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 Audubon County, Iowa, and

Benton County, Iowa, give the percentage contributions from specific air pollution sources.  The Audubon County Seat is Audubon, Iowa, and the Benton County Seat is Vinton, Iowa.