UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

The Honorable John Hickenlooper Governor ofColorado 136 State Capitol Denver, Colorado 80203-1792 Dear Governor Hickenlooper: 

# llC 1 8 2014

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 ofthe standard. On December 14, 2012 , the EPA strengthened the annual, health-based fine particle standard from 15.0 micrograms per cubic meter (l!g/m3) to 12.0 l!g/m3

. Thousands of scientific studies have linked exposure to these tiny particles-approximately 1/30th the size ofa human hair-with serious human health problems including premature death in people 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 staffhave shared with the EPA throughout this process to assess fine particle pollution levels in communities across your state and the impact ofemission sources that could 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 offine particle pollution, I have determined that no area within Colorado violates the 20 12 standard or contributes to a nearby violation ofthe standard. As a result, the EPA is designating all of Colorado "unclassifiablei attainment." Because air quality monitoring for 2014 is nearly complete, ifa state or tribe requests it, the EPA will eva! uate the status ofan area based on its annual fine particle monitoring data for 2012-2014. If you would like the EPA to re-evaluate any areas within your state, please submit to the EPA, complete, quality-assured and certified air quality data for 2014 by February 27 , 2015. The EPA shares responsibi lity with the states and tribes for managing particle pollution levels. Efforts by states and tribes to attain the 1997 and 2006 fine particle pollution standards are already working to reduce unhealthy levels of fine particle pollution. In addition, current and upcoming federal standards and safeguards, including pollution reduction rules for power plants , vehicles and fuels will assure steady reductions offine particle pollution and will protect public health in communities across the country.

Internet Address (URL) • http://www

. epa .gov Recycled/Recyclable • Printed with Vegetable 01 1 Based Inks on 100% Postconsumer, Process Chlorine Free Recycled PaperTogether, we have made considerable progress t o reduce fine particl e pollution. Nationw ide , monitored leve l s of fine particle pollution fell 34 percent since 2000 when we first began na t ionwide monitor i ng

for particles of t hi s s i ze . I am confident this progress will acce l erate as together we continue to work towards our s har e d goal of clean air. For additional ' inform at ion about th e se designations , p l ease visit our webs i te at: www.epa.gov / pmdesignations .

If you have questions or concerns, please contact me or your staff may contact M ark Rupp, Deputy Associate Administrator for Int ergovernmen ta l Rela t ions , at rupp.mark@.epa.gov or at (202) 56 4 -7 178 . Since r ely ,