National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units: Final Repeal

A. Executive Summary

B. Does this action apply to me?

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

D. Judicial Review and Administrative Reconsideration II. Background

A. What is the authority for this action?

B. What is the coal- and oil-fired EGU source category, and how does the NESHAP regulate emissions from the source category?

C. Summary of the 2020 Final Rule

D. Summary of the 2024 Review of the 2020 Final Rule

E. Summary of the 2025 Proposed Repeal III. Basis for Final Repeal of the 2024 Final Rule

A. Filterable PM Emission Standard for Existing Coal-Fired EGUs

B. Required Compliance Demonstration for the Filterable PM Standard

C. Hg Emission Standard for Lignite-Fired EGUs IV. Comments and Responses on the Relevance of Residual Risk to Technology Reviews Under CAA Section 112(d)(6)

A. What did the EPA propose and solicit comment on regarding the relevance of residual risk to technology reviews under CAA section 112(d)(6)?

B. What is the EPA finalizing regarding the relevance of residual risk to technology reviews under CAA section 112(d)(6)?

C. What key comments did the EPA receive regarding the relevance of residual risk to technology reviews under CAA section 112(d)(6), and what are our responses? V. What is the rationale for other final decisions and amendments from the reevaluation of the 2024 Final Rule? VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

C. Paperwork Reduction Act (PRA)

D. Regulatory Flexibility Act (RFA)

E. Unfunded Mandates Reform Act (UMRA)

F. Executive Order 13132: Federalism

G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

J. National Technology Transfer and Advancement Act (NTTAA)

K. Congressional Review Act (CRA)

In 2012, the EPA promulgated standards to address HAP emissions-- including mercury, lead, arsenic, chromium, nickel, and cadmium, as well as hydrogen chloride from coal- and oil-fired EGUs (“2012 MATS Rule”).\1\ Under CAA section 112, the EPA was required to review the standards within eight years to identify and address any residual risk to human health and the environment and, separately, to revise the standards as “necessary” in light of developments in practices, processes, and control technologies.\2\ The Agency timely completed these reviews in 2020, finding, among other things, that the existing standards in the 2012 MATS Rule protected public health with an ample margin of safety and that further changes to the standards were not “necessary” because there were no cost-effective developments in technology that supported revision (“2020 Final Rule”).\3\

\1\ 77 FR 9304 (February 16, 2012).

\2\ CAA section 112(d)(6), (f)(2). CAA section 112 is codified at 42 U.S.C. 7412.

\3\ 85 FR 31286 (May 22, 2020).

Following a change in administration, however, an Executive Order instructed the EPA to reconsider and suspend, revise, or rescind the 2020 Final Rule if appropriate.\4\ On May 7, 2024, the EPA finalized several MATS amendments after initiating a rulemaking in response to the Executive Order (“2024 Final Rule”).\5\ In the 2024 Final Rule, the EPA confirmed that the 2020 risk review finding that the 2012 MATS Rule protected public health and the environment with an ample margin of safety as required by CAA section 112(f)(2) was correct.\6\ Nevertheless, upon reconsideration of the technology review under section 112(d)(6), the Agency established more stringent standards for the non-Hg metal HAP emissions and for fPM emissions (which serves as a surrogate for non-Hg metal HAP) from coal-fired EGUs and for mercury emissions from lignite-fired units and required all EGUs to install continuous emissions monitoring systems (CEMS) to monitor emissions of fPM, thereby removing existing compliance flexibilities in favor of a uniform, one-size-fits-all approach. The Agency reasoned that the revisions to MATS were warranted because “the size and unique nature of the coal-fired power sector” made the revisions “necessary,” but the revisions were based on relatively limited data concerning potential improvements in control technology and established despite the fact that the costs of the revisions were and are higher than anything the Agency has previously determined “necessary” pursuant to section 112(d)(6).\7\

\4\ Executive Order 13990, “Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis,” 86 FR 7037 (January 25, 2021), since rescinded by Executive Order 14148, “Initial Rescissions of Harmful Executive Orders and Actions,” 90 FR 8237 (January 28, 2025).

\5\ 89 FR 38508 (May 7, 2024).

\6\ Id. at 38518; see 88 FR 24866 (April 24, 2023) (proposed rule for the 2024 Final Rule).

\7\ 89 FR 38534 (May 7, 2024).

On March 12, 2025, Administrator Zeldin announced that the Agency would reconsider the 2024 Final Rule.\8\ On June 17, 2025, the EPA undertook a review of the 2024 Final Rule and proposed to repeal most of its amendments (“2025 Proposal”).\9\ This action was consistent with several Executive Orders and other Presidential Actions. In particular, Executive Order 14154, “Unleashing American Energy,” specifies that it is the policy of the United States to “protect the United States's economic and national security and military preparedness by ensuring that an abundant supply of reliable energy is readily accessible in every State and territory of the Nation” and “to ensure that all regulatory requirements related to energy are grounded in clearly applicable law” (among other considerations).\10\ The Executive Order directed the heads of all agencies to review all existing regulations to identify agency actions that impose an undue burden on the identification, development, or use of domestic energy resources, with particular attention to oil, natural gas, coal, hydropower, biofuels, critical minerals, and nuclear energy resources. This Executive Order also directed agencies, consistent with applicable law, to suspend, revise, or rescind all agency actions identified as unduly burdensome and revoked Executive Order 13990. This Executive Order was followed by Executive Order 14179, “Removing Barriers to American Leadership in Artificial Intelligence;” \11\ Executive Order 14192, “Unleashing Prosperity Through Deregulation;” \12\ Executive Order 14262, “Strengthening the Reliability and Security of the United States Electric Grid;” \13\ and Executive Order 14261, “Reinvigorating America's Beautiful Clean Coal Industry and Amending Executive Order 14241,” 90 FR 15517 (April 14, 2025).

\8\ https://www.epa.gov/newsreleases/epa-launches-biggest-deregulatory-action-us-history.

\9\ 90 FR 25535 (June 17, 2025).

\10\ 90 FR 8353 (January 29, 2025).

\11\ 90 FR 8741 (January 31, 2025).

\12\ 90 FR 9065 (February 6, 2025).

\13\ 90 FR 15521 (April 14, 2025).

In addition, on April 8, 2025, President Trump signed a Proclamation titled “Regulatory Relief for Certain Stationary Sources to Promote American Energy.” \14\ This Proclamation exempted certain stationary sources, identified in Annex 1 of the Proclamation, from compliance with the 2024 Final Rule pursuant to CAA section 112(i)(4).\15\ The President's exemption is for a period of two years beyond the 2024 Final Rule's compliance date (i.e., for the period beginning July 8, 2027, and concluding July 8, 2029). Sources identified in Annex 1 will remain subject to the 2012 MATS Rule during the two-year extension period. Copies of the Presidential Proclamation and

Annex 1 are available in the rulemaking docket.\16\

\14\ 90 FR 16777 (April 21, 2025).

\15\ “Regulatory Relief for Certain Stationary Sources to Further Promote American Energy” was issued on July 17, 2025, and added six sources to Annex 1. See 90 FR 34583 (July 23, 2025).

\16\ Document ID No. EPA-HQ-OAR-2018-0794-6980.

In the 2025 Proposal, the EPA proposed to repeal the three key amendments finalized in the 2024 Final Rule based on the EPA's authority under CAA section 112 and the EPA's authority to reconsider previous decisions taken under that authority to the extent permitted by law and supported by a reasoned explanation.\17\ The Agency noted that the proposed repeal was in accordance with the above-noted Executive Orders and solicited comment on whether the 2024 Final Rule had erred in evaluating cost-effectiveness and technical feasibility when deciding that revisions were “necessary.” \18\ In addition, the Agency sought comment on whether it should consider the potential for meaningful risk reduction when evaluating costs as part of determining whether revisions are “necessary” in a technology review.\19\

\17\ FDA v. Wages & White Lion Invs., L.L.C., 604 U.S. 542, 568 (2025); FCC v. Fox Television Stations, Inc., 556 U.S. 502, 515 (2009); see also Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 42 (1983).

\18\ 90 FR 25544-45 (June 17, 2025).

\19\ Id. at 25545.

In this final rule, the EPA is repealing the following three MATS amendments from the 2024 Final Rule:

The fPM emission standard for existing coal-fired EGUs, which the EPA revised from 0.030 pounds per million British thermal units (lb/MMBtu) to 0.010 lb/MMBtu;

The compliance demonstration requirement for the fPM emission standard for all coal- and oil-fired EGUs, which the EPA revised from allowing EGU owners and operators to choose between use of quarterly stack testing, use of continuous parametric monitoring systems (CPMS), or use of PM continuous emission monitoring systems (CEMS) to allowing only the use of PM CEMS; and

The Hg emission standard for existing lignite-fired EGUs, which the EPA revised from 4.0 pounds per trillion British thermal units (lb/TBtu) to 1.2 lb/TBtu.

The EPA has reevaluated the 2024 Final Rule and, after considering public comments, finds that the revisions to the emissions standards were not “necessary” because they impose unwarranted compliance costs or raise potential technical feasibility concerns. With respect to the revised fPM emission standard, the EPA has two separate, and severable, bases for this finding. First, the EPA finds that the cost- effectiveness values associated with this standard (i.e., the cost per mass of fPM or non-Hg HAP metal(s) reduced) are significantly higher than cost-effectiveness values that the Agency previously accepted in other technology reviews and related CAA section 112 actions for which cost is a factor. Unlike in the 2024 Final Rule, the Agency does not believe it is consistent with prior practice or reasonable to disregard such cost-effectiveness comparators and does not believe that differences between the EGU source category and other source categories justify establishment of a new high-cost benchmark for fPM as a surrogate for non-Hg metal HAP. Second, in undertaking review of the 2024 rule, the EPA also considered the Agency's conclusion from the 2020 residual risk review, confirmed by the 2024 Final Rule, that there is little risk remaining from emissions of non-Hg HAP metals following the implementation of the emissions standards promulgated in the 2012 MATS Rule. For the reasons set forth later in this preamble, the Agency concludes that the low levels of remaining risk found in the prior residual risk review are relevant to the cost reasonableness of revised standards and therefore to whether it is “necessary” to promulgate revised standards that impose additional costs.

With respect to the requirement to utilize PM CEMS for compliance demonstrations, the EPA finds this requirement is an unnecessary expense for coal- and oil-fired EGUs and that owners and operators should retain the option of using other monitoring methods to demonstrate compliance with the fPM emission standard. For the reasons set forth later in this preamble, mandating the use of PM CEMS and removing previously available compliance alternatives was not “necessary” pursuant to CAA section 112(d)(6). Furthermore, although the EPA in the 2024 Final Rule invoked CAA section 114(a)(1)(C) as offering additional authority for the PM CEMS requirement, that provision is equally applicable to the alternative compliance demonstration options restored in this final rule.

Finally, the EPA finds that the revised Hg emission standard for lignite-fired EGUs is not achievable given the broad range of boiler types and varying compositions of the different lignite fuels used at those facilities. As set forth later in this preamble, in light of this variability, the revised standard was based on insufficient data. As a result, the EPA finds that these revisions to the emission standards were not “necessary” under CAA section 112(d)(6), and is repealing them. As noted above, this action is consistent with Executive Order 14192, “Unleashing Prosperity Through Deregulation,” \20\ Executive Order 14154, “Unleashing American Energy,” \21\ and Executive Order 14261, “Reinvigorating America's Beautiful Clean Coal Industry and Amending Executive Order 14241,” \22\ among other recent Presidential actions.

\20\ 90 FR 9065 (February 6, 2025).

\21\ 90 FR 8353 (January 29, 2025).

\22\ 90 FR 15517 (April 14, 2025).

The EPA estimates that this action will result in present value cost savings of $670 million at a 3 percent discount rate and $490 million at a 7 percent discount rate over the 2028 to 2037 timeframe, with total annualized cost savings of $78 and $69 million per year, respectively (in 2024 dollars).

Under CAA section 307(b)(1), judicial review of this final action is available only by filing a petition for review in the United States Court of Appeals for the District of Columbia Circuit (“D.C. Circuit”) by April 27, 2026. CAA section 307(b)(2) prohibits a party from challenging this final rule separately in any civil or criminal proceedings brought by the EPA for enforcement.

CAA section 307(d)(7)(B) further provides that only an objection to a rule or procedure that was raised with reasonable specificity during the period for public comment (including any public hearing) may be raised during judicial review. This section also requires the EPA to reconsider the rule if the person raising an objection can demonstrate to the Administrator that it was impracticable to raise such objection within the period for public comment or if the grounds for such objection arose after the period for public comment (but within the time specified for judicial review) and if such objection is of central relevance to the outcome of the rule. Any person seeking to make such a demonstration should submit a Petition for Reconsideration to the Office of the Administrator, U.S. EPA, Room 3000, WJC South Building, 1200 Pennsylvania Ave. NW, Washington, DC 20460, with a copy to both the person(s) listed in the preceding FOR FURTHER INFORMATION CONTACT section and the Associate General Counsel for the Air and Radiation Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW, Washington, DC 20460.

The statutory authority for this action is provided by CAA section 112, as amended (42 U.S.C. 7412). CAA section 112 establishes a multi- stage regulatory process to develop standards for emissions of HAP from stationary sources. Generally, the first stage involves establishing technology-based standards that reflect the maximum achievable control technology (MACT) or an appropriate alternative.\23\ The second stage involves evaluating those standards within eight years under CAA section 112(f)(2) to determine whether additional standards are needed to address any remaining risk associated with HAP emissions.\24\ This second stage is commonly referred to as the “residual risk review.” In addition to the residual risk review, CAA section 112(d)(6) also requires the EPA to review the standards every eight years and “revise as necessary” taking into account “developments in practices, processes, and control technologies.” \25\ This review is commonly referred to as the “technology review.” The discussion that follows identifies the most relevant statutory sections and briefly explains the contours of the methodology used to implement these statutory requirements.

\23\ 42 U.S.C. 7412(d)(1)-(4).

\24\ Id. 7412(f)(2).

\25\ Id. 7412(d)(6).

In the first stage of the CAA section 112 standard-setting process, the EPA promulgates technology-based standards under CAA section 112(d) for categories of sources identified as emitting one or more of the HAP listed in CAA section 112(b). Sources of HAP emissions are either major sources or area sources, and CAA section 112 establishes different requirements for major source standards and area source standards. The requirements for major sources are the relevant requirements for the present rulemaking. “Major sources” are those that emit or have the potential to emit 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of HAP.\26\ For major sources, CAA section 112(d)(2) provides that the technology-based NESHAP must reflect the maximum degree of reduction in emissions of HAP achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts). These standards are commonly referred to as MACT standards. CAA section 112(d)(3) also establishes a minimum control level for MACT standards, known as the MACT “floor,” which is based on emission controls achieved in practice by a certain percentage of the best performing sources. The EPA also considers control options that are more stringent than the floor. Standards more stringent than the floor are commonly referred to as “beyond-the- floor” standards.

\26\ Id. 7412(a)(1).

The next stage in standard-setting focuses on identifying and addressing any remaining (i.e., “residual”) risk within eight years pursuant to CAA section 112(f)(2) and concurrently conducting a technology review pursuant to CAA section 112(d)(6). This latter provision requires the EPA to review standards promulgated under CAA section 112 and revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less often than every eight years. In conducting this review, which we call the “technology review,” the EPA is not required to recalculate the MACT floors that were established in earlier rulemakings.\27\ The EPA considers cost in deciding whether to revise the standards pursuant to CAA section 112(d)(6).

\27\ Ass'n of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 2013); Natural Resources Def. Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008).

CAA section 112(d)(6) and relevant case law provide the EPA with flexibility to consider additional relevant factors other than those enumerated in section 112(d)(6) when deciding whether revisions to existing

standards are “necessary.” The D.C. Circuit has held that the CAA section 112(d)(6) requirement to periodically review and revise CAA section 112 emission standards “as necessary” is not limited to the consideration of “developments in practices, processes and control technologies.” \28\ Rather, “the operative standard is `revise as necessary,' with the parenthetical pointing to a non-exhaustive list of considerations.” \29\ The Supreme Court also emphasized in Michigan v. EPA that unless the statute provides otherwise, broad terms such as “necessary” direct the relevant agency to consider all relevant factors, including by assessing the cost of an action relative to the anticipated benefits.\30\ That decision is particularly relevant here because the Court was interpreting a related provision of CAA section 112 that instructs the Administrator to determine whether it is “appropriate and necessary” to regulate HAP emissions from EGUs.\31\ Thus, under relevant case law, when the EPA is deciding whether it is “necessary” to revise standards pursuant to CAA section 112(d)(6), the Agency can consider the costs of any developments in practices, processes, and control technologies.

\28\ La. Envtl. Action Network (LEAN) v. EPA, 955 F.3d 1088, 1097 (D.C. Cir. 2020).

\29\ Id.; see also Nat'l Ass'n for Surface Finishing v. EPA, 795 F.3d 1, 11 (D.C. Cir. 2015); Ass'n of Battery Recyclers, 716 F.3d at 673-74.

\30\ 576 U.S. 743, 752-53 (2015).

\31\ See id. (interpreting 42 U.S.C. 7412(n)(1)(A)).

The EPA is also finalizing that the results of a prior residual risk review under CAA section 112(f)(2) can be relevant under certain circumstances when evaluating whether it is “necessary” to revise standards under CAA section 112(d)(6). Specifically, as relevant here, where the remaining risk of cancer from the sources in this category is below 1-in-1 million, cost considerations bear additional weight in determining whether revised standards are “necessary” under CAA section 112(d)(6). In section III.A.2 of this preamble, we elaborate on this approach, including discussing its basis in CAA section 112 and its consistency with prior NESHAP technology reviews. 2. What is the authority for revisiting the 2024 Final Rule?

The EPA's authority to revisit existing regulations under CAA section 112 is well-grounded in law. Specifically, the EPA has authority to reconsider, repeal, or revise past decisions to the extent permitted by law so long as the Agency provides a reasoned explanation.\32\ This is true when, as is the case here, an agency reconsiders a prior regulation after a change in administration.\33\ When permitted by the statutory scheme, “[a]gencies obviously have broad discretion to reconsider a regulation at any time.” \34\

\32\ See, e.g., Motor Vehicle Mfrs. Ass'n, 463 U.S. at 42 (“[R]egulatory agencies do not establish rules of conduct to last forever [and] an agency must be given able latitude to adapt their rules and policies to . . . changing circumstances.”); see also Clean Water Action v. EPA, 936 F.3d 308, 313 (5th Cir. 2019) (“EPA correctly surmised that, in addition to its statutory authority to revise rules . . . administrative agencies possess the inherent authority to revise previously-promulgated rules, so long as they follow the proper administrative requirements and provide a reasoned basis for the agency decision.”).

\33\ Nat'l Ass'n of Home Builders v. EPA, 682 F.3d 1032, 1038, 1043 (D.C. Cir. 2012) (explaining that an agency's “reevaluation of which policy would be better in light of the facts” is “well within” its discretion and that a change in administration is a “perfectly reasonable basis for an executive agency's reappraisal of the costs and benefits of its programs and regulations” (internal quotation marks omitted)). For this rulemaking, no commenters contested that the EPA has authority to reconsider a prior rule under CAA section 112(d)(6), although some argued that the EPA is impermissibly weakening a prior CAA section 112 rule.

\34\ Clean Air Council v. Pruitt, 862 F.3d 1, 8-9 (D.C. Cir. 2017).

The EPA promulgated the Mercury and Air Toxics Standards on February 16, 2012. The standards are codified at 40 CFR part 63, subpart UUUUU. Coal- and oil-fired EGUs are combustion units of more than 25 megawatts (MW) that serve a generator that produces electricity for sale and are located at both major and area sources of HAP emissions.\35\ For coal-fired EGUs, the 2012 MATS Rule established standards to limit emissions of Hg, acid gas HAP (e.g., hydrogen chloride (HCl), hydrogen fluoride (HF)), non-Hg HAP metals (e.g., nickel, lead, chromium), and organic HAP (e.g., formaldehyde, dioxin/ furan). Emission standards for HCl serve as a surrogate for all the acid gas HAP. For coal-fired EGUs with flue gas desulfurization (FGD), an alternate standard for sulfur dioxide (SO2) may be used as a surrogate for all acid gas HAP if SO2 CEMS are installed and operational. Standards for fPM serve as a surrogate for the non-Hg HAP metals, with total and individual HAP metals standards provided as an alternative. The EPA chose fPM as a surrogate for non-Hg HAP metals because non-Hg HAP metals are predominantly a component of the filterable fraction of total PM (which is composed of a filterable and condensable fraction), and control of fPM emissions also results in control of emissions of non-Hg HAP metals.\36\ Additionally, not all fuels emit the same type and amount of non-Hg HAP metals, but most generally emit fPM that includes some amount and combination of all the non-Hg HAP metals. Finally, using fPM as a surrogate eliminates the cost of performance testing to demonstrate compliance with numerous standards for individual non-Hg HAP metals.\37\

\35\ A unit that cogenerates steam and electricity and supplies more than one-third of its potential electric output capacity and more than 25 MW electrical output to any utility power distribution system for sale is also an electric utility steam generating unit.

\36\ Selenium may be present in the filterable PM or the condensable fraction as the acid gas, SeO2.

\37\ Document ID No. EPA-HQ-OAR-2009-0234.

In addition, the EPA established work practice standards to limit the formation and emissions of organic HAP. For oil-fired EGUs, the 2012 MATS Rule established standards to limit emissions of HCl and HF, total HAP metals (e.g., Hg, nickel, lead), and organic HAP (e.g., formaldehyde, dioxin/furan). Standards for fPM also serve as a surrogate for total HAP metals, with standards for total and individual HAP metals provided as alternative equivalent standards.

The 2020 Final Rule included two separate decisions. First, the EPA responded to the Supreme Court's remand in Michigan by concluding that it is not “appropriate and necessary” pursuant to CAA section 112(n)(1)(A) to regulate coal- and oil-fired EGUs under CAA section 112.\38\ Second, the EPA completed the combined RTR for MATS due 8 years from the promulgation of the 2012 MATS Rule. As part of the RTR, the EPA conducted the residual risk review (“2020 Residual Risk Review”) pursuant to CAA section 112(f)(2), which requires the EPA to determine whether promulgation of additional standards is needed to provide an ample margin of safety to protect public health or to prevent an adverse environmental effect. Also, the EPA conducted a technology review (“2020 Technology Review”) pursuant to CAA section 112(d)(6), which focused on identifying and evaluating developments in practices, processes, and control technologies that occurred

since promulgation of the 2012 MATS Rule to determine whether revisions to the standards were otherwise “necessary.”

\38\ As noted below, in 2023, the EPA reversed its position from the 2020 Final Rule and concluded that regulation of coal- and oil- fired EGUs is “appropriate and necessary” under CAA section 112(n)(1)(A). 88 FR 13956 (March 6, 2023) (“2023 Final Rule”). In the present rulemaking, the EPA is not reconsidering the “appropriate and necessary” finding in the 2020 Final Rule or 2023 Final Rule.

The EPA presented the results of the 2020 Residual Risk Review, including the Agency's decisions regarding risk acceptability, ample margin of safety, and adverse environmental effects, in the 2020 Final Rule. Table 2 below summarizes the results of the risk assessment; more detail is available in the document entitled Residual Risk Assessment for the Coal- and Oil-Fired EGU Source Category in Support of the 2020 Risk and Technology Review Final Rule, which is available in the docket for this rulemaking.\39\ The EPA found the residual risk due to emissions of air toxics from this source category to be acceptable and determined that the 2012 MATS Rule provided an ample margin of safety to protect public health and prevent adverse environmental effects. Therefore, the EPA did not make any revisions to the 2012 MATS Rule to address residual risk.

\39\ Document ID No. EPA-HQ-OAR-2018-0794-4553.

Table 2--Coal- and Oil-Fired EGU Inhalation Risk Assessment Results in the 2020 Final Rule

[85 FR 31286, May 22, 2020]

Maximum individual Population at increased Annual cancer incidence Maximum chronic Maximum screening

cancer risk (in 1 risk of cancer >=1-in-1 (cases per year) noncancer TOSHI \3\ acute noncancer HQ

million) \2\ million -------------------------------------------------- \4\

-------------------------------------------------- Based on . . . Based on . . . --------------------

Number of facilities \1\ Based on . . . Based on . . . --------------------------------------------------

Actual Allowable Actual Allowable Actual Allowable Actual Allowable Based on actual

emissions emissions emissions emissions emissions emissions emissions emissions emissions level

level level level level level level level level

322............................ 9 10 193,000 636,000 0.04 0.1 0.2 0.4 HQREL = 0.09

(arsenic).

\1\ Number of facilities evaluated in the risk analysis. At the time of the risk analysis there were an estimated 323 facilities in the coal- and oil-

fired EGU source category; however, one facility is in Guam, which was beyond the geographic range of the model used to estimate risks. Therefore, the

Guam facility was not modeled and the emissions for that facility were not included in the assessment. \2\ Maximum individual excess lifetime cancer risk due to HAP emissions from the source category. \3\ Maximum target organ-specific hazard index (TOSHI). The target organ systems with the highest TOSHI for the source category are respiratory and

immunological. \4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of hazard quotient (HQ)

values. HQ values shown use the lowest available acute threshold value, which in most cases is the reference exposure level (REL). When an HQ exceeds

1.0, we also show the HQ using the next lowest available acute dose-response value.

The 2020 Residual Risk Review also included more particularized risk determinations. As relevant here, these included determining that the maximum lifetime cancer risk from coal-fired EGUs ranged from 0.002-in-1 million to 0.3-in-1 million.\40\

\40\ Residual Risk Assessment for the Coal- and Oil-Fired EGU Source Category in Support of the 2020 Risk and Technology Review Final Rule. This report is referred to as the 2020 Residual Risk Review throughout the preamble.

The 2020 Final Rule also presented the results of the 2020 Technology Review, which focused on identifying and evaluating developments in practices, processes, and control technologies that occurred since promulgation of the 2012 MATS Rule to determine whether revisions are “necessary” in light of all relevant considerations. Control technologies typically used to minimize emissions of pollutants that have numeric emission limits under the 2012 MATS Rule include electrostatic precipitators (ESPs) and fabric filters (FFs) for control of fPM as a surrogate for non-Hg HAP metals; wet scrubbers, dry scrubbers, and dry sorbent injection for control of acid gases (e.g., SO2, HCl, and HF); and activated carbon injection (ACI) and other Hg-specific technologies for control of Hg. In the 2020 Technology Review, the EPA did not identify any developments in practices, processes, or control technologies that would achieve further cost-effective emissions reductions and thus did not make any changes to the emission standards or other requirements in the 2012 MATS Rule. More information on the 2020 Technology Review is presented in the memorandum entitled Technology Review for the Coal- and Oil- Fired EGU Source Category, which is available in the docket for this rulemaking.\41\

\41\ Document ID No. EPA-HQ-OAR-2018-0794-0015.

Executive Order 13990, “Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis,” instructed the EPA to review the 2020 Final Rule and to consider publishing a notice of proposed rulemaking suspending, revising, or rescinding that action.\42\ The EPA reviewed the finding in the 2020 Final Rule that it was not appropriate and necessary to regulate coal- and oil-fired EGUs under CAA section 112 and, on February 9, 2022, proposed to find that it is appropriate and necessary to regulate coal- and oil-fired EGUs under CAA section 112.\43\ The EPA made the affirmative finding on March 6, 2023.\44\

\42\ 86 FR 7037 (January 25, 2021), rescinded by Executive Order 14148, “Initial Rescissions of Harmful Executive Orders and Actions,” 90 FR 8237 (January 28, 2025).

\43\ 87 FR 7624 (February 9, 2022).

\44\ 88 FR 13956 (March 6, 2023).

On April 24, 2023, the EPA proposed the results of the Agency's review of the RTR from the 2020 Final Rule.\45\ In the 2023 proposed rule, the EPA noted the conclusions from the 2020 Residual Risk Review, as shown in Table 2 of this preamble, including the finding that residual risk due to emissions of air toxics from this source category was acceptable and that the 2012 MATS Rule provided an ample margin of safety to protect public health and prevent adverse environmental effects. Further, the EPA explained that it had “review[ed] the 2020 residual risk analysis, [and] . . . determined that the risk analysis was rigorous, robust, and conducted using approaches and methodologies that are consistent with those that have been utilized in residual risk analyses and reviews for other industrial sectors.” \46\ For these reasons, the EPA did not reopen the 2020 Residual Risk Review and did not propose changes to any emissions standards or other requirements for the purpose of addressing the remaining risk.\47\

\45\ 88 FR 24854 (April 24, 2023).

\46\ Id. at 24866.

\47\ Id.

The EPA's review of the 2020 Technology Review included evaluating the technology review \48\ and focused on

the identification of any developments in practices, processes, and control technologies that have occurred since the finalization of the 2012 MATS Rule and since publishing the 2020 Technology Review. Based on that review, the EPA concluded that revisions to certain standards were warranted and proposed three changes. First, the EPA proposed to revise the existing coal-fired EGU fPM emissions standard, which is a surrogate for non-Hg HAP metals, from 0.030 lb/MMBtu to 0.010 lb/MMBtu, and proposed corresponding reductions in the alternative emission standards for total and individual non-Hg HAP metals. Second, the EPA proposed to require that all coal- and oil-fired EGUs demonstrate compliance with the applicable fPM emission standard exclusively by using PM CEMS, and to remove the option of using alternative compliance demonstrations. Third, the EPA proposed to revise the Hg emission standard for lignite-fired EGUs from 4.0 lb/TBtu to 1.2 lb/TBtu with an alternative output-based standard of 0.013 lb/gigawatt-hour (GWh). All proposed changes were ultimately promulgated in the 2024 Final Rule.\49\

\48\ Described in Document ID No. EPA-HQ-OAR-2018-0794-0015.

\49\ In the 2024 Final Rule, the EPA also removed paragraph (2) of the definition of “startup” in 40 CFR 63.10042. See 89 FR 38550 (May 7, 2024). The regulation now requires that all EGUs use the work practice standards in paragraph (1) of the definition of “startup” in 40 CFR 63.10042, which was already being used by virtually all affected EGUs. The EPA made this revision in response to Chesapeake Climate Action Network v. EPA, 952 F.3d 310 (D.C. Cir. 2020), in which the D.C. Circuit remanded the alternative “startup” work practice standard in paragraph (2) to the EPA for reconsideration. The compliance deadline for the changes to the “startup” definition was January 2, 2025. The EPA did not propose amendments to this aspect of the 2024 Final Rule and is not finalizing any changes to the “startup” definition at this time.

In the 2024 Final Rule, the EPA established a substantially more stringent fPM emission standard, which serves as a surrogate for the non-Hg HAP metals. The fPM standard was lowered from 0.030 lb/MMBtu to 0.010 lb/MMBtu for all existing coal-fired EGUs. The 2024 Final Rule also proportionally lowered the individual and total non-Hg HAP metal emission limits.

In the 2024 Final Rule, the EPA revised its conclusion in the 2020 Final Rule by finding that there were developments in practices, processes, and control technologies to reduce fPM emissions, that the costs to comply with the more stringent fPM standard based on these developments were reasonable, and in light of those considerations, that the revised standard was “necessary.” The EPA stated that it had considered costs in several ways, including cost effectiveness, the total capital costs of proposed measures, annual costs, and costs compared to total revenues. In addition, in the 2024 Final Rule, the EPA found that most existing coal-fired EGUs had reporting fPM levels that were below the 2012 MATS Rule 0.030 lb/MMBtu emission limit and that costs were lower than estimated during promulgation of the 2012 MATS Rule fPM emission limit.\50\

\50\ For instance, the EPA found at the time that the median fPM rate of the 296 coal-fired EGUs assessed in the 2024 Final Rule was 0.004 lb/MMBtu, or 60 percent below the revised fPM limit of 0.010 lb/MMBtu. See 89 FR 38522 (May 7, 2024).

In this section, the EPA describes what aspects of the proposal the Agency is finalizing, a summary of key comments and responses, and the rationale for each final decision. For all comments not discussed in this preamble, comment excerpts and the EPA's responses are available in the comment summary and response document entitled National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units, Repeal of Amendments, Summary of Public Comments and Responses on Proposed Rule, available in the docket for this rulemaking.\52\

\52\ Docket ID No. EPA-HQ-OAR-2018-0794.

Because this final rule repeals three requirements of the 2024 Final Rule--revisions to the emissions standards for fPM as a surrogate for non-Hg HAP metals for existing coal-fired EGUs, the fPM emission standard compliance demonstration requirements, and the Hg emission standard for lignite-fired EGUs--the EPA intends the repeal of each requirement to be severable from one another. Just as each requirement added in the 2024 Final Rule addressed distinct aspects of MATS and employed a distinct rationale, so also is the EPA finalizing the repeal of each requirement for separate and independent reasons. When the EPA adopted these three requirements in the 2024 Final Rule, the EPA explained that each of the three requirements were severable from each other as each is “multifaceted and addresses several distinct aspects of MATS for independent reasons.” \53\ By the same token, the repeal of each of requirement is severable from the repeal of the remaining requirements.

\53\ 90 FR 38518 (May 7, 2024).

The EPA intends that the various components of this final rule operate independently of the other and be considered independently. For example, the EPA notes that our justifications for repealing the revised fPM standard as a surrogate for non-Hg HAP metals (and related revised standards for each non-Hg HAP metal) are rooted in the poor cost-effectiveness of the controls, while our justifications for repealing the requirements for lignite-fired EGUs to meet the same standard for Hg emissions as other coal- and oil-fired EGUs rest on a separate analysis specific to the variability of lignite-fired units and lack of sufficient data. Similarly, our justifications for repealing the changes to the fPM compliance demonstration requirement are based on the cost of CEMs and the determination that it is not necessary to make CEMS the exclusive means of demonstrating compliance to further transparency and informational values.

Each of these actions is independent from each other. In particular, the repeal of the revised emission standard for fPM

as a surrogate for non-Hg HAP metals (and related revised standards for each non-Hg HAP metal) and the repeal of the fPM compliance demonstration requirement to utilize PM CEMS are independent and based on separate rationales. While the EPA considered the technical feasibility of PM CEMS in establishing the revised fPM standard, the EPA finds there are independent reasons for repealing each requirement, as just noted. If the EPA were to repeal any one or two of the three requirements, but not the other one or two, each repeal would reinstate requirements from the 2012 MATS Rule that continue to be workable without the other one or two revisions in place.

Accordingly, the EPA finds that the repeal of each set of revised standards and requirements is severable from the repeal of the other revised standards and requirements. Thus, the EPA has independently considered and adopted each portion of this final rule, which includes the repeal of the revised fPM emission standard as a surrogate for non- Hg HAP metals (and related revised standards for each non-Hg HAP metal), the repeal of the fPM compliance demonstration requirement, and the repeal of the revised Hg emission standard for lignite-fired units, and each is severable should there be judicial review. If a court were to invalidate any one of these elements of the final rule, the EPA intends the remainder of this action to remain effective. Importantly, the EPA designed the different elements of this final rule to function sensibly and independently. Further, the supporting bases for each element of the final rule reflect the Agency's judgment that the element is independently justified and appropriate, and that each element can function independently even if one or more other parts of the rule has been set aside.

The EPA proposed repealing the lower fPM limit of 0.010 lb/MMBtu for existing coal-fired EGUs based on a determination that the cost of the revision to the standard are unreasonable, and thus, not “necessary” as required by CAA section 112(d)(6). The EPA also proposed to revert the corresponding total and individual HAP metal emission standards to the limits that were promulgated in the 2012 MATS Rule if the repeal of the more stringent fPM limit were finalized. The EPA solicited comment on whether the cost-effectiveness rationale used to justify the revised fPM emission standard is consistent with the Agency's prior CAA section 112(d)(6) technology review determinations (Question #1) and on whether there are other cost-effective and achievable alternative standards that the EPA should consider as an alternative to a standalone repeal of the 0.010 lb/MMBtu fPM emission standard (Question #2). The EPA also took comment on whether risk should be a factor that the Agency considers when conducting technology reviews and if so, how.

The EPA is finalizing its proposal to repeal the more stringent fPM emission standard and the corresponding total and individual non-Hg HAP metal standards that were promulgated in the 2024 Final Rule and to revert to the limits set in the 2012 MATS Rule, which reduce risk to acceptable levels and provide an ample margin of safety. Commenters provided both supportive and opposing arguments for issues regarding the fPM emission standard. Neither these comments nor the Agency's updated analyses altered the EPA's views of the conclusions proposed or required changes to the proposed regulatory language. 2. What is the rationale for the EPA's final decision to repeal the filterable PM standard for existing coal-fired EGUs?

In this final rule, the EPA is repealing the lower fPM standard of 0.010 lb/MMBtu for existing coal-fired EGUs that the EPA established in the 2024 Final Rule, as well as the alternative total and individual non-Hg HAP metal limits and returning all of them to the emissions standards promulgated in the 2012 MATS Rule. As discussed in this section, the EPA determines upon further review that the cost- effectiveness of the revised standards is not reasonable and compares unfavorably to prior Agency decisions on cost-reasonableness across other technology reviews and other section 112 actions where costs are considered. In addition, after reviewing the comments the EPA received concerning the consideration of risk in the context of a CAA section 112(d)(6) review, the Agency concludes that the results of the residual risk review may be considered when evaluating whether revisions to the emission standards are cost-reasonable and therefore “necessary” under CAA section 112(d)(6). As explained further in section III.A of this preamble, the EPA finds that it is appropriate to consider the conclusions of the section 112(f)(2) risk review in all subsequent section 112(d)(6) reviews. For a risk review, the Agency determines the risk remaining from HAP emissions from every source in a source category, and the statute includes specific risk thresholds for remaining cancer risk. Specifically, the statute incorporates a rebuttable presumption that a cancer risk above 100 in 1 million is unacceptable \54\ and establishes an aspirational goal of using standards to reduce cancer risk for each source in a category to no greater than one in one million.\55\ The Agency finds that the results of the residual risk review can be considered in technical reviews going forward to inform the potential for meaningful risk reduction when evaluating cost.

\54\ See CAA section 112(f)(2)(B), 42 U.S.C. 7412(f)(2)(B) (preserving the EPA's approach in the Benzene NESHAP, under which cancer risk above 100 in 1 million is presumptively unacceptable unless the presumption is overcome on a category-specific basis).

\55\ See CAA section 112(f)(2)(A), 42 U.S.C. 7412(f)(2)(A) (requiring the EPA to promulgate standards if the cancer risk to the most exposed individual exceeds one-in-one million eight years after the EPA established MACT standards for the source category.

In this case, the MACT standard for non-Hg HAP metals in the 2012 MATS Rule lowered the maximum individual lifetime cancer risk (cancer MIR) from such HAP metals to below one-in-one million for every coal- fired EGU in the country, thereby achieving the aspirational goal of CAA section 112(f)(2)(A). In such cases, the EPA now concludes that a greater emphasis on cost is warranted in light of the low potential for further risk reduction, and that additional controls would generally only be “necessary” when the costs are on the lower end of what has been found acceptable from a cost perspective in prior CAA section 112 actions. For emissions of non-Hg HAP metals from coal-fired EGUs, in light of the high cost of the controls, a common metric the EPA considers in CAA section 112(d)(6) technology reviews, and the low remaining risk of cancer from these emissions, the Agency concludes that the 2024 revisions are not necessary. The EPA views each of the rationales set out in this section--a change of views on cost reasonableness of the additional controls evaluated in the 2024 Final Rule and the additional consideration of the low remaining risk for this source category--as separate and independent bases for repeal, either one of which would lead the Agency to conclude that the revised standards in the 2024 Final Rule were not “necessary” under CAA section 112(d)(6).

As the EPA noted in the 2024 Final Rule, the Agency considers costs in various ways depending on the rule and

the affected sector. For example, the EPA has considered the cost effectiveness of controls in the vast majority of CAA section 112 rulemakings where costs are considered, and the Agency has also considered total capital costs of control measures, annual compliance costs, and the compliance costs compared to total revenues (e.g., cost- to-revenue ratios). In the 2024 Final Rule and, by the same token, in this rule, the most important indicator of cost is cost effectiveness, which is the relationship of costs to emission reductions, because that indicator sheds the most light on whether the revised emissions standard that is based on those controls is “necessary” under CAA section 112(d)(6). As the EPA acknowledged in the 2024 Final Rule, the cost-effectiveness ratio of the revised 0.010 lb/MMBtu fPM standard was significantly higher than cost-effectiveness ratios the EPA rejected in past technology reviews conducted under CAA section 112(d)(6) for other source categories.\56\ Moreover, the cost effectiveness values for the specific non-Hg HAP metals (i.e., the metals for which fPM serves as a surrogate) emitted from EGUs are almost an order of magnitude higher than the highest values accepted for such HAP metals under CAA section 112(d)(6) reviews for other source categories. See section III.A.3 of this preamble, below, for a more detailed discussion. The EPA now finds that the costs for this source category to achieve the revised standard, in relation to the amount of emission reductions, are unreasonable, such that the revised standard is not “necessary” under CAA section 112(d)(6). As noted below, the EPA also finds that the limited risk posed by emissions from coal-fired power plants, coupled with the high cost-effectiveness values, are a separate and additional reason for its determination that the revised standard is not “necessary” under CAA section 112(d)(6).

\56\ 89 FR 38533-34 (May 7, 2024). These rules are also noted in section III.A.3 of this preamble.

In the 2024 Final Rule, the EPA estimated the cost effectiveness for EGUs that were reporting average fPM rates above the 0.010 lb/MMBtu fPM emission standard to be $10.5 million per ton of non-Hg HAP metals and $34,500 per ton of fPM (2019$). The EPA has since revised these cost effectiveness estimates based on updated expectations regarding the existing coal-fired EGU fleet, reflecting fewer planned retirements. Table 3 of this preamble summarizes the updated cost effectiveness of the more stringent fPM emission standard. For the purpose of estimating cost effectiveness, the analysis presented in this table is based on the observed emission rates of all existing coal-fired EGUs except those with retirements reported to the U.S. Energy Information Administration (EIA) via EIA Form 860.\57\ The analysis presented in Table 3 estimated the costs associated for each unit to upgrade its existing PM controls to meet a fPM emission standard of 0.010 lb/MMBtu, using the same methodology as the 2024 Final Rule. In the cases where existing PM controls would not achieve the necessary reductions, unit-specific FF installation costs were estimated.\58\

\57\ This is described in detail in the 2023 Technical Memo, 2024 Technical Memo, and the 2025 Update to the 2024 Technology Review for the Coal- and Oil-Fired EGU Source Category memorandum (“2025 Technical Memo”) available in the rulemaking docket (Docket ID No. EPA-HQ-OAR-2018-0794).

\58\ Note that unlike the cost projections presented in the Regulatory Impact Analysis (RIA), the updated estimates do not account for the two-year compliance extensions for units listed on Annex 1 of the Presidential Proclamation or any future changes in the composition of the operational coal-fired EGU fleet that may occur by 2028 as a result of other factors affecting the power sector.

Based on this updated analysis, total annual costs are estimated to be approximately $93.7 million with a cost effectiveness of $11.1 million per ton of non-Hg HAP metals, and $36,502 per ton of fPM, for the 0.010 lb/MMBtu fPM emission standard, which is about 5 percent higher than the 2024 Final Rule estimated.

Table 3--Summary of Revised Cost Effectiveness Analysis for the

Updated fPM Emission Limit

(i.e., 0.010 lb/MMBtu)

2025 Final

Repeal Rule

Number of Affected Units (Capacity, GW)................. 37 (16.8) Annual Cost, ($M, 2019 dollars)......................... 93.7 fPM Reductions (tpy).................................... 2,567 Total Non-Hg HAP Metals Reductions (tpy)................ 8.4 Total Non-Hg HAP Metals Cost Effectiveness ($M/ton)..... 11.1 Total Non-Hg HAP Metals Cost Effectiveness ($/lb)....... 5,600

Upon reconsideration, the EPA is finalizing the repeal of the more stringent fPM standard and corresponding total and individual HAP metal standards promulgated in the 2024 Final Rule because the cost effectiveness of the revised standard is inconsistent with that of the EPA's prior technology review determinations. In the 2024 Final Rule, the EPA asserted that differences between the power sector and the other source categories subject to previous technology reviews justified accepting an unusually high cost-effectiveness ratio. Upon further review, the Agency no longer believes the unique nature of the utility power industry supports the decision to revise the fPM standard for coal-fired EGU's.

In particular, the EPA stated in the 2024 Final Rule that the large size of the power sector relative to other industrial sectors meant that the amount of its emissions were relatively greater than other source categories.\59\ The EPA added that the size of the sector also includes relatively large revenues, which the Agency believed at the time further justified the control costs.\60\ The EPA also stated in the 2024 Final Rule that because of the emission rates already achieved by most of the coal-fired EGUs in the source category, the costs of complying with the revised standard would be borne by only some of the sources in the source category.\61\ On that basis, the EPA asserted that the controls would not have “significant effects” on the industry, i.e., the power sector.\62\ Finally, the EPA claimed that the cost effectiveness of the controls should be considered in light of these characteristics of the source category, which distinguish it from other source

categories that the EPA has regulated under CAA section 112.\63\

\59\ 90 FR 38524 (May 7, 2024).

\60\ Id. at 38534.

\61\ Id.

\62\ Id. at 38524.

\63\ Id.

The EPA now believes that it was inappropriate to rely on the differences between the EGU sector and other sectors with respect to consideration of costs in the development of standards. The EPA has consistently maintained that the statute treats the EGU source category the same as all other major source categories with respect to regulation under CAA section 112(d) once the Agency decides pursuant to CAA section 112(n)(1)(A) to add the EGU source category to the list of regulated major sources under CAA section 112(c)(1).\64\ In the 2024 Final Rule, however, the Agency ignored that position and used certain unique factors about the power sector in an attempt justify otherwise unreasonable costs. Specifically, the Agency no longer believes it was reasonable to establish a fPM standard with one of the highest cost- effectiveness values ever accepted for fPM under CAA section 112(d)(6), particularly when the cost-effectiveness ratio for the actual non-Hg HAP metal emissions was approximately an order of magnitude higher than any cost-effectiveness value the Agency has ever found reasonable for non-Hg HAP metals. The longstanding use of fPM as a surrogate for non- Hg HAP metals does not excuse the Agency from considering cost- effectiveness as to the non-Hg HAP metals themselves. The purpose of CAA section 112 is to regulate HAP emissions, and when there exists a disparity in cost effectiveness between a surrogate and the associated HAP, it is important to give sufficient consideration to that disparity, but the Agency failed to do so in the 2024 Final Rule. Thus, although the Agency identified what it considered at the time to be “developments” in some control strategies in the 2024 Final Rule, the costs for the power sector to implement those developments are not reasonable, such that the revised standards are not “necessary” under CAA section 112(d)(6). As a result of this final rule, the fPM and corresponding total and individual non-Hg HAP metal emission standards will revert to the standards that were promulgated in the 2012 MATS Rule (e.g., 0.030 lb/MMBtu for fPM and associated prior standards for non-Hg HAP metals).

\64\ After the EPA makes the “appropriate and necessary” finding for the EGU source category required in CAA section 112(n)(1)(A), the EGU source category becomes included in the “list of all categories and subcategories of major sources” in CAA subsection 112(c)(1). 42 U.S.C. 7412(c)(1), (n)(1)(A). That listing, in turn, triggers the same, general regulatory requirements for the EGU source category as apply to the other listed source categories, under CAA section 112. See, e.g., 42 U.S.C. 7412(c)(2); 88 FR 13956, 13960-61 (March 6, 2023) (recounting the EPA's position since 2000 that an affirmative “appropriate and necessary” finding puts the EGU source category in the same position as all source categories listed in CAA section 112(c)(1)).

In addition to finding that the costs are unreasonable on their face, circumstances have changed materially since promulgation of the 2024 Final Rule. Fewer coal-fired EGUs are likely to retire instead of complying with MATS because of an increasing need for electricity generation, including to support growing demand from the technology sector. Moreover, Congress recently passed, and President Trump signed into law, new legislation that repealed, amended, or defunded relevant provisions of the Inflation Reduction Act (IRA), including tax credits for solar and wind generation that the EPA cited in the 2024 Final Rule to predict an “accelerated” transition away from coal- and oil-fired generation.\65\ Coupled with the Executive Orders discussed earlier in this preamble that establish different policies and programs to promote power generation from this source category, the EPA's prior predictions about the future of the power sector and conclusion that the unique characteristics of the power sector support a finding that the additional controls are “necessary” are no longer accurate.\66\ Instead, that unique character of the power sector and the increasing demand supports this repeal because any unnecessary downward pressure on the power industry at this time is not in the national interest or in the interest of consumers.

\65\ Compare 89 FR 38534 (May 7, 2024) (citing Pub. L. 117-169 (2022)), with Pub. L. 119-21 (2025).

\66\ The EPA further clarifies that statements in the 2024 Final Rule regarding planned EGU retirements “due to factors independent of the EPA's regulation” were overbroad and did not reflect a detailed, source-by-source analysis of the costs of regulation. See, e.g., 89 FR 38524-25 (May 7, 2024). In several recent cases, the Supreme Court has vacated EPA rules for misusing statutory authority and failing to consider the costs of regulation. See West Virginia v. EPA, 597 U.S. 697 (2022) (vacating CAA section 111(d) standards for pursuing generation shifting in violation of the major questions doctrine); Michigan, 576 U.S. at 749-50 (faulting the EPA's decision to regulate EGUs under CAA section 112 for failing to account for an estimated $9.6 billion in annual compliance costs). Although trends in a source category can be relevant under CAA section 112(d)(6), the inherent difficulty in determining whether a planned retirement is independent of regulatory pressure cautions against making such an assumption for regulatory purposes absent more direct engagement with and analysis of each source.

The EPA's decision to repeal these standards from the 2024 Final Rule is further supported by the low remaining cancer risk attributed to HAP emissions from this source category. As noted in section II.A.1 of this preamble and discussed in greater detail in section IV of this preamble, CAA section 112(d)(6) and relevant case law support considering additional factors beyond developments in technology when deciding whether revisions to existing standards are “necessary,” including cost. Considering risk in the context of the first technology review would be duplicative of the one-time risk review requirement, which is conducted at the same time and which generally includes an ample-margin-of-safety analysis that takes the costs of controls into account. However, Congress did include risk benchmarks in CAA section 112(f), and considering those benchmarks in subsequent technology reviews is consistent with the broad scope of the term “necessary” and reasonable because that information is part of the overall CAA section 112 record for each source category. Specifically, CAA section 112(f)(2)(A) directs the EPA to “promulgate standards” if the cancer risk to the most exposed individual is greater than one-in-one million.\67\ Additionally, CAA section 112(f)(2)(B) incorporates the Benzene NESHAP approach, which generally presumes that a cancer risk of greater than 1-in-10,000 is unacceptable unless such presumption is overcome.\68\

\67\ 42 U.S.C. 7412(f)(2)(A).

\68\ Id. 7412(f)(2)(B).

The decision to consider the low remaining risk in the prior residual risk assessment in assessing the need for additional standards in the second and subsequent CAA section 112(d)(6) reviews is consistent with the ordinary meaning of the term “necessary,” which is “required,” “compulsory,” or “determined or produced by the previous condition of things.” \69\ CAA section 112(d)(6), by its terms, expressly requires the EPA to consider “developments in practices, processes, and control technologies” when determining whether it is “necessary” to revise existing section 112 standards (e.g., standards based on the MACT floor, a beyond-the-floor level of control, or a risk review). The EPA also considers the costs of potential revisions even though CAA section 112(d)(6) does not explicitly reference cost. The D.C. Circuit has upheld that interpretation,\70\ and it is consistent with the Supreme Court's interpretation of the term “appropriate and necessary” in another

provision of CAA section 112.\71\ As with costs, the EPA interprets CAA section 112(d)(6) to authorize the EPA to take the low remaining risk identified in the prior residual risk review into account even though the provision does not explicitly refer to health risks. When the Agency has previously determined that residual risk for a source category is consistent with Congress' risk-reduction goals, that relatively low risk is relevant to determining whether additional standards are “necessary” and, if so, which standards are “necessary.” That follows from the overall purpose of CAA section 112, which is to promote public health by reducing the hazards presented by the emission of air toxics, and from Congress' decision to establish and adopt the particular risk thresholds in the statute described above.

\69\ Webster's Ninth New Collegiate Dictionary 790 (1984).

\70\ Ass'n of Battery Recyclers, 716 F.3d at 673-74.

\71\ Michigan, 576 U.S. at 748-49.

This interpretation is consistent with how the EPA has interpreted “necessary” under CAA section 112(n)(1)(A) by taking into consideration health risks. The Supreme Court explained the provisions of CAA section 112(n)(1)(A), including their background and context, in Michigan v. EPA, as follows:

[T]he Clean Air Act Amendments of 1990 subjected power plants to various regulatory requirements. . . . [T]hese 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. Congress directed the Agency to “perform a study of the hazards to public health reasonably anticipated to occur as a result of emissions by [power plants] of [hazardous air pollutants] after imposition of the requirements of this chapter.” If the Agency “finds . . . regulation is appropriate and necessary after considering the results of the study,” it “shall regulate [power plants] under [CAA section 112].” \72\

\72\ Michigan, 576 U.S. at 748 (quoting 42 U.S.C. 7412(n)(1)(A)).

The Court went on to explain, with approval, the EPA's interpretation of “necessary,” which, as noted, takes into

consideration health risks:

In 2012, [the EPA] reaffirmed [its prior] appropriate-and- necessary finding. . . . The Agency found regulation “appropriate” because (1) power plants' emissions of mercury and other hazardous air pollutants posed risks to human health and the environment and (2) controls were available to reduce these emissions. It found regulation “necessary” because the imposition of the Act's other requirements did not eliminate these risks.\73\

\73\ Id. at 749 (citing 77 FR 9304, 9363 (February 16, 2012)).

Interpreting “necessary” to authorize consideration of the prior residual risk review in the way described in this preamble is also consistent with CAA section 112(d)(6)'s direction to revise “emission standards promulgated under this section.” Specifically, after the EPA conducts the mandatory section 112(f)(2) residual risk review, subsequent section 112(d)(6) technology reviews will include a review and potential revision of all section 112 standards.\74\ Considering the findings of the prior risk review, which are part of the record before the Agency, during those technology reviews is reasonable and accounts for CAA section 112's purpose of protecting public health.

\74\ Ass'n of Battery Recyclers, 716 F.3d at 673.

The approach that the EPA is taking in this rulemaking, i.e., considering the low residual risk findings from the 2020 Residual Risk Review, marks a change from the Agency's stated approach in the 2024 Final Rule, in which the Agency declined to consider the health-risk findings from the 2020 Residual Risk Review as part of the technology review. Specifically, the EPA stated that it was “not compel[led]” to “consider[] risks as a factor” in technology reviews under CAA section 112(d)(6).\75\ The EPA explained that the CAA section 112(d)(6) technology review and the section 112(f) residual risk determination were “independent” of each other, and that “a determination under section 112(f) of an ample margin of safety and no adverse environmental effects alone will [not] . . . cause us to determine that a revision is not necessary under CAA section 112(d)(6).” \76\

\75\ 89 FR 38525 (May 7, 2024).

\76\ Id. (quotation marks omitted).

However, in the 2024 Final Rule, the EPA did not say that CAA section 112 precludes the Agency from considering risks in connection with a CAA section 112(d)(6) technology review. Moreover, the EPA acknowledged that in some prior section 112(d)(6) reviews, the Agency has considered risks.\77\

\77\ Id. at 38525 & n.31 (citing National Emission Standards for Organic Hazardous Air Pollutants From the Synthetic Organic Chemical Manufacturing Industry, 71 FR 76603, 76606 (December 21, 2006), and Proposed Rules: National Emission Standards for Halogenated Solvent Cleaning, 73 FR 62384, 62404 (October 20, 2008)).

For all of these reasons, the EPA concludes that it is reasonable to consider the low remaining risks identified in a prior residual risk review--particularly where, as here, such risks are consistent with the thresholds Congress set out or adopted by statute--when determining in a second and subsequent CAA section 112(d)(6) review whether additional standards are “necessary.” For this rule, the Agency considered the 2020 Residual Risk Review of MATS in the manner and for the reasons described elsewhere in this final action.

Having concluded that CAA section 112(d)(6) allows the EPA to consider the results of an earlier CAA section 112(f)(2) residual risk review in subsequent technology reviews, we must determine how and to what extent the Agency may consider risk in determining whether revised standards are “necessary.” As noted above, the clearest benchmark is in CAA section 112(f)(2)(A), which the EPA has long interpreted as requiring an ample-margin-of-safety analysis but not mandating that the Agency require additional reductions in HAP emissions after considering costs and other factors. The D.C. Circuit upheld this interpretation, describing the one-in-one million risk level as an “aspirational goal” of the statute for sources of HAP emissions and not as the level that every source category must achieve under CAA section 112(f)(2).\78\

\78\ NRDC, 529 F.3d at 1082 (rejecting the argument that risks must be reduced to the one-in-one million threshold).

The EPA thus concludes that the statutory benchmarks for risk provide relevant guidance on whether additional regulation is “necessary” under CAA section 112(d)(6). If the remaining risk found during a prior residual risk review is below the one-in-one million risk level, the EPA may place greater emphasis on costs of the new controls. Over the years of implementing CAA section 112, the EPA developed cost metrics for evaluating whether it is reasonable to consider a particular control to be “necessary,” and the Agency uses those metrics when evaluating whether controls are reasonable in several CAA section 112 contexts (e.g., beyond the floor (BTF), ample margin of safety, generally available control technologies (GACT)). The EPA also uses these metrics when determining whether additional controls are necessary under CAA section 112(d)(6) on the theory that if the costs of such controls are within the range of what had been found reasonable in one rule, then those same costs are potentially reasonable for other source categories. If additional controls cost more than the historical range, we generally conclude that such controls are unnecessary. The EPA maintains that this approach is appropriate when the CAA section 112(f)(2) risk analysis shows remaining risks above statutorily set benchmarks (e.g., risks greater than one-in-one million) or where noncancer risk from the source category emissions exceed a level adequate to protect

public health with an ample margin of safety. However, where the MACT standard lowers cancer risks to below the statutory one-in-one million cancer risk threshold, the EPA concludes that more emphasis may be placed on cost in determining whether additional controls are “necessary” under CAA section 112(d)(6) within the context of the statute as a whole.

The statute makes clear that CAA section 112(d)(6) technology reviews are required even when a CAA section 112(f)(2) residual risk review finds cancer risk is below the one-in-one million threshold, and additional controls may be “necessary” when ongoing reductions in HAP are possible at relatively low cost. In cases like MATS, however, the EPA maintains that the effectiveness of the original MACT standard at lowering risks should be given greater weight. As noted in the 2020 Final Rule, no coal-fired EGU facility posed a cancer risk greater than one-in-one million. In fact, the highest cancer risk from non-Hg HAP metals from a coal-fired EGU was 0.3-in-one million, and most coal- fired EGUs were assessed to pose considerably lower cancer risks from such HAP emissions.\79\ Despite these facts, in the 2024 Final Rule, the EPA established CAA section 112(d)(6) standards for emissions of fPM and corresponding standards for emissions of non-Hg HAP metals though the cost-effectiveness values of such controls were the highest (or among the highest) of any CAA section 112(d)(6) standard the Agency has established.\80\ We now conclude it was not “necessary” to establish a new high-cost benchmark for non-Hg HAP metals from EGUs because the MACT standards in the 2012 MATS Rule achieved the aspirational goal for cancer risks from such HAP emissions. Instead, in such situations, the EPA believes a harder look at costs should be conducted and additional controls will be considered unnecessary unless the costs of such controls are at the lower range of cost acceptability. Imposing costs that are below historically accepted levels will continue to satisfy the statutory goal of continuing to reduce HAP emissions without unreasonably burdening source categories that pose very low risks due to HAP emissions. In addition, as noted above, even if the EPA did not consider the low remaining risks from the 2012 MACT standards as determined in the 2020 Final Rule, the EPA would conclude that the costs of the 2024 standards are unacceptably high in light of their high cost-effectiveness values, such that the 2024 standards are not necessary.

\79\ Document ID No. EPA-HQ-OAR-2018-0794-0070.

\80\ 89 FR 38530-35 (May 7, 2024).

3. What key comments did the EPA receive on the filterable PM emission standard for existing coal-fired EGUs and what are our responses?

Comment: Some commenters agreed with the EPA's proposal that the costs for the power sector to achieve the more stringent fPM standard are too high and are inconsistent with other technology review determinations. In the 2024 Final Rule, the EPA estimated that the cost-effectiveness for the 0.010 lb/MMBtu fPM emission limit was $10.5 million per ton of non-Hg HAP metals and $34,500 per ton of fPM. Commenters stated that these costs are not reasonable when compared to other technology reviews, including those cited by the EPA in the proposed rule, that rejected controls as not cost-effective. These technology reviews included the Petroleum Refinery Sector technology review \81\ ($10 million per ton of total non-Hg HAP metals reduced), the Integrated Iron and Steel Manufacturing Facilities technology review \82\ ($7 million per ton of non-Hg HAP metals reduced), and the Taconite Iron Ore Processing RTR \83\ ($16 million per ton of non-Hg HAP metals reduced). Furthermore, commenters noted that the EPA has rejected similar or even smaller cost-effectiveness values in other CAA section 112 rulemakings:

\81\ Petroleum Refinery Sector Risk and Technology Review and New Source Performance Standards, 80 FR 75178, 75201 (December 1, 2015).

\82\ National Emission Standards for Hazardous Air Pollutants: Integrated Iron and Steel Manufacturing Facilities Residual Risk and Technology Review, 85 FR 42074, 42088 (July 13, 2020).

\83\ National Emission Standards for Hazardous Air Pollutants: Taconite Iron Ore Processing Residual Risk and Technology Review, 85 FR 45476, 45483 (July 28, 2020).

In the Hazardous Waste Combustors NESHAP beyond-the-floor analysis,\84\ the EPA declined to impose a more stringent dioxin/furan emission limit because of cost, finding $2.5 million to $4.9 million per gram toxicity equivalence of dioxin/furan removed.

\84\ National Emission Standards for Hazardous Air Pollutants: Final Standards for Hazardous Air Pollutants for Hazardous Waste Combustors (Phase I Final Replacement Standards and Phase II), 70 FR 59402, 59462 (October 12, 2005).

In the Shipbuilding and Ship Repair NESHAP RTR,\85\ the EPA declined to revise the formaldehyde emission limit after finding that spray line reconfiguration would cost $43,000 per ton of formaldehyde reduced.

\85\ National Emission Standards for Hazardous Air Pollutants for Shipbuilding and Ship Repair (Surface Coating); National Emission Standards for Wood Furniture Manufacturing Operations, 76 FR 72050, 72056 (November 21, 2011).

In the Pulp and Paper NESHAP RTR,\86\ the EPA declined to update standards in the final rule \87\ for controlling kraft condensates emissions that would cost $1,000 per ton of HAP removed or $4 million per year.

\86\ National Emission Standards for Hazardous Air Pollutants: Pulp and Paper Residual Risk and Technology Review, 76 FR 81328, 81345 (December 27, 2011).

\87\ National Emission Standards for Hazardous Air Pollutants: Pulp and Paper Residual Risk and Technology Review, 77 FR 55698, 55701 (September 11, 2012).

Additionally, commenters stated that the cost analysis for the 2024 Final Rule underestimates overall compliance costs, as the EPA failed to identify all sources that would need to make air pollution control device upgrade investments and to account for unit-level operational challenges that could increase compliance costs. For example, commenters cited declarations submitted as part of challenges to the 2024 Final Rule, which stated that compliance with the 0.010 lb/MMBtu fPM emission standard at the Colstrip facility would have cost over $350 million, with more recent estimates of over $500 million that incorporate more accurate wage rates, structural steel install rates, scaffolding costs, duct installation costs, and total delivery costs.\88\ Commenters pointed to the 2025 Proposal and stated that industrywide cost-effectiveness was at minimum $10.5 million per ton of non-Hg HAP metals controlled, but the largest costs were found predominantly at Colstrip which results in approximately $16 million per ton of non-Hg HAP metals reductions using the EPA's “underestimated” costs.

\88\ Document ID No. EPA-HQ-OAR-2018-0794-7154.

Other commenters argued that the EPA was wrong in proposing that the cost effectiveness of the 0.010 lb/MMBtu fPM emission standard (as estimated in the 2024 Final Rule) is too high. Commenters stated that the examples rejecting high cost-effectiveness values that the EPA provided in the 2025 Proposal are flawed and should not be relied upon. These commenters asserted that the RTR for the Integrated Iron and Steel NESHAP also estimated a fPM cost effectiveness of $160,000 per ton, well above the $35,000 per ton of fPM estimated for the 2024 Final Rule. Further, these commenters stated that if the cost per ton of any of the non-Hg HAP metals is reasonable, then the control costs should also be regarded as reasonable. These commenters stated

that the EPA has previously accepted Hg cost effectiveness values of up to approximately $32,000 per pound, which is the equivalent of $64 million per ton reduced. Commenters noted that the rejected cost effectiveness values from the Petroleum Refinery NESHAP RTR ($10 million per ton) and Integrated Iron and Steel NESHAP ($7 million per ton) are at the low end of the accepted Hg cost-effectiveness value, highlighting that the EPA has approved higher dollar per ton values in the past. Lastly, commenters argued that the EPA ignored the 2024 Final Rule's explanation for why the Petroleum Refinery Sector and Integrated Iron and Steel Manufacturing Facilities reviews were not comparable,\89\ and that the Agency also ignored the 2024 Final Rule's comparison of cost-effectiveness values with the Ferroalloys Production source category, in which the EPA approved higher cost-effectiveness values for PM than those estimated in the 2024 Final Rule.

\89\ In the 2024 Final Rule, the EPA noted that the 2020 Integrated Iron and Steel Manufacturing rulemaking source category only covered 11 facilities with 3 tons per year (tpy) of HAP and 120 tpy of PM reductions, compared to MATS, which affected 314 coal- fired EGUs with estimated reductions of 8.3 tpy HAP and 2,537 tpy of fPM. See 89 FR 38524 (May 7, 2024).

Other commenters stated that the cost effectiveness comparison for a single facility bearing the highest costs under the 2024 Final Rule is inappropriate and arbitrary, as the cost-effectiveness ratio across an entire sector is very different than the cost-effectiveness ratio of a single facility. Commenters argued that it is expected that some facilities would face higher costs than others for a given regulation given differences in air pollution control devices. The commenters stated that it is irrational for the EPA to imply that the highest-cost facility's cost-effectiveness ratio cannot exceed a ratio rejected for a fleetwide average.

Response: The EPA generally agrees with commenters that cost effectiveness (i.e., the costs per unit of emissions reduction) is a metric that the Agency consistently considers, alongside other cost metrics, in CAA section 112 rulemakings where it can consider costs. The EPA also agrees that the Agency has the discretion in how it considers statutory factors, including costs, under CAA section 112(d)(6).\90\ The Agency disagrees, however, that there is any particular threshold that renders a potential control technology cost- effective or not.\91\

\90\ See, e.g., Ass'n of Battery Recyclers, 716 F.3d at 673-74 (allowing that the EPA may consider costs in conducting technology reviews under CAA section 112(d)(6)); Nat'l Ass'n for Surface Finishing, 795 F.3d at 11.

\91\ See, e.g., National Emissions Standards for Hazardous Air Pollutants: Ferroalloys Production, 80 FR 37366, 37381 (June 30, 2015) (“[I]t is important to note that there is no bright line for determining acceptable cost effectiveness for HAP metals. Each rulemaking is different, and various factors must be considered.”).

The EPA disagrees with the commenters who sought to distinguish prior rules in which the EPA declined to revise standards for non-Hg HAP metals due to the high cost-effectiveness values of those standards. As noted above, the cost-effectiveness of the 2024 Final Rule's revised standards for non-Hg HAP metals is substantially less favorable than in any other rule the EPA has promulgated under CAA section 112(d)(6). In several rules under CAA section 112(d)(6), the EPA declined to revise standards for non-Hg metal HAPs on grounds that the cost-effectiveness values were in the millions of dollars per ton reduced, which are roughly comparable to the cost-effectiveness values in the 2024 Final Rule. As commenters point out, in some of those cases, the EPA also noted industry-specific reasons for declining to adopt the revised standards, but the key reason in those rules, as here, was the high cost-effectiveness values. In addition, the commenters point to multiple cost-effectiveness values that the EPA has accepted in past actions for Hg control that are significantly higher than the values that the agency is rejecting for control of non-Hg HAP metals, but the EPA considers those values inappropriate for determining cost effectiveness of non-Hg HAP metals.

The EPA disagrees with commenters who argued that the 2025 Proposal focused on costs to a single facility. Although the EPA pointed out at proposal that the units at the Colstrip facility accounted for almost half of the 2024 Final Action's total compliance costs, that was not the basis for the proposed repeal and it is not the rationale for this final action repealing the more stringent fPM standard. Rather, the rationale is the high cost-effectiveness values, especially when coupled with the limited risk, including from the Colstrip facility.

Comment: Some commenters argued that the EPA failed to adequately explain why it is “necessary” under CAA section 112(d)(6) to revert to the 2012 MATS Rule standards when the CAA requires that the Agency “take into account developments in practices, processes, and control technologies” that have occurred since the EPA promulgated the original 2012 MATS Rule.\92\ Commenters further asserted that the EPA must explain why the 2012 emissions standards are the maximum achievable emissions standards given major developments in control technology since 2012, including reduced costs and improvements of existing control technologies, better practices for monitoring the operation of ESPs, and more durable filter bag materials for FF, which commenters asserted the EPA did not dispute in the proposed rule. Commenters stated the EPA chose to disregard these developments and that the Agency's own analysis in the 2024 Final Rule showed that at least 93 percent of the industry is already attaining a 0.010 lb/MMBtu fPM emission standard.

\92\ See CAA section 112(d)(6), 42 U.S.C. 7412(d)(6) (requiring the Administrator to “review, and revise as necessary (taking into account developments in practices, processes, and control technologies), emission standards promulgated under [section 112] no less often than every 8 years”).

Response: The EPA notes that it has authority to reconsider past decisions and to revise, replace, or repeal a decision to the extent permitted by law and supported by a reasoned explanation.\93\ In this case, as in the 2024 Final Rule, the EPA did not conduct a new mandatory technology review but, instead, reviewed a prior technology review. The next technology review for this source category is due within 8 years of the prior review, which was finalized in 2020. The EPA further disagrees with these commenters to the extent they suggest that CAA section 112(d)(6) requires the Agency to select the maximum degree of emissions reductions in setting standards. The technology review under CAA section 112(d)(6) does not allow the Agency to recalculate the MACT floor for any currently regulated HAPs. Rather, CAA section 112(d)(2) provides that the EPA must require the maximum degree of reduction in emissions of HAP that the Administrator determines to be achievable, taking into consideration cost, non-air quality health and environmental impacts, and energy requirements, and CAA section 112(d)(3) prescribes specific requirements for calculating the MACT. The EPA's task under CAA section 112(d)(6) is not to recalculate a new, lower MACT, but to determine whether, taking into account developments in technology and other relevant information, it is “necessary” to revise the standards. Further, EPA regulated all HAP emitted from EGUs in 2012 so there are no gaps to fill.

\93\ See, e.g., Fox Television Stations, 556 U.S. at 515; Motor Vehicle Mfrs. Ass'n, 463 U.S. at 42.

In this instance, the EPA reevaluated the 2024 Final Rule and determined that a more stringent fPM emission standard is not “necessary,” including because of cost-effectiveness estimates, in light of the Agency's 2020 Technology Review. In this action, the EPA updated its evaluation of fPM compliance data for the coal-fired fleet and associated costs of PM controls to achieve a lower standard; specifically, total annual costs are estimated to be approximately $93.7 million with a cost effectiveness of $11.1 million per ton of non-Hg HAP metals for the 0.010 lb/MMBtu fPM emission standard.\94\ The EPA acknowledges the reduced costs and improvements of existing ESP and FF control technologies compared to estimates from the 2012 MATS Rule and acknowledges that the fleet is largely overperforming with the fPM emission standard, but that fact alone does not make the high cost- effectiveness number reasonable or necessary under section 112(d)(6), particularly in light of the low remaining risk.

\94\ Updates and revisions to the 2024 Technical Memo are described in detail in the 2025 Update to the 2024 Technology Review for the Coal- and Oil-Fired EGU Source Category memorandum (“2025 Technical Memo”) available in the rulemaking docket (Docket ID No. EPA-HQ-OAR-2018-0794).

Comment: Several commenters generally supportive of the proposal urged the EPA to acknowledge additional considerations for rejecting the 0.010 lb/MMBtu fPM emission standard. First, commenters stated that the 2024 Final Rule's reliance on “considering cost in various ways”--such as comparing them to typical capital and total expenditures for the power sector, total power sector sales, and total PM upgrade control costs and emissions of the fleet--to explain its acceptance of high cost-effectiveness values should be rejected. Commenters questioned the use of compliance costs compared to revenues, arguing that the EPA would be hard-pressed to find that the utility sector as a whole cannot afford the cost of virtually any regulatory action, especially when such action is viewed in isolation. Commenters argued that the framing of considering costs in various ways in the 2024 Final Rule departed from the EPA's longstanding precedent regarding cost consideration in an RTR.

Second, a commenter requested that the EPA also reject the 0.010 lb/MMBtu fPM emission standard because of a flawed technical analysis based on truncated and unrepresentative data. Commenters noted that, for many units, the EPA relied on only two quarters of data and failed to explain the reasoning behind the EPA's decision to not incorporate all compliance data. Commenters also said that the cost analysis should account for other indirect impacts on grid reliability, such as security risks associated with temporarily reduced electric generation capacity and lost revenues during the downtime required to engineer and retrofit additional control technologies required to comply with the 2024 Final Rule.

Alternatively, other commenters said that the EPA reasonably explained costs in the 2024 Final Rule and that the EPA's proposal to repeal the fPM emission standard based on high costs is arbitrary and capricious. These commenters argued that the EPA's view about what is cost-effective is subjective and has nothing to do with what can be achieved--considering costs or otherwise. Commenters stated that the EPA did not cite any example of cost being the sole factor supporting a decision to revise or not to revise standards, as it did in the proposed rule here.

Response: The EPA disagrees in part with commenters stating that the Agency does not consider costs in various ways in CAA section 112 rulemakings. As stated earlier in this preamble, the EPA routinely considers cost effectiveness metrics together with additional factors, such as other relevant cost metrics (e.g., total costs, annual costs, and costs compared to revenues), and impacts to the regulated industry, to determine whether, taking into account developments in practices, processes, and control technologies, it is “necessary” to revise emissions standards pursuant to CAA section 112(d)(6). For example, in the 2015 Ferroalloys rulemaking, the EPA rejected a potential control option due to concerns about technical feasibility and the significant economic impacts the option would create for the industry, including potential facility closures that would impact significant portions of industry production.\95\ The EPA agrees with these commenters, however, that the Agency's statements about the power sector in the 2024 Final Rule are not appropriate reasons to accept higher cost-effectiveness values relative to other source categories. As explained in section III.A.1 of this preamble, cost-effectiveness metrics are an important means of evaluating whether developments in technology make a revision “necessary” because they present the emission-reduction benefit relative to the cost of such emission reduction. Characteristics of the power sector such as number of units and quantity of emissions do not mean that metric is not reasonable, because the metric is already keyed to ton of HAP emissions reduced.

\95\ 79 FR 60238, 60273 (October 6, 2014) (supplemental proposed rule).

With respect to commenters' argument that the EPA's view about what is cost effective is subjective and therefore an improper basis for repealing the revised standards in the 2024 Final Rule, the EPA disagrees. Congress vested the EPA with authority to make judgments about when a revision is “necessary” under CAA section 112(d)(6), and cost-effectiveness metrics are an important input to the exercise of that reasoned judgment. To the extent that the EPA's view now differs from the view adopted in the 2024 Final Rule, the law is clear that the Agency has authority to reconsider, repeal, or revise past decisions to the extent permitted by law so long as the EPA provides a reasoned explanation.\96\ Indeed, the position taken in the 2024 Final Rule was itself a departure from the conclusions reached in the 2020 Final Rule, as the Agency acknowledged at the time and asserted was permissible under the same legal doctrine supporting this reconsideration.\97\ As noted in the 2024 Final Rule, the cost effectiveness ratio of the revised fPM standard for non-Hg metal HAPs was significantly higher than the cost-effectiveness ratios for those HAPs the EPA has rejected in the past in technology reviews conducted under CAA section 112(d)(6) for other industries.\98\ The cost effectiveness ratio of the revised fPM standard was also higher than cost-effectiveness ratios that the EPA accepted for fPM emissions in other industries in other CAA section 112(d)(6) reviews. The EPA now finds that the costs for the power sector to achieve the revised standard are too high, and, separately, certainly too high in light of the low remaining risks, such that the revised standard is not necessary under CAA section 112(d)(6).

\96\ See, e.g., Motor Vehicle Mfrs. Ass'n, 463 U.S. at 42 (“[R]egulatory agencies do not establish rules of conduct to last forever [and] an agency must be given latitude to adapt their rules and policies to . . . changing circumstances.”).

\97\ 89 FR 38513 (May 7, 2024).

\98\ Id. at 38533-34.