- “nonattainment” – not meeting the 1-hour health-based national air quality standard for SO2 (six areas in three states and two territories),
- “unclassifiable” – not enough information to make a determination (23 areas in ten states), or
- “attainment/unclassifiable” - meeting the standard and not contributing to a violation of the standard (all remaining areas except where additional SO2 air quality monitoring is underway).
Read the Federal Register Notice: Air Quality Designations for the 2010 Sulfur Dioxide (SO2) Primary National Ambient Air Quality Standard - Round 3
Note: On March 28, 2018, the EPA withdrew the designation of Unclassifiable for the Citrus County, Florida, area that the EPA originally issued on December 21, 2017, and established a designation of Attainment/Unclassifiable for that area. Learn MoreYou may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.
- Fact Sheet — Final Area Designations for the 1-Hour Primary National Ambient Air Quality Standard for Sulfur Dioxide Established in 2010 (Round 3) (PDF)(6 pp, 682 K)
- Responses to Comments on the EPA’s Intended Round 3 Designations for the 2010 Sulfur Dioxide Primary National Ambient Air Quality Standard (NAAQS) (PDF)(88 pp, 465 K)
- Sulfur Dioxide Designations Summary Table (PDF)(19 pp, 583 K)