Revised Air Quality Designations for the 2015 Ozone NAAQS

In response to a July 2020, D.C. Circuit Court remand, EPA is taking action on its review of the Agency’s original designation for 16 counties for the 2015 National Ambient Air Quality Standards for ozone.  EPA is taking final action to revise the boundaries for six nonattainment areas in four states (Illinois, Indiana, Missouri and Wisconsin) and reaffirming the April 30, 2018, designation associated with Ottawa County, Michigan.  In the case of the Doña Ana County, NM and Denver Metro/North Front Range, CO nonattainment areas, upon further review, EPA intends to revise its initial designation. Because EPA’s intended designations for the associated remanded counties of El Paso, TX and Weld, CO, respectively, disagree with the states’ area recommendations, EPA is sending letters to each state opening a 120-day period for the states to provide additional information based on the existing record. The Agency will notify both New Mexico and Texas of this planned addition.  EPA is also opening a 30-day period for the public to comment. Additional information:;

EPA 120-day letter to Texas:

Technical Support Document:

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