This polygon shapefile displays particulate matter &lt; 10 microns (PM 10) area designations pursuant to 40CFR81.305, the federal national ambient air quality standard which monitors pollutants in accordance with the Clean Air Act. There are three designation categories: nonattainment, unclassifiable and attainment areas. Non-attainment areas are those which are in violation of the standard. Nonattainment areas have various classifications. Each designation and classification area has an associated date field that represents the "effective" date of the action as published in 40CFR81.305. This data layer is current as of November 2003. Projection: Teale Albers, NAD83 Designation areas are defined purThis shapefile can be used to identify designation areas that are defined pursuant to the corresponding federal national ambient air quality standard for inhalable coarse particles (PM 10) as per the Clean Air Act.suant to the corresponding federal national ambient air quality standard for each pollutant as per the Clean Air Act. Teale Data Center GIS Lab. California Air Resources Board. (2003). Federal Particulate Matter (PM10) Area Designations: California, 2003. California Air Resources Board. Available at: http://purl.stanford.edu/gn558bp2442. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.