Abstract: The Environmental Protection Agency (EPA) compiles data on emission tonnages of air pollutants for US counties.  US Air Quality Gradebook ("AirGrades") source sheets give the percentage contributions from specific air pollution sources.  This source sheet is for

Ravalli County, Montana; Richland County, Montana; and Roosevelt County, Montana.  The Ravalli County Seat is Hamilton, Montana; the Richland County Seat is Sidney, Montana; and the Roosevelt County Seat is Wolf Point, Montana.