EPA to Brief NDWAC on Proposed PFAS MCLs

On August 8, 2023, from 10:30 am to 5 pm (ET) EPA will hold a public (virtual) meeting with the National Drinking Water Advisory Council (NDWAC or Council). The stated purpose of the meeting is to “…update the Council on Safe Drinking Water Act programs and to consult with the NDWAC as required by the SDWA on a final National Primary Drinking Water Regulation (NPDWR) for per- and polyfluoroalkyl substances (PFAS).” Link to copy of Federal Register notice (Fed Reg EPA to Brief NDWAC on Proposed PFAS MCLs ). Information on how to register to join the public meeting will be posted at the following location:
(Registration information has not yet been posted)

Background on Proposed MCLs for PFAS
On March 29, 2023 EPA published for public review and comment, proposed MCLs of 4 parts per trillion (ppt) for PFOA and 4 ppt for PFOS. EPA also proposed “….to use a Hazard Index (HI) approach to protecting public health from mixtures of PFHxS, HFPO-DA and its ammonium salt, PFNA, and PFBS because of their known and additive toxic effects and occurrence and likely co-occurrence in drinking water.”

Proposed Definition of Hazard Index: “Hazard index (HI) is the sum of component hazard quotients (HQs), which are calculated by dividing the measured regulated PFAS component contaminant concentration in water (e.g., expressed as ppt) by the associated Health-Based Water Concentration (e.g., HBWC expressed as ppt). For PFAS, a mixture HI greater than 1.0 is an exceedance of the MCL.” [emphasis added]

How To Calculate the Hazard Index: Steps to calculate the HI: “….a ratio called a hazard quotient (HQ) is calculated for each of the four PFAS (PFHxS, HFPO-DA and its ammonium salt (also known as GenX chemicals), PFNA, and PFBS) by dividing….the measured level of each of the four PFAS in drinking water, by a health reference value for that particular PFAS. For health reference values, in this proposal, EPA is using Health Based Water Concentration (HBWCs) as follows: 9.0 ppt for PFHxS, 10.0 ppt for HFPO-DA; 10.0 ppt for PFNA; and 2000 ppt for PFBS. The individual PFAS ratios (HQs) are then summed….to yield the HI. If the resulting HI is greater than one (1.0), then the exposure metric is greater than the health metric and potential risk is indicated

The public comment period for the proposed PFAS MCLs closed May 30, 2023.