On July 21, 2025, the Environmental Protection Agency (EPA) published a final rule titled “Prevention of Significant Deterioration (PSD) and Nonattainment New Source Review (NNSR): Project Emissions Accounting.” This final rule responded to a rule EPA proposed on May 3, 2024, that would have redefined the term “project” under the Clean Air Act’s NSR program, and increased reporting requirements applicable to modifications at existing major stationary sources. The EPA determined that the proposed rule would increase unnecessary burdens on regulated entities that implement NSR regulations.