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 Fond du Lac County, Wisconsin, and

Forest County, Wisconsin, give the percentage contributions from specific air pollution sources.  The Fond du Lac County Seat is Fond du Lac, Wisconsin, and the Forest County Seat is Crandon, Wisconsin.