<prompt> 1 part per million fluoride is:1 mg in 10 L of water1 mg in 1 L of water10 mg in 1 L of water100 mg in 10 L of water  <response>: 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 mgliter. 