On March 14, 2023, EPA proposed the first national primary drinking water standards for six PFAS.
The EPA proposal establishes maximum contaminant levels goals (MCLGs) and maximum contaminant levels (MCLs) for six PFAS. Individual MCLGs and MCLs are proposed for both PFOA and PFOS on the EPA’s determination that these compounds are carcinogenic. An additional MCLG and MCL has been proposed for PFHxS, PFNA, PFBS, and HFPO-DA using a hazard index of 1.0. A hazard index is a tool used to evaluate combined risk from exposure to a mixture of contaminants. It is determined by adding hazard quotients for each PFAS, which are calculating by dividing the concentration of the PFAS by the health-based water concentration (HBWC). The HBWC for each PFAS respectively is 9.0 ppt for PFHxS, 10.0 ppt for GenX and PFNA each, and 2,000.0 ppt for PFBS.
The proposal also includes the following requirements for water systems:
- Initial Monitoring: Large groundwater systems serving greater than 10,000 people and surface water systems will need to complete quarterly monitoring over a 12-month period using either EPA Method 533 or 537.1. Small groundwater systems serving less than 10,000 people will need to complete monitoring twice over a 12-month period. Initial monitoring will need to be complete within 3 years of the final rule. Previous monitoring results from state or national monitoring programs may be used.
- Compliance Monitoring: Water systems will be required to monitor quarterly initially but will be eligible for reduced monitoring if PFAS levels are less than one-third of the MCLs. Compliance will be determined based on a running annual average.
- Public Notification: Water systems will be required to notify the public within 30 days of any PFAS MCL violations. Systems must also report compliance monitoring results as part of their Consumer Confidence Reports.
Small System Compliance Technologies: In addition to the use of GAC, IX, NF, and RO as BATs for water systems, EPA provides for smaller systems serving less than 3,300 people to use point-of-use (POU) RO and NF filters to comply with the rule. It is important to note that POU filters are currently not certified by NSF/ANSI for removal of PFAS to levels below the proposed standards.
The proposal is not yet finalized and is subject to changes based on comments from the public. The EPA intends to finalize the rule the end of 2023 or early 2024.