UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
 

REGION IX
 

75 Hawthorne Street
 

San Francisco, CA 94105·3901
 

OFFICE OF THE 

REGIONAL ADMINISTRATOR JUN 2 9 2011 

The Honorable Janice Brewer 

Governor of Arizona 

1700 West Washington 

Phoenix, Arizona 85007 

Dear Governor Brewer: 

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

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

Standard (NAAQS) for nitrogen dioxide (N02) 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 previous recommendations, to provide you an opportunity to revise your previous 

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

designations for the revised N02 NAAQS. 

On January 22, 2010, the EPA strengthened the health-based NAAQS for N02 by setting a new I-hour 

N02 standard at the level of 100 parts per billion (ppb). The EPA also retained the annual N02 standard 

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

peak concentrations of N02 and by limiting community-wide N02 concentrations to levels below those 

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

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

monitoring and reporting requirements for N02. 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 N02 that occur more 

broadly across communities. 

In our November 2010 letter to you requesting your 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 N02 NAAQS. The EPA 

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

requirements associated with the revised N02 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 

N02monitors in the existing N02network do not provide adequate evidence to determine whether or 

not the new NAAQS is met at other locations, especially those closer to N02 emission sources such as 

roadways. 

After reviewing all the recommendations we received including Arizona'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 N02 NAAQS. While the EPA acknowledges that the existing N02 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 Arizona as unclassifiable/attainment using the boundaries you 

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 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 Arizona and the general public by 

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

Thank you again for your January 2011 recommendations for designations for the new I-hour NO2 

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:	 Henry Darwin, 

Director, ADEQ 

Eric Massey 

Director, Air Quality Division, ADEQ 

Nancy Wrona 

Policy Advisor, ADEQ