• Rule Summary
• Rule History
• Additional Resources

Rule Summary

In 2006, based on the EPA’s review of the air quality criteria and national ambient air quality standards (NAAQS) for particulate matter (PM), EPA made revisions to the primary and secondary NAAQS for PM.

With regard to primary standards for fine particles (generally referring to particles less than or equal to 2.5 micrometers (μm) in diameter, PM_2.5), EPA revised the level of the 24-hour PM_2.5 standard to 35 micrograms per cubic meter (μg/m³) and retained the level of the annual PM_2.5 standard at 15μg/m³.

With regard to primary standards for particles generally less than or equal to 10μm in diameter (PM₁₀), EPA retained the 24-hour PM₁₀ and revoked the annual PM₁₀ standard. With regard to secondary PM standards, EPA made them identical in all respects to the primary PM standards, as revised.

Rule History

10/17/2006 – Final Rule

01/17/2006 – Proposed Rule

Additional Resources

Fact Sheets and Additional Information Regarding the 2006 Particulate Matter (PM) National Ambient Air Quality Standards (NAAQS)

Regulatory Impact Analysis (RIA) for the Review of the Particulate Matter (PM) National Ambient Air Quality Standards (NAAQS)

Scientific and Technical Documents Supporting the 2006 Review of the PM Standards

Related Rules

01/09/2008 – Proposed Rule & Direct Final Rule (Correcting and Simplifying Amendments) for Interpretation of the National Ambient Air Quality Standards for PM_2.5

Implementation of the 2006 Particulate Matter (PM_2.5) National Ambient Air Quality Standards (NAAQS)

2006 Particulate Matter (PM_2.5) National Ambient Air Quality Standards (NAAQS) Infrastructure Actions

2012 National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM_2.5)