An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to www.epa.gov. This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Sulfur Dioxide Designations

Initial Technical Support Documents for Area Designations Round 4

The Technical Support Documents below support EPA's intended Round 4 area designations for the 2010 sulfur dioxide air quality standard.

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.