The California Air Districts layer is a polygon shapefile coverage representing the California air pollution control and air quality management districts, as defined in federal and state law. See 40 CFR, Chapter I Section 81, et seq., and California Health and Safety Code, Section 40000 et seq. Air districts identify the local and regional authorities who have primary responsibility for control of air pollution from sources that are not motor vehicles. This layer shows the air district boundaries and their names as of March 2004. Air Districts are designated pursuant to federal and state statute. Air districts identify the local and regional authorities who have primary responsibility for control of air pollution from sources that are not motor vehicles. (Motor vehicles are the responsibility of the state Air Resources Board.) Teale Data Center GIS Lab. California Air Resources Board. (2004). California Air Districts, 2004. California Air Resources Board. Available at: http://purl.stanford.edu/vc226fs6069. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.