UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 8 

Ref: 8P-AR 

The Honorable Matthew H. Mead 

Governor of Wyoming 

State Capitol 

Cheyenne, Wyoming 82002 

Dear Governor Mead: 

1595 Wynkoop Street 

DENVER, CO 80202-1129 

Phone 800-227-8917 

http://www.epa.gov/region08 

AUG 1 9 2014 

Thank you for your recommendations dated December 13, 20 13 of air quality designations for the 2012 

revised primary annual fine particle (PM2.s) National Ambient Air Quality Standard (NAAQS) 

throughout Wyoming. I appreciate the information Wyoming shared with the U.S. Environmental 

Protection Agency as we move forward to improve PM2.s air quality. This letter is to notify you of the 

EPA's preliminary response to Wyoming's recommendations and to inform you of our approach for 

completing the initial area designations for the 2012 revised primary annual PM2.s standard. 

On December 14, 2012, the EPA promulgated a revised primary annual PM2.s NAAQS (78 FR 3086, 

January 15, 2013). In that action, the EPA revised the primary annual PM2.s standard, strengthening it 

from 15.0 micrograms per cubic meter (!lg/m3

) to 12.0 !lg/m3; retained the existing 24-hour PM2.s 

standard at 35 !lglm3 ; retained the existing 24-hour PM10 (coarse particle) standard at 150 !lg/m3

; and 

retained the current suite of secondary PM standards. The EPA revised the primary annual PM2.s 

standard based on an integrated assessment of an extensive body of new scientific evidence, which 

substantially strengthens our body ofknowledgeregarding PM2.s-related health effects. The revised 

primary annual PM2.s standard will provide increased protection for children, older adults, persons with 

pre-existing heart and lung disease, and other at-risk populations against an array ofPM2.s-related 

adverse health effects, including premature mortality, increased hospital admissions and emergency 

department visits, and development and exacerbation of chronic respiratory disease. 

History shows us that better health and cleaner air go hand-in-hand with economic growth. Working 

closely with the states and tribes, the EPA is implementing the standards using a commonsense approach 

that improves air quality and minimizes the burden on state, local, and tribal governments. As part of 

this routine process, the EPA is working with the states and tribes to identify areas in the country that 

meet the standards and those that need to take steps to reduce PM2.s air pollution. Within one year of 

promulgating a new or revised air quality standard, the Clean Air Act (CAA) requires the governor of 

each state to submit to the EPA a list of all areas in the state, with a designation recommendation for 

each area. As a first step in implementing the 2012 annual PM2.s standard, governors were to submit 

their designation recommendations, including appropriate area boundaries, by December 13, 2013. 
As required by the CAA, the EPA then promulgates designations for all areas across the country. The 

EPA designates an area as "nonattainment" if it is violating the 2012 annual PM2.s NAAQS or if it is 

contributing to a violation of the NAAQS in a nearby area. Consistent with designations for previous 

PM2.s standards, the EPA intends to use a designation category of "unclassifiable/attainment" for areas 

that are monitoring attainment or do not have monitors, but for which the EPA has reason to believe are 

likely attainment and are not contributing to nearby violations. Additionally, the EPA intends to 

designate as "unclassifiable" those areas where the EPA cannot determine based on available 

information whether the area is meeting the NAAQS or where EPA has not determined that the area 

contributes to a nearby violation. At this time, the EPA is proceeding with intended initial area 

designations using quality-assured, certified air quality monitoring data from 2011 to 2013. 

We have considered the annual PM2.s designation recommendations submitted by Wyoming on 

December 13, 2013, and have reviewed the relevant technical information, including 2011-2013 air 

quality data. These data do not indicate any violation ofthe 2012 annual PM2.s NAAQS in Wyoming or 

contribution to any nearby area. Accordingly, the EPA intends to designate the entire state of Wyoming 

as unclassifiable/attainment. 

The EPA will make its preliminary designation decisions and supporting documentation available to the 

general public for review and comment. We will be announcing a 30-day public comment period shortly 

in the Federal Register. After considering the additional information we receive, the EPA plans to 

promulgate final annual PM2.s designations in December of 2014. 

The EPA is committed to working with the states and tribes to share the responsibility of reducing PM2.s 

air pollution. Current and upcoming federal standards and safeguards- including pollution reduction 

rules for power plants, vehicles, and fuels - will ensure steady progress to reduce PM2.s-forming 

pollution and will protect public health in communities across the country. We look forward to a 

continued dialogue with you and your staff as we work together to implement the 2012 annual PM2.s 

standard. Should you have any questions, please do not hesitate to contact me, or have your staff contact 

Crystal Ostigaard of my staff at (303) 312-6602 or ostigaard.crystal@epa.gov. 

Shaun L. 

Regional Administrator 

cc: Todd Parfitt, Director, WDEQ 

Steven A. Dietrich, Administrator, AQD 

Janet G. McCabe, Acting Assistant Administrator for Air and Radiation 

Stephen D. Page, Director, Office of Air Quality Planning and Standards