On this page:

• Rule Summary
• Rule History
• Additional Resources

Rule Summary

On April 6, 2018, based on a review of the full body of scientific evidence, EPA issued a decision to retain the current national ambient air quality standards (NAAQS) for oxides of nitrogen (NOx). The EPA has concluded that the current NAAQS protect the public health, including the at-risk populations of older adults, children and people with asthma, with an adequate margin of safety. The NAAQS for nitrogen oxides are a 1-hour standard at a level of 100 ppb based on the 3-year average of 98th percentile of the yearly distribution of 1-hour daily maximum concentrations, and an annual standard at a level of 53 ppb.

Rule History

04/6/2018 - Review of the National Ambient Air Quality Standards for Oxides of Nitrogen, Final Decision 

07/26/2017 - Review of the National Ambient Air Quality Standards for Oxides of Nitrogen, Proposed Decision

02/09/2010 – Final Rule Revising the Nitrogen Dioxide National Ambient Air Quality Standards & Nitrogen Dioxide Monitoring Requirements

07/15/2009 – Proposed Revision to Nitrogen Dioxide National Ambient Air Quality Standards (NAAQS) & Proposed Nitrogen Dioxide Ambient Air Monitoring Requirements Rule

Additional Resources

Fact Sheets and Additional Information Regarding the Primary National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide (NO₂)

Scientific and Technical Documents Supporting the Primary NAAQS for NO₂

Related Rules

Secondary National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide (NO₂) and Sulfur Dioxide (SO₂)

Revision to the Near-Road Nitrogen Dioxide Monitoring Requirements

03/14/2013 – Final Rule; Revision to Ambient Nitrogen Dioxide Monitoring Requirements

10/19/2012 – Proposed Revisions to Ambient Nitrogen Dioxide Monitoring Requirements