A coalition of 21 state and local governments filed a lawsuit Tuesday challenging the Trump administration’s repeal of a 2024 rule that established limits for toxic air pollutants.

The regulation, known as the Mercury and Air Toxics Standards rule, limits emissions from coal- and oil-fired power plants. It covers pollutants including mercury, arsenic, lead and other toxic metals, as well as acid gases.

The U.S. Environmental Protection Agency updated the rule in 2024, which proponents of the rule said followed significant upgrades in pollution control technologies. But President Donald Trump’s administration repealed that updated standard last month. 

EPA said in a statement last month that it was repealing the rule “to ensure affordable, dependable energy for American families” and that it expected $670 million in regulatory compliance costs savings from lower costs of transportation, heating, utilities, farming and manufacturing, and more reliable energy. 

The coalition of states and local governments argues that the rollback is unlawful, saying the federal agency has failed to provide a reasoned basis for it or consider the new technologies. 

The states taking part in the lawsuit are Arizona, Connecticut, Delaware, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, Washington and Wisconsin. The District of Columbia, New York City, Chicago and Harris County, Texas, also joined.

“Here, we have the Trump Administration once again acting recklessly and without good reason in rolling back important emissions standards that help mitigate the potentially disastrous health effects of toxic air pollutants associated with power plants like mercury and arsenic,” Rhode Island Attorney General Peter Neronha, a Democrat, said in a statement. 

Stateline reporter Alex Brown can be reached at abrown@stateline.org.