The U.S. EPA has adopted final nonattainment designations for 51 areas across the country for the agency’s 2015 national ambient air quality standards (NAAQS) for ozone. In a previous action, EPA had issued its attainment and unclassifiable designations, finding that 85% of the nation’s counties qualify for one of those designations (a designation of unclassifiable means that the agency does not have enough information to determine whether the areas is in attainment or. nonattainment). Still to come, likely by July 17, 2018, is action by EPA on eight counties around San Antonio, Texas.

A majority of the nonattainment designations outside of California specify that the areas are in marginal nonattainment. These areas are not required to submit state plans demonstrating how they will be attain the standards. Nevertheless, all nonattainment areas are required to attain the standards, with different time periods allowed for compliance depending on the severity of the designation. All nonattainment areas are also potentially subject to development restrictions. Only in California were there designations of serious, severe or extreme nonattainment.

The 2015 ozone standard was more stringent than previous iterations of that standard and has led to pending litigation brought by some states and industry groups. The Trump administration is reportedly examining whether it wishes to reconsider the standard.

EPA provides a table at the end of the preamble listing the areas designated.