"Unboxing” the PFAS National Primary Drinking Water Regulation

Waters Corporation | Ken Rosnack

On April 10th, 2024, the EPA announced a finalized version of the new PFAS National Primary Drinking Water Regulation (NPDWR). The new rule, proposed about a year ago, sets enforceable Maximum Contaminant Levels (MCLs), with drinking water providers required to complete initial monitoring of several well-known PFAS within the next three years.? Based on population served and source water type, public water systems will conduct initial monitoring 2 or 4 times in a 12-month timeframe.? Results of that initial monitoring will then determine how often compliance monitoring will be required from 2027 onward. From 2029 onward, the public water systems whose testing have found PFAS above these MCLs are obliged to notify the public and to take action to reduce levels in the drinking water.???

The EPA also set final Maximum Contaminant Level Goals (MCLGs), which are not enforceable as they do not consider technology or methodology but are quite relevant from the point-of-view of health-based studies. The MCLs are set as close to the MCLGs as possible to make it reasonable for current laboratory technology to meet the scope of work.? Additional information and resources from the EPA on the NPDWR can be found in the PFAS NPDWR Fact Sheet.?

The PFAS included in the list of enforceable MCLs are PFOA, PFNA, PFBS, PFHxS, PFOS, and HFPO-Da (commonly known as GenX).? PFOA and PFOS each have an individual MCL value set at 4 parts per trillion (ppt) or ng/L while PFNA, PFHxS and HFPO-DA have a 10 ppt MCL individual value.? Also, a Hazard Index of 1 cannot be exceeded when two or more of PFBS, PFNA, PFHxS and HFPO-Da occur as a mixture in a drinking water sample.? The Hazard Index, an well-established tool for the EPA, was proposed since “mixtures of PFAS can pose a health risk greater than each chemical on its own.” That Hazard Index calculation, determined by the sum of fractions of each PFAS compared to health-based water concentrations, can be found in the EPA Fact Sheet titled “Understanding the Final PFAS National Primary Drinking Water Proposal Hazard Index MCL.? The final rule goes into effect 60 days after it is published in the US Federal Register however, the pre-publication version can be found here.?

To achieve the parts per trillion (ppt) or ng/L measurements required by the NPDWR PFAS regulation, a workflow including a mass spectrometer with sufficient sensitivity, such as the Xevo TQ-S micro, is necessary. However, the need goes beyond just detecting and quantifying PFAS at the MCLs, but at a sufficient level below them for continual water quality monitoring purposes.? The EPA advises “Trigger Levels” at ? the MCLs to establish monitoring frequency.? Sample preparation using solid phase extraction (SPE) enriches the PFAS in the sample to increase method sensitivity.? For example, EPA method 537.1 using Sep-Pak? PS2 and EPA method 533 using Oasis? WAX for PFAS cartridges provide a sample enrichment of 250x achieved by concentrating 250 mL of drinking water to a final sample extract volume of 1.0 mL.? A robust comprehensive solution must also consist of proper laboratory practices to keep PFAS contamination to a minimum, certified reference standards and proficiency testing standards to ensure workflow robustness, and PFAS analytical training from a qualified professional service provider.?

We can expect and are pioneering further innovations that will enhance our ability to detect and quantify PFAS compounds more efficiently and accurately. These advancements will not only improve our understanding of PFAS distribution and fate in the environment but also inform regulatory actions and mitigation strategies to protect human health and the ecosystem.? Technology and technique advances will continue to offer more sensitive, accurate, and comprehensive analysis of PFAS in drinking water and other environmental matrices, facilitating better environmental management and protection efforts.?

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To learn more about how you can conquer your Analytical PFAS challenges, explore the Waters PFAS Resource Hub.

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