Establishes maximum contaminant levels in drinking water for certain per- and polyfluoroalkyl substances (PFAS); sets such levels at 4 parts per trillion (ppt) for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) and 10 parts per trillion (ppt) for perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS), hexafluoropropylene oxide dimer acid (HFPO-DA), and perfluorobutane sulfonate (PFBS).