On June 11, 2025, EPA Administrator Zeldin proposed to repeal two regulations finalized by the Biden administration that limited pollution from fossil fuel-fired power plants: updates to the Mercury and Air Toxics Rule and the Carbon Pollution Standards. If finalized, these proposed repeals would allow emissions from power plants to increase.
In this legal analysis, we focus on the repeal of the Updates to the Mercury and Air Toxics Standards (MATS). This proposed rule follows President Trump’s April 2025 proclamation that exempted 68 coal-fired electric generating units from the previous MATS rule, promulgated during the Biden administration, for two years.
Section 112 of the Clean Air Act provides the statutory obligation for EPA to regulate hazardous air pollutants (HAPs), including mercury and other toxic metals, from power plants. These metals have been shown to cause adverse health impacts, particularly to the brain and nervous system. EPA established standards regulating mercury and air toxics in 2012 and finalized updates to those standards under its residual risk and technology review (RTR) in 2020 and 2024. In 2024, the Biden EPA, as part of its technology review, determined that changes in emissions control technology and methods required updated standards. The Trump Administration is now proposing to repeal the 2024 updates, concluding that they are either not cost-effective or technically feasible. This proposed repeal would leave the 2012 standards in place.