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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. 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.