PFAS-4 (also written PFAS4) is the sum of four closely watched PFAS compounds: PFOA, PFOS, PFNA and PFHxS. It is the parameter behind EFSA’s health-based tolerable weekly intake, and the basis for Sweden’s national drinking-water limit of 4 ng/L.
PFAS-4 is not the same as “short-chain PFAS”. The four compounds are among the most studied longer-chain carboxylates and sulfonates. PFAS-4 is a subset of both PFAS-11 and PFAS-21 — the sums must not be added together.
Which substances are in PFAS-4?
| Abbreviation | Name |
|---|---|
| PFOA | Perfluorooctanoic acid |
| PFOS | Perfluorooctane sulfonic acid |
| PFNA | Perfluorononanoic acid |
| PFHxS | Perfluorohexane sulfonic acid |
Simplified PFOA structure: CF₃-(CF₂)₆-COOH. See also What are PFAS?.
Limit value in Sweden
Under the Swedish Food Agency regulations (LIVSFS 2022:12) the drinking-water limit for PFAS-4 is 4.0 ng/L from 1 January 2026. The value is stricter than the EU Sum of PFAS (100 ng/L for 20 substances) because Sweden followed the EFSA 2020 health assessment. The same level is used as a guideline for private wells.
See PFAS limit values in Sweden and the EU and PFAS regulations.
How does PFAS-4 relate to PFAS-11 and PFAS-21?
- PFAS-4 — four compounds, 4 ng/L in Swedish drinking water.
- PFAS-11 — eleven compounds (including PFAS-4); 90 ng/L as EQS for many groundwater bodies until a new threshold is adopted.
- PFAS-21 — 21 compounds (EU 20 + 6:2 FTS), 100 ng/L in Swedish drinking water.