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Why it Matters
Mercury and Air Toxics Standards (MATS) limit the amount of mercury and other toxic emissions from power plants. Mercury is a powerful neurotoxin that ends up in the water and soil, and concentrates up the food chain, especially in fish. It is particularly dangerous for pregnant women and young children. In response to the Supreme Court’s decision, Michigan v. EPA, EPA must determine whether it was “appropriate and necessary” to regulate toxic pollution from power plants. While the Trump administration finalized a rule that reversed the Obama administration’s determination that it was appropriate and necessary, the Biden administration has stated the the D.C. Circuit that it is reviewing that reversal. The power sector has already complied with the MATS standards, but if it were to be determined that it was not appropriate and necessary to regulate toxic emissions from power plants, companies may stop operating with installed pollution controls.
Read legal analyses on potential impacts of changes to the rule by the Trump administration:
The Obama EPA issued the MATS rule on February 16, 2012. Industry groups and some states challenged the rule, and on June 29, 2015, the Supreme Court directed EPA to determine whether its standards were appropriate and necessary. The Obama administration determined that the standards were appropriate and necessary but under the Trump administration, EPA withdrew the appropriate and necessary finding on April 16, 2020 and finalized the Residual Risk and Technology Review (RTR) retaining the standards. Environmental, civil rights, and public health groups, states, cities, counties, power companies, and utilities challenged the new finding in the D.C. Circuit.
On January 20, 2021, President Biden directed EPA to revisit the 2020 rule by August 2021, and EPA has asked the D.C. Circuit to pause the ongoing litigation as it does so. In response, EPA submitted a proposed rule to OMB for interagency review on August 3, 2021.
Timeline of Events
Obama AdministrationRead more
Dec. 21, 2011 EPA releases the Mercury and Air Toxics Standards, and coal- and oil-fired power plants are required to make reductions to achieve those standards by Spring 2016.
Feb. 16, 2012 EPA publishes the final Mercury and Air Toxics Standards requiring coal- and oil-fired power plants to achieve the standards by Spring 2016. Industry groups and several states challenge the rule. (lead case) (D.C. Cir.).
Apr. 15, 2014 The D.C. Circuit upholds the rule on all questions presented to the court by the industry and state petitioners who challenge the rule. White Stallion Energy Center v. EPA, 748 F.3d, 1222 (D.C. Cir. 2014).
June 29, 2015 The Supreme Court holds that EPA interpreted §7412(n)(1)(A) of the Clean Air Act unreasonably when it “deemed cost irrelevant to the decision to regulate [HAP emissions from] power plants” and remands the rule to the D.C. Circuit to assess how EPA should proceed with additional cost-benefit analyses. The D.C. Circuit sends the MATS back to EPA to determine if the standards are “appropriate and necessary.”
April 25, 2016 EPA publishes its Supplemental Finding on the costs and benefits of MATS and finds them to be justified in light of the enormous anticipated health benefits. Within hours, opponents sue. Murray Energy v. EPA, No. 16-1127 (D.C. Cir.).
Trump AdministrationRead more
Jan. 31, 2017 Petitioners seek a 45-day extension in the briefing schedule.
April 18, 2017 EPA asks the Court to delay oral arguments, scheduled for May 18, 2017.
April 27, 2017 The D.C. Circuit removes the argument from its calendar, suspending the case indefinitely, and directs EPA to file 90-day status reports.
July 10, 2018 The Edison Electric Institute and several other industry trade groups and unions send a letter to EPA air chief Bill Wehrum asking him to leave the MATS in place and finish the residual risk and technology review “as expeditiously as possible.” The letter also emphasizes that “…all covered plants have implemented the regulations and that pollution controls — where needed — are installed and operating.”
Aug. 24, 2018 Senators Tom Carper (D-Del.) and Lamar Alexander (R-Tenn.) send a letter to acting EPA Administrator Andrew Wheeler urging EPA to retain MATS. The senators explain, “Keeping the current rule in place will provide much-needed certainty for the electric power industry and help protect the health of all Americans.”
Oct. 1, 2018 EPA confirms it has sent a draft proposal to the White House Office of Management & Budget (OMB) for review that would change the agency’s methodology for weighing economic costs and benefits used in the 2012 rule. The new proposal would eliminate consideration of co-benefits of the regulation—the benefits associated with reducing other emissions, besides mercury and other toxic pollutant emissions, that also occur as a result of the rule.
Dec. 28, 2018 EPA releases a proposal to revise the 2016 Supplemental Cost Finding and Residual Risk and Technology Review for MATS. The proposal would limit consideration of health benefits in regulation. For more information about the impacts of the issues in this proposal, read EELP Executive Director Joe Goffman’s discussion of potential changes EPA could make here.
Jan. 22, 2019 Michigan Attorney General files a motion withdrawing from litigation challenging the Obama-era MATS rule.
March 18, 2019 A bipartisan group of six senators send a letter to EPA Administrator Wheeler, urging him to withdraw the proposal to revise the appropriate and necessary finding and voicing their opposition to any action that could lead to undoing the Mercury and Air Toxics Standards.
March 21, 2019 Wisconsin withdraws from legal challenge to Obama-era MATS rule.
March 26, 2019 Several industry trade groups and labor unions send a letter to EPA air chief Bill Wehrum urging EPA to maintain its 2012 regulations and “…take no action that would jeopardize these investments or the underlying rule.” The letter also suggested that “…EPA should consider the impacts such an action would have on these costs already borne by industry and how the recovery of these sunk costs could be put in jeopardy….”
April 17, 2019 The attorneys general of 21 states submit comments to EPA opposing its proposal to withdraw the appropriate and necessary finding.
Oct. 4, 2019 EPA sends the revised Supplemental Cost Finding and Residual Risk and Technology Review to the Office of Management and Budget for review. This is typically the last step before the final rule is released.
Dec. 31, 2019 EPA’s Science Advisory Board releases a draft report that recommends a new risk assessment be completed for the revised Supplemental Cost Finding and Residual Risk and Technology Review and any future mercury regulation. The new risk assessment should include the mercury-related health effects of consuming all fish, going beyond recreationally caught freshwater fish.
Jan. 29, 2020 EPA sends a draft rule to the Office of Management and Budget with its final decision on adjusting emissions limits for power plants that burn eastern bituminous coal refuse (a form of coal mining waste). The industry expects that the new rule will relax emissions limits for acid gases. EPA proposed changing these emissions limits in its Dec. 2018 proposed rule. The agency is now finalizing these limits separately from the rest of the 2018 proposal.
April 9, 2020 EPA issues a final rule adjusting emissions limits for four power plants that burn eastern bituminous coal refuse (a form of coal mining waste). The new standards allow the affected plants to release higher amounts of acid gases and SO2 emissions.
April 9, 2020 EPA’s Science Advisory Board critiques EPA’s assessment of the residual risks to human health from pollutants regulated by MATS. The results of EPA’s final assessment (known as the Residual Risk Assessment) will determine whether EPA must set more stringent pollution control requirements for power plants.
April 16, 2020 EPA releases the final rule withdrawing the appropriate and necessary finding. EPA also finalizes the residual risk and technology review and determines that after compliance with MATS, the residual risks from power plant hazardous air pollutant emissions are acceptable and the standards should not be tightened. EPA publishes the final rule in the Federal Register on May 22.
May 22, 2020 Westmoreland Mining Holdings LLC files a petition for review in the D.C. Circuit challenging the legality of MATS. Westmoreland Mining Holdings v. EPA, No. 20-1160 (D.C. Cir.).
The D.C. Circuit has consolidated the following petitions under Westmoreland Mining Holdings v. EPA, No. 20-1160 (D.C. Cir.). Many of the parties have also moved to intervene in the lawsuit to defend EPA’s decision to not rescind MATS, including the power companies, coalitions of states, and coalition of advocacy organizations.
- June 19, 2020 Environmental, civil rights, and public health groups file a lawsuit challenging EPA’s reversal of the appropriate and necessary finding. The court later consolidates this case with Westmoreland’s challenge to MATS. American Academy of Pediatrics v. Andrew Wheeler, No. 20-01221 (D.C. Cir.).
- July 20, 2020 A coalition of 25 states, cities, and counties led by Massachusetts file a lawsuit challenging the reversal of the MATS appropriate and necessary finding. Massachusetts v. EPA, No. 20-01265 (D.C. Cir.).
- July 20, 2020 A coalition of power companies files a petition challenging the 2020 reversal. Advanced Emissions Solutions v. EPA, No. 20-01266 (D.C. Cir.).
- July 21, 2020 A coalition of environmental organizations file a lawsuit challenging EPA’s residual risk and technology review, in which EPA concluded MATS adequately protects public health. Air Alliance Houston v. EPA, No. 20-02168 (D.C. Cir.).
- July 21, 2020 A group of utilities file a lawsuit challenging the reversal of the MATS appropriate and necessary finding. Calpine Corporation v. EPA, No. 20-01270 (D.C. Cir.).
- July 21, 2020 Puget Sound Energy files a lawsuit challenging the reversal of the MATS appropriate and necessary finding. Puget Sound Energy v. EPA, No. 20-1271 (D.C. Cir.).
June 15, 2020 a coalition of environmental groups file a lawsuit challenging EPA’s less stringent emissions limits for the four power plants that burn eastern bituminous coal refuse. Citizens for Pennsylvania’s Future v. EPA, No. 20-1207 (D.C. Cir.). The groups also file a petition for reconsideration with EPA.
July 31, 2020 The D.C. Circuit suspends (holds in abeyance) for 90 days the challenge to EPA’s less stringent acid gases and SO2 limits for power plants burning eastern bituminous coal refuse. The environmental groups requested this hold to give EPA time to respond to their request that the agency reconsider the final rule. Citizens for Pennsylvania’s Future v. EPA, No. 20-1207 (D.C. Cir.).
Aug. 28, 2020 Westmoreland Mining Holdings LLC requests that the D.C. Circuit sever and put on hold its case challenging the legality of MATS. This would allow the cases challenging the reversal of the appropriate and necessary finding to advance separately. The public health and environmental organizations that intervened in the case support this motion. Westmoreland Mining Holdings v. EPA, No. 20-1160 (D.C. Cir.).
Sep. 28, 2020 The D.C. Circuit grants Westmoreland’s request to sever and put on hold its case challenging the legality of MATS. Westmoreland Mining Holdings v. EPA, No. 20-1160 (D.C. Cir.).
Biden AdministrationRead more
Feb. 12, 2021 EPA files motions to hold in abeyance several cases challenging EPA’s reversal of the appropriate and necessary finding. The D.C. Circuit grants those motions on Feb. 16, directing EPA to file an abeyance status report on June 16, 2021, and at 120-day intervals thereafter. American Academy of Pediatrics v. Andrew 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.); Puget Sound Energy v. EPA, No. 20-1271 (D.C. Cir.).
August 3, 2021 In response, on August 3, 2021, EPA submitted a proposed rule to OMB for the interagency review process.