Power plant pollution rules: repeal of the 2024 mercury standards and of most greenhouse-gas standards (2025-2026)

Case

On Feb. 20, 2026 EPA finalized a repeal of the 2024 amendments to the Mercury and Air Toxics Standards for coal- and oil-fired power plants, reverting to the weaker 2012 limits. On Sept. 14, 2026 EPA finalized a repeal of most of the 2024 greenhouse-gas standards for fossil-fuel power plants, including every standard for existing coal plants, and proposed to rescind all the rest. Environmental and public-health groups have sued over both.

Mercury and Air Toxics Standards repeal (Feb. 2026)
On Feb. 20, 2026 EPA Administrator Lee Zeldin announced, at a power plant in Kentucky, a final repeal of the 2024 amendments to the Mercury and Air Toxics Standards (MATS) for coal- and oil-fired power plants.
The repeal was published in the Federal Register on Feb. 24, 2026 and took effect April 27, 2026. It returns plants to the 2012 MATS standards by repealing the 2024 tighter limit on filterable particulate matter (and the associated metals limits) for existing coal-fired units and the revised mercury limit for lignite-fired units, and it reinstates a low-emitting-unit program.
EPA says the 2012 rule remains in full force and is fully protective of human health, that mercury emissions from coal-fired plants were already 90% below pre-MATS levels in 2021, and that the repeal gives immediate relief to owners who faced substantial capital investments to comply with the 2024 standards.
Environmental groups say the repeal lets coal- and oil-fired plants emit more mercury, other heavy metals and soot, and drops a requirement that plants install systems to continuously monitor their pollution. They say it follows a two-year exemption granted to some of the dirtiest plants.
In March 2026 a coalition of 20 environmental and public-health organizations sued to challenge the repeal.

Greenhouse-gas standards for power plants (2025-2026)
On June 11, 2025 EPA proposed repealing the greenhouse-gas standards for fossil fuel-fired power plants, arguing that the plants "do not contribute significantly to dangerous air pollution" under section 111 of the Clean Air Act. EPA sent the final rule to OMB for review on May 14, 2026.
On Sept. 14, 2026 EPA finalized a partial repeal of the 2024 Carbon Pollution Standards. It repeals all standards for existing coal-fired plants, all standards for existing natural gas- and oil-fired plants, all standards for coal-fired units undertaking a large modification, and certain standards for new plants.
Among the repealed provisions is the 2024 requirement that coal plants operating beyond 2032 and retiring before 2039 co-fire 40% natural gas. The repeal eliminates the requirement that states develop plans to control greenhouse-gas emissions from existing steam units, and is scheduled to take effect Nov. 16, 2026.
EPA also issued a supplemental proposal to rescind the findings underlying power-plant standards under section 111 and repeal all remaining greenhouse-gas requirements. Together, the final rule and the proposal would eliminate all remaining federal greenhouse-gas standards for fossil-fuel power plants.
EPA's stated rationale is that the 2024 standards required control technologies, such as carbon capture and storage, that were not adequately demonstrated and effectively forced plants to retire. EPA projects the repeal will save $310 billion, and certain rules for gas-fired plants remain in effect.
A coalition of environmental and public-health organizations filed a petition for review of the repeal on Sept. 17, 2026.

What the sources do not establish
The sources reviewed do not include an independent estimate of the health effects of either repeal, or the outcome of the court challenges.

Perspectives

Official position — EPA and Administrator Lee Zeldin
EPA says the 2012 MATS rule is fully protective of human health, that repealing the 2024 revisions is a victory for American energy dominance, and that compliance obligations under the 2012 rule remain in force. On carbon, EPA says the 2024 standards required control technology, such as carbon capture, that was not adequately demonstrated, effectively forcing plants to retire.

Critic — Environmental and public-health groups (EDF, Earthjustice and a coalition of 20 organizations)
Earthjustice attorney Nicholas Morales called the MATS repeal an attack on public health that will unlawfully result in higher levels of mercury, soot and other hazardous pollution, and said it puts polluters' interests over public health by loosening limits for the largest domestic emitter of mercury. A coalition of 20 organizations sued in March 2026, and a coalition petitioned for review of the carbon repeal on Sept. 17, 2026.

Editorial read — The Author (site author)
The Author's view is that loosening limits on mercury, soot and carbon from power plants favors a small number of dirty plants over public health. This is interpretation. EPA says the 2012 mercury rule remains protective and that the 2024 carbon standards required unproven technology, and the sources reviewed do not include an independent estimate of the health effects of either repeal.

Research notes
Open leads: (1) The health and cost estimates in EPA's regulatory impact analyses for both rules, compared with outside estimates; (2) the outcome of the D.C. Circuit challenges; (3) the supplemental proposal's comment period and final status; (4) the coal-ash waste and power-plant wastewater rollbacks and compliance-deadline extensions, which are not covered here; (5) the EDF release used for the continuous-monitoring point is an advocacy document; (6) presidential Clean Air Act exemptions for some power plants are covered in the separate entry on EPA's exemption mailbox.

Note
EPA says the 2012 mercury rule remains in force and is fully protective of health, and that the 2024 carbon standards required control technology that was not adequately demonstrated and would have forced plants to retire. Environmental groups say the repeals allow more mercury, metals, soot and carbon pollution. The sources reviewed do not include an independent estimate of the health effects, and litigation is pending.

Sources
[1] EPA press release: EPA Continues to Reverse Democrats' War on Beautiful Clean Coal, Finalizes Repeal of Costly Restrictions on Baseload Power Generation (https://www.epa.gov/node/299028) · 2026-02-20
[2] Venable: EPA Repeals the 2024 Updates to the Mercury and Air Toxics Standards (MATS) for Coal- and Oil-Fired Power Plants (https://www.vnf.com/epa-repeals-the-2024-updates-to-the-mercury-and-air-toxics-standards-mats-for-coal-and-oil-fired-power-plants) · 2026-02-25
[3] Environmental Defense Fund: EPA Dismantles Protections for Mercury and Air Toxics from Power Plants (https://www.edf.org/media/epa-dismantles-protections-mercury-and-air-toxics-power-plants) · 2026-02-20
[4] Goldberg Segalla: Mercury and Air Toxics Standards (MATS) overview and 2026 repeal (https://www.goldbergsegalla.com/?p=75205) · 2026-03
[5] Harvard Environmental and Energy Law Program: Regulating Greenhouse Gases for New and Existing Fossil Fuel-Fired Power Plants (tracker) (https://eelp.law.harvard.edu/tracker/regulating-greenhouse-gases-for-new-and-existing-fossil-fuel-fired-power/) · 2026-09
[6] Harvard Environmental and Energy Law Program: EPA Finalized Power Plant GHG Rule Repeal and Proposed Broader Deregulation (https://eelp.law.harvard.edu/tracker/epa-finalized-power-plant-ghg-rule-repeal-and-proposed-broader-deregulation/) · 2026-09-14
[7] Clifford Chance: EPA Partially Repeals Power Plant Greenhouse Gas Emissions Standards and Proposes Complete Rescission (https://www.cliffordchance.com/briefings/2026/09/epa-partially-repeals-power-plant-greenhouse-gas-emissions-standards-and-proposes-complete-rescission.html) · 2026-09-24
[8] DieselNet: US EPA repeals GHG emission regulations for power plants (https://dieselnet.com/news/2026/09epa2.php) · 2026-09-15
[9] Federal Register (public inspection): Partial Repeal of the Carbon Pollution Standards for Fossil Fuel-Fired Electric Generating Units (https://public-inspection.federalregister.gov/2026-19071.pdf) · 2026-09-17

Connections

Same context — Coal ash and power-plant wastewater: deadline extensions and proposed relaxations (2025-2026)
Air, carbon, water and waste rules for the same coal- and fossil-fired power plants.

Related — Collapse of environmental enforcement against polluters
Fewer rules and weaker enforcement of those remaining: that entry covers the drop in enforcement against polluters.

Related — DOE emergency orders keeping retiring coal plants open at ratepayers' expense
Both support coal and fossil power plants: this entry covers relaxed pollution limits, that one covers DOE orders keeping retiring plants open.

Related — Endangerment finding rescission and the repeal of vehicle greenhouse-gas standards (Feb. 2026)
EPA's September 2026 supplemental proposal on power-plant greenhouse-gas standards says it is made in light of this rescission.

Same context — Environmental deregulation under EPA Administrator Lee Zeldin
The power-plant repeals are specific rules within the broader Zeldin-era rollback documented there.

Related — EPA's "electronic mailbox" for Clean Air Act exemptions and the presidential proclamations (2025-2026)
EDF says the MATS repeal followed a two-year exemption granted to some of the dirtiest plants, which that entry covers.