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. Region IX. This polygon shapefile represents nonattainment areas for carbon monoxide (CO) in EPA Region 9, including California, Nevada and Arizona, for 2011.... United States. Environmental Protection Agency. Region IX.