Forever Chemicals and the Advancement of Filtration Standards

If you drink tap water in the United States, you may have been exposed to “forever chemicals.” These per- and poly-fluoroalkyl substances (PFAS) are pervasive in surface and groundwater (the most common sources of drinking water) and toxic at low levels. Manufacture of these chemicals started in the 1940s for applications like nonstick cookware, and they have also been used in products like popcorn bags, rain gear, furniture fabric, paints, plumbing tape and, until 2021, firefighting foam.

Their long-term chemical stability and resistance to grease, oil, water and heat have made these forever chemicals prevalent in manufacturing. Unfortunately, PFAS can also build up in humans and the environment over time, resulting in significant health concerns. Exposure to unsafe levels of PFAS in drinking water have been linked to health problems including birth defects, cancer, liver effects, immune effects, and thyroid effects.

In 2016, the EPA established a health advisory limit of 70 ppt for the combined concentration of PFOA and PFOS. Increased consumer knowledge about these contaminants prompted demand for filters that protect against exposure to PFAS. A standardized testing method was needed to evaluate the ability of typical point-of-use (POU) water filters to reduce these compounds in drinking water to the health advisory limit at the time. Responding to this need, NSF developed NSF Protocol P473, offering scientifically derived test methods for this evaluation.

In 2017, the NSF Joint Committee on Drinking Water Treatment Units (DWTU) — made up of industry representatives, public health and regulatory officials, and user representatives — formed a task group to incorporate NSF P473 and the reduction claims for PFOA/PFOS into the NSF/ANSI standards. This provided additional validity of the test methodology and allowed for the maintenance and updates of the performance claims to be governed by an accredited consensus process outlined by the American National Standards Institute (ANSI). The task group was charged with incorporating the test methodology into NSF/ANSI Standard 53 for water treatment devices that use activated carbon or anion exchange resins, and NSF/ANSI Standard 58 for reverse osmosis systems. The task group validated the test methods already put in place under NSF P473 and voted to add the claims to the NSF standards. This resulted in all products and references to NSF P473 being removed and replaced by the NSF/ANSI 53 or 58 standards.

The current versions of NSF/ANSI Standards 53 and 58 are based on updates made in 2022 that aimed to further limit exposure to PFAS and to ensure water treatment devices can reduce various PFAS in addition to PFOA and PFOS. The NSF DWTU Joint Committee approved a ballot to add PFHpA, PFHxS, PFNA, and PFBS to create a “Total PFAS” reduction claim, and lowered the limit of combined PFAS from 70 ppt to 20 ppt.

In April 2024, the U.S. EPA issued the first-ever national, legally enforceable drinking water standard for PFAS in drinking water. This rule sets maximum contaminant levels (MCL’s) for PFOA at 4.0 ppt, PFOS at 4.0 ppt, PFHxS at 10 ppt, PFNA at 10 ppt, and HFPO-DA (also known as GenX) at 10 ppt. Additionally, the rule established a hazard index for mixtures containing two or more of PFHxS, PFNA, HFPO-DA, and PFBS.

Task groups and subtask groups serving under the NSF Drinking Water Treatment Units Joint Committee have been working to propose updates to NSF/ANSI Standard 53 and NSF/ANSI Standard 58 to align with the EPA PFAS rule. Once this work is complete, a ballot will be submitted to incorporate the updates into Standards. Once a ballot passes both the Joint Committee and Public Health Council, the updates will be implemented.

Any proposed updates to a standard must follow the NSF Standards process that is accredited by the American National Standards Institute (ANSI) and the Standards Council of Canada (SCC). NSF/ANSI and NSF/ANSI/CAN standards are developed and revised through a public process which incorporates balanced input from industry representatives, public health and regulatory officials, certification bodies and testing labs, and users.

There are a variety of ways to achieve PFAS reduction that vary depending on drinking water application and location. Currently, the most common technologies for PFAS removal are granular activated carbon, anion exchange resin, and reverse osmosis membranes. Multiple technologies, including carbon-based prefilters with a reverse osmosis membrane and point-of-use carbon filters with anion exchange resins, can be used in line to provide a more efficient contaminant reduction train.