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National Ambient Air Quality Standards for Particulate Matter and Ozone
By Hannah Oakes and Hannah Perls
EPA is reviewing the basis to strengthen both the particulate matter and ozone standards.
The Biden administration prioritized revising the Trump EPA’s no-action stance on increasing the national ambient air quality standards (NAAQS) for both particulate matter (PM or soot) and ground-level ozone (smog). Under the Clean Air Act, the NAAQS must be revisited every five years to review the latest science and determine if the current standards adequately protect human health. Under President Obama, EPA issued a revised PM standard in 2013 and a revised ozone standard in 2015.
The Trump EPA issued two final rules refusing to update the NAAQS for both PM and ground-level ozone in December 2020 as part of an accelerated review process established under Administrator Pruitt. However, EPA, under the Biden administration, has announced that it will reconsider both the PM and the ground-level ozone standards, and litigation over the Trump standards has been held in abeyance. In a recent meeting of the Clean Air Scientific Advisory Committee (CASAC), an independent expert advisory body within EPA, a majority of CASAC members voiced support for tightening the annual and daily standards for particulate matter two- and one-half microns or less in width (PM2.5). EPA is working to propose a revised PM standard by August 2022 and finalize the rule by March 2023.
While there is no clear timeline for revising the ground-level ozone NAAQS, on April 28, 2022, EPA staff released a draft policy assessment stating that there is insufficient evidence to strengthen those standards. The CASAC’s ozone advisory panel began reviewing the draft policy assessment, and in a June 10, 2022 virtual meeting, determined that it would further review the Trump-era science underlying the recommendations, which will delay EPA’s goal of implementing the new federal standards by the end of 2024.
While litigation over updated NAAQS is inevitable, EPA has the statutory authority to strengthen the PM standards if it can establish the regulatory record based on public health and welfare considerations. Importantly, unlike other air programs, the CAA does not allow EPA to consider feasibility or cost implications when setting the NAAQS. However, if EPA were to finalize new NAAQS for PM, the agency would then face the complex challenge of approving or disapproving, and enforcing, state implementation plans (SIPs), and assessing whether those SIPs sufficiently capture interstate contributions to nonattainment.
For more, see our Regulatory Tracker posts on National Ambient Air Quality Standards, National Ambient Air Quality Standards for Ozone, National Ambient Air Quality Standards for Particulate Matter, our EPA Mission Tracker post, and listen to our podcast with Laura Bloomer and Gretchen Goldman.
 PM and ground-level ozone are two of six “criteria pollutants” identified by EPA as pervasive yet extremely harmful environmental pollutants regulated under the NAAQS program. The other four pollutants are lead, sulfur dioxide, nitrogen dioxide, and carbon monoxide. Criteria Air Pollutants, EPA, https://www.epa.gov/criteria-air-pollutants (last visited February 1, 2022).
 42 U.S.C. § 7409(d)(1).
 National Ambient Air Quality Standards for Particulate Matter, 78 Fed. Reg. 3,085 (Jan. 15, 2013) (codified at 40 C.F.R. pts. 50, 51, 52, 53, 58); National Ambient Air Quality Standards for Ozone, 80 Fed. Reg. 65,291 (Dec. 28, 2015) (codified at 40 C.F.R. pts. 50, 51, 52, 53, 58).
 Review of the National Ambient Air Quality Standards for Particulate Matter, 85 Fed. Reg. 82,684 (Dec. 18, 2020) (codified at 40 C.F.R. pt. 50); Review of the Ozone National Ambient Air Quality Standards, 85 Fed. Reg. 87,256 (Dec. 31, 2020) (codified at 40 C.F.R. pt. 50).
 E. Scott Pruitt, MEMORANDUM: Back-to-Basics Process for Reviewing National Ambient Air Quality Standards, EPA (May 9, 2018), https://www.epa.gov/sites/default/files/2018-05/documents/image2018-05-09-173219.pdf [https://perma.cc/J6YL-66HH].
 EPA under the Biden administration also reconvened the CASAC’s independent expert review panels on both pollutants. National Ambient Air Quality Standards for Particulate Matter and Ozone, Harv. Env’t & Energy L. Program, https://eelp.law.harvard.edu/2020/07/national-ambient-air-quality-standards-for-pm-and-ozone/ (last visited Feb. 1, 2022).
 Unified Agenda: Review of the National Ambient Air Quality Standards for Particulate Matter, Off. of Info & Regul. Affs., https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202110&RIN=2060-AV52 (last visited Aug. 24, 2022) [https://perma.cc/B3W7-YLXB].
 Policy Assessment for the Reconsideration of the Ozone National Ambient Air Quality Standards, External Review Draft, EPA (Apr. 28, 2022), https://www.epa.gov/system/files/documents/2022-04/o3_reconsideration_draft_pa-v_final-compressedfinal.pdf [https://perma.cc/C6T3-Q4R9].
 Whitman v. American Trucking Assns., Inc., 531 U.S. 457 (2001).
Air Transport Rules
by Hannah Oakes
EPA is working to finalize the transport rule for the 2015 ozone standard, and litigation is proceeding for the transport rule related to the 2008 ozone standard.
Air pollution that is generated in one state and crosses into others can interfere with downwind states’ ability to meet the NAAQS. To manage these downstream effects, the Clean Air Act good neighbor provision requires upwind states to ensure that the air pollution that they generate does not prevent downwind states from achieving their NAAQS. EPA carries out this provision by requiring upwind states to submit state implementation plans (SIPs) that adequately assure that their state does not contribute significantly to nonattainment of NAAQS in downwind states. If EPA finds that a state failed to provide an adequate SIP by its required deadline, EPA must issue a federal implementation plan (FIP) for that state within two years. Downwind states and environmental groups can bring litigation to enforce these deadlines, and because of the number of plans that need to be approved, litigation on this rule is frequent. In 2011, EPA promulgated the first Cross-State Air Pollution Rule (CSAPR) FIP to achieve these reductions through emissions trading programs and has since issued updated CSAPR regulations to ensure states maintain and achieve attainment with the NAAQS as EPA updates them.
Downwind states and environmental groups have challenged the Trump and Biden administrations on what satisfies EPA’s obligation to address interstate transport related to the 2008 ozone NAAQS, and there is extensive case law on these issues. Through several cases, the DC Circuit directed the Trump administration to address downwind states inability to meet its NAAQS deadlines due to upwind contribution. In response, EPA reviewed twenty-one state plans and found that twelve states had inadequate SIPs that significantly contribute to nonattainment of the 2008 ozone NAAQS in downwind states. EPA proposed a rule implementing a FIP for these states in October 2020, which was finalized on April 30, 2021. On June 25, 2022, the Midwest Ozone Group filed a petition for review of EPA’s 2021 CSAPR update with the DC Circuit, alleging EPA failed to conduct a legally and technically appropriate assessment of the rule leading to requirements that the petitioners argue are too stringent for upwind sources. Oral argument is scheduled for the end of September.
With respect to the 2015 ozone NAAQS, in on December 5, 2019, the Trump administration finalized its finding that the SIPs from seven states (Maine, New Mexico, Pennsylvania, Rhode Island, Virginia, South Dakota, and Utah) failed to satisfy the Clean Air Act’s good neighbor provision. However, President Biden identified this action for review in his early list of priorities and pursuant to two consent decrees, EPA agreed to review 32 states’ SIPs.
On April 6, 2022, EPA proposed a rule to implement FIPs to address interstate contribution for twenty-six states, and noted that EPA had subsequently received and took final action to approve SIPs from Maine, Rhode Island, and South Dakota and found that the remaining states contribute below the one percent NAAQS threshold. EPA also proposed to establish emissions limitations for both EGUs and non-EGUs, which EPA concludes would eliminate downwind ozone contributions. In addition, EPA proposed to include California, Delaware, Minnesota, Nevada, Utah, and Wyoming in the ozone NAAQS CSAPR for the first time.
EPA is working to finalize the rule in Spring 2023, and given the long litigation history for transport rules, it is likely this rule will be challenged in the DC Circuit. Thus, the regulatory record finalized to support the new aspects of the rulemaking will be critical. For more on this rule see our Air Transport Rules Regulatory Tracker page.
 New York v. EPA, No. 19-1019 (D.C. Cir. 2019) (rejecting the “Close-Out” rule); Wisconsin v. EPA, No. 16-1406 (D.C. Cir.) (upholding in part and vacating in part the 2016 CSAPR Update, which the Trump administration relied on in creating the “Close-Out” Rule).
 EPA, Findings of Failure To Submit a Clean Air Act Section 110 State Implementation Plan for Interstate Transport for the 2015 Ozone National Ambient Air Quality Standards (NAAQS), 84 Fed. Reg. 66,612 (Dec. 5, 2019) (codified at 40 C.F.R. § 52).
 In Downwinders at Risk v. Regan, EPA reviewed SIPs from: Alabama, Arizona, Arkansas, California, Connecticut, Florida, Georgia, Hawaii, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Missouri, Montana, Nevada, New Jersey, New York, North Carolina, Ohio, Oklahoma, South Carolina, Tennessee, Texas, West Virginia, Wisconsin, and Wyoming. , No. 21-cv-03551 (N.D. Cal.). In New York v. Regan, EPA reviewed SIPs from: Indiana, Kentucky, Michigan, Ohio, Texas, and West Virginia. No. 21 Civ. 252 (ALC) (S.D.N.Y.).
Reestablishing MATS “Appropriate and Necessary” Finding
by Carrie Jenks and Abby Husselbee
EPA proposed to find it is appropriate and necessary to regulate hazardous air pollutant (HAP) emissions from power plants, but additional regulatory steps and litigation remain, including EPA’s review of the residual risk and technology review, which could result in EPA strengthening the current standards.
Under authority of section 112 of the Clean Air Act, EPA finalized the Mercury and Air Toxics Standards (MATS) for coal- and oil-fired electric generating units (EGUs) in February 2012. Through subsequent litigation, the Supreme Court directed EPA to determine whether its standards were appropriate and necessary.
The Obama EPA determined that it was appropriate and necessary to regulate mercury and other hazardous air pollutants (HAPs) from power plants, but the Trump administration reversed that determination. Despite this reversal, EPA retained the 2012 standards and finalized the residual risk and technology review (RTR). Several states, environmental NGOs, and power companies challenged the appropriate and necessary reversal.
When President Biden entered office, he directed EPA to review the appropriate and necessary reversal. In response, EPA requested that the Court pause the litigation and proposed a new determination in January 2022 finding that it remains appropriate and necessary to regulate HAP emissions from power plants and revoking the Trump administration’s finding to the contrary. EPA is now in the process of reviewing the comments submitted on the proposal and the next step will be to finalize the rule.
To justify the revocation of the Trump administration’s finding, the proposal concludes that the “framework used to consider cost in 2020, which centered the Agency’s mandated determination under CAA section 112(n)(1)(A) on a comparison of costs to monetized HAP benefits, was an approach ill-suited to making the appropriate and necessary determination.” EPA also notes that “the statutory text and legislative history do not support a conclusion that the 2020 framework is required under CAA section 112(n)(1)(A), and we exercise our discretion to adopt a different approach.” Given the litigation history, it is likely that parties will challenge EPA’s final rule. Some of the issues likely to be raised by opponents of the rule include whether EPA must consider a full cost-benefit analysis and what costs should be considered compared to what benefits.
In anticipation of these arguments, EPA’s proposal included both a “totality of the circumstances” test and a formal cost-benefit analysis. In addition to the record evidence available in 2012, the proposal also included information available since the 2011 regulatory impact analysis (RIA), including larger estimates of health effects of mercury emitted by electric generating units, the ecological impacts of mercury, and the health effects of additional hazardous air pollutants. While some benefits are not quantifiable, the proposal discusses the significance of the benefits, including reduced neurodevelopmental and cardiovascular harms from exposure to methylmercury, reduced health risks from non-mercury HAPs, and reduced health risks to subpopulations that face disproportionally high exposure to HAPs from EGUs.
This last consideration is consistent with what we are observing in other rulemakings—frank consideration of public health impacts associated with the rulemaking. The proposal notes that Congress created “the clear goal in CAA section 112(n)(1)(C) and elsewhere to consider risks to the most exposed and susceptible populations.” EPA states “[w]e think it is highly relevant that while EGUs generate power for all, and EGU HAP pollution poses risks to all Americans exposed to such HAP, a smaller set of Americans who live near EGUs face a disproportionate risk of being significantly harmed by toxic pollution.”
Additionally, recognizing that the industry has complied with the rule since 2015, the proposal also includes updated compliance costs, which were far below EPA’s 2011 projections.
As a result, under both frameworks (totality of the circumstances and a formal cost-benefit analysis) and based on the cost and benefit projections in the original regulatory impact analysis and under the updated information, EPA proposed to conclude that it is appropriate and necessary to regulate mercury and other hazardous air pollutants from power plants. A final rule is expected this year, then EPA will evaluate whether to update the RTR. Any changes to the RTR would need to be proposed by EPA, so the agency has already requested data or information to assist it in that review, including performance and cost of new or additional control technologies. In comments, several stakeholders noted that coal- and oil-fired EGUs have already reduced emissions well beyond the current standards for HAPs. In deciding whether there is a technology or residual risk basis to revise the standard, EPA will need to evaluate if the lower emissions being achieved can serve as the legal basis for a more stringent standard.
For more on the legal basis of EPA’s MATS proposal, see our recent blog post on EPA’s Authority to Regulate Hazardous Air Pollutants from Power Plants, and for a comprehensive history on the rulemakings see the MATS section of our Power Plant Regulations page.
 Michigan v. EPA, 576 U.S. 743, 753 (2015).
 Section 112 requires EPA to establish standards for HAPs—referred to as a Maximum Achievable Control Technology (MACT) standard. Within eight years of setting a MACT, EPA must assess any remaining health risks from each source category to determine whether the MACT standards protect public health with an “ample margin of safety”. This second step to assess residual risks is in addition to the requirement for EPA to also review the standards to account for any improvements in air pollution control technology (i.e., technology review). The combination of these reviews are often referred to as the Risk and Technology Review (RTR).
 See American Academy of Pediatrics v. Wheeler, No. 20-01221 (D.C. Cir.); Massachusetts v. EPA, No. 20-01265 (D.C. Cir.); Advanced Emissions Solutions v. EPA, No. 20-01266 (D.C. Cir.).
Coal Ash Standards, Litigation, and Enforcement
by Abby Husselbee
EPA is implementing the Trump-era rules while it works on additional rulemakings.
Coal-fired power plants must properly dispose of toxic coal combustion residuals (CCR), also called coal ash, to ensure that the waste does not contaminate drinking water with metals such as arsenic, lead, and mercury. EPA began regulating the disposal of CCRs in 2015 when the Obama administration set “national minimum criteria for existing and new CCR landfills and existing and new CCR surface impoundments.” The 2015 rule designated CCRs as “nonhazardous waste” under subtitle D of the Resource Conservation and Recovery Act (RCRA). It required leaking unlined impoundments to close but allowed other unlined impoundments to continue operating, classified clay-lined impoundments as lined impoundments, and created exemptions for inactive facilities. The Trump administration finalized two rules that effectively weakened the existing CCR restrictions. The “Part A” Rule, released in August 2020, pushed back certain compliance deadlines of the rule, and its “Part B” Rule allowed some unlined facilities to apply to EPA for continued operation. Environmental organizations petitioned the DC Circuit to review the “Part A” rule.
President Biden directed EPA to review the Trump administration’s two rules. EPA did so, and determined that the “[m]ost environmentally protective course is to implement the  rules.” However, EPA has applied stringent interpretations of the 2020 rules. For example, in January 2022, EPA reviewed facilities’ requests for extensions to keep receiving waste under the 2020 Rule and denied four requests. Industry groups have challenged EPA’s recent proposed denials of closure deadline extensions and other actions that the petitioners claim amount to revisions of the existing rules and that litigation is ongoing.
In addition to continuing to review extension requests plant-by-plant, EPA is also working to evaluate whether to strengthen coal ash protections and review state-level programs to ensure that they are at least as strict as federal standards. Under RCRA, states may adopt a CCR plan in place of the federal standard, but the plans must be reviewed by EPA and approved only where they are at least as strict as the federal plan.
 Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals From Electric Utilities, 80 Fed. Reg. 21,311 (Oct. 14, 2015).
 Right before the D.C. Circuit released its opinion in Utility Solid Waste Activities Group. v. EPA (USWAG) that remanded certain provisions to the agency, the Trump administration had finalized a set of amendments to the 2015 rule. Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals From Electric Utilities; Amendments to the National Minimum Criteria (Phase One, Part One), 83 Fed. Reg. 36,435 (July 30, 2018)(codified at 40 C.F.R. § 257). USWAG focused on the 2015 rule, but a later case, Waterkeeper Alliance, directed the Trump administration to revise the 2018 amendments consistent with USWAG. Waterkeeper Alliance v. EPA, No. 18-1289 (Mar. 13, 2019).
 Under President Biden‘s directives, EPA also reviewed the Phase One, Part One rule and chose to implement it as written.
 The court has been holding this case in abeyance since March 2021.
 See Ottumwa Generating Station CCR Part A Site-Specific Alternative Deadline to Initiation of Closure, EPA- (Jan. 11, 2022); Clifty Creek Power Station CCR Part A Site-Specific Alternative Deadline to Initiation of Closure, (Jan. 11, 2022); Gavin Power Station CCR Part A Site-Specific Alternative Deadline to Initiation of Closure, EPA- (Jan. 11, 2022), https://www.epa.gov/coalash/coal-combustion-residuals-ccr-part-implementation (last visited Aug. 24, 2022) [https://perma.cc/Z832-YU49].