2011. United States. Environmental Protection Agency. Region IX. This polygon shapefile shows designated areas for particulate matter < 10 microns according to the 24-Hour National Ambient Air Quality Standard... California. Air Resources Board.
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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. United States. Environmental Protection Agency, Region IX. This polygon shapefile contains designated areas for particulate matter < 2.5 microns, according to the annual National Ambient Air Quality Stan... United States. Environmental Protection Agency, Region IX.