PFNA (Perfluorononanoic Acid)

What is PFNA (Perfluorononanoic Acid)?

PFNA (perfluorononanoic acid) is a nine-carbon PFAS that labs measure in blood serum or plasma, usually in ng/mL, and that persists in the body for years.

PFNA is a perfluoroalkyl carboxylic acid with a nine-carbon chain, one carbon longer than PFOA. It belongs to the PFAS family of synthetic chemicals built to resist breaking down, and that one extra carbon matters: in the human data it clears more slowly than PFOA (the PFOA (Perfluorooctanoic Acid) page covers the family basics). PFNA's best-documented industrial job was as a processing aid, a surfactant that helps fluoropolymers form during manufacturing. A Massachusetts toxics-reduction summary describes it as a processing aid in fluoropolymer and polyvinylidene fluoride (PVDF) production, and a New Jersey Department of Environmental Protection (NJDEP) health document names Surflon S-111 as a PFNA-based product used for that purpose. Arkema told EPA in a response letter that it used ammonium perfluorononanoate in some of its fluoropolymers and aimed to eliminate it from 95 percent of its PVDF products by 2010. At the Solvay plant in West Deptford, New Jersey, the company used a proprietary process aid that contained PFNA; WHYY reported that the plant voluntarily stopped using PFNA in 2010. The same Massachusetts summary notes that PFNA can also form when other fluorinated coatings break down. That history explains why PFNA became a regulatory story in one state before it became a national one. New Jersey's Drinking Water Quality Institute recommended a limit of 13 ng/L in July 2015. NJDEP adopted it on September 4, 2018, and water systems began testing for PFNA in the first quarter of 2019. WBGO's headline at the time called New Jersey the first state to set a PFNA standard for water. Massachusetts followed a different route: its PFAS6 standard, in effect since October 2, 2020, caps the combined concentration of six PFAS at 20 ng/L, and PFNA is one of the six. The federal picture is less settled. On April 10, 2024, EPA set an enforceable limit (a maximum contaminant level, or MCL) of 10 ppt for PFNA in public drinking water, and also counted it in a Hazard Index for mixtures. Then, on May 18, 2026, EPA proposed to rescind the PFNA limit, along with PFHxS, GenX, and the Hazard Index. Its stated reason is procedural: the agency now reads the Safe Drinking Water Act as barring it from proposing a standard at the same time as a preliminary determination. The comment period closed July 20, 2026. As of October 2026 the proposal isn't final, a challenge to the 2024 rule (American Water Works Association v. EPA, No. 24-1188) was argued in the D.C. Circuit on September 18, 2026, and coverage of the case reports no decision yet. Until a court or a final rule changes it, the 2024 provisions remain in effect. The 4.0 ppt PFOA and PFOS limits are outside the rescission proposal; the PFOA page has that detail. Either way, an MCL is a limit on what a water system delivers. It isn't a blood level, and the two shouldn't be compared. Two numbers describe how PFNA behaves once it's in the body. A 2022 Bayesian analysis of contaminated-drinking-water studies put the population median half-life at 2.35 years, with a 95% confidence interval of 1.65 to 3.16 years. An earlier urinary-clearance estimate by Zhang and colleagues, as summarized by NJDEP, found a median of 3.5 years for men and older women and 1.5 years for younger women, a figure that models menstrual clearance in younger women. Half-life estimates depend on the population and method, which is why they differ. The US blood-level pattern is the most distinctive thing about PFNA. Most legacy PFAS fell steadily after the early 2000s. PFNA didn't. In NHANES, the CDC's national survey, the geometric mean was 0.548 µg/L in 1999-2000 and 0.460 µg/L in 2017-March 2020, a net drop of 16 percent. In between, it rose about 130 percent through 2009-2010 and then fell about 63 percent (Botelho and colleagues, Environmental Research, 2025). An earlier analysis of 1999-2018 data reported rises of 125 percent in males and 134 percent in females over the same first decade (Sonnenberg and colleagues, 2023). The sources I read report the pattern but don't settle why it differed from PFOS and PFOA. Finally, PFNA is one of the seven PFAS in the National Academies of Sciences, Engineering, and Medicine (NASEM) 2022 clinical guidance, which sums them rather than judging each alone; the PFOS (Perfluorooctane Sulfonate) page owns that framework.

Typical reference context

These numbers answer different questions. Blood results are usually in ng/mL (the same as µg/L), and drinking-water limits are in ng/L, a unit one thousand times smaller. A water limit tells you what a utility may deliver, not what a blood result means. For your own result, your doctor reads it against the lab's report and your history.

What changed recently

The strongest recent developments are regulatory, plus a thin layer of PFNA-specific research.

EPA released a draft IRIS toxicological review of PFNA for public comment on March 7, 2024. The draft concluded that oral PFNA exposure causes developmental effects in humans and is likely to cause male reproductive and liver effects, and that evidence on cancer was insufficient (ASDWA summary). External peer review wrapped up in 2024, and EPA posted the reviewers' report on September 27, 2024. ProPublica reported in October 2025 that two EPA scientists said the final assessment had been ready to post since April 2025 but was unreleased. I couldn't confirm a final release as of October 2026.

In January 2025, NHANES researchers at CDC published the 1999-March 2020 trend described above. In 2026, a cross-sectional study of 10,093 participants in Archives of Toxicology (Li and colleagues) found PFNA was the largest contributor, 31.8 to 52.7 percent, to a positive mixture association with several chronic conditions. These are statistical associations in observational data, not evidence that PFNA caused anything in any person.

In 2026 the federal limit itself moved: the May rescission proposal and the September court argument above. Most newer human papers study PFAS as mixtures, so PFNA-specific findings remain limited.

Tests often checked alongside this

On a lab report, PFNA usually appears as one line in a PFAS panel. The CDC's national survey panel pairs it with PFOA, PFOS, PFHxS, PFDA, PFUnDA, MeFOSAA, and PFDoDA. Neighbor pages cover PFOA (Perfluorooctanoic Acid), PFOS (Perfluorooctane Sulfonate), PFHxS (Perfluorohexane Sulfonate), PFDA (Perfluorodecanoic Acid), PFUnDA (Perfluoroundecanoic Acid), and Me-PFOSA-AcOH, the last one a component of the NASEM sum under its alternate lab names. A sum on your report means something only if you know which analytes the lab included.

What to track over time

Keep three details with each PFNA result: the draw date, the lab, and the unit. NHANES-style reports use ng/mL, while water reports use ng/L, so the same digits can mean very different things. Note whether the lab printed a reporting limit; PFUnDA (Perfluoroundecanoic Acid) explains how "<LOD" reads. With a half-life of years, a result is a snapshot of one draw, and values from different labs or methods aren't always directly comparable.

What to ask your doctor

• My report lists PFNA on its own and inside a sum of PFAS. Which number do you use, and which analytes does the sum include?
• Is the lab's method and reporting limit the same as on my earlier results?
• I've lived near or worked at a site with a documented PFAS history. How does that change how you look at this result?
• Does your practice follow the NASEM 2022 guidance, and which of my other results does it bring into the conversation?

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