PFHxS (Perfluorohexane Sulfonate)

PFHxS (perfluorohexane sulfonate) is a PFAS "forever chemical" that was widely used as a replacement for PFOS in firefighting foams, metal plating, and stain-resistant treatments. Like all PFAS, it does not break down in the environment — earning these chemicals the name "forever chemicals."

The EPA regulates PFHxS under the PFAS Hazard Index, which sets a combined limit for PFHxS, PFNA, HFPO-DA (GenX), and PFBS. Individually, PFHxS has a health-based reference value of 10 parts per trillion (ppt).

Why Is PFHxS a Concern?

PFHxS has one of the longest half-lives among PFAS in the human body — estimated at 5 to 9 years, even longer than PFOS (5.4 years) and PFOA (3.5 years). This means it accumulates in the body over a lifetime of exposure. In 2023, the Stockholm Convention on Persistent Organic Pollutants added PFHxS to its list of globally banned chemicals.

Key health concerns include:

• Thyroid hormone disruption — multiple population studies show associations between PFHxS exposure and altered thyroid function
• Immune system effects, including reduced vaccine response in children (documented in the Faroe Islands cohort study)
• Liver damage and elevated cholesterol
• Potential reproductive and developmental effects
• Possible associations with attention deficit disorders in children

Where Does PFHxS Come From?

PFHxS contamination is primarily linked to:

• Firefighting foam (AFFF): Used extensively at military bases and airports. PFHxS is frequently found alongside PFOS at these sites.
• Metal plating operations: PFHxS was used in chrome plating processes
• Stain-resistant products: Used as a replacement for PFOS in fabric and carpet treatments

PFHxS is particularly persistent in groundwater and has been detected at contamination sites decades after the original discharge occurred.

PFHxS vs. Other PFAS

PFHxS is a 6-carbon PFAS, shorter than PFOS (8 carbons) but still classified as "long-chain" by the OECD. Its key distinguishing feature is its extremely long half-life — it stays in the body longer than nearly any other PFAS. The EPA regulates it under the Hazard Index rather than with an individual MCL like PFOA and PFOS.

How to Remove PFHxS From Your Water

• Reverse Osmosis: Most effective, removing 90%+ of PFHxS. Under-sink systems cost $150-$500.
• Granular Activated Carbon: Effective when properly maintained and replaced on schedule. Look for NSF P473 certification.
• Ion Exchange Resins: Effective in whole-house systems, particularly anion exchange resins designed for PFAS.

Standard pitcher filters may have limited effectiveness against PFHxS. For reliable removal, choose a reverse osmosis system or a filter specifically certified for PFAS under NSF P473.