EPA is designating 31 areas across the country as not meeting the agency’s daily standards for fine particle air pollution (PM 2.5), or particulate matter. Particulate matter, which is emitted by power plants, factories and motor vehicles, can cause a number of serious health problems including aggravated asthma, increased hospital admissions and emergency room visits, heart attacks and premature death. These areas, made up of 120 full or partial counties, were designated as “nonattainment” because their 2006 to 2008 air quality monitoring data showed that they did not meet the agency’s health-based standards.

In December 2008, after closely reviewing recommendations from states and tribes along with public comments, EPA identified attainment and nonattainment areas based on air quality monitoring data from 2005 through 2007. The December 2008 designations were never published in the Federal Register and have been under review. Because the 2008 air quality data is the most recent, EPA used this data to make final designations.

Using the 2006 to 2008 data, 91 U.S. counties that were identified as nonattainment in December 2008 are now meeting the standards. The new data also showed that four new counties in three states are violating the daily PM 2.5 standards, the annual PM 2.5 standards, or both. EPA will work with these four counties to evaluate air monitoring data and other factors to make final designations by early 2010.

Nonattainment areas include counties with monitors showing violations of the standards and the nearby areas that also contribute to that violation. Affected states and tribes will be required to take steps to reduce the pollution that forms fine particles. The majority of U.S. counties and tribal lands are meeting these standards, but will need to continue working to maintain clean air.

In 2006, EPA strengthened the 24-hour fine particle standards from 65 micrograms per cubic meter to 35 micrograms per cubic meter of air to protect public health. Nationwide, monitored levels of fine particle pollution fell 19 percent from 2000 to 2008. Fine particles can either be emitted directly from power plants, factories, and motor vehicles, particularly diesel trucks and buses, or they can form in the atmosphere from reactions of sulfur dioxide and nitrogen oxides.

More information on the designations: