PFHxS (Perfluorohexane Sulfonate)

What is PFHxS (Perfluorohexane Sulfonate)?

PFHxS is a PFAS, or "forever chemical," that stays in human blood for years: published half-lives run from about 5 to 35 years.

PFHxS (perfluorohexane sulfonate, also called perfluorohexane sulfonic acid) belongs to the PFAS family, and its defining trait is how long it lasts in the human body. A lab measures it in blood serum. In CDC's national survey, PFHxS, PFOS, PFOA, and PFNA turned up in nearly all people tested. PFHxS is a sulfonate, and ATSDR notes that perfluoroalkyl sulfonates are eliminated more slowly than carboxylates such as PFOA. Published half-lives for PFHxS in people span roughly 5 to 35 years. In a 2007 study of 26 adults (24 men and 2 women), Olsen and colleagues found 8.5 years (95% CI 6.4 to 10.6) for PFHxS, against 3.8 years for PFOA and 5.4 years for PFOS in the same people. Li and colleagues (2018) reported 7.4 years in men and 4.7 years in women aged 15 to 50. Zhang and colleagues (2013) reported 7.7 years in women up to age 50 and 35 years in people over 50, and Worley and colleagues (2017) reported 15.5 years. The studies followed different people with different methods, which is why the range is so wide. ATSDR lists all of them in its 2021 toxicological profile. A half-life measured in years changes what one result is. It isn't a reading of this week. It's what remains of everything that went in over a long stretch, minus what has left. For scale, and as plain arithmetic on the published figures: with a 4.7-year half-life, about 48% of the amount in the blood would remain after five years without new intake, and with 7.4 years, about 63%. ATSDR is blunt about the limit of this: it can't use PFAS blood levels to decide what harmful effects might be possible. A single value also can't separate recent intake from old. The sources are mostly products and sites, not food you chose. The Stockholm Convention documentation lists intentional uses in firefighting foams (AFFF), metal plating, textiles, leather and upholstery, polishing and cleaning agents, moisture-protective coatings, and electronics manufacturing, and notes that PFHxS replaced PFOS in many applications. ATSDR names stain-resistant carpets and fabrics and firefighting foams, and lists living near contaminated drinking water as an exposure pathway. 3M, a major manufacturer, ended production in 2002, but manufacturing continues elsewhere and imported products can still contain it. Across the US population, serum levels roughly halved between 1999-2000 and 2017-2018 (see the table below). Drinking water has its own rule, and it isn't a blood rule. In April 2024 EPA set a maximum contaminant level (MCL) of 10 parts per trillion (ng/L) for PFHxS. It also put PFHxS into a Hazard Index with PFNA, HFPO-DA (GenX), and PFBS: each water concentration is divided by a health-based water concentration (10, 10, 10, and 2,000 ng/L), the results are added, and a total above 1 exceeds the limit. That applies to public water systems. One ng/mL in blood equals 1,000 ng/L, so a number from a lab report and a number from a water report don't carry over to each other. As of October 2026, EPA is proposing to rescind these PFHxS provisions while a federal court weighs the 2024 rule; the dated details are under "What's new." PFOA (Perfluorooctanoic Acid) covers the PFOA and PFOS limits. Two other frameworks mention PFHxS. In June 2022 the parties to the Stockholm Convention listed PFHxS, its salts, and related compounds in Annex A (elimination) without specific exemptions, a treaty on production and use that says nothing about any one person's blood. And PFHxS is one of the seven PFAS in the 2022 National Academies (NASEM) sum, a framework written for clinicians and explained on PFOS (Perfluorooctane Sulfonate). It has no PFHxS-only band.

Typical reference context

These are population distributions and a water rule, not health thresholds. A percentile describes how many people in a survey fell below a value; it doesn't say what any value means for you. Your lab prints its own units and, if it prints one, its own range, and that printed range is the one that belongs with your result.

What changed recently

The biggest shift is regulatory. On May 14, 2025, EPA announced it would keep the PFOA and PFOS limits, extend their compliance date from 2029 to 2031, and rescind and reconsider the rules for PFHxS, PFNA, HFPO-DA, and the Hazard Index. In January 2026 the D.C. Circuit refused EPA's request to vacate those provisions early, so the 2024 rule stayed in force, with initial monitoring due by April 2027 and compliance by April 2029. On May 18, 2026, EPA proposed the rescission formally (91 FR 29413, published May 20, 2026); the comment period closed July 20, 2026. The court heard arguments in the challenge to the 2024 rule on September 18, 2026. As of October 2026 no final rescission has been issued and the status is unsettled.

On the science side, EPA finalized its IRIS toxicological review of PFHxS in January 2025. A summary of it says the review concluded PFHxS exposure is likely to cause thyroid and immune effects in humans, including decreased antibody responses to tetanus or diphtheria vaccination in children. For cancer, the review states there is inadequate information to assess carcinogenic potential by the oral or inhalation routes.

Two 2025 biomonitoring papers add context. A pilot of 630 adults in Switzerland found PFHxS in every serum sample (geometric mean 1.2 ng/mL). In two New York communities with PFOA-contaminated water, PFHxS, PFNA, and PFOS levels in the second testing round were almost identical to national levels, which shows how source-specific contamination is.

Tests often checked alongside this

PFHxS is usually reported next to the other PFAS in a panel, including PFOS (Perfluorooctane Sulfonate), PFOA (Perfluorooctanoic Acid), PFNA (Perfluorononanoic Acid), and PFBS (Perfluorobutane Sulfonate), because the water rule and the NASEM guidance both group them. The NASEM guidance, written for clinicians, lists lipid panels and thyroid function testing among follow-up tests depending on the summed band, so those results often sit in the same record.

What to track over time

The useful habit is clerical. Keep the lab name, the collection date, and the unit printed next to each PFHxS value, because labs report in ng/mL or µg/L (the same thing) while water reports use ng/L or ppt (a thousand times smaller). Longetic keeps those details attached so you can see your own values over time. Because the half-life is measured in years, one result is a snapshot of a long accumulation, not a daily reading.

What to ask your doctor

• Does this report list PFHxS on its own, or only inside a sum of PFAS, and which lab ran it?
• Is my result being compared with any published guidance, and who was that guidance written for?
• Does anything in my history (where I've lived, worked, or served) belong in my record next to this result?
• Which follow-up tests, if any, apply to me, and why?

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