On March 15, 2021, the U.S. Environmental Protection Agency (EPA or the Agency) published a final rule, pursuant to the good-neighbor provision of the Clean Air Act, which directs EPA and states to address interstate transport of air pollution that affects downwind states’ ability to attain and maintain compliance with the 2008 National Ambient Air Quality Standard (NAAQS) for ozone. As we explained previously, the Revised Cross-State Air Pollution Rule (CSAPR) Update is EPA’s rulemaking in response to the U.S. Court of Appeals for the D.C. Circuit’s decision in Wisconsin v. EPA, in which the court remanded an earlier EPA CSAPR update rule. EPA here found nine states (Alabama, Arkansas, Iowa, Kansas, Mississippi, Missouri, Oklahoma, Texas, and Wisconsin) required no additional regulation. For 12 states (Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia, and West Virginia), EPA found that projected 2021 ozone season nitrogen oxides (NOx) emissions contribute significantly to downwind states’ nonattainment or maintenance problems for the 2008 ozone NAAQS. Accordingly, EPA issued new or amended Federal Implementation Plans, which include replacement of NOX Ozone Season Group 2 emissions budgets for electric generating units (EGUs). In the final rule, EPA maintained its determination not to require additional controls on non-EGUs.
This rule does not address state obligations under the more stringent 2015 ozone NAAQS, which bears close watching. The 2015 rule likewise was challenged in court, with the most recent action on remand at the end of the last administration among the EPA regulations being reviewed by the Biden administration.