US EPA issues final rule requiring NOx cuts at power plants in 12 upwind states

The U.S. Environmental Protection Agency has finalized a rule requiring power plants in 12 upwind states starting this year to curb smog-forming emissions that drift across state lines.

The regulation is largely in line with an earlier Trump EPA proposal, but it also departs from the prior administration's practice of heavily discounting the societal cost of emitting carbon dioxide into the atmosphere.

Signed on March 15, the rule was issued in response to a 2019 federal appeals court ruling that vacated an update to the EPA's Cross-State Air Pollution Rule, or CSAPR. Issued under the Clean Air Act's "good neighbor" provisions, CSAPR requires upwind states to address nitrogen oxide, or NOx, emissions — one of the main ingredients in ground-level ozone, also known as smog — that drift across state lines.

In vacating the CSAPR update, the U.S. Court of Appeals for the District of Columbia Circuit faulted the EPA for failing to require upwind states to eliminate their significant contributions to downwind ozone pollution by July 2018, the same date downwind states were required to meet the 2008 National Ambient Air Quality Standards, or NAAQS, for ozone.

The Trump EPA eventually responded to that ruling with an October 2020 proposed rule targeting coal plants in 12 upwind states projected to significantly contribute to their downwind neighbors' nonattainment or maintenance problems for the 2021 summer ozone season. Those states are Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia and West Virginia.

While the March 15 rule covers the same states, it goes beyond the Trump EPA's earlier proposal by requiring selective non-catalytic reduction controls in addition to the optimization of already-installed emission control technology.

The EPA estimated the final rule will reduce NOx emissions from power plants in the 12 affected states by 17,000 tons in 2021. Using an updated version of the Obama administration's methodology for calculating the social cost of carbon, which accounts for global impacts, the EPA projected the rule will produce $2.8 billion in annual public health and climate benefits through 2040.

"The action we are taking today will not only help states meet their clean air obligations but, more importantly, deliver cleaner, healthier air to millions of Americans starting this summer," newly confirmed EPA Administrator Michael Regan said in a statement.

The rule is effective 60 days after publication in the Federal Register.