The U.S. Environmental Protection Agency (EPA) is progressing forward with implementing the 2015 ozone NAAQS (the "2015 ozone NAAQS") promulgated on October 1, 2015.

This rule proposal contains three main components:

  1. Non-attainment area classification thresholds and the timing of attainment dates for each non-attainment area classification. In doing so, EPA has decided to retain the "percent-above-the-standard" (PATS) methodology used to establish area classification thresholds for the 1997 and 2008 8-hour ozone NAAQS (81 FR 81283; November 17, 2016);
  2. Options to revoke the 2008 ozone NAAQS and, where applicable, provide anti-backsliding requirements to help smooth the transition between the two standards for non-attainment areas; and
  3. SIP requirements for states with non-attainment areas and states in an ozone transport region under the 2015 ozone NAAQS.

On November 6, 2017 EPA designated areas in the U.S. "attainment/unclassifiable" for the 2015 ozone standards. Further on December 22, 2017, EPA responded to state and tribal recommendations by indicating the anticipated area designations for the portions of the country not already designated for the 2015 ozone standards. These responses started a 120-day period in accordance with Section 107(d) of the Clean Air Act (CAA) for states and tribes to provide additional information before EPA determines the final designations. Subsequently, on March 19, 2018 EPA published a summary table that can be found here of its non-attainment recommendations for each state. The 120-day period will be final on April 30, 2018 and designations will be finalized shortly thereafter.