Perfluorohexane sulfonic acid: a six-carbon PFAS used in AFFF firefighting foam, stain repellents, and metal plating. Listed under the Stockholm Convention in 2022 and regulated at 10 parts per trillion under the U.S. EPA's 2024 drinking water rule.
PFHxS is a six-carbon perfluoroalkyl sulfonic acid and one of the most persistent PFAS measured in human serum, with a half-life of roughly 8.5 years. It was a primary component of legacy AFFF firefighting foams used at military bases, civilian airports, and refineries between the 1970s and the early 2010s, which is why PFHxS contamination tracks closely with AFFF release sites.
The Stockholm Convention added PFHxS, its salts, and related compounds to Annex A (elimination) in June 2022. The U.S. EPA's April 2024 PFAS drinking water rule sets an MCL of 10 parts per trillion for PFHxS, alongside PFOA and PFOS limits of 4 parts per trillion. Health Canada's 2024 objective for total PFAS in drinking water is 30 parts per trillion summed across 25 named compounds, including PFHxS.
Like other long- and intermediate-chain PFAS, PFHxS resists biodegradation and conventional treatment. Destruction requires breaking the carbon-fluorine bond through high-temperature thermal treatment or emerging non-thermal processes such as supercritical water oxidation and electrochemical oxidation.
Also known as: perfluorohexane sulfonic acid, perfluorohexanesulfonate.
PFAS (Per- and Polyfluoroalkyl Substances): treatment approach
A family of thousands of synthetic fluorinated organics — including PFOA, PFOS, GenX, PFHxS, and AFFF constituents — defined by C-F bonds that resist conventional treatment and require destruction technologies to close a site.
Per- and polyfluoroalkyl substances: a class of more than 12,000 synthetic compounds built around exceptionally stable carbon-fluorine bonds. PFAS is the family name, not a single chemical. PFOA and PFOS are two specific members of this class.
Perfluorooctanoic acid: a specific eight-carbon long-chain PFAS compound, historically used in non-stick coatings and AFFF firefighting foam. Classified by IARC in 2023 as Group 1, carcinogenic to humans.
Perfluorooctane sulfonic acid: a specific eight-carbon long-chain PFAS compound, historically the active surfactant in 3M Scotchgard and AFFF firefighting foam. Classified by IARC in 2023 as Group 2B, possibly carcinogenic to humans.
Polychlorinated dibenzo-p-dioxins and related furans: highly persistent, fat-soluble chlorinated compounds formed as unintended byproducts of combustion, chlorine-based manufacturing, and herbicide production, with TCDD among the most toxic substances ever characterized.