THE ADMINISTRATOR OF THE ENVIRONMENTAL PROTECTION AGENCY 

The Honorable Lynn Valbuena 

Chairwoman of San Manuel Band 

of Serrano Mission Indians 

26569 Community Center Drive 

Highland, California 92346 

Dear Chairwoman Valbuena: 

WASHINGTON, D.C. 20460 

'D£c 1 B 2074 

I would like to summarize the U.S. Environmental Protection Agency's recent action to address fineparticle pollution on your reservation. 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. 

The EPA on December 14, 2012, strengthened the annual, health-based fine-particle standard from 15.0 

micrograms per cubic meter (J..lg/m3

) to 12.0 J..lg/m3. Thousands of scientific studies have linked exposure 

to these tiny particles - approximately 1130th the size of a human hair- with serious 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 reservation and the impact of emission 

sources that could be contributing to unhealthy air. After reviewing the most recent certified fineparticle air-quality data for the state of California and evaluating factors to assess contribution to nearby 

levels of fine particle pollution, I have determined that some areas in California do not meet the 2012 

annual fine particle standard or they contribute to a nearby violation of the standard. The EPA is 

designating those areas "nonattainment." Some of these areas also include areas of Indian country, 

including the reservation of the San Manuel Band of Serrano Mission Indians. Nonattainment areas will 

be required to take action to reduce fine-particle pollution and meet the standard no later than 2021. As 

required by the Clean Air Act, those actions may include stricter controls on industrial facilities and 

additional planning requirements for transportation-related sources. While tribes are not required to take 

actions, the EPA will work with tribes to develop plans as necessary or appropriate to ensure tribal areas 

meet the standard no later than 2021. 

Because air-quality monitoring for 2014 is nearly complete, the EPA, at a tribe's request, will evaluate 

the status of an area based on its annual fine-particle-monitoring data for 2012-14. If you would like the 

EPA to re-evaluate any areas within your reservation, please submit complete, quality-assured and 

certified air-quality data for 2014 to the EPA by February 27,2015. 

I recognize that 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 

This paper is printed with vegetable-oil-based inks and is 100-percent postconsumer recycled material. chlorine-free-processed and recyclable. 
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 ensure steady reductions of fine-particle pollution and will protect public health in communities 

across the nation. 

Together we have made considerable progress in reducing fine-particle pollution. Nationwide 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. 

Sincerely,