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11Cl-PF3OUdS

11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid

2-(8-chloro-1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-hexadecafluorooctoxy)-1,1,2,2-tetrafluoroethanesulfonic acid

Also known as 11Cl-PF3OUdS8:2 Cl-PFESA
11-Chloroperfluoro-3-oxaundecanesulfonic acid11Cl-PF3OUdS11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid2-((8-chloro-1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-hexadecafluorooctyl)oxy)-1,1,2,2-tetrafluoroethanesulfonic acidClOPFLSA n=88:2 Cl-PFESAPD19265411-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (F-53B Minor)

A chlorinated perfluoroether sulfonic acid (8:2 Cl-PFESA), the minor component of F-53B chromium-plating mist suppressant. Persistent and bioaccumulative; detected at low ppt levels in U.S. drinking water under UCMR 5.

Group
PFAS
Regulatory status
UCMR
Unregulated Contaminant Monitoring Rule
Top removal tech
Activated carbon

Primary concern: Immune and liver toxicity

Affected organ systems

Liver Immune Developmental Endocrine Affecting the body's hormone system — thyroid, adrenal, reproductive, or metabolic hormones. Thyroid

Health effects

Immunotoxin Suppresses or alters the immune system. Can increase risk of infection or reduce vaccine effectiveness. Endocrine disruptor Mimics or blocks the body's hormones (estrogen, thyroid, testosterone). Can affect development, reproduction, and metabolism at very low doses. Developmental toxin Causes harm during development before birth or in early childhood — birth defects, low birth weight, delayed growth, or learning problems later in life. Hepatotoxin Damages the liver. Effects range from elevated liver enzymes on a blood test to fatty liver disease and, with prolonged exposure, liver cancer.

Exposure routes

Drinking water Dietary Occupational In utero

Vulnerable populations

Pregnant Infants Children

Overview

11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS), also known as 8:2 Cl-PFESA, is a chlorinated perfluoroether sulfonic acid. It is the minor component (~10%) of F-53B, a chromium-electroplating mist suppressant developed in China in the 1970s as a replacement for PFOS in metal-finishing applications. The major component of F-53B is 9Cl-PF3ONS (6:2 Cl-PFESA); 11Cl-PF3OUdS is the longer-chain analogue. Despite its niche industrial origin, 11Cl-PF3OUdS has been detected in surface waters, drinking water, and human serum across multiple continents, and was found in 51 U.S. public water systems serving roughly 399,000 people under EPA's UCMR 5 monitoring program.

Pollution sources

Industry Manufacturing Consumer products

Sources

11Cl-PF3OUdS enters drinking water primarily through industrial discharges from metal-finishing operations that historically used F-53B as a chromium mist suppressant. Although F-53B production and use have been concentrated in China, atmospheric long-range transport, imported consumer goods, and U.S. industrial emissions have led to widespread environmental occurrence. UCMR 5 detections cluster in Massachusetts, New York, New Jersey, Alabama, and Michigan, suggesting both direct industrial sources and broader background contamination. As with other PFAS, 11Cl-PF3OUdS is highly mobile in groundwater and resists degradation indefinitely.

Health risks

11Cl-PF3OUdS has not been formally classified as a carcinogen by IARC or NTP, but it shares the structural and toxicological profile of other PFAS of concern. In animal and human studies, Cl-PFESAs have been linked to hepatotoxicity, thyroid hormone disruption, immune suppression, and adverse developmental effects. Occupational studies of F-53B-exposed Chinese electroplating workers (Shi et al. 2016) have documented serum half-lives substantially longer than PFOA or PFOS — on the order of 15 years for the major 6:2 Cl-PFESA component, with comparable persistence expected for 11Cl-PF3OUdS. This analyte is monitored under UCMR 5 but is not currently subject to a federal MCL.

Effective treatments

Activated carbon Granular or block carbon that traps organic contaminants as water flows through. The most common point-of-use filter media — handles chlorine taste, VOCs, pesticides, and many PFAS. Reverse osmosis A semipermeable membrane that pushes water through under pressure, leaving most dissolved contaminants behind. Removes a very broad range — PFAS, lead, arsenic, nitrate, salts — at the cost of slower flow and some wastewater. Ion exchange Resin beads that swap unwanted ions (lead, calcium, certain PFAS, perchlorate) for harmless ones like sodium. Common in water softeners and PFAS treatment columns.

Does not remove

UV Ultraviolet light that disrupts the DNA of bacteria, viruses, and protozoa as water flows past the lamp. Disinfects but doesn't remove chemicals or particles. Chlorination Adds chlorine or hypochlorite to kill bacteria and viruses. The most common disinfection method in US water systems; leaves a residual that keeps water protected through the distribution pipes. Boil Kills bacteria, viruses, and protozoa after a one-minute rolling boil. Does NOT remove chemicals like lead, nitrate, or PFAS — boiling actually concentrates them as water evaporates.

NSF certifications

NSF/ANSI 53 Health-related contaminants NSF/ANSI 58 Reverse osmosis systems

Water treatment

11Cl-PF3OUdS is removed effectively by granular activated carbon (GAC), anion exchange resin, and high-pressure membranes including reverse osmosis and nanofiltration. Its longer perfluorinated chain (relative to short-chain PFAS) means it adsorbs more strongly to GAC media. Conventional treatment processes — coagulation, sand filtration, disinfection, UV, and ozonation — do not remove it. Boiling concentrates rather than removes it. NSF/ANSI 53 and NSF P473 certify point-of-use filters for PFAS reduction; NSF/ANSI 58 covers RO systems.

Gallery

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Related contaminants

9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS) A chlorinated perfluoroether sulfonic acid (6:2 Cl-PFESA), the major component (~90%) of the Chinese-made F-53B chromium-plating mist suppressant. Persistent, bioaccumulative, and detected at low ppt levels under UCMR 5.

Chemistry + classification data sourced from public databases (PubChem, EPA CompTox, IARC monographs); 3D molecular models from 3d.nih.gov where available.