SO2 (2010) NAAQS NotesReturn to Report
More detailed design value data can be found on the Air Quality Design Value site.
The 2010 NAAQS for SO2 is a 1-hour SO2 standard at a level of 75 parts per billion (ppb), based on the 3-year average of the annual 99th percentile of 1-hour daily maximum concentrations. The previous 24-hour and annual primary SO2 standards remain in effect until the effective date of an area's designation for the 2010 1-hour standard.
A group of 29 areas were designated nonattainment for the 2010 SO2 NAAQS effective October 4, 2013.
Effective September 12, 2016, four additional areas were designated nonattainment: Alton Township IL, Williamson County IL, Anne Arundel County and Baltimore County MD, and St. Clair MI. See: 81 FR 45039
Effective January 17, 2017, three additional areas were designated nonattainment: Freestone and Anderson Counties TX, Rusk and Panola Counties TX, and Titus County TX. See: 81 FR 89870
Effective April 9, 2018, six additional areas were designated nonattainment: Hillsborough-Polk County FL, Huntington IN, Evangeline Parish (Partial) LA, Piti-Cabras GU, San Juan PR, Guayama-Salinas PR. See: 83 FR 1098
In a future fourth round, the EPA expects to designate all remaining undesignated areas (approximately 50 areas) where states have installed and begun timely operation of a new SO2 monitoring network.