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6:2 FTS

6:2 Fluorotelomer Sulfonic Acid

3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctane-1-sulfonic acid

Also known as 6:2 FTS6:2 FTSATHPFOS
1h,1h,2h,2h-perfluorooctanesulfonic acid1-Octanesulfonic acid, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctanesulphonic acid6:2 FTSA248-580-63,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctane-1-sulfonic acid6:2 Fluorotelomer sulfonic acidTHPFOS

A short-chain fluorotelomer sulfonic acid (6 perfluorinated + 2 alkyl carbons) and the principal PFAS-replacement chemistry in post-2002 AFFF firefighting foams. Detected in 275 U.S. utilities serving ~15 million people 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

6:2 Fluorotelomer sulfonic acid (6:2 FTS or 6:2 FTSA; also THPFOS) is a short-chain fluorotelomer sulfonic acid consisting of a perfluorinated six-carbon tail (C6F13) bonded to a two-carbon CH2CH2- spacer terminating in a sulfonic acid head group. After the 3M-led phaseout of PFOS-based aqueous film-forming foam (AFFF) in 2000-2002, 6:2 FTS-based fluorotelomer surfactants became the principal replacement chemistry for firefighting foams marketed as safer alternatives. The compound has since become one of the most environmentally widespread PFAS analytes under UCMR 5, detected in 275 U.S. public water systems serving roughly 15 million people, with highest concentrations clustered in Florida, Texas, and Virginia.

Pollution sources

Military AFFF Aqueous Film-Forming Foam — firefighting foam used at military bases and airports for fuel fires. The leading source of PFAS contamination in groundwater near former training sites. Industry Manufacturing Consumer products

Sources

6:2 FTS enters drinking water primarily through fluorotelomer-based AFFF use at military airfields, civilian airports, oil refineries, fire-training facilities, and chemical-plant fire suppression systems. Unlike 4:2 FTS (a degradation byproduct), 6:2 FTS is an intentional commercial product as well as an environmental transformation intermediate of polyfluoroalkyl precursors in modern AFFF formulations. Contamination plumes are especially well-documented at Pensacola NAS, Dallas-Fort Worth area airports, Miami-Dade utilities, and Northern Virginia drinking-water systems serving the DC metro. Like other PFAS, 6:2 FTS is highly mobile in groundwater and resists further degradation, migrating with little attenuation from source areas into source-water wells and surface intakes.

Health risks

6:2 FTS was originally marketed as a 'safer' short-chain alternative to PFOS, but emerging toxicology indicates it shares many of the same hazards. Subchronic animal studies (Sheng et al. 2018 and others) have linked 6:2 FTS to hepatotoxicity, thyroid hormone disruption, and altered serum lipid profiles at low ppm exposures. It has not been formally classified as a carcinogen by IARC or NTP, but its environmental persistence, mobility, and structural similarity to PFOS keep it under active regulatory review. Of particular concern is its potential to transform in the environment and human body into shorter-chain perfluoroalkyl carboxylic acids, complicating risk assessment. 6:2 FTS 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

6:2 FTS is removed by granular activated carbon (GAC), anion exchange resin, and high-pressure membranes including reverse osmosis and nanofiltration. Short-chain fluorotelomers like 6:2 FTS tend to break through GAC media earlier than long-chain PFAS such as PFOA and PFOS, so column run times must be shortened or anion exchange resins selective for short-chain PFAS deployed. Conventional treatment processes — coagulation, sand filtration, disinfection, UV, and ozonation — do not remove 6:2 FTS. 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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Chemistry + classification data sourced from public databases (PubChem, EPA CompTox, IARC monographs); 3D molecular models from 3d.nih.gov where available.