Details: The rule, which updates ozone requirements under the Cross-State Air Pollution Rule and is largely in line with the Trump administrations proposal, will require power plants in the 12 states to optimize their use of already-installed pollution controls for 2021. Plants may also have to install or upgrade their NOx combustion controls for the 2022 season.

The rule lists emissions budgets for those states through 2024, with figures tweaked slightly from last year’s proposal.

The 12 states facing additional requirements because of their contribution to downwind states air quality problems are Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia and West Virginia. (Some states, like New York and New Jersey, are both upwind and downwind states.)

As with the Trump proposal, the final rule does not cover non-power plant sources, which the agency said are less likely to be able to provide cost-effective, significant reductions compared to power plants. The agency also reaffirmed no additional requirements on nine other states that previously were subject to the update.

Costs and benefits: The rule will reduce emissions of NOx, which mixes with other pollutants and sunlight to form ground-level ozone, by 17,000 tons this year, in line with the Trump administration’s October proposal. Combined with other reductions already expected, summer season NOx emissions will be 19 percent below 2019 levels, according to EPA. Public health and climate benefits total up to $2.8 billion annually between 2021 and 2040, according to EPA.

Annual costs over that period will average $25 million, EPA said.

Documents: EPA released a pre-publication copy of the rule, as well as a fact sheet and various technical support documents.