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 Throckmorton County, Texas, and

Titus County, Texas, give the percentage contributions from specific air pollution sources.  The Throckmorton County Seat is Throckmorton, Texas, and the Titus County Seat is Mount Pleasant, Texas.