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 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 This website is no longer updated and links to external websites and some internal pages may not work.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 »

PM2.5 Clean Data Policy Clarification Memorandum

This memorandum issued on May 22, 2008, to EPA's Regional Air Division Directors, provides clarification regarding language in the preamble of EPA's particulate matter (PM2.5) implementation rule (April 25, 2007) as it relates to EPA's Clean Data Policy.

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