PFAS in Drinking Water

What Are PFAS?

Per- and polyfluoroalkyl substances (PFAS) are a group of more than 12,000 man-made chemicals used since the 1940s in a vast range of products: non-stick cookware, waterproof clothing, food packaging, firefighting foam, semiconductor manufacturing, and many industrial processes. Their defining feature is extreme chemical stability, the carbon-fluorine bond is among the strongest in organic chemistry.

That stability means PFAS do not break down in soil, water, or living organisms. They accumulate in the food chain and in human tissue over time. Once released into the environment, they persist for decades. This is why they earned the name "forever chemicals" - a term now used widely by scientists, regulators, and the media.

The most extensively studied PFAS compounds are PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid), both of which were phased out by major manufacturers in the early 2000s after research linked them to health effects. However, they persist in the environment, and in water supplies, for many years after production ends. Newer "short-chain" PFAS replacements are now also being monitored.

How PFAS Reaches Drinking Water

PFAS contamination of drinking water typically originates from several sources:

• Military and airport firefighting foam (AFFF): Aqueous film-forming foam containing PFOS and PFOA was used at military installations and civilian airports for decades. Spills and training exercises contaminated groundwater at hundreds of sites across the country.
• Industrial manufacturing: Facilities producing or using PFAS-containing products have historically discharged these chemicals into waterways and groundwater.
• Biosolids land application: Treated sewage sludge, applied as fertilizer on farmland, can contain elevated PFAS levels that leach into wells and surface water.
• Landfill leachate: Consumer products containing PFAS end up in landfills; leachate from these sites can contaminate surrounding groundwater.

Once PFAS enters an aquifer, it spreads slowly through groundwater and is extraordinarily difficult to remove. Remediation costs at known contamination sites run into the billions of dollars. Browse PFAS detection rates by state to see where contamination is most widespread.

The UCMR5 Monitoring Program

The Fifth Unregulated Contaminant Monitoring Rule (UCMR5) is the most comprehensive national PFAS screening of drinking water ever conducted. Under this program, EPA required water systems serving more than 10,000 people, plus a random sample of smaller systems, to test for 29 PFAS compounds and lithium between 2023 and 2025.

The program generated approximately 1.93 million individual test results, now available through PlainWater. Key PFAS compounds monitored include:

• PFOA and PFOS: The two most-studied PFAS; subject to the 2024 MCL of 4 ppt.
• PFNA, PFHxS, HFPO-DA (GenX): Regulated under a combined Hazard Index in the 2024 rule.
• PFBS and other short-chain PFAS: Replacement chemicals used after PFOA/PFOS phase-out; emerging data on health effects.

Search the PFAS tracker or browse county-level PFAS data to see how many systems in your county were tested and how many had detections.

The 2024 EPA Drinking Water Rule

In April 2024, the EPA finalized the first-ever National Primary Drinking Water Regulation specifically for PFAS. The key limits established:

At 4 parts per trillion, the PFOA and PFOS limits are set near the current laboratory detection threshold. This reflects the EPA's determination that there is no safe level of exposure for these compounds and that treatment must be as protective as feasible. Water systems serving an estimated 100 million people will need to install treatment, primarily granular activated carbon (GAC) or reverse osmosis, to comply.

Update, May 2026: The EPA has proposed rescinding the Hazard Index regulation for PFNA, PFHxS, HFPO-DA (GenX), and PFBS entirely, and separately proposed extending the PFOA/PFOS compliance deadline from 2029 to 2031 for water systems that apply for the extension. Neither proposal is final: the public comment period runs through July 20, 2026, and litigation is expected regardless of the outcome. The 4 ppt PFOA/PFOS limits themselves are not proposed to change. Check the EPA's PFAS drinking water rulemaking page for the current status before relying on the 2029 date above.

Treatment Options for PFAS Removal

Current water treatment technologies that can effectively reduce PFAS include:

• Granular Activated Carbon (GAC): Widely used at the treatment plant level. Effective for many PFAS compounds, especially longer-chain PFAS. Requires regular replacement of carbon media.
• High-Pressure Membrane Filtration (Reverse Osmosis): Highly effective at removing PFAS, including short-chain compounds. More expensive and generates concentrate waste requiring disposal.
• Ion Exchange Resins: Emerging technology with strong PFAS removal performance, particularly for short-chain PFAS that GAC handles less effectively.

For household use, point-of-use reverse osmosis filters certified to NSF Standard 58 and activated carbon filters certified to NSF Standard 53 can reduce PFAS in tap water. Note: standard pitcher filters (Brita, etc.) are not certified to remove PFAS.

Frequently Asked Questions