Dental General 2ac9f51a 1 part per million fluoride is: A 1 mg in 10 L of water B 1 mg in 1 L of water C 10 mg in 1 L of water D 100 mg in 10 L of water High-Yield Explanation ppm (or ppmm) is used to measure the concentration of a contaminant in soils and sediments. In that case, 1 ppm equals 1 mg of substance per liter of solid (mg/liter).