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.