What is Perfluoroundecanoic acid (PFUnA) and Why Does It Matter?

Perfluoroundecanoic acid — most people call it PFUnA — is one of the lesser-known members of the PFAS family. PFAS (per- and polyfluoroalkyl substances) are a group of man-made chemicals used in industrial manufacturing, firefighting foam, and consumer products like stain-resistant coatings and food packaging. PFUnA is a long-chain PFAS, meaning its chemical structure makes it especially stubborn in the environment. It doesn't break down easily in soil or water, which is why scientists sometimes call PFAS chemicals "forever chemicals." Once PFUnA enters a water source — through industrial discharge, landfill runoff, or contaminated groundwater — it tends to stay there.

The health concerns around PFUnA are serious, even at very low levels. Research reviewed by the Environmental Working Group (EWG) links long-chain PFAS exposure to liver damage, thyroid disruption, immune system suppression, and increased cancer risk. Children and pregnant women face the greatest risk, because these chemicals can interfere with hormone development and may affect fetal growth. The EWG has set a health guideline of 0.01 parts per trillion (ppt) for PFUnA — an extremely conservative number that reflects just how potent this chemical can be at trace levels.

Right now, the EPA does not enforce a specific legal limit for PFUnA on its own. In 2024, the EPA finalized maximum contaminant levels for several PFAS compounds, but PFUnA falls under a combined PFAS group limit rather than a standalone standard. That regulatory gap matters. Of the 80 water systems tested across the country that detected PFUnA, 78 of them — that's 97.5% — came in above the EWG health guideline. The average detected level was 1.055 ppt, which is more than 100 times the EWG benchmark. The highest recorded level hit 21.1 ppt, more than 2,000 times above that guideline. These numbers don't mean your water is immediately dangerous, but they do suggest that current legal standards aren't designed to protect the most vulnerable people in your household.

Geographically, PFUnA contamination clusters in states with heavy industrial history and dense manufacturing corridors. New York leads the country with 27 affected water systems — not surprising given the state's long industrial legacy and the presence of military bases that historically used PFAS-containing firefighting foam. Massachusetts follows with 12 systems, then North Carolina with 10, and New Jersey and Alabama each with 7. The Northeast pattern reflects decades of chemical manufacturing and military activity near water sources. North Carolina's presence on this list ties closely to its concentration of chemical plants along the Cape Fear River basin, an area that has faced significant PFAS scrutiny in recent years. Alabama's numbers likely connect to military installations and industrial sites in the Tennessee Valley region.

The good news is that effective filtration options exist. Reverse osmosis (RO) filtration is the gold standard for removing PFAS compounds, including PFUnA. A quality RO system removes up to 99% of PFAS from drinking water, according to EPA and NSF International testing data. Activated carbon filters — especially those using granular activated carbon (GAC) — also reduce PFAS levels significantly, though they're generally less effective than RO for long-chain compounds. When choosing a filter, look for one certified to NSF/ANSI Standard 58 (for RO systems) or Standard 53 (for activated carbon). Echo Water's reverse osmosis systems are tested to meet these standards, giving you a reliable way to reduce PFUnA and other PFAS chemicals at the tap. If you're in New York, Massachusetts, North Carolina, New Jersey, or Alabama, testing your water first is a smart move — it tells you exactly what you're dealing with before you choose a solution. You can request a water quality report from your utility or use a certified home testing kit to get a clearer picture of what's coming out of your tap.

Regulatory Standards for Perfluoroundecanoic acid (PFUnA)

Cities With the Highest Perfluoroundecanoic acid (PFUnA) Levels

States Most Affected by Perfluoroundecanoic acid (PFUnA)

Frequently Asked Questions

Related Contaminant Guides