PFHxS (Perfluorohexane Sulfonate)
Cities measured
87
Detected in
87 / 87
Elevated / alert
1
EU limit
10 ng/L
Highest
2.8 ng/L — Delhi
Overview
PFHxS is a short-chain PFAS introduced as a 'safer' substitute for PFOS in firefighting foams and industrial applications. It is more mobile in the environment than PFOS but less bioaccumulative. Like PFOS, it was adopted as a substitute before its own hazard profile was understood.
Health Relevance
PFHxS is associated with thyroid hormone disruption. It crosses the placental barrier and is detected in breast milk. The same regulatory cycle applied: introduced as 'safe', used for decades, then found to have similar concerns as the substance it replaced.
Regulatory Limits
Drinking Water Directive 2020/2184
0.1 μg/L sum of long-chain PFAS. Included in EU PFAS sum parameter (20 PFAS).
Controversy & Contested Science
PFHxS exemplifies the 'regrettable substitution' problem in chemical regulation: when a hazardous chemical is banned, industry replaces it with a structurally similar compound lacking regulatory evidence — until it accumulates. This cycle has occurred repeatedly: PFOS → PFHxS; PFOA → GenX (HFPO-DA); BPA → BPS/BPF. The EU's 2022 PFAS Restriction Proposal under REACH seeks to restrict the entire PFAS class (~10,000+ compounds) simultaneously — addressing regrettable substitution at its root. Estimated industry compliance cost: €50–100 billion over 12 years.