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

Silver Bow County, Montana; Stillwater County, Montana; and Sweet Grass County, Montana.  The Silver Bow County Seat is Butte, Montana; the Stillwater County Seat is Columbus, Montana; and the Sweet Grass County Seat is Big Timber, Montana.