UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

The Honorable John Hickenlooper 

Governor of Colorado 

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 of the 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 of a 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 staff have shared with the EPA throughout this process to 

assess fine particle pollution levels in communities across your state and the impact of emission 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 of fine particle pollution, I have determined that no area within Colorado violates the 2012 

standard or contributes to a nearby violation of the standard. As a result, the EPA is designating all of 

Colorado "unclassifiab lei attainment." 

Because air quality monitoring for 2014 is nearly complete, if a state or tribe requests it, the EPA will 

eva! uate the status of an 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 responsibility 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 of fine particle pollution and will protect public health in communities across the 

country. 

Internet Address (URL) • http://www.epa.gov 

Recycled/Recyclable • Printed with Vegetable 011 Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper 
Together, we have made considerable progress to reduce fine particle pollution. Nationwide, monitored 

levels of fine particle pollution fell 34 percent since 2000 when we first began nationwide monitoring 

for particles of this size. I am confident this progress will accelerate as together we continue to work 

towards our shared goal of clean air. For additional 'information about these 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. 

Sincerely,