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 ofArizona 1700 WestWashington Phoenix, Arizona 85007
Dear Governor Brewer:
I am writing to notify you ofthe U.S. Environmental Protection Agency's (EPA's) intention to designate all areas ofArizona as unclassifiable/attainmentfor 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 yourprevious recommendations, to provide you an opportunity to revise yourprevious recommendations for area boundaries, and to infonn you ofourapproach for completing the designations for the revised N02NAAQS. On January 22, 2010, the EPA strengthened the health-based NAAQS for N02by setting a new I-hour N02 standard at the level of 100parts perbillion (ppb). The EPA also retained the annual N02standard of53 ppb. This suite ofstandards will protectpublic health by limiting people's exposures to short-term peakconcentrations ofN02and 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 majorroads 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 ofN02that occur more broadly across communities.
In ourNovember2010 letterto you requesting your designation recommendations, the EPA stated that we anticipated designating most areas ofthe 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 N02NAAQS will notbe effective until January 2013, so air quality data from these new monitors would not be available to informinitial designations; and (2) the N02monitors in the existing N02networkdo not provide adequate evidence to determine whether or not the new NAAQS is met at otherlocations, especially those closerto N02 emission sources such as roadways. Afterreviewing all the recommendations we received including Arizona's, the EPA now intends to designate all areas ofthe 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 N02NAAQS. While the EPA acknowledges that the existing N02 monitoring network

Prinud on Rl!Cycltd Papt,.does not provide adequate evidence to determine whether or not the new NAAQS is meteverywhere, there currently is no evidence ofviolations 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 airquality data from the new monitoring network are available. The EPA intends to designate all areas ofArizona 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 thateach state carefully consider the implications ofthe boundaries it selects for its Prevention ofSignificantDeterioration permitting program for new ormodified sources to ensure that they are consistent with its objectives for managing air quality deterioration and economic growth. Ifyour State has additional information that you want the EPA to consider with respect to the designations including any revisions to your recommended boundaries, please submitit 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 oftheir availability is published in the Federal Register. We will review any information we receive from the state ofArizona and the general public by these dates. We plan to promulgate the final designations by October 31, 2011. Thank you again for yourJanuary 2011 recommendations for designations for the new I-hourNO2 NAAQS. Welook forward to a continued dialogue with you and your staffas we work together to implementthis NAAQS. Should you have any questions, please do not hesitate to call me, orhave your staffcontact Deborah Jordan ofmy staffat (415) 947-8715. Sincerely,

cc: HenryDarwin, Director, ADEQ Eric Massey Director, Air Quality Division, ADEQ Nancy Wrona Policy Advisor, ADEQ