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.