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

Petroleum County, Montana; Phillips County, Montana; and Pondera County, Montana.  The Petroleum County Seat is Winnett, Montana; the Phillips County Seat is Malta, Montana; and the Pondera County Seat is Conrad, Montana.