How Low Did U.S. EPA Go--U.S. EPA Issues Its Long-Awaited Draft PFAS Drinking Water Standards

Almost two years to the date after U.S. EPA issued its regulatory determination for contaminants on the forth Contaminant Candidate List, U.S. EPA has issued its draft rule setting drinking water limits for several PFAS compounds. Specifically. U.S. EPA's draft rule proposes a four part per trillion (ppt) maximum contaminant level (MCL) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). According to an U.S. EPA fact sheet that accompanied the proposed rule, the four ppt level is the lowest concentration that can be reliably detected within "specified limits of precision and accuracy during routine laboratory operations conditions".

These proposed MCLs are higher than U.S. EPA's previously issued health advisory levels (HALs) of 0.004 ppt for PFOA and 0.02 ppt for PFOS. The reason for the higher proposed MCL levels is due in large part to the fact that U.S. EPA is required to consider available treatment technologies and treatment costs when