EPA repeals stricter Mercury and Air Toxics Standards for coal-, oil-fired power plants

On February 24, 2026, the Environmental Protection Agency (EPA) published a final rule repealing the 2024 amendments made to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Coal- and Oil-Fired Electric Utility Steam Generating Units (EGUs). It’s also referred to as the Mercury and Air Toxics Standards (MATS) for power plants.

Effective April 27, 2026, this rule (2026 Final Rule) repeals stricter compliance requirements made to the MATS rule in May 2024 (2024 Final Rule) and reverts them to the less stringent standards established by the 2012 MATS Rule.

Who’s affected?

The rule applies to power plants with coal- and oil-fired EGUs subject to the NESHAP (40 CFR 63 Subpart UUUUU).

What are the changes?

The final rule repeals these 2024 amendments:

• The revised filterable particulate matter (fPM) emission standard and corresponding total and individual non-metal hazardous air pollutant (HAP) metal standards for existing coal-fired EGUs (reverting to the 2012 MATS Rule requirements);
• The revised compliance demonstration requirements for all EGUs to install continuous emission monitoring systems (CEMS) for fPM emissions and the adjusted quality assurance (QA) criteria (reverting to the previous standard, allowing EGUs to choose from three compliance demonstration methods); and
• The revised mercury (Hg) emission standard for lignite-fired EGUs (reverting to the 2012 MATS Rule limit).

The 2026 Final Rule also reinstates the low-emitting EGU (LEE) program for fPM and non-Hg HAP metals. The LEE program requires less frequent stack testing for sources with emissions below 50 percent of the corresponding limit for 3 consecutive years.

Further, EPA’s final rule updates the fPM sampling requirements for EGUs that demonstrate compliance with a PM CEMS. These units must collect either a minimum catch of 6.0 milligrams or a minimum sample volume of 4 dry standard cubic meters (dscm) per test run. EGUs demonstrating compliance using other methods must collect a lower minimum sample volume of 1 dscm per PM test run.

Compliance requirement	2024 Final Rule	2026 Final Rule
fPM emission limit for existing coal-fired EGUs	0.010 pounds per million British thermal units of heat input (lb/MMBtu)	0.030 lb/MMBTu
fPM emission compliance demonstration for all coal-and oil-fired EGUs	EGUs must use PM CEMS.	EGUs may use: Quarterly stack testing, PM continuous parametric monitoring systems, or PM CEMS.
Hg emission limit for existing lignite-fired EGUs	1.2 pounds per trillion British thermal units of heat input (lb/TBtu)	4.0 lb/TBtu

Key to remember: EPA’s final rule repeals the stricter emission limits set by the 2024 amendments to the Mercury and Air Toxics Standard for coal- and oil-fired power plants.