EPA took interim final action to stay, for emissions sources in Arkansas, Kentucky, Louisiana, Mississippi, Missouri, and Texas only, the effectiveness of the federal implementation plan requirements established to address the "good neighbor" plan obligations of these and other states to mitigate interstate air pollution with respect to the 2015 ozone NAAQS.

EPA entered into a proposed consent decree under the CAA in Sierra Club v. Regan, No. 3:22-cv-01992-JD (N.D. Cal.), that would establish deadlines for the Agency to promulgate federal implementation plans to address the "good neighbor" requirements for the 2015 ozone NAAQS for Pennsylvania, Utah, Virginia, and New Mexico.

SIP Approval: Colorado (finalizing EPA conclusions that Colorado's infrastructure SIP submission meets the state’s good neighbor obligations and provides “necessary assurances” of the state’s authority to regulate agricultural sources).

EPA proposed to determine that the Cross-State Air Pollution Rule Update for the 2008 ozone NAAQS fully addresses certain states' obligations under CAA §110(a)(2)(D)(i)(I) regarding interstate pollution transport for the 2008 ozone NAAQS.