At a glance
| Chemical family | Chlorinated polyfluoroalkyl ether sulfonic acid (Cl-PFESA); a C10 homologue. Systematic name 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid; formula C10HClF20O4S, molecular weight ≈632. The minor component of the commercial mixture F-53B (major component: 6:2 Cl-PFESA / 9Cl-PF3ONS) |
| CAS number | 763051-92-9 (acid form; PubChem CID 15099039) |
| Classification | Not evaluated by IARC (the 2023 Monograph Vol. 135 covered only PFOA, Group 1, and PFOS, Group 2B); NOT in the EPA 2024 federal PFAS NPDWR (no MCL); INCLUDED as a monitored analyte in US EPA UCMR 5 (EPA Method 533), 2023–2025; NOT listed under the Stockholm Convention (whose only listed PFAS are PFOS, PFOA and PFHxS) |
| Where you encounter it | As the minor F-53B homologue in and around the Chinese chrome-electroplating industry. Detected in China and East Asia in water, seafood and wildlife — but consistently at lower concentrations than the 6:2 major component. In the United States: effectively absent — monitored in 10,289 UCMR 5 systems and detected in none |
| Sleep micro environment relevance | None identified in North America. There is no domestic manufacturing, consumer-product, textile or drinking-water pathway by which this compound would reach a US or Canadian bedroom. It is included in the Atlas for completeness and as a "PFOS replacement" cautionary case, not as a local exposure. Inferred from zero UCMR 5 detection and the absence of any North American use of F-53B |
| Activated carbon capture | Not applicable for VOC-phase capture. As a non-volatile perfluorinated sulfonic acid it is a water/solid-phase contaminant, not an off-gassing bedroom VOC; where it occurs in water, granular activated carbon and reverse osmosis reduce Cl-PFESAs as they do other long-chain PFAS. Inferred from general long-chain PFAS water-treatment performance; no US water pathway makes this practically relevant here |
Regulatory & certification status
Where 11Cl-PF3OUdS stands across the major regulatory systems. Where a jurisdiction has no compound-specific measure, that is stated plainly as "not identified" rather than presented as confirmed absence — several agency databases (notably ECHA) are difficult to query exhaustively.
| United States | NOT included in the EPA April 2024 Final PFAS National Primary Drinking Water Regulation — no individual MCL and not part of the four-compound Hazard Index. It IS an included analyte in EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5), measured by EPA Method 533; UCMR monitoring informs future federal prioritization rather than setting an enforceable limit. Occurrence result: detected in 0 of 10,289 monitored systems. Regulatory — Federal Register (NPDWR) · EPA UCMR 5 |
| International | NOT listed under the Stockholm Convention on Persistent Organic Pollutants: the only PFAS subgroups listed are PFOS (2009), PFOA (2019) and PFHxS (2022) — 11Cl-PF3OUdS is outside all of these. It was not evaluated by IARC, whose 2023 Monograph (Vol. 135) assessed only PFOA (Group 1) and PFOS (Group 2B). Regulatory — Stockholm Convention |
| European Union | No compound-specific EU measure was identified for 11Cl-PF3OUdS. It is not individually named in the substances checked; the draft universal PFAS restriction under REACH, if adopted, would capture the broad PFAS class including Cl-PFESAs, but that remains a proposal. Treat as not identified rather than confirmed absent — ECHA databases are difficult to query exhaustively. Inferred — no compound-specific listing located; class-wide REACH proposal still in draft |
| Canada | No compound-specific Canadian measure was identified. Canada's proposed Order to add the broad class of PFAS (excluding fluoropolymers) to Part 2 of Schedule 1 under CEPA would, if finalised, encompass Cl-PFESAs as a class — but that is a draft, phased measure, not a current restriction on this compound. Inferred — captured only under a draft class-wide proposal, no substance-specific rule located |
| Australia | No compound-specific Australian measure was identified. Australia's industrial PFAS ban that took effect 1 July 2025 applies to PFOS, PFOA and PFHxS; 11Cl-PF3OUdS is not among them. It may fall within the broad AICIS Inventory PFAS evaluation, but no dedicated assessment was located. Inferred — not among the three banned PFAS; no substance-specific AICIS assessment located |
| United Kingdom | No PFHpA-style GB-specific measure is identified for 11Cl-PF3OUdS: it is not on the UK REACH Candidate List and carries no GB Mandatory Classification. Treat as not independently confirmed beyond the absence of a GB-specific listing. Inferred — from the absence of a GB-specific listing |
| Certifications | No bedroom-product certification screens for this compound by name. CertiPUR-US does not test foam for PFAS at all. OEKO-TEX Standard 100 regulates PFAS in certified textiles via a total-fluorine limit and a defined-substance PFAS test — an approach that would in principle capture a Cl-PFESA even though it is not individually named — but this is moot for North American products, which are not made with F-53B. GREENGUARD is a low-VOC emissions program and does not screen for a non-volatile PFAS. Industry — CertiPUR-US · OEKO-TEX |
| The 72-hour test window | Not applicable. 11Cl-PF3OUdS is a non-volatile, surface-active perfluorinated sulfonic acid that partitions to water and solids rather than off-gassing, so a short ~72-hour VOC chamber emissions test would not detect it; it is measured by targeted PFAS analysis (LC-MS/MS) of water, biota or biofluids. Inferred — from the compound's volatility/emission profile versus the VOC focus of short chamber tests |
What it is
11Cl-PF3OUdS — CAS 763051-92-9, PubChem CID 15099039 — is a C10 chlorinated polyfluoroalkyl ether sulfonic acid (formula C10HClF20O4S, molecular weight ≈632). It is easier to understand as one of two ingredients in a product. That product is F-53B, a Chinese chrome-plating mist suppressant that was adopted domestically as a replacement for PFOS in electroplating baths. F-53B is a mixture of two chlorinated-ether-sulfonate homologues: the major component, 6:2 Cl-PFESA (also called 9Cl-PF3ONS), and the minor component, this compound, 8:2 Cl-PFESA. The two share the same chlorinated-ether-sulfonate backbone and differ only by a single –C2F4– unit; 8:2 is the longer-chain, less-abundant homologue.
F-53B was first characterised in the open literature in 2013. Wang and colleagues 2013 in Environmental Science & Technology reported it as a Chinese PFOS alternative that had been in use for roughly three decades before it was studied, and found it to be as degradation-resistant as PFOS itself. Peer-reviewed That is the paradox that makes this compound worth documenting: it was reached for precisely because PFOS was being restricted, yet it belongs to the same intractably persistent chemistry.
Where you encounter it
In the United States — you don't
This is the whole story for a North American reader. Under EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5), 11Cl-PF3OUdS was one of the monitored PFAS analytes, measured by EPA Method 533 across 10,289 US public water systems between 2023 and 2025. It was detected in none of them — zero detections, 0%. Regulatory — EPA UCMR 5 occurrence data, 2023–2025 There is no domestic manufacturing, no consumer product, no textile treatment and no firefighting foam in North America that uses F-53B. The compound has no pathway into a US or Canadian bedroom, and the national monitoring data confirm the expectation: it is not in the water.
In China and East Asia — as the minor F-53B homologue
Where F-53B is used, both homologues turn up in the environment — in water, in seafood and in wildlife. But the C10 (8:2) homologue consistently occurs at lower concentrations than the C8 (6:2) major component. Jin, Shi and Cai 2020 in Science of the Total Environment measured Cl-PFESAs in seafood from local markets and found the 6:2 component dominant while the 8:2 component sat markedly lower — in Beijing-market seafood, the C8 ranged from below detection to 1.27 ng/g while the C10 ranged only from below detection to 0.109 ng/g. Peer-reviewed That ordering — 8:2 present but minor — holds across the occurrence literature and is why this compound is the secondary, not the primary, F-53B concern.
Why F-53B is on the map at all
He and colleagues 2022 in Environment International reviewed human exposure to F-53B in China: the mixture (mainly 6:2 plus 8:2 Cl-PFESA) is detected in roughly 80% of sampled blood, crosses the placenta, and has been associated in observational studies with lipid, endocrine and birth-outcome effects. Peer-reviewed Most of that body of work characterises the mixture or its dominant 6:2 component; the 8:2 homologue is typically carried along in the same analyses rather than studied on its own.
What the research says
Biopersistence — measured for the sibling, expected for this one
Shi and colleagues 2016 in Environmental Science & Technology studied human exposure and elimination kinetics of Cl-PFESAs, detecting them in over 98% of sampled people and reporting a median total-elimination half-life of 15.3 years — among the longest ever measured for any PFAS. Peer-reviewed One honesty note matters here: that 15.3-year figure is for the 6:2 (major) component, not for 8:2. No measured human serum half-life specific to 11Cl-PF3OUdS was found. As the longer-chain homologue, 8:2 is expected or predicted to be comparable or greater, but that has not been directly measured. Speculation — extrapolating an 8:2-specific half-life from the measured 6:2 value and chain-length trends
The 2025 protein-binding prediction — a model, not a measurement
Li and colleagues 2025 in Toxicology ran a proteome-wide in-silico docking study using AlphaFold3 structures and predicted that 8:2 Cl-PFESA has the strongest human-protein binding of the group — 413 ultra-strong predicted targets, versus 98 for 6:2 Cl-PFESA and 78 for PFOS. The paper is peer-reviewed, but its result is explicitly a computational prediction: the authors state it needs experimental validation. Peer-reviewed — computational prediction It is a hypothesis about binding potential, generated in a computer, not a demonstration of measured toxicity in animals or people. We flag it as a prediction because treating a docking score as a toxicity finding is exactly the kind of overreach this Atlas exists to avoid. Speculation — a modelled binding hypothesis awaiting experimental confirmation
What this means for your bedroom
Practically: nothing to do. For a US or Canadian household, 11Cl-PF3OUdS is not a bedroom exposure, not a drinking-water exposure, and not a consumer-product exposure. The national monitoring found it in zero of 10,289 water systems, and there is no domestic use that would put it in your home. If you are working through PFAS in your own environment, your attention belongs on the compounds that are actually detected in US water and products — start with PFOA and PFOS, and see the broader water overview.
The reason to know this name is different: it is a worked example of how a "PFOS replacement" can carry the same problem it was meant to solve. F-53B swapped one persistent fluorinated surfactant for another, and its most biopersistent behaviour — a median 15.3-year half-life for the sibling homologue — was only characterised years after the chemical was already in wide industrial use. When you evaluate any product marketed as "PFAS-free" or "PFOS-free," the useful question is not only what was removed but what replaced it.
Open research questions
- An 8:2-specific human elimination half-life — the measured 15.3-year value belongs to the 6:2 component; the 8:2 figure is expected but not measured. Speculation — no measured 8:2-specific serum half-life exceeding the 6:2 value was found
- Experimental validation of the 2025 AlphaFold3 binding prediction — whether the predicted 413 ultra-strong protein targets translate into measured toxicity in living systems. Speculation — prediction awaiting experimental confirmation
- Whether any North American occurrence exists below the UCMR 5 minimum reporting level — zero detections at the method's reporting threshold is strong evidence of practical absence, but not proof of true zero. Inferred — from the limits of a national monitoring reporting level
Where you meet 11Cl Pf3Ouds across your home
The same compound turns up in more than one place you live. Here's where it shows up in Embr — each links to the full breakdown for that part of your home.
Citations
- US Environmental Protection Agency. Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) occurrence data, 2023–2025 — 11Cl-PF3OUdS monitored (EPA Method 533) in 10,289 US public water systems, detected in 0 (0%). epa.gov/dwucmr Regulatory — the zero-detection occurrence source
- US Environmental Protection Agency (2024). PFAS National Primary Drinking Water Regulation — Final Rule. Federal Register, 89(82):32532-32757. Note: 11Cl-PF3OUdS NOT included; no individual MCL. federalregister.gov Regulatory
- Wang S, Huang J, Yang Y, Hui Y, Ge Y, Larssen T, Yu G, Deng S, Wang B, Harman C (2013). First report of a Chinese PFOS alternative overlooked for 30 years: its toxicity, persistence, and presence in the environment. Environmental Science & Technology, 47(18):10163-10170. DOI 10.1021/es401525n Peer-reviewed — first report of F-53B; as degradation-resistant as PFOS
- Shi Y, Vestergren R, Xu L, Zhou Z, Li C, Liang Y, Cai Y (2016). Human exposure and elimination kinetics of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs). Environmental Science & Technology, 50(5):2396-2404. DOI 10.1021/acs.est.5b05849 Peer-reviewed — median 15.3-yr half-life is for the 6:2 component
- He Y, Lv D, Li C, Liu X, Liu W, Han W (2022). Human exposure to F-53B in China and the evaluation of its potential toxicity: An overview. Environment International, 161:107108. DOI 10.1016/j.envint.2022.107108 Peer-reviewed — F-53B review; ~80% blood detection in China
- Jin Q, Shi Y, Cai Y (2020). Occurrence and partitioning of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) in seafood from local markets. Science of the Total Environment, 726:138538. DOI 10.1016/j.scitotenv.2020.138538 Peer-reviewed — 6:2 dominant, 8:2 the minor occurring homologue
- Li H et al. (2025). Proteome-wide in silico screening of chlorinated polyfluoroalkyl ether sulfonic acid human protein targets (AlphaFold3 docking; computational prediction requiring experimental validation). Toxicology, 519:154308. DOI 10.1016/j.tox.2025.154308 Peer-reviewed — a computational prediction (413 vs 98 vs 78 targets), not measured toxicity
- Stockholm Convention on Persistent Organic Pollutants — All POPs listing. Note: the only listed PFAS are PFOS, PFOA and PFHxS; 11Cl-PF3OUdS is not listed. pops.int Regulatory — not listed
- PubChem Compound Summary for CID 15099039, 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (C10HClF20O4S, MW ≈632; CAS 763051-92-9). pubchem.ncbi.nlm.nih.gov Regulatory — identity and CAS
Frequently asked questions
What is 11Cl-PF3OUdS?
11Cl-PF3OUdS — also written 8:2 Cl-PFESA, CAS 763051-92-9 — is a C10 chlorinated polyfluoroalkyl ether sulfonic acid. It is the minor component of the commercial mixture F-53B, a Chinese chrome-plating mist suppressant marketed as a PFOS replacement. The major component of F-53B is 6:2 Cl-PFESA (9Cl-PF3ONS); the two differ by a single –C2F4– unit, with 11Cl-PF3OUdS being the longer-chain, less-abundant homologue. It is a bioaccumulative PFAS where it occurs, but it has no North American consumer or bedroom pathway.
Is 11Cl-PF3OUdS in US drinking water?
No — as far as national monitoring can determine. Under EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5, occurrence data 2023-2025), 11Cl-PF3OUdS was monitored using EPA Method 533 in 10,289 US public water systems and detected in exactly zero of them (0%). It is a watch-list PFAS that simply does not appear in US tap water, because it is the minor component of a Chinese industrial chemical with no domestic manufacturing or use footprint.
Is 11Cl-PF3OUdS regulated?
It is monitored, not regulated. 11Cl-PF3OUdS is NOT in the EPA April 2024 Final PFAS National Primary Drinking Water Regulation — it has no enforceable federal MCL. It IS included as a monitored analyte in UCMR 5 (EPA Method 533). It is not listed under the Stockholm Convention, whose only listed PFAS are PFOS, PFOA and PFHxS, and it was not evaluated by IARC, whose 2023 Monograph (Vol. 135) covered only PFOA (Group 1) and PFOS (Group 2B). No compound-specific EU, Canadian, Australian or UK measure was identified.
Where does 11Cl-PF3OUdS occur?
As the minor F-53B homologue in and around the Chinese chrome-electroplating industry. It has been detected in China and East Asia in water, seafood and wildlife — but the 8:2 (C10) homologue consistently occurs at lower concentrations than the 6:2 (C8) major component. In Beijing-market seafood, for example, the C8 component dominated at less-than-detection to 1.27 ng/g while the C10 homologue ranged from less-than-detection to only 0.109 ng/g. In the United States it is effectively absent: monitored in 10,289 UCMR 5 systems and detected in none.
How persistent is 11Cl-PF3OUdS in the body?
The F-53B mixture it belongs to is among the most biopersistent PFAS ever measured in humans. A 2016 study reported a median total-elimination half-life of 15.3 years — but that figure is for the 6:2 (major) component, not for 8:2 itself. No measured human serum half-life specific to 11Cl-PF3OUdS was found. As a longer-chain homologue, 8:2 is expected or predicted to be comparable or greater, but that expectation has not been directly measured.
Is 11Cl-PF3OUdS more toxic than PFOS?
That claim rests on a computational prediction, not a measurement. A 2025 in-silico study using AlphaFold3 proteome-wide docking predicted that 8:2 Cl-PFESA has the strongest human-protein binding of the group — 413 ultra-strong predicted targets versus 98 for 6:2 Cl-PFESA and 78 for PFOS. The authors explicitly state this requires experimental validation. It is a modelling hypothesis about binding potential, not a demonstration of measured toxicity in people.
Should a North American reader worry about 11Cl-PF3OUdS?
For US and Canadian households this is the most reassuring entry the UCMR 5 dataset offers: monitored in 10,289 systems and found in none. It has no bedroom, consumer-product or domestic-water pathway here. It earns an Atlas page not as a personal exposure risk in North America but as a cautionary note about PFOS replacements abroad — F-53B was adopted as a "safer" substitute yet turns out to be one of the most biopersistent PFAS measured in humans.
Related compounds
Embr is a sleep environment company researching the chemistry of the bedroom. See the methodology page for how this Atlas tags claims by evidence strength. For broader context on PFAS in the home and in drinking water, see the water overview and the non-toxic bedroom guide.
Last reviewed 2026-07-13. If you find a factual error, contact us.