This polygon shapefile contains designated areas for particulate matter < 2.5 microns, according to the annual National Ambient Air Quality Standards (NAAQS) standard of 15 ug/m3. Designated area coverage is EPA Region 9 including Hawaii, California, Nevada, and Arizona.Non-Attainment areas are geographic areas which have not met National Ambient Air Quality Standards for Particulate Matter air pollution. These standards are part of the Clean Air Act. See Code of Federal Regulations, Section 40 Part 81, for detailed information about Ambient Air Quality Standards. This data set is specifically designed for use with Arc/Info and related software. Data may be used for reference to boundaries of attainment areas in Region 9. These data are intended for small scale mapping. U.S. Environmental Protection Agency, Region 9 GIS Center. (2011). Annual Particulate Matter (Annual PM-2.5) Non-Attainment Designations in Region 9, 2011. California Air Resources Board. Available at: http://purl.stanford.edu/mh274gx7614 This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.