PFAS ("forever chemicals")
Perfluorohexanesulfonic acid in U.S. tap water
282 public water systems across 31 U.S. states report Perfluorohexanesulfonic acid in their annual Consumer Confidence Report. 27 sit at or above the federal limit.
See the PFAS Hotspots leaderboard → — every U.S. water system over EPA's finalized PFAS limit, ranked by severity, from the 2023–2025 UCMR5 lab dataset.
What it is
Perfluorohexanesulfonic acid, a PFAS 'forever chemical.'
Why it's regulated
Regulated by the EPA at 10 parts per trillion and included in the PFAS Hazard Index.
At or above the federal limit (27)
| Water system | Measured | vs. limit |
|---|---|---|
| Poolesville, MD 2024 annual report | 913 ng/L | 91.3× the limit |
| Riverside Highland Water Company — Grand Terrace, Ca, CA 2023 annual report | 900 ng/L | 90.0× the limit |
| San Bernardino Valley Wd — San Bernardino, Ca, CA 2023 annual report | 0–229 ng/L | 22.9× the limit |
| Home Gardens County Wd — Corona, Ca, CA 2022 annual report | 0–58 ng/L | 5.8× the limit |
| Montara Water and Sanitary District — Montara, Ca, CA 2023 annual report | 0–47 ng/L | 4.7× the limit |
| Burbank, CA 2024 annual report | 0–45 ng/L | 4.5× the limit |
| Atascadero State Hospital — Atascadero, Ca, CA 2022 annual report | 4.4–34 ng/L | 3.4× the limit |
| Chula Vista Sweetwater, CA 2024 annual report | 0–26 ng/L | 2.6× the limit |
| Sweetwater Authority — Chula Vista, Ca, CA 2023 annual report | 0–26 ng/L | 2.6× the limit |
| City of Pleasanton — Pleasanton, Ca, CA 2023 annual report | 23.2 ng/L | 2.3× the limit |
| West Valley Water District — Rialto, Ca, CA 2023 annual report | 0–22 ng/L | 2.2× the limit |
| Abilene, TX 2024 annual report | 20.2 ng/L | 2.0× the limit |
| Fort Worth, TX 2024 annual report | 19.2 ng/L | 1.9× the limit |
| Atascadero Mutual Water Co — Atascadero, Ca, CA 2023 annual report | 18 ng/L | 1.8× the limit |
| Reno, NV 2024 annual report | 15 ng/L | 1.5× the limit |
| Dayton, OH 2024 annual report | 13.05 ng/L | 1.3× the limit |
| Big Bear City Csd — Big Bear City, Ca, CA 2023 annual report | 11.75 ng/L | 1.2× the limit |
| Hesperia, CA 2024 annual report | 0–10.5 ng/L | 1.1× the limit |
| Backbone Mountain Boys Camp, MD 2024 annual report | 10 ng/L | 1.0× the limit |
| Campus Hills, MD 2024 annual report | 10 ng/L | 1.0× the limit |
| Cheltenham Youth Facility, MD 2024 annual report | 10 ng/L | 1.0× the limit |
| City of Hialeah, FL 2023 annual report | 1–10 ng/L | 1.0× the limit |
| City of Lincoln — Lincoln, Ca, CA 2023 annual report | 10 ng/L | 1.0× the limit |
| City of North Miami Beach, FL 2023 annual report | 1–10 ng/L | 1.0× the limit |
| Eastern Correctional Institute, MD 2024 annual report | 10 ng/L | 1.0× the limit |
| Miami Dade, FL 2023 annual report | 1–10 ng/L | 1.0× the limit |
| Town of Accident, MD 2024 annual report | 10 ng/L | 1.0× the limit |
Approaching the limit (8)
| Water system | Measured | vs. limit |
|---|---|---|
| Greensboro, NC 2024 annual report | 9.1 ng/L | 0.9× the limit |
| Midland, TX 2024 annual report | 9.1 ng/L | 0.9× the limit |
| Avondale, AZ 2024 annual report | 0–9 ng/L | 0.9× the limit |
| Bradford Estates, MD 2024 annual report | 8.9 ng/L | 0.9× the limit |
| Augusta, GA 2024 annual report | 8.6 ng/L | 0.9× the limit |
| San Angelo, TX 2024 annual report | 8.6 ng/L | 0.9× the limit |
| Boh Nak Mhp, MD 2024 annual report | 8.5 ng/L | 0.8× the limit |
| Los Angeles Cwwd 36-val Verde — Alhambra, Ca, CA 2023 annual report | 8.3 ng/L | 0.8× the limit |
Within the federal limit (247)
Showing 50 of 247. The full list is in the JSON API.
Frequently asked
+What is Perfluorohexanesulfonic acid?
Perfluorohexanesulfonic acid, a PFAS 'forever chemical.' Regulated by the EPA at 10 parts per trillion and included in the PFAS Hazard Index.
+What is the federal limit for Perfluorohexanesulfonic acid in drinking water?
The federal MCL for Perfluorohexanesulfonic acid is 10 ng/L. The EPA enforces this against the regulated reporting statistic (typically a running annual average or 90th percentile), not a single-sample spike.
+How many U.S. water systems have Perfluorohexanesulfonic acid over the federal limit?
27 of the 282 public water systems on The Water Map report Perfluorohexanesulfonic acid at or above its federal limit, spanning 31 U.S. states. The full list is on this page.
+How can I check if Perfluorohexanesulfonic acid is in my city's tap water?
Search your city on The Water Map (https://www.thewatermap.com/) or browse the list on this page. Every U.S. public water utility is required to publish an annual Consumer Confidence Report that lists every contaminant it measured, including Perfluorohexanesulfonic acid.
See Perfluorohexanesulfonic acid on the map
Color-coded by status across the whole country.
Open the map →