SAN FRANCISCO— The U.S. Environmental Protection Agency declared a portion of Western Pinal County, Ariz. to be in nonattainment for the 1987 federal PM10 coarse particulate matter standard.

The redesignation is based on EPA’s October 2010 proposal and recent air quality monitoring data for PM10. Based on comments in response to the 2010 proposal, EPA reduced the size of the nonattainment area, relative to its proposed nonattainment area, by about 36 percent. Monitoring results showed widespread, frequent, and in some instances, severe, violations over the last decade. In fact, western Pinal County PM10 levels are among the worst in the country.

The Clean Air Act requires the state to submit a plan containing measures that will reduce airborne particulate matter until the area meets the federal air quality standard. The plan is due within 18 months and the EPA is working closely with the Arizona Department of Environmental Quality on the plan and expects a submission soon. The primary causes of dust pollution in the Pinal County area are from roads, agriculture, feedlots, construction and industrial processes.

For more information including a link to a map of the nonattainment area, please visit: http://www.epa.gov/region9/air/az/pinal/index.html