Abstract: The Environmental Protection Agency (EPA) compiles data on emission tonnages of air pollutants for US counties.  US Air Quality Gradebook ("AirGrades") source sheets such as this one for Pitkin County, Colorado, and

Prowers County, Colorado, give the percentage contributions from specific air pollution sources.  The Pitkin County Seat is Aspen, Colorado, and the Prowers County Seat is Lamar, Colorado.