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

The Honorable Mark Dayton Governor of Minne sota 116 Veterans Service Building 20 W 12th Street St. Paul, Minnesota 55155 Dear Governor Dayton: 

## DEC 1 

## 8 2 014 THE ADM I NISTRATOR

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 th e national ambient air quality standards for fine particle pollution and which areas must take step s to reduce emiss ion s 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 ( !lg/m3 ) to 12.0 11g/m3

. Thousands of scientific studies have linked expo sure to these tiny particles-

- approximately l /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 incr eased 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 fin e 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 Minnesota violates the 2012 standard or contributes to a nearby violation of the standard. As a result, the EPA is designating all of Minnesota " unclassifiable /attainment. " Because air quality monitoring for 2014 is nearly comp lete, if a state or tribe requests it, the EPA will evaluat e 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, comp lete, quality

-assured and certified air quality data for 2014 by February 27,20 15. 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 standard s 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) • h llp : //www.epa

.gov Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled PaperTogether, we have m ade considerable progress to reduce fine particle pollution . Nationwide , monitored levels of fine particle pollut ion fell34 p ercent since 2000 when we fi r st began nationwide monitoring for particles of this size . I am confiden t this progress will acce l erate as together we continue to work towards our shared goal of clean air. For additional informa tion about the se designations , please visit our website at: www . epa . gov / pmdesignations .

If you have questions or concerns , ple as e contact me or your s taf f may contact Mark Rupp , Deputy Associate Administrator for Intergov e rnmental Relations , a t rupp.mark@epa.gov or at (202) 564-7178.