Updated: 9/1/2023

Since 2005, CBF has successfully pushed EPA to require stringent controls on coal-fired power plants to reduce airborne hazardous pollutants, including mercury. In collaboration with other public interest groups, CBF’s legal actions led to the creation of a federal regulation known as the Mercury and Air Toxics Standards (MATS), 77 Fed. Reg. 9304 (Feb. 16, 2012). Unfortunately, it was again threatened in 2020.

MATS was based on EPA’s finding that it is “appropriate and necessary,” under the Clean Air Act, to regulate mercury and toxic air emissions from fossil fuel-fired power plants that pose a significant hazard to the environment and to human health. The mercury from power plants falls from the air into rivers, lakes, streams, and the Bay where it is taken up by plants and small organisms and gradually travels up the food chain into fish and other wildlife. The mercury is converted into methylmercury, a neurotoxin that attacks the human nervous system and causes IQ deficits in children. This toxin can eventually be ingested by people who consume contaminated fish and can cause serious adverse health effects. Mercury contamination is especially damaging for developing fetuses and young children. Low-income communities, communities of color, and subsistence fishers who rely on self-caught fish to feed their families, are also at greater risk.

Despite the dangers caused by exposure to mercury pollution, the MATS have been repeatedly challenged in court by industry groups and some states. While those actions were initially defeated in the lower courts, the challengers asked the U.S. Supreme Court to overturn those decisions and vacate the MATS in 2013. CBF joined in the filing of a brief opposing the challengers’ petition for certiorari. The petition was granted, and the U.S. Supreme Court in Michigan v. EPA, found that EPA had unreasonably failed to consider costs when conducting its “appropriate and necessary” finding.

In response to the Supreme Court’s ruling, EPA completed an economic analysis and in April 2016 issued a Supplemental Finding that the costs of the MATS Rule were reasonable, and the standards remained “appropriate and necessary.” This finding was immediately challenged in court by Murray Energy, a coal mining company. CBF joined a coalition of NGOs to intervene and defend the Supplemental Finding. In April 2017, with the case fully briefed and scheduled for oral arguments, the government moved to hold the case in abeyance while it reconsidered its position supporting the Supplemental Finding; the Court granted EPA’s request and suspended the case.

In April 2020, EPA issued a final rule attempting to reverse the 2016 Supplemental Finding. The 2020 rule changed how EPA considered the costs and benefits of the MATS Rule and determined that regulating hazardous air emissions from coal-and oil-fired power plants is not “appropriate and necessary,” even though studies show that as fully implemented, the MATS Rule led to a 96-percent reduction in emissions of mercury and other hazardous air pollutants at significantly less cost than industry had anticipated. During the public participation process, CBF submitted a comment letter on how EPA’s proposal to undermine MATS could lead to increased mercury emissions within the Chesapeake Bay airshed and how reducing mercury pollution is crucial for Bay restoration and protecting the region’s communities.

In June 2020, CBF joined a coalition of public interest groups challenging the 2020 rule at the U.S. Court of Appeals for the D.C. Circuit. CBF’s case was consolidated with other appeals filed by industry groups and a coalition of states, including Bay watershed states. The case is docketed as Westmoreland Mining Holdings v. EPA (Case No.: 20-1160). On February 17, 2021, the Court issued an Order holding the cases in abeyance pending EPA’s implementation of Executive order 13990 directing EPA to review the MATS Supplemental Finding. On February 8, 2022, EPA issued a proposed rule to revoke the 2020 finding that stated it is not appropriate and necessary to regulate coal- and oil-fired electric utility generating units under the CAA. CBF joined public health and environmental organizations and submitted comments supporting EPA’s proposal.  

On March 6, 2023, EPA finalized a new rule in the Federal Register superseding the 2020 rulemaking and reinstated the “appropriate and necessary” finding. No challenges to the new rule were filed, and the parties voluntarily dismissed the consolidated cases on July 5, 2023. 

CBF was represented in these matters by counsel for Earthjustice, CBF current Director of Litigation Ariel Solaski, and former Vice President for Litigation Jon Mueller.