PFAS ("forever chemicals")
Perfluorobutanesulfonic acid in U.S. tap water
146 public water systems across 28 U.S. states report Perfluorobutanesulfonic acid in their annual Consumer Confidence Report. 8 sit at or above the federal limit.
What it is
Perfluorobutanesulfonic acid, a shorter-chain PFAS 'forever chemical.'
Why it's regulated
Has no standalone limit but is part of the EPA PFAS Hazard Index that limits PFAS in combination.
At or above the federal limit (8)
| Water system | Measured | vs. limit |
|---|---|---|
| Gilbert, AZ 2024 annual report | 25 | 25.0× the limit |
| Chula Vista Sweetwater, CA 2024 annual report | 0–11 ng/L | 11.0× the limit |
| Charleston, SC 2024 annual report | 4 ng/L | 2.0× the limit |
| North Charleston, SC 2024 annual report | 4 ng/L | 2.0× the limit |
| Boonsboro Keedysville, MD 2024 annual report | 5.8 ng/L | 1.9× the limit |
| Kent, WA 2024 annual report | 3.37 ng/L | 1.7× the limit |
| Goodyear, AZ 2024 annual report | 13 ng/L | 1.3× the limit |
| Tampa, FL 2024 annual report | 0.0037 ug/L | 1.2× the limit |
Approaching the limit (1)
| Water system | Measured | vs. limit |
|---|---|---|
| Renton, WA 2024 annual report | 2.98 ng/L | 1.0× the limit |
Within the federal limit (66)
| Water system | Measured |
|---|---|
| Palm Bay, FL 2024 annual report | 0.0065–0.0061 ug/L |
| Chandler, AZ 2024 annual report | 1.23 ng/L |
| Burbank, CA 2024 annual report | 0–20 ng/L |
| Saint Paul, MN 2024 annual report | 0–2.2 |
| Pomona, CA 2024 annual report | 0–5 ng/L |
| Fullerton, CA 2024 annual report | 3.6 ng/L |
| Rochester, MN 2025 annual report | 0.55 |
| Ansonia, CT 2024 annual report | 0–3.5 ng/L |
| Bethany, CT 2024 annual report | 0–3.5 ng/L |
| Branford, CT 2024 annual report | 0–3.5 ng/L |
| Cheshire, CT 2024 annual report | 0–3.5 ng/L |
| Derby, CT 2024 annual report | 0–3.5 ng/L |
| East Haven, CT 2024 annual report | 0–3.5 ng/L |
| Hamden, CT 2024 annual report | 0–3.5 ng/L |
| Milford, CT 2024 annual report | 0–3.5 ng/L |
| New Haven, CT 2024 annual report | 0–3.5 ng/L |
| North Haven, CT 2024 annual report | 0–3.5 ng/L |
| Orange, CT 2024 annual report | 0–3.5 ng/L |
| Seymour, CT 2024 annual report | 0–3.5 ng/L |
| West Haven, CT 2024 annual report | 0–3.5 ng/L |
| Woodbridge, CT 2024 annual report | 0–3.5 ng/L |
| West Covina, CA 2024 annual report | 1.43 ng/L |
| Knoxville, TN 2024 annual report | 0.0037 |
| Chico, CA 2024 annual report | 0.75 ng/L |
| Green Bay, WI 2024 annual report | 0.32–0.57 ng/L |
| Fishers, IN 2024 annual report | 0.73 |
| Indianapolis, IN 2024 annual report | 0.73 |
| Morgan County, IN 2024 annual report | 0.73 |
| Westfield, IN 2024 annual report | 0.73 |
| Bakersfield, CA 2024 annual report | 0.18 ng/L |
| Visalia, CA 2024 annual report | 0.12 ng/L |
| Colorado Springs, CO 2024 annual report | 0.34 ng/L |
| Albuquerque, NM 2024 annual report | Not detected |
| Anchorage, AK 2024 annual report | Not detected ng/L |
| Brown Deer, WI 2024 annual report | Not detected ug/L |
| Butler, WI 2024 annual report | Not detected ug/L |
| Calvert Manor, MD 2024 annual report | Not detected |
| Dearborn, MI 2024 annual report | Not detected ug/L |
| Eastern Correctional Institute, MD 2024 annual report | Not detected ng/L |
| El Cajon, CA 2024 annual report | Not detected ng/L |
| Franklin, WI 2024 annual report | Not detected ug/L |
| Freedom District, MD 2024 annual report | Not detected ng/L |
| Glendale, AZ 2024 annual report | Not detected ug/L |
| Grand Rapids, MI 2025 annual report | Not detected ng/L |
| Greendale, WI 2024 annual report | Not detected ug/L |
| Greenfield, WI 2024 annual report | Not detected ug/L |
| Hales Corners, WI 2024 annual report | Not detected ug/L |
| Menomonee Falls, WI 2024 annual report | Not detected ug/L |
| Mequon, WI 2024 annual report | Not detected ug/L |
| Milwaukee, WI 2024 annual report | Not detected ug/L |
Showing 50 of 66. The full list is in the JSON API.
Frequently asked
+What is Perfluorobutanesulfonic acid?
Perfluorobutanesulfonic acid, a shorter-chain PFAS 'forever chemical.' Has no standalone limit but is part of the EPA PFAS Hazard Index that limits PFAS in combination.
+What is the federal limit for Perfluorobutanesulfonic acid in drinking water?
The federal MCL for Perfluorobutanesulfonic acid is 1.6 . 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 Perfluorobutanesulfonic acid over the federal limit?
8 of the 146 public water systems on The Water Map report Perfluorobutanesulfonic acid at or above its federal limit, spanning 28 U.S. states. The full list is on this page.
+How can I check if Perfluorobutanesulfonic 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 Perfluorobutanesulfonic acid.
See Perfluorobutanesulfonic acid on the map
Color-coded by status across the whole country.
Open the map →