New PFAS National Primary Drinking Water Regulation Finalized

On April 10, 2024, the United States Environmental Protection Agency (U.S. EPA) finalized the National Primary Drinking Water Standard (NPDWS) for per-and polyfluoroalkyl substances (PFAS). The rule establishes legally enforceable limits, Maximum Contaminant Levels (MCLs), as well as non-enforceable health-based levels, Maximum Contaminant Level Goals (MCLGs). This rule will protect an estimated 100 million people from PFAS contamination in their drinking water.

What PFAS will have limits?

This rule sets individual numeric MCLs for five PFAS: perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid, (PFHxS) and hexafluoropropylene oxide dimer acid (HFPO-DA, also known as “GenX”). The rule also sets a combined MCL for mixtures of any two or more of following four PFAS: PFNA, PFHxS, GenX, and perfluorobutane sulfonate (PFBS). In comparison to the draft published in March 2023 this rule does not include an individual MCL for perfluorobutane sulfonic acid (PFBS), only a mixture containing PFBS.

PFAS mixtures containing at least two or more of PFHxS, PFNA, GenX Chemicals, and PFBS will use a “Hazard Index” MCL to account for the combined and co-occurring levels of these PFAS in drinking water. The Hazard Index (HI) is made up of a sum of fractions. Each fraction compares the level of each PFAS measured in the water to the highest level determined not to have risk of health effects.

To determine HI compliance, calculate the average HI for all the samples taken in the past year and if the running annual average HI is greater than 1.0, it is a violation of the proposed HI MCLs. The final MCLs are shown in the table below.

Additionally, U.S. EPA is setting MCLGs for these PFAS, which are also shown in the table below. Of note, the MCLGs were set at zero parts per trillion (ppt) for PFOA and PFOS.

Am I subject to the new standard?

Any public water system (PWS) is subject to the newly established NPDWS and must monitor for these PFAS. PWSs will have three years to complete initial monitoring (by 2027). Consequently, small community water systems (CWS) and non-transient, non-community water systems (NTNCWS) that may need to take actions to reduce levels of regulated PFAS will have an additional two years to take any of these necessary actions and comply with all regulated PFAS MCLs (by 2029). If subject, you can expect that your state will send you a monitoring schedule that will tell you when to monitor for PFAS. You must use a lab that is certified in EPA Method 537.1 and 533.

Is there flexibility for small water systems?

The rule provides burden reduction for small systems during the initial monitoring requirements. All CWS and NTNCWS are required to complete initial monitoring within three years after the date of the final rule promulgation. All surface water systems are required to initially monitor quarterly in a 12-month period. However, small groundwater systems serving 10,000 or fewer are only required to monitor twice within a 12-month period. The PFAS drinking water rule also allows water systems to utilize previously collected monitoring data to satisfy the initial monitoring requirements.

What happens if I exceed the MCL for PFAS?

Public water systems have five years (by 2029) to implement solutions that reduce these PFAS if monitoring shows that drinking water levels exceed these MCLs. Beginning in five years (2029), public water systems that have PFAS in drinking water that violates one or more of these MCLs must take action to reduce levels of these PFAS in their drinking water and must provide notification to the public of the violation. Water systems must also provide the public with information on the levels of these PFAS in their drinking water beginning in 2027, even if they do not exceed any MCLs.

How can I limit PFAS in my public water system?

The new limits in this rule are achievable using a range of technologies including granular activated carbon, reverse osmosis, and ion exchange systems.

What can ALL4 do for you?

If the PFAS drinking water limits may affect you, ALL4 can partner with you to develop strategies for initial and long-term compliance. This rule may change in subsequent years based on the results of the Unregulated Contaminant Monitoring Rule 5 (UCMR5) that is occurring during 2023-2025. The UCMR5 measures 29 PFAS and Lithium and the NPDWSR may account for more PFAS in the future. If you would like to know more about the PFAS NPDWR, or how ALL4 can assist you, please reach out to Tia Sova at tsova@all4inc.com