UNITED STATES EN VI RONMENTAL PROTECTION AGENC Y WASHINGTON, D.C. 20460

The Honorable Matt Mead Governor of Wyoming 200 West 24th Street Cheyenne, Wyoming 82002-0010
Dear Governor Mead: 

## · DECt 

## 8 20H THE ADMINISTRATOR

I am writing to summarize the U.S. Environmental Protection Agency ' s recent action to address fine particle pollution in your state. As required by the Clean Air Act , the EPA has determined which areas are meeting the national ambient air quality standards for fine particle pollution and which areas must take steps to reduce emissions that contribute to violations of the standard

. On December 14,20 12, the EPA st rengthened the annual, health-based fine particle standard from 15.0 micrograms per cubic meter (J..tg/m3 ) to 12.0 J..t g/ m3

. Thousands of scientific studies have linked exposure to these tiny particles-approximately 1130th the si ze of a human hair-with serious human health problems including premature death in peopl e with heart and lung disease , nonfatal heart attacks , and increased hospital admissions and doctor and emergency room visits for respiratory and cardiovascular disease.
I appreciate the information you and your staff have shared with the EPA throughout this process to assess fme particle pollution levels in communities across your state and the impact of emission sources that cou ld be contributing to unhealthy air. After considering your recommendations , reviewing the most recent certified fine particle air quality data for your state and evaluating factors to assess contribution to nearby levels of fine particl e pollution, I have determined that no area within Wyoming violates the 2012 standard or contributes to a nearby vio lation of the standard. As a result , the EPA is designating all of Wyoming " unclassifiable/attainment. " Because air quality monitoring for 2014 is nearl y complete, ifa state or tribe reque sts it, the EPA will evaluate the status of an area based on its annual fine particle monitoring data for 2012-2014. I f you would like the EPA to re-evaluate any areas within your state, please submi t to the EPA , complete, quality

-assured and certified air quality data for 2014 by February 27, 2015. The EPA shares responsibility with the stat es and tribes for managing particle pollution levels. Efforts by states and tribes to attain the 1997 and 2006 fine particle pollution standard s are already working to reduce unhealthy levels of fin e particle pollution. In addition , current a nd upcoming federal standards and safeguards, including pollution reduction rules for power plants, vehicles and fuels will assure steady reductions of fine particle pollution and will protect public health in communities across the country.

Internet Address (URL) • http :// www
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.gov Recycled/Recyclable • Pri nted with Vegetable O i l Based Inks on 100% Postconsumer, Process Ch l orine Free Recycled PaperTogether, we have made considerabl e progress to reduce fme particle pollution. Nationwide, monitored levels of fine particle pollution fell 34 p ercent since 2000 when we first began nationwide monitoring for particles of this size. I am confiden t this progress will accelerate as together we continue to work towards our shared goal of clean air. For additional information about th ese designations, please visit our website at: www . epa . gov / pmdesignations .

If you have questions or concerns, please contact me or your staff may contact Mark Rupp , Deputy Associate Administrator for Intergovernmental Relations, at rupp.mark @ epa.gov or at (202) 564-7178.