In the 2011 RIA, the EPA did not 

quantify the benefits associated with 

ozone reductions resulting from the 

emissions controls under MATS, but we 

did include estimates of the projected 

benefits associated with reductions in 

PM2.5. These benefits were quite 

substantial and had a large economic 

value. Newer scientific studies 

strengthen our understanding of the link 

between PM2.5 exposure to a variety of 

health problems, including: premature 

death, lung cancer, non-fatal heart 

attacks, new onset asthma, irregular 

heartbeat, aggravated asthma, decreased 

lung function, and respiratory 

symptoms, such as irritation of the 

airways, coughing or difficulty 

breathing. Furthermore, since the RIA 

was completed in 2011, the EPA has 

updated its conclusions about how 

PM2.5 emissions can adversely affect the 

environment through acidic deposition, 

materials damage, visibility impairment, 

and exacerbating climate change (EPA, 

2019).120 In its most recent review of the 

effects of ozone pollution, the EPA 

concluded that ozone is associated with 

a separate but similarly significant set of 

adverse outcomes including respiratoryrelated premature death, increased 

frequency of asthma attacks, aggravated 

lung disease, and damage to vegetation 

(EPA, 2020).121

BCAs are a useful tool to ‘‘estimate 

the total costs and benefits to society of 

an activity or program,’’ and ‘‘can be 

thought of as an accounting framework 

of the overall social welfare of a 

program.’’ EPA Economic Guidelines, 

Appendix A, A–6 (emphasis in 


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122U.S. EPA. 2014. Guidelines for Preparing 

Economic Analyses. EPA–240–R–10–001. National 

Center for Environmental Economics, Office of 

Policy. Washington, DC. December. Available at 

https://www.epa.gov/environmental-economics/ 

guidelines-preparing-economic-analyses, accessed 

July 23, 2021. Docket ID Item No. EPA–HQ–OAR– 

2009–0234–20503. 

123U.S. OMB. 2003. Circular A–4 Guidance to 

Federal Agencies on Preparation of Regulatory 

Analysis. Available at https://www.whitehouse.gov/ 

sites/whitehouse.gov/files/omb/circulars/A4/a4.pdf, accessed July 23, 2021. 

124 In addition, CAA section 112(n)(1)(A) directs 

the EPA to evaluate the hazards to public health 

from EGU HAP emissions that a reasonably 

anticipated ‘‘after imposition of the other 

requirements of the [CAA].’’ The direction to 

consider the impacts of non-CAA section 112 

requirements on HAP emissions from EGUs 

demonstrates that Congress understood that criteria 

pollutant controls would achieve HAP reductions. 

Given this understanding, it is reasonable for the 

EPA to consider the consequent criteria pollutant 

reductions attributable to CAA section 112 

standards if a BCA is used to evaluate cost in the 

context of the appropriate finding. Furthermore, 

CAA section 112 legislative history not specifically 

directed at EGUs also supports the consideration of 

criteria pollutant benefits attributable to the 

regulation of HAP emissions. Specifically, the 

Senate report for the 1990 CAA amendments states: 

‘‘When establishing technology-based [MACT] 

standards under this subsection, the Administrator 

may consider the benefits which result from control 

of air pollutants that are not listed but the emissions 

of which are, nevertheless, reduced by control 

technologies or practices necessary to meet the 

prescribed limitation.’’ A Legislative History of the 

Clean Air Act Amendments of 1990 (CAA 

Legislative History), Vol. 5, pp. 8512 (CAA 

Amendments of 1989; p. 172; Report of the 

Committee on Environment and Public Works S. 

1630). 

original).122 In a BCA, ‘‘[t]he favorable 

effects of a regulation are the benefits, 

and the foregone opportunities or losses 

in utility are the costs. Subtracting the 

total costs from the total monetized 

benefits provides an estimate of the 

regulation’s net benefits to society.’’ Id. 

Importantly, however, ‘‘[t]he key to 

performing BCA lies in the ability to 

measure both benefits and costs in 

monetary terms so that they are 

comparable.’’ Id.; see also OMB Circular 

A–4 (‘‘A distinctive feature of BCA is 

that both benefits and costs are 

expressed as monetary units, which 

allows you to evaluate different 

regulatory options with a variety of 

attributes using a common 

measure.’’).123

In the 2020 Final Action, the EPA 

rescinded the 2016 alternative approach 

on the basis that it was ‘‘fundamentally 

flawed’’ because it applied ‘‘a formal 

cost-benefit analysis’’ to the CAA 

section 112(n)(1)(A) determination. The 

Agency’s objection at the time to the use 

of ‘‘a formal cost-benefit analysis’’ in the 

context of this determination was that 

doing so ‘‘implied that an equal weight 

was given to the non-HAP co-benefit 

emission reductions and the HAPspecific benefits of the regulation.’’ See 

85 FR 31299 (May 22, 2020). The 

Agency concluded that it was not 

appropriate to use a formal BCA in this 

situation because ‘‘to give equal weight 

to the monetized PM2.5 co-benefits 

would permit those benefits to become 

the driver of the regulatory 

determination, which the EPA believes 

would not be appropriate.’’ Id. The EPA 

reiterated in the 2020 Final Action that 

‘‘HAP benefits, as compared to costs, 

must be the primary question in making 

the ‘appropriate and necessary’ 

determination’’ and ‘‘the massive 

disparity between co-benefits and HAP 

benefits on this record would mean that 

that alternative approach clearly 

elevated co-benefits beyond their 

permissible role.’’ Id. at 31303. ‘‘To be 

valid, the EPA’s analytical approach to 

[CAA section 112(n)(1)(A)] must 

recognize Congress’ particular concern 

about risks associated with HAP and the 

benefits that would accrue from 

reducing those risks.’’ Id. at 31301. 

We agree that the analytical 

framework for the appropriate and 

necessary determination should first 

and foremost be one that is focused on 

‘‘Congress’ particular concern about 

risks associated with HAP and the 

benefits that would accrue from 

reducing those risks.’’ Id. It is for this 

reason, as discussed in section III.C of 

this preamble, that we propose to revoke 

the analytical framework advanced for 

the appropriate and necessary 

determination by the 2020 Final Action, 

as being insufficiently attentive to the 

public health advantages of regulation. 

However, if the decisional framework is 

going to be one that considers 

advantages to regulation primarily in 

terms of potential monetized outcomes 

(see 85 FR 31296–97; May 22, 2020), a 

formal BCA that estimates net outcomes 

(i.e., by comparing total losses and 

gains) and conforms to established 

economic best practices and accounts 

for all of the effects of the rule that can 

be quantified should be used.124

Consistent with scientific principles 

underlying BCA, both OMB Circular A– 

4 and the EPA’s Guidelines for 

Preparation of Economic Analyses 

direct the Agency to include all benefits 

in a BCA. Per Circular A–4, OMB 

instructs ‘‘Your analysis should look 

beyond the direct benefits and direct 

costs of your rulemaking and consider 

any important ancillary benefits and 

countervailing risks. An ancillary 

benefit is a favorable impact of the rule 

that is typically unrelated or secondary 

to the statutory purpose of the 

rulemaking.’’ Circular A–4 at 26. 

Similarly, the Guidelines state, ‘‘An 

economic analysis of regulatory or 

policy options should present all 

identifiable costs and benefits that are 

incremental to the regulation or policy 

under consideration. These should 

include directly intended effects and 

associated costs, as well as ancillary (or 

co-) benefits and costs.’’ Guidelines at 

11–2. As discussed in prior MATS 

rulemakings (see, e.g., 80 FR 75041; 

December 1, 2015), installing control 

technologies and implementing the 

compliance strategies necessary to 

reduce the HAP emissions directly 

regulated by the MATS rule also results 

in reductions in the emissions of other 

pollutants such as directly emitted 

PM2.5 and SO2 (a PM2.5 precursor). A 

particularly cost-effective control of 

emissions of particulate-bound mercury 

and non-mercury metal HAP is through 

the use of PM control devices that 

indiscriminately collect PM along with 

the metal HAP, which are 

predominately present as particles. 

Similarly, emissions of the acid gas HAP 

are reduced by acid gas controls that are 

also effective at reducing emissions of 

SO2 (also an acid gas, but not a HAP). 

Id. While these PM2.5 and SO2 emission 

reductions are not the objective of the 

MATS rule, the reductions are, in fact, 

a direct consequence of regulating the 

HAP emissions from EGUs. Specifically, 

controls on direct PM2.5 emissions are 

required to reduce non-mercury metal 

HAP, while SO2 emissions reductions 

come from controls needed to reduce 

acid gas emissions from power plants. 

However, we recognize that there are 

significant reasons to question whether 

a formal BCA is the best way to interpret 

the Agency’s mandate in CAA section 

112(n)(1)(A), and we take comment on 

whether the Agency should continue to 

rely on this alternative basis for making 

its determination. We have consistently 

taken the position that a formal BCA is 

not required under CAA section 

112(n)(1)(A). See 80 FR 75039 

(December 1, 2015). As set forth above, 

in Michigan, the Supreme Court 

declined to hold that CAA section 

112(n)(1)(A) required such an 

assessment, stating, ‘‘We need not and 

do not hold that the law unambiguously 

required the Agency, when making this 

preliminary estimate, to conduct a 

formal cost-benefit analysis in which 

each advantage and disadvantage is 

assigned a monetary value.’’ Michigan, 

576 U.S. at 759. However, the Court did 

note that ‘‘[c]onsideration of cost 

reflects the understanding that 

reasonable regulation ordinarily 

requires paying attention to the 

advantages and disadvantages of agency 

decisions.’’ Id. at 2707. Moreover, in 

finding the EPA’s decision not to 


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consider cost irrational, the Court 

suggested that unintended 

disadvantages of a regulation could be 

considered costs as well, implying that 

such disadvantages should be accounted 

for. Id. at 2707 (‘‘The Government 

concedes that if the Agency were to find 

that emissions from power plants do 

damage to human health, but that the 

technologies needed to eliminate these 

emissions do even more damage to 

human health, it would still deem 

regulation appropriate. No regulation is 

‘appropriate’ if it does significantly 

more harm than good.’’). 

In the 2015 Proposal, we identified 

several policy reasons for preferring to 

apply a totality-of-the-circumstances 

approach to weighing costs and benefits 

over using a formal BCA as our 

decisional framework under CAA 

section 112(n)(1)(A). See 80 FR 75025 

(December 1, 2015). We recognized that 

benefits like those associated with 

reduction of HAP can be difficult to 

monetize, and this incomplete 

quantitative characterization of the 

positive consequences can 

underestimate the monetary value of net 

benefits. See 80 FR 75039 (December 1, 

2015). This is well-established in the 

economic literature. As noted in OMB 

Circular A–4, ‘‘[w]here all benefits and 

costs can be expressed as monetary 

units, BCA provides decision makers 

with a clear indication of the most 

efficient alternative.’’ Circular A–4 at 2. 

However, ‘‘[w]hen important benefits 

and costs cannot be expressed in 

monetary units, BCA is less useful, and 

it can even be misleading, because the 

calculation of net benefits in such cases 

does not provide a full evaluation of all 

relevant benefits and costs.’’ Circular A– 

4 at 10. The EPA’s Guidelines for 

Preparation of Economic Analyses also 

recognizes the limitations of BCA, 

noting that ‘‘[m]ost important, [BCA] 

requires assigning monetized values to 

non-market benefits and costs. In 

practice it can be very difficult or even 

impossible to quantify gains and losses 

in monetary terms (e.g., the loss of a 

species, intangible effects).’’ Guidelines, 

Appendix A at A–7. 

We also pointed out in the 2015 

Proposal that national level BCAs may 

not account for important distributional 

effects, such as impacts to the most 

exposed and most sensitive individuals 

in a population. See 80 FR 75040 

(December 1, 2015). These distributional 

effects and equity considerations are 

often considered outside of (or 

supplementary to) analyses like BCAs 

that evaluate whether actions improve 

economic efficiency (i.e., increase net 

benefits). For example, children near a 

facility emitting substantial amounts of 

lead are at significantly greater risk of 

neurocognitive effects (including lost 

IQ) and other adverse health effects. 

One perspective on the costs and 

benefits of controlling lead pollution 

would be to aggregate those costs and 

benefits across society, as in a BCA net 

benefits calculation. However, neither 

costs nor benefits are spread uniformly 

across society and failing to take 

account of that can overlook significant 

health risks for sensitive 

subpopulations, such as children 

exposed to lead pollution. Similarly, in 

the context of this determination, where 

we have found disproportionate risk for 

certain highly exposed or sensitive 

populations, such considerations are 

also particularly relevant. See section 

II.B; section III.A. 

We note too that OMB Circular A–4 

highlights the special challenges 

associated with the valuation of health 

outcomes for children and infants, 

because it is ‘‘rarely feasible to measure 

a child’s willingness to pay for health 

improvement’’ and market valuations 

such as increased ‘‘wage premiums 

demanded by workers to accept 

hazardous jobs are not readily 

transferred to rules that accomplish 

health gains for children.’’ Circular A– 

4 at 31. We take comment on whether 

a BCA, on its own, is an appropriate tool 

to make a determination of whether to 

regulate under CAA section 

112(n)(1)(A), given that it may not 

meaningfully capture all the societal 

interests the statute intends the EPA to 

consider. See Guidelines, Appendix A 

at A–7 (‘‘In some cases a policy may be 

considered desirable even if the benefits 

do not outweigh the costs, particularly 

if there are ethical or equity concerns.’’). 

With those caveats, we propose to 

reaffirm using a BCA approach, based 

on the 2011 RIA performed as part of 

the original MATS rulemaking, as 

another way to make the CAA section 

112(n)(1)(A) determination of whether it 

is appropriate to regulate HAP 

emissions from EGUs. 

Applying the alternative approach, 

based on the 2011 RIA, we propose to 

find that it is appropriate to regulate 

EGUs for HAP under CAA section 

112(n)(1)(A). In the 2011 RIA, the total 

benefits of MATS were estimated to 

vastly exceed the total costs of the 

regulation. As we found when applying 

the 2016 alternative approach, the 

formal BCA that the EPA performed for 

the 2012 MATS Final Rule estimated 

that the final MATS rule would yield 

annual monetized total 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; this 

compares to projected annual 

compliance costs of $9.6 billion. This 

estimate of benefits was limited to those 

health outcomes the EPA was able to 

monetize. Despite the fact that these 

estimates captured only a portion of the 

benefits of the rule, excluding many 

important HAP and criteria pollutantrelated endpoints which the Agency 

was unable to monetize (see section 

III.A.4) and instead discussed 

qualitatively in the 2011 RIA, it was 

clear that MATS was projected to 

generate overwhelmingly net positive 

effects on society. We continue to think 

that the BCA approach independently 

supports the conclusion that regulation 

of HAP emissions from EGUs is 

appropriate. 

Although as discussed in section 

III.B.2 it was not possible for the EPA 

to update the entire comprehensive cost 

estimate found in the 2011 RIA, we 

think the new information presented in 

sections III.A and III.B directionally 

supports the net benefits calculation of 

the 2016 alternative approach. That is, 

we have attempted to quantify 

additional risks, including risks of 

premature death from heart attacks that 

result from exposure to methylmercury 

associated with domestic EGU 

emissions, and we believe the 2011 

RIA’s projected cost was almost 

certainly significantly overestimated. 

Therefore, we propose that if BCA is a 

reasonable tool to use in the context of 

the EPA’s determination under CAA 

section 112(n)(1)(A), newer data 

collected since 2011 overwhelmingly 

support an affirmative determination. 

Further, that both analytical approaches 

to addressing the inquiry posed by 

Michigan lead to the same result 

reinforces the reasonableness of the 

EPA’s ultimate decision that it is 

appropriate and necessary to regulate 

HAP emissions from EGUs after 

considering cost. 

In this proposal, the EPA has reexamined the extensive record, amassed 

over 2 decades, identifying the 

advantages of regulating HAP from 

EGUs and evaluating the costs of doing 

so. We have, for purposes of this 

proposal, also updated information on 

both benefits and costs. Of note, we find 

that new scientific literature indicates 

that methylmercury exposure from 

EGUs, absent regulation, poses 

cardiovascular and neurodevelopmental 

risks to all Americans and particularly 

those most exposed to this pollution. 

With respect to costs, we explain the 

combination of factors that occurred 

since the promulgation of MATS that 

leads us to believe that the projected, 

sector-level $9.6 billion estimate of the 

cost of compliance of the rule in 2015 


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was almost certainly significantly 

overestimated. We propose two different 

approaches to considering all of this 

information, applying first a totality-ofthe-circumstances methodology 

weighing of benefits and costs and 

focusing particularly on those factors 

that we were instructed by the statute to 

study under CAA section 112(n)(1), and 

next using a formal benefit-cost 

approach consistent with established 

guidance and economic principles. 

Under either approach, whether looking 

at only the information available at the 

time of our initial decision to regulate 

or at all currently available information, 

we propose to conclude that it remains 

appropriate and necessary to regulate 

EGUs for HAP. Substantial emission 

reductions have occurred after 

implementation of MATS, the emission 

limits established pursuant to the 

Agency’s 2012 affirmative appropriate 

and necessary determination, and these 

limits provide the only Federal 

guarantee of these emission reductions 

from EGUs, which, absent regulation, 

were the largest domestic anthropogenic 

source of a number of HAP. Finalizing 

this affirmative threshold determination 

would provide important certainty 

about the future of MATS for regulated 

industry, states, other stakeholders, and 

the American public. We take comment 

on the information relied upon in this 

proposal and the EPA’s proposed 

approaches to considering that 

information for this determination. 

IV. Summary of Cost, Environmental, 

and Economic Impacts 

The EPA estimates that there are 557 

existing EGUs located at 265 facilities 

that are subject to the MATS rule. 

Because the EPA is not proposing any 

amendments to the MATS rule, there 

would not be any cost, environmental, 

or economic impacts as a result of the 

proposed action. 

V. Request for Comments and for 

Information To Assist With Review of 

the 2020 RTR 

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). That order, among 

other things, instructs the EPA to 

consider publishing a proposed rule 

suspending, revising, or rescinding the 

May 22, 2020 final action, ‘‘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.’’ The 2020 Final 

Action contained two distinct, but 

related, final actions—(1) a 

reconsideration of the 2016 

Supplemental Finding and (2) the RTR. 

This notice fulfills the Agency’s 

obligation to address the first action. We 

solicit comments on all aspects of this 

proposed action. 

Separate from this proposal, the EPA 

has initiated a review of the RTR, taking 

into account the latest information 

available on the experience of EGUs in 

complying with MATS and 

implementing measures to reduce HAP 

emissions. As previously noted, since 

MATS was promulgated in 2012, power 

sector emissions of mercury, acid gas 

HAP, and non-mercury metal HAP have 

decreased by about 86 percent, 96 

percent, and 81 percent, respectively, as 

compared to 2010 emissions levels 

(Table 4 at 84 FR 2689, February 7, 

2019). While EGUs remain the largest 

domestic emitter of mercury (and other 

HAP), their emissions and contribution 

to total mercury in the environment is 

significantly less now than before 

MATS implementation. The EPA is 

seeking input into how both of these 

facts should factor into its review of the 

RTR. 

In this notice, the EPA is soliciting 

information to allow for a more 

thorough review of the 2020 MATS 

RTR. The EPA is soliciting broadly for 

any data or information—including riskrelated information—that will assist in 

the review of the RTR. The EPA is also 

soliciting specifically for any 

information on performance or cost of 

new or additional control technologies, 

improved methods of operation, or other 

practices and technologies that may 

result in cost-effective reductions of 

HAP emissions from coal- or oil-fired 

EGUs. In addition, the EPA is interested 

in receiving information on 

improvements or upgrades to existing 

controls that may result in cost-effective 

reductions of HAP emissions from coalor oil-fired EGUs. The EPA also seeks 

information on the cost or performance 

of technologies and practices relating to 

monitoring of HAP emissions, and 

control of HAP emissions during startup 

and shutdown events, that could result 

in cost-effective reductions in HAP or 

assure improved operation of existing 

controls. We are seeking input from all 

interested stakeholders, including 

states, owners of EGUs, technology 

vendors and developers, and 

communities impacted by the emissions 

from EGUs. 

VI. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and Executive Orders can be 

found at https://www.epa.gov/lawsregulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

This action is a significant regulatory 

action that was submitted to OMB for 

review under Executive Order 12866. 

Any changes made in response to OMB 

recommendations have been 

documented in the docket. The EPA 

does not project any incremental costs 

or benefits associated with this action 

because it does not impose standards or 

other requirements on affected sources. 

B. Paperwork Reduction Act (PRA) 

This action does not impose any new 

information collection burden under the 

PRA. OMB has previously approved the 

information collection activities 

contained in the existing regulations 

and has assigned OMB control number 

2060–0567. This action does not impose 

an information collection burden 

because the EPA is not proposing any 

changes to the information collection 

requirements. 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. This action will not 

impose any requirements on small 

entities. The EPA does not project any 

incremental costs or benefits associated 

with this action because it does not 

impose standards or other requirements 

on affected sources. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain an 

unfunded mandate of $100 million or 

more as described in UMRA, 2 U.S.C. 

1531–1538, and does not significantly or 

uniquely affect small governments. The 

action imposes no enforceable duty on 

any state, local, or tribal governments or 

the private sector. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the national 

government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have tribal 

implications as specified in Executive 


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Order 13175. The executive order 

defines tribal implications as ‘‘actions 

that have substantial direct effects on 

one or more Indian tribes, on the 

relationship between the Federal 

Government and Indian tribes, or on the 

distribution of power and 

responsibilities between the Federal 

Government and Indian tribes.’’ 

Revocation of the 2020 determination 

that it is not appropriate and necessary 

to regulate HAP emissions from coaland oil-fired EGUs under CAA section 

112 and reaffirmation of the 2016 

Supplemental Finding that it remains 

appropriate and necessary to regulate 

HAP emissions from EGUs after 

considering cost would not have a 

substantial direct effect on one or more 

tribes, change the relationship between 

the Federal Government and tribes, or 

affect the distribution of power and 

responsibilities between the Federal 

Government and Indian tribes. Thus, 

Executive Order 13175 does not apply 

to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

This action is not subject to Executive 

Order 13045 because it is not 

economically significant as defined in 

Executive Order 12866, and because this 

action does not impose new regulatory 

requirements that might present a 

disproportionate risk to children. This 

action reaffirms the 2016 Supplemental 

Finding that it is appropriate and 

necessary to regulate HAP emissions 

from U.S. EGUs, but does not impose 

control requirements, which were 

implemented through MATS (77 FR 

9304; February 16, 2012). While this 

action does not impose or change any 

standards or other requirements, it 

addresses the underpinning for the HAP 

emission standards in MATS. The EPA 

believes the reductions in HAP 

emissions achieved under MATS have 

provided and will continue to provide 

significant benefits to children in the 

form of improved neurodevelopment 

and respiratory health and reduced risk 

of adverse outcomes. Analyses 

supporting the 2012 MATS Final Rule 

estimated substantial health 

improvements for children in 2016 in 

the form of 130,000 fewer asthma 

attacks, 3,100 fewer emergency room 

visits due to asthma, 6,300 fewer cases 

of acute bronchitis, and approximately 

140,000 fewer cases of upper and lower 

respiratory illness. See 77 FR 9441 

(February 16, 2012). Reaffirming the 

appropriate and necessary 

determination assures those benefits 

will continue to accrue among children. 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not a ‘‘significant 

energy action’’ because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

This action is not anticipated to have 

impacts on emissions, costs, or energy 

supply decisions for the affected electric 

utility industry as it does not impose 

standards or other requirements on 

affected sources. 

I. National Technology Transfer and 

Advancement Act (NTTAA) 

This action does not involve technical 

standards. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

The EPA believes that this action will 

not have disproportionately high and 

adverse human health or environmental 

effects on minority populations, lowincome populations, and/or indigenous 

peoples, as specified in Executive Order 

12898 (59 FR 7629; February 16, 1994), 

because it does not impose standards or 

other requirements on affected sources 

and is limited in scope to only consider 

whether it is appropriate and necessary 

to regulate HAP emissions from coaland oil-fired EGUs. While this action 

does not impose or modify any 

standards or other requirements, it 

provides the underpinning for the 

emission standards regulating HAP from 

EGUs. As documented in both the NAS 

Study and Mercury Study, fish and 

seafood consumption is the primary 

route of human exposure to 

methylmercury originating from U.S. 

EGUs, with populations engaged in 

subsistence-levels of consumption being 

of particular concern. As shown in 

section III.A.5 of this preamble, certain 

minority, low-income, and indigenous 

populations are more likely to 

experience elevated exposures, thus 

higher health risks relative of the 

general population due to subsistence 

fishing. Furthermore, subpopulations 

with the higher exposure tend to 

overlap with those subpopulations that 

are particularly vulnerability to small 

changes in health risk because of other 

social determinants of health (e.g., lack 

of access to health care and access to 

strong schooling), thereby compounding 

the implications of the implications of 

mercury exposure. Reaffirming the 

appropriate and necessary 

determination assures that the reduction 

in risks achieved by MATS continue. 

Michael S. Regan, 

Administrator. 

[FR Doc. 2022–02343 Filed 2–8–22; 8:45 am] 

BILLING CODE 6560–50–P 


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