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.
2002. Stephen P. Teale Data Center (Calif.). and California. Air Resources Board. Planning and Technical Support Division. This point shapefile represents all air monitoring stations active in California from 2001 until 2003. The data within the shapefile was obtained f... California. Air Resources Board.