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 Cuming County, Nebraska, and

Custer County, Nebraska, give the percentage contributions from specific air pollution sources.  The Cuming County Seat is West Point, Nebraska, and the Custer County Seat is Broken Bow, Nebraska.