2024 SO2 NAAQS Final Decision
On December 10, 2024, EPA revised the secondary sulfur dioxide (SO2) national ambient quality standard (NAAQS) to an annual average standard averaged over three consecutive years with a level of 10 parts per billion (ppb), effective January 27, 2025. The Clean Air Act (CAA) section 107(d) outlines the timeline and processes for designating all areas of the United States as nonattainment, attainment, or unclassifiable compared to the current NAAQS. The Arkansas Department of Energy and Environment, as designated by the Governor of Arkansas, has submitted initial area designation recommendations with additional technical support to EPA for review.
Infrastructure and Transport SIP Updates
Under CAA sections 110(a)(1) and 110(a)(2), each state is required to submit a state implementation plan (SIP) that provides for the implementation, maintenance, and enforcement of a revised primary or secondary NAAQS. CAA section 110(a)(1) and section 110(a)(2) require each state to make this new SIP submission within three years after the EPA promulgates a new or revised NAAQS. After EPA finalizes area designations for Arkansas, DEQ will begin work on the elements required under CAA section 110. EPA has up to three years from promulgation of a new NAAQS to finalize area designations.