No Areas of Non-attainment of Sulfur Dioxide Standard in Arkansas

The United States Environmental Protection Agency (EPA) recently issued attainment designations for the National Ambient Air Quality Standard (NAAQS) for Sulfur Dioxide (SO₂) for counties in Arkansas. All counties in Arkansas have been designated Attainment, Unclassifiable/Attainment, or Unclassifiable.

EPA requires states to perform ambient air quality monitoring or dispersion modeling in areas with SO₂ emissions above a specific threshold in order to evaluate the potential for those sources to contribute to a violation of the SO₂ NAAQS in those areas or in any nearby areas classified as non-attainment for the SO₂ NAAQS. SO₂ monitors are located in Pulaski and Union Counties, where monitoring data shows the counties to be in attainment of the standard. Dispersion modeling performed in other areas with SO₂ emissions above the threshold requiring evaluation also showed all areas to be in attainment. Most counties in Arkansas do not have SO₂ monitors because there is no indication that emission sources within those counties might contribute to a NAAQS violation. In the case of counties that have not previously been designated as non-attainment for sulfur dioxide, where dispersion modeling has indicated no contribution to a NAAQS violation from emissions in the county, or where no monitoring data is available because emissions in those counties are not believed to pose a risk of a NAAQS violation, EPA designates the counties as Unclassifiable/Attainment or Unclassifiable. As EPA recently clarified in a letter to ADEQ’s Office of Air Quality, those counties in Arkansas where no monitor is present fall into one of these two categories.