What is Hexafluoropropylene oxide dimer acid (HFPO-DA)* and Why Does It Matter?

HFPO-DA: The "GenX" Chemical Hiding in Your Tap Water

You may not recognize the name hexafluoropropylene oxide dimer acid (HFPO-DA), but you've probably heard its nickname: GenX. It's a synthetic chemical that DuPont developed as a replacement for PFOA — one of the original "forever chemicals" that regulators forced off the market. The problem? GenX appears to carry many of the same risks as the chemical it replaced. It enters drinking water primarily through industrial discharge, particularly from fluorochemical manufacturing plants. Factories release it into nearby rivers and streams, and from there it works its way into municipal water systems. Unlike many contaminants that break down over time, GenX is extraordinarily persistent. Once it's in the environment, it stays there.

The health research on GenX is still developing, but what scientists have found so far is concerning. Animal studies show exposure is linked to liver damage, kidney disease, immune system disruption, and developmental problems in fetuses (National Toxicology Program). Some research also points to a possible connection with certain cancers. Because GenX is a relatively new chemical, long-term human studies are limited — but that doesn't mean it's safe. The EPA has classified HFPO-DA as a possible human carcinogen. Even low-level, chronic exposure — meaning small amounts consumed over many years — is what worries researchers most.

Right now, the EPA's enforceable legal limit (called a Maximum Contaminant Level, or MCL) for HFPO-DA is 10 parts per trillion (ppt). The Environmental Working Group (EWG) sets its own health guideline far lower, at just 1 ppt, based on the most protective available science. Across the 48 water systems where HFPO-DA was detected in this dataset, the average concentration was 2.952 ppt and the highest recorded level was 8.24 ppt. Technically, none of those systems exceeded the EPA's legal limit. But 2.952 ppt is nearly 3 times above the EWG's health guideline — which means millions of people may be drinking water that meets the legal standard but still poses a measurable health risk. That gap between "legal" and "safe" is exactly why independent health guidelines matter.

The geographic pattern of GenX contamination tells a clear story about industrial activity. South Carolina tops the list with 20 affected water systems — more than any other state by a wide margin. North Carolina and New York each show 8 affected systems, followed by Kentucky with 6 and Virginia with 3. This concentration in the Carolinas is not a coincidence. The Cape Fear River basin in North Carolina has been heavily contaminated by a Chemours manufacturing facility (formerly DuPont) that discharged GenX for decades. Communities downstream, including those in South Carolina, have felt the effects. New York's detections are largely tied to industrial sites in the Hudson Valley region. If you live in any of these states — especially near a river that serves as a drinking water source — GenX is worth paying attention to.

The good news is that effective filtration options exist. Reverse osmosis (RO) filtration is the most reliable method for removing HFPO-DA from drinking water. Studies show that RO systems remove 94% or more of PFAS compounds, including GenX, from tap water (EPA). Activated carbon filters — particularly those using granular activated carbon — also reduce GenX levels, though not as completely as RO. If you're in South Carolina, North Carolina, or another affected state, an under-sink reverse osmosis system is one of the most practical steps you can take. Echo Water's RO systems are designed specifically to target PFAS compounds like HFPO-DA, giving your family a reliable layer of protection beyond what your municipal treatment plant provides. Checking your local water utility's annual Consumer Confidence Report is also a smart first step — it will tell you whether GenX has been detected in your supply and at what levels.

Regulatory Standards for Hexafluoropropylene oxide dimer acid (HFPO-DA)*

Cities With the Highest Hexafluoropropylene oxide dimer acid (HFPO-DA)* Levels

States Most Affected by Hexafluoropropylene oxide dimer acid (HFPO-DA)*

Frequently Asked Questions

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