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In 2024, the EPA issued a risk and technology review for Mercury and Air Toxics Standards (MATS) that updated certain standards for coal- and oil-fired electric generating units (EGUs). Specifically, the rule updated the filterable particulate matter standard (surrogate for the non-mercury hazardous air pollutant metals) for existing coal-fired EGUs, the mercury standard for lignite coal-fired EGUs, and revised the particulate matter compliance demonstration requirements to only allow particulate matter continuous emission monitoring systems. On June 17, 2025, the EPA published a proposal (90 FR 25535) to repeal these changes.

Statement of Need: On March 12, 2025, EPA Administrator Zeldin announced that the Agency would undertake 31 deregulatory actions to Power the Great American Comeback. “Reconsideration of Mercury and Air Toxics Standards that improperly targeted coal-fired power plants (MATS)” was among the deregulatory actions that were announced. This action will reevaluate the amendments made to MATS in a 2024 action.

Summary of the Legal Basis: CAA section 112, 42 U.S.C. 7412, provides the legal framework and basis for regulatory actions addressing emissions of hazardous air pollutants from stationary sources.

Alternatives: There are no alternatives at this time.

Anticipated Costs and Benefits: EPA estimates that the proposed repeal of the 2024 MATS Amendments would save up to $1 billion in regulatory costs over a decade beginning in 2028.

Risks: The EPA found the residual risks due to emissions of air toxics from this source category are acceptable.