The Nonattainment Area - Sulfur Dioxide (SO2-2010) dataset was updated on November 30, 2025 by the Environmental Protection Agency (EPA) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). This dataset provides detailed information about areas identified in the U.S. where sulfur oxide levels have not met the National Ambient Air Quality Standards (NAAQS) established in 2010 for sulfur oxides and have been designated "nonattainment areas (NAA)". A second round of area designations was effective September 12, 2016. A supplement to the second round of area designations was effective January 17, 2017. A third round of area designations was effective April 9, 2018. A fourth round of area designations was effective April 30, 2021. These data are weekly from an OAQPS internal database. However, that does not necessarily mean the data have changed. For more information about this non-attainment area, please see the website https://www.epa.gov/green-book/green-book-sulfur-dioxide-2010-area-information. A data dictionary, or other source of attribute information, is accessible at https://doi.org/10.21949/1529069