California Air Resources Board

There are two federal primary standards for nitrogen dioxide (NO₂) - a 1-hour standard of 100 parts per billion (ppb) and an annual average of 0.053 parts per million (ppm).  There is one federal secondary standard - an annual average of 0.053 ppm (same as the primary standard).  All areas in California are designated as attainment/unclassified for the federal NO₂ standards.

Maps of current area designations can be found through the Resources tab on the left.  Information about specific NO₂ nonattainment areas and the efforts to bring them into attainment of the NO₂ standards can be found on the California State Implementation Plan (SIP) webpage.

Nitrogen Dioxide Primary Standards

• December 2012 - CARB submitted the NO₂ Infrastructure SIP to U.S. EPA
• January 2012 - U.S. EPA issued final area designations  (Federal Register (FR) Notice February 17, 2012; effective February 29, 2012).
• January 2011 - CARB submitted recommended area designations to U.S. EPA. The full submittal package and U.S. EPA's response are available on the U.S. EPA website.
• January 2010 - U.S. EPA revised the primary nitrogen dioxide (NO₂) standards (FR Notice February 9, 2010; effective April 12, 2010).

Information about activities related to the NO₂ standards can be found on U.S. EPA's NO2 home page.

Nitrogen Dioxide Secondary Standards

• March 2012 - U.S. EPA retained the existing SO₂ and NO₂ secondary standards (FR Notice April 3, 2012; effective June 4, 2012).

Additional information about activities related to the secondary standards can be found on U.S. EPA's NO₂/SO₂ secondary standards webpage.