On Feb. 24, 2026, EPA finalized its rescission of the 2024 Mercury and Air Toxics Standards (MATS) and reinstated the 2012 MATS. Under the Biden administration, EPA made three substantive changes to the 2012 standards. The 2024 rule: (1) strengthened the emissions standards for filterable particulate matter (fPM) (which is regulated as a way to capture non-mercury hazardous air pollution emissions such as arsenic, cadmium, chromium, lead, and nickel), (2) required coal- and oil-fired power plants to use continuous monitoring systems (PM CEMS) to measure compliance with the new fPM standard, and (3) required lignite-fired power plants to comply with the same standards as other coal-fired power plants. The 2026 rule rescinded these three changes and provided a new statutory basis for determining when EPA is required to update hazardous air pollutant (HAP) regulations under the residual risk and technology review provision of the Clean Air Act.
This analysis explains the statutory basis and regulatory history of MATS and EPA’s legal rationales for repealing the 2024 MATS. It also looks at the agency’s response to adverse public comments and EPA’s decision to not monetize public health harms when assessing the costs and benefits of the rule.
