Review of the Ambient Air Quality Standard: Nitrogen Dioxide (NO2)
Staff Report and Technical Support Document

This page reviewed November 25, 2009.

The staff of the Air Resources Board (ARB) in consultation with the Office of Environmental Health Hazard Assessment (OEHHA) are currently reviewing the California Ambient Air Quality Standard (AAQS) for nitrogen dioxide (NO2).

Based on the results of the staff review, the ARB staff is recommending that the existing NO2 standard be as follows:


Lower the existing 1-hour-average standard for nitrogen dioxide to 0.18 ppm, not to be exceeded.


Establish a new annual average standard for nitrogen dioxide at 0.030 ppm, not to be exceeded.   
Staff have completed their review of the scientific literature on NO2. This review includes infomation on the human health effects, welfare effects (animal, ecological, environmental), public exposure, and atmospheric chemistry of NO2. The findings of that review are contained in a Staff Report and Technical Support Document which are available below.

The staff recommendation to amend the State nitrogen dioxide standard is scheduled for consideration by the ARB at a public hearing on February 22, 2007. The release of the Staff Report on January 5, 2007 begins the official 45-day comment period prior to the Board meeting. The public may present comments relating to this matter orally or in writing at the hearing, and in writing or by email before the hearing. To be considered by the Board, written submissions not physically submitted at the hearing must be received no later than 12:00 noon, February 21, 2007, and addressed to the following:

Postal mail is to be sent to:

Clerk of the Board
Air Resources Board
1001 I Street, 23rd Floor
Sacramento, CA 95814

Electronic mail is to be sent to: and received at the ARB no later than 12:00 noon, February 21, 2007.

Facsimile transmissions are to be transmitted to the Clerk of the Board at (916) 322-3928 and received at the ARB no later than 12:00 noon February 21, 2007.

NO2 Standard Staff Report and Technical Review Document

Staff Report Complete Staff Report (291B - PDF)
Technical Support Document Complete Technical Support Document (5,245KB - PDF)

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


Ambient Air Quality Standards
Nitrogen Dioxide Review Schedule