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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

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Q WASHINGTON, D.C. 20460 

JAN z s Zo» 

THE ADMINISTRATOR 

The Honorable Jerry Brown 

Governor of California 

State Capitol, Suite 1173 

Sacramento, CA 95814 

Dear Governor Brown : 

Based on 2006-2008 air quality data, the U.S . Environmental Protection Agency (EPA) 

has determined that Plumas and Shasta and the 8 surrounding counties (Lassen, Modoc, Sierra, 

Siskiyou, Tehama, and Trinity, and the deferred portions of Butte and Yuba) in California meet 

the 2006 24-hour fine particle (PMZ,5) national ambient air quality standards (NAAQS). These 

counties are linked because they impact air quality monitored in Plumas and Shasta Counties . As 

directed by the Clean Air Act, EPA is designating these counties as "unclassifiable/attainment" 

for those standards. Congratulations on this good news. Note that the portions of Butte and 

Yuba counties that were previously designated as part of the Chico and Yuba City-Marysville 

nonattainment areas, respectively, retain that designation. 

Fine particle pollution represents one of the most significant barriers to clean air facing 

our nation today. Health studies link these tiny particles - about 1/30t1' the diameter 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. On October 17, 2006, EPA strengthened 

the primary and secondary 24-hour PMZ,5 NAAQS from 65 pg/m3 to 35 iug/m3 . 

In November 2009, EPA deferred final designations in these counties so that tile Agency 

could collect and evaluate additional information about monitored air quality in Plumas and 

Shasta Counties. At that time, the California Air Resources Board (ARB) requested that EPA 

exclude certain monitored violations in these counties consistent with the "Treatment of Data 

Influenced by Exceptional Events" rule (the Exceptional Events Rule). Following a review of 

the exceptional event claims and supporting documentation, EPA agreed with the ARB claims as 

documented in letters dated March 11, 2010 and April 2, 2010 from Jared Blumenfeld, Regional 

Administrator, EPA Region 9, to Mary D. Nichols, Chairman, California ARB . After excluding 

the data collected on days with exceptional events, the 2006-2008 air quality in Plumas and 

Shasta counties meets the 24-hour PM2.5 standards. Your staff may find additional technical 

information regarding the designations at lhttp ://www.epa. 7ov/pmdesignations . 

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

Recycled/Recyclable 9 Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper 
Thank you for your continued efforts to improve air quality. Together, we have made 

considerable progress in reducing air pollution and its impacts on public health and the 

environment. If you have further questions, please contact me or your staff may call Sarah 

Hospodor-Pallone, Deputy Associate Administrator for Intergovernmental Relations, at 202-564-

7178 . 

Sincerely, 

c- = 

Lisa P. Jackson