EPA

The Clean Air Act’s “Good Neighbor” provision requires upwind states to ensure that the air pollution they create does not affect downwind states’ ability to meet the NAAQS. Upwind states are required to address interstate pollution in their State Implementation Plans for implementing the NAAQS and if EPA finds the SIP inadequate it must issue a Federal Implementation Plan.

EPA has begun proposing and finalizing approvals and disapprovals of SIP revisions in accordance with the Consent Decree.

The Clean Air Act requires EPA to review the NAAQS every five years to ensure adequacy. The review process is a multi-stage, robust evaluation of current science and requires significant expert input.

States have until May 2026 to develop state plans for existing coal-fired power plants. Litigation commenced immediately upon EPA’s finalization of the standards in the D.C. Circuit.