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 setting an MCL which it is not required to do when setting a HAL. U.S. EPA’s proposed maximum contaminant level goal (MCLG) for these specific PFAS which doesn’t need to consider technical feasibility of cost is “0”. With respect to its previously issued HALs, U.S. EPA specifically noted that following receipt of public comments and finalization of the PFAS MCL, it will decide whether to update or remove the HALs for PFOA and PFOS.
U.S. EPA’s draft rule also proposes to regulate several additional PFAS, including hexafluoropropylene oxide dimer acid (commonly referred to as GenX), perfluorononanoate (PFNA), perfluorohexanesulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS). Rather than proposing an MCL for these PFAS, U.S. EPA instead seeks to regulate these PFAS utilizing a hazard index which is a screening level approach that provides a risk indicator rather than a risk estimate for a mixture of components.
This hazard index approach is sometimes used by other federal agencies, including the Agency for Toxic Substances and Disease Registry. Under this hazard index approach, U.S. EPA has identified health-based water concentrations (HBWCs) (i.e., the level at which no health effects are expected for that PFAS) for PFHxS (9 ppt); GenX (10 ppt), PFNA (10 ppt) and PFBS (200 ppt). The detected concentration of each PFAS in drinking water is then divided by the HBWC to get a individual hazard quotient (HQ). The hazard index is the summation of each of these HQs—if the hazard index value exceeds 1.0, then that would be an exceedance of the MCL.
The MCLs will become effective three years after they are finalized. At that time, public drinking water systems will be obligated to test for these specific PFAS and take steps to mitigate any exceedances that are identified.
U.S. EPA has proposed a 60-day comment period on the draft rule; however, in light of what are expected to be significant public comments, it is likely that this comment period will be extended.
We will continue to provide timely updates on U.S. EPA’s ongoing efforts to regulate PFAS under the various environmental statutes at the Corporate Environmental Lawyer.
[View source.]
