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Sulfur Dioxide Designations

EPA Completes Fourth Round of Sulfur Dioxide Designations

On December 21, 2020, EPA took the final step to implement the health-based national air quality standard for sulfur dioxide (SO2) set in 2010. EPA has identified or “designated” all remaining portions of the U.S.:
  • “nonattainment” – not meeting the 1-hour health-based national air quality standard for SO2,
  • “unclassifiable” – not enough information to make a determination, or
  • “attainment/unclassifiable” - meeting the standard and not contributing to a violation of the standard.

Read a pre-publication version of the Federal Register Notice, EPA's response to comments, and a summary fact sheet below.

Read the Technical Support Documents supporting this action.

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