¹ 8-Hour Ozone (2008) NAAQS nonattainment area boundary differs from 8-Hour Ozone (1997) and (where applicable) 1-Hour Ozone (1997) NAAQS nonattainment area boundary.

² Former subpart 1 areas with Determinations of Attainment prior to subpart 2 classification on May 14, 2012 (77 FR 28424). An Attainment Deadline Determination for these areas for the 8-Hour Ozone (1997) NAAQS attainment dates is pending with the EPA.

³ Part of Los Angeles-South Coast Air Basin Area, CA (South Coast) for 8-Hour Ozone (1997) and 1-Hour Ozone (1979) nonattainment area boundaries. The EPA published a correction of the classification for the 8-Hour Ozone (1997) and 1-Hour Ozone (1979) NAAQS on September 23, 2013 (78 FR 58189).

⁴ Part of Los Angeles-South Coast Air Basin Area, CA (South Coast) for 8-Hour Ozone (1997) and 1-Hour Ozone (1979) nonattainment area boundaries. The EPA published a correction of the classification for the 8-Hour Ozone (1997) NAAQS on May 5, 2010 (75 FR 24409).

⁵ Part of the Philadelphia-Wilmington-Atlantic City Area, PA, NJ, MD, DE for 8-Hour Ozone (1997) nonattainment area boundary, and part of the Sussex County, DE Ozone nonattainment area boundary for the 1-Hour Ozone (1979) NAAQS.

⁶ The Houston-Galveston-Brazoria Area was designated and classified as ''Severe-17'' nonattainment on November 15, 1990 and was so designated and classified when the 1-hour ozone standard was revoked. The area has since attained the 1-hour ozone standard and met all the Clean Air Act criteria for redesignation. All 1-hour ozone standard anti-backsliding obligations for the area are terminated effective March 16, 2020. (85 FR 8411)

⁷ The Houston-Galveston-Brazoria, TX area was designated nonattainment effective June 15, 2004 and was classified as ''Severe-15'' effective October 31, 2008. The area has since attained the 1997 8-hour ozone standard and met all the Clean Air Act criteria for redesignation. All 1997 8-hour ozone standard anti-backsliding obligations for the area are terminated effective March 16, 2020. (85 FR 8411)

⁸ The Dallas-Fort Worth, TX area was designated and classified as a Moderate nonattainment area effective June 15, 2004. The area was classified as Serious nonattainment effective January 19, 2011. The area has since attained the 1997 ozone standard and met all the Clean Air Act criteria for redesignation. All 1997 8-hour ozone standard anti-backsliding obligations for the area are terminated effective May 6, 2020. (85 FR 19096)

⁹ The Dallas-Fort Worth Area was designated and classified as Moderate nonattainment on November 15, 1990. The area was classified as Serious nonattainment on March 20, 1998 and was so designated and classified when the 1-hour ozone standard, designations and classifications were revoked. The area has since attained the 1-hour ozone standard and met all the Clean Air Act criteria for redesignation. All 1-hour ozone standard anti-backsliding obligations for the area are terminated effective May 6, 2020. (85 FR 19096)

¹⁰ On February 27, 2020, the EPA determined, based on an analysis from California, that the Imperial County nonattainment area would have attained the 2008 ozone NAAQS by the 'Moderate' area attainment date of July 20, 2018, but for emissions emanating from Mexico, and therefore is not subject to the CAA requirements pertaining to reclassification upon failure to attain. (85 FR 11817)