UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
 

REGION IX
 

75 Hawthome Street
 

San Francisco, CA 94105·3901
 

OFFICE OF THE 

REGIONAL ADMINISTRATOR 

JUN 2 9 2011 

The Honorable Edmund G. Brown, Jr 

Governor of California 

State Capitol Building, Suite #1173 

Sacramento, California 95814 

Dear Governor Brown: 

I am writing to notify you of the U.S. Environmental Protection Agency's (EPA's) intention to designate 

all areas of California as unclassifiable/attainment for the revised primary National Ambient Air Quality 

Standard (NAAQS) for nitrogen dioxide (NOz) using the boundaries your State recommended in 

January 2011 or any revised boundaries that you submit in response to this letter. I am also writing to 

thank you for your State's previous recommendations, to provide you an opportunity to revise these 

previous recommendations for area boundaries, and to inform you of our approach for completing the 

designations for the revised NOz NAAQS. 

On January 22,2010, the EPA strengthened the health-based NAAQS for NOz by setting a new I-hour 

NOz standard at the level of 100 parts per billion (ppb). The EPA also retained the annual NOz standard 

of 53 ppb. This suite of standards will protect public health by limiting people's exposures to short-term 

peak concentrations of NOz and by limiting community-wide NOz concentrations to levels below those 

that have been linked to respiratory-related emergency department visits and hospital admissions in the 

United States. To determine compliance with the new standard, the EPA established new ambient air 

monitoring and reporting requirements for NOzo In urban areas, monitors are required near major roads 

as well as in other locations where maximum concentrations are expected. Additional monitors will be 

required in some large urban areas to measure the highest concentrations of NOz that occur more 

broadly across communities. 

In our November 2010 letter to California requesting designation recommendations, the EPA stated that 

we anticipated designating most areas of the country as "unclassifiable," indicating that there are 

insufficient data to determine whether or not an area is attaining the revised NOz NAAQS. The EPA 

believed this approach was appropriate given that: (1) the new near-road monitoring network 

requirements associated with the revised NOz NAAQS will not be effective until January 2013, so air 

quality data from these new monitors would not be available to inform initial designations; and (2) the 

NOz monitors in the existing NOz network do not provide adequate evidence to determine whether or 

not the new NAAQS is met at other locations, especially those closer to NOz emission sources such as 

roadways. 

After reviewing all the recommendations we received including California's, the EPA now intends to 

designate all areas of the country as "unclassifiable/attainment." The EPA is making this change 

because, based on the most recent air quality data from 2008-2010, all monitored areas in the country 

meet the 2010 NOz NAAQS. Whjle the EPA acknowledges that the existing NOz monitoring network 

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does not provide adequate evidence to determine whether or not the new NAAQS is met everywhere, 

there currently is no evidence of violations anywhere in the country. Based on this, the EPA believes 

"unclassifiable/attainment" is the most appropriate designation to use at this time. The EPA intends to 

redesignate areas, as appropriate, after sufficient air quality data from the new monitoring network are 

available. 

The EPA intends to designate all areas of California as unclassifiable/attainment using the boundaries 

your State recommended to the EPA in January 2011 or any revised boundaries you may provide in 

response to this letter. As we did in our November 2010 letter, EPA recommends that each state 

carefully consider the implications of the boundaries it selects for its Prevention of Significant 

Deterioration permitting program for new or modified sources to ensure that they are consistent with its 

objectives for managing air quality deterioration and economic growth. 

If your State has additional information that you want the EPA to consider with respect to the 

designations including any revisions to your State's recommended boundaries, please submit it to us by 

August 29,2011. We are also making the EPA's preliminary designation decisions and supporting 

documentation available to the general public for review. We are accepting public comments on our 

preliminary decisions for 30 days after the notice of their availability is published in the Federal 

Register. We will review any information we receive from the state of California and the general public 

by these dates. We plan to promulgate the final designations by October 31, 2011. 

Thank you again for California's January 2011 recommendations for designations for the new I-hour 

N02 NAAQS. We look forward to a continued dialogue with you and your staff as we work together to 

implement this NAAQS. Should you have any questions, please do not hesitate to call me, or have your 

staff contact Deborah Jordan of my staff at (415) 947-8715. 

Sincerely, 

cc:	 Linda S. Adams 

Acting Secretary, California EPA 

Mary Nichols
 

Chairman, CARB
 

James Goldstene 

Executive Officer, CARB 

Lynn Terry 

Deputy Executive Officer. CARB 

Kenneth Koyama 

Executive Director, CAPCOA