THE ADMINISTRATOR OF THE ENVIRONMENTAL PROTECTION AGENCY

The Honorable Darrell O ' Neal Sr. Chairman ofNorthem Arapaho Tribe P.O. Box 396 Ft. Washakie , Wyomi n g 82514 Dear Chairman O'Neal: WASHINGTON, D.C

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I would like to summarize the U .S. Environmental Protection Agency's recent action to address fin e particle po ll ution on your reservation. As required by the Clean Air Act, the EPA has determined which areas are meeting the national ambient-air-qu ality standards for fine-particle pollution and which areas must take steps to reduce emissions that co ntribute to violations of the s tand ard. The EPA on December 14 , 2012 , strengthened the annual , health-based fine-particle standard from 15.0 microgram s pe r cubic meter (j.! g/ m 3) to 12.0 jlg/ m3

. Thousands o f s cientific studi es have linked expo sure to these tiny p a rticles- appro ximately 1/ 30th the s ize of a human hair

- with seriou s health proble ms including pr e mature death in people with heart and lung disease, nonfatal heart attacks and increas ed hospital adm is s ions and doctor and emergency-room visits for resp iratory and card iovascular dis e ase . I appreciate the information you and your staff have shared with the EPA throughout this proce s s to assess fine-particle -p o llution levels in communities across your res ervation and the impact of emi ss ion sources that could be contributing to unhealthy air. After considering your recommendations , reviewing the most recent certified fine-particle air-quality data for your reservation and evaluating factors to assess contribution to nearby levels of fine-particle pollution, I have determined that no area within the Nort hern Arapaho Tribe reservation violates the 2012 standard or contributes to a nearby v io lation ofthe standard. A s a result, t h e EPA is designating all of the Northern Arapaho Tribe re servation " unclassifi abl e /attainment. " Because air-quality monitoring for 2014 is ne arly complete, the EPA, at a tribe 's r e quest, will evaluate the statu s of an area based on its annual fine-particle-monitoring data for 2012-14. lfyou wou ld like the EPA to re-evaluate any area s within your reservation, please submit comp lete , quality

- assured and certified air-qu a lity data for 2014 to the EPA b y Februar y 27 , 2 015. I recognize that the E PA shares responsibility with the states and tribes for managing particle-pollution levels. E f fort s by states and tribes to attain the 1997 and 2006 fine-particle-pollution standards are already working to redu ce unhealthy levels of fine-particl e pollution. In addition , current and upcoming fede ra l standards and safeguards , including pollution-reduction rules for power plants, vehicles and fuels will ensure s teady reductions of fine-particle pollution and will protect public health in communiti e s across the nation.

This paper is printed with vegetable-oil-based inks and is 100-percent postconsumer recycled material chlorine-free-processed and recyclable

.Together we have made considerable progress in reducing fine-particle pollution. Na t ionwide monitored levels of fine-particle pollution have fallen 34 percent since 2000 when we first began such monitoring for particles of this size. I am confident this progress will continue as we work toward our shared goal of clean air.

For additional information about these designations, please visit www.epa.gov/pmdesignations. Si n ce rel y,