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2013. United States. Environmental Protection Agency. Region IX. This polygon shapefile contains nonattainment areas for particulate matter < 10 microns. Nonattainment areas are geographic areas which have not... United States. Environmental Protection Agency. Region IX.
2011. United States. Environmental Protection Agency. This polygon shapefile identifies areas in the U.S. where air pollution levels have not met the 2006 National Ambient Air Quality Standards (NAAQS)... California. Air Resources Board.
2011. Stephen P. Teale Data Center (Calif.). and California. Air Resources Board. Planning and Technical Support Division. This polygon shapefile shows area designations in California as required under Health and Safety Code section 39608 for ozone, nitrogen dioxide, su... California. Air Resources Board.