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 Slope County, North Dakota, and

Stark County, North Dakota, give the percentage contributions from specific air pollution sources.  The Slope County Seat is Amidon, North Dakota, and the Stark County Seat is Dickinson, North Dakota.