# Federal — PFOS — PFAS drinking water concentration limits by US state — MCLs, notification levels, action levels, and health advisories for PFOA, PFOS, and other per- and polyfluoroalkyl substances

For Federal, state–chemical pair is Federal — PFOS; pfas compound is PFOS; concentration limit (ppt) is 4.0; regulation type is MCL; stricter than federal mcl is n/a, recorded from its source on 2026-08-14.

- **State–chemical pair:** Federal — PFOS
- **State:** Federal
- **PFAS compound:** PFOS _(verified: appears in the quote below)_
- **Concentration limit (ppt):** 4.0 _(verified: appears in the quote below)_
- **Regulation type:** MCL
- **Stricter than federal MCL:** n/a _(our reading, not quoted from the source)_
- **Effective date:** 2024-04-10
- **Regulatory citation:** PFAS National Primary Drinking Water Regulation, 89 FR 32532

## What the source says

> PFOS | Zero | 4.0 ppt

## Source

- https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas

Last verified: 2026-08-14. Review by: 2027-02-10.
Part of [PFAS drinking water concentration limits by US state — MCLs, notification levels, action levels, and health advisories for PFOA, PFOS, and other per- and polyfluoroalkyl substances](https://referencesource.org/pfas-drinking-water-limits-by-state/).