Review of the Ambient Air Quality Standard for Nitrogen Dioxide

This page last reviewed September 14, 2017

Nitrogen Dioxide (NO2) is a gas capable of damaging the lungs. ARB staff reviewed the scientific literature and recommended revisions to the NO2 standards based on that review. On February 19, 2007, the Board adopted staff's recommendations. On February 19, 2008, the Office of Administrative Law approved amendments to the regulations for the State Ambient Air Quality Standard (AAQS) for nitrogen dioxide; the revised standards became effective on March 20, 2008. 

The Air Resources Board approved staff recommendations to amend the NO2 standard on February 22, 2007. The recommendations were based on a review of the scientific literature on the health effects of NO2 that was conducted by staff from the Air Resources Board and the Office of Environmental Health Hazard Assessment.  The review and final recommendations for the NO2 standard were released in a final staff report on January 5, 2007. In this report, staff recommended lowering the existing 1-hour-average standard for NO2 of 0.25 ppm to 0.18 ppm, not to be exceeded, and established a new annual-average standard of 0.030 ppm, not to be exceeded. The Staff Report and Technical Support Document are available at this link.

The staff recommendations and supporting information were peer-reviewed by the Air Quality Advisory Committee. Members of this committee, appointed by the Office of the President of the University of California, are experts in health sciences, exposure assessment, monitoring methods, and atmospheric sciences. All meeting and workshop notices are posted below.

This action follows a preliminary evaluation of all health-based ambient air quality standards to determine their adequacy to protect public health, particularly that of infants and children. A December 2000 report found that harmful health effects may occur among both children and adults when outdoor NO2 concentrations are at or near the then-current State standards. The evaluation was a requirement of The Children's Environmental Health Protection Act (Senate Bill 25, Escutia, 1999).
The review and final recommendations for the NO2 standard were released as a final Staff Report for public comment on January 5, 2007. The Staff Report recommended revisions to the existing NO2 standard as follows:


The Milestones of the NO2 Standard Review are listed below:

February 19, 2008 Office of Administrative Law approved amendments to the regulations for the State Ambient Air Quality Standard for nitrogen dioxide (NO2).  The new standards become effective on March 20, 2008

February 23, 2007

Air Board Approves Stronger Nitrogen Dioxide Standards - (News Release)

February 22, 2007

- Board Hearing Presentation (PDF - 977 KB)
- AQAC Presentation
- Regulatory Documents

February 1, 2007

Public Workshop for Public Comment on the NO2 Documents and Recommendations

January 5, 2007

Staff Report and Technical Support Document

June 12-13, 2006

Air Quality Advisory Committee (AQAC) Meeting
FIndings, Presentations and Trancripts

The AQAC is an independent scientific peer review committee that evaluates the scientific basis of recommendations for revising the California ambient air quality standards.

May 8 and 11, 2006

Public Workshops for Public Comment on the NO2 Documents

April 14, 2006

First Public Review of the Draft Staff Report and Draft Technical Support Document

August 1, 2004

Deadline for Submission of Scientific Information

March 24, 2003

Public Request for Peer-Reviewed Scientific Information - Please click here for the request letter

For more info on review of the NO2 ambient air quality standard, please contact
Dr. Norman Kado at (916) 323-1500.