PFAS ("forever chemicals")
PFOS in U.S. tap water
147 public water systems across 30 U.S. states report PFOS in their annual Consumer Confidence Report. 48 sit at or above the federal limit.
147
systems measuring
48
over the limit
30
states represented
What it is
Perfluorooctanesulfonic acid, a PFAS 'forever chemical' once used in firefighting foam and coatings.
Why it's regulated
Linked to cancer, thyroid disease, and immune effects; the EPA set an enforceable limit of 4 parts per trillion.
Federal limit4 ng/L· MCL
At or above the federal limit (48)
| Water system | Measured | vs. limit |
|---|---|---|
| Charleston, SC 2024 annual report | 9.7 ng/L | 485.0× the limit |
| North Charleston, SC 2024 annual report | 9.7 ng/L | 485.0× the limit |
| City of Hialeah, FL 2023 annual report | 35–35 ng/L | 8.8× the limit |
| City of Homestead, FL 2023 annual report | 35–35 ng/L | 8.8× the limit |
| City of North Miami Beach, FL 2023 annual report | 35–35 ng/L | 8.8× the limit |
| Miami Dade, FL 2023 annual report | 35–35 ng/L | 8.8× the limit |
| Chula Vista Sweetwater, CA 2024 annual report | 0–33 ng/L | 8.3× the limit |
| Vancouver, WA 2024 annual report | 0–23.1 | 5.8× the limit |
| Glendale, CA 2024 annual report | 13 ng/L | 3.3× the limit |
| Pomona, CA 2024 annual report | 0–18 ng/L | 2.8× the limit |
| Ansonia, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Bethany, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Branford, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Cheshire, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Derby, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| East Haven, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Hamden, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Milford, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| New Haven, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| North Haven, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Orange, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Seymour, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| West Haven, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| Woodbridge, CT 2024 annual report | 0–10.7 ng/L | 2.7× the limit |
| City of Hampton, VA 2024 annual report | 4.9 ng/L | 2.5× the limit |
| City of Newport News, VA 2025 annual report | 4.9 ng/L | 2.5× the limit |
| City of Poquoson, VA 2025 annual report | 4.9 ng/L | 2.5× the limit |
| City of Poquoson, VA 2024 annual report | 3.7–4.9 ng/L | 2.5× the limit |
| Gilbert, AZ 2024 annual report | 9.8 ng/L | 2.5× the limit |
| Hampton, VA 2025 annual report | 4.9 ng/L | 2.5× the limit |
| James City County, VA 2025 annual report | 3.7–4.9 ng/L | 2.5× the limit |
| James City County, VA 2024 annual report | 3.7–4.9 ng/L | 2.5× the limit |
| Newport News, VA 2024 annual report | 4.9 ng/L | 2.5× the limit |
| York County, VA 2024 annual report | 4.9 ng/L | 2.5× the limit |
| York County, VA 2025 annual report | 3.7–4.9 ng/L | 2.5× the limit |
| Columbus, GA 2024 annual report | 5–8.4 | 2.1× the limit |
| Goodyear, AZ 2024 annual report | 7 ng/L | 1.8× the limit |
| Burbank, CA 2024 annual report | 0–5.8 ng/L | 1.4× the limit |
| Raleigh, NC 2024 annual report | 4.57 | 1.1× the limit |
| Town of Garner, NC 2024 annual report | 4.57 | 1.1× the limit |
| Town of Knightdale, NC 2024 annual report | 4.57 | 1.1× the limit |
| Town of Rolesville, NC 2024 annual report | 4.57 | 1.1× the limit |
| Town of Wake Forest, NC 2024 annual report | 4.57 | 1.1× the limit |
| Town of Wendell, NC 2024 annual report | 4.57 | 1.1× the limit |
| Town of Zebulon, NC 2024 annual report | 4.57 | 1.1× the limit |
| Washington Dc, DC 2023 annual report | 2.1 | 1.1× the limit |
| Lynn, MA 2024 annual report | 4.2 ng/L | 1.1× the limit |
| Santa Clarita, CA 2024 annual report | 0.0065 ug/L | 1.0× the limit |
Approaching the limit (2)
| Water system | Measured | vs. limit |
|---|---|---|
| Fullerton, CA 2024 annual report | 6.4 ng/L | 1.0× the limit |
| Birmingham, AL 2024 annual report | 0.0025–0.0036 | 0.9× the limit |
Within the federal limit (61)
| Water system | Measured |
|---|---|
| Saint Paul, MN 2024 annual report | 0–1.8 |
| Huntington Beach, CA 2025 annual report | 5 ng/L |
| Centennial, CO 2023 annual report | 3.02 ng/L |
| City of Baltimore, MD 2024 annual report | 2.43 |
| Santa Ana, CA 2024 annual report | 3.8 ng/L |
| Kent, WA 2024 annual report | 2.28 |
| Albany, NY 2024 annual report | 2 ng/L |
| Rockville, MD 2024 annual report | 2 |
| Jersey City, NJ 2024 annual report | 6.8 ng/L |
| Yonkers, NY 2024 annual report | 1.9 ng/L |
| Elizabeth, NJ 2024 annual report | 5 ng/L |
| Allentown, PA 2024 annual report | 0–6.87 ng/L |
| Boonsboro Keedysville, MD 2024 annual report | 1763–1 |
| Georgetown, TX 2024 annual report | 0.7 ng/L |
| Grand Rapids, MI 2025 annual report | 2.4 ng/L |
| Brown Deer, WI 2024 annual report | 2.2 ng/L |
| Butler, WI 2024 annual report | 2.2 ng/L |
| Franklin, WI 2024 annual report | 2.2 ng/L |
| Green Bay, WI 2024 annual report | 2.2 ng/L |
| Greendale, WI 2024 annual report | 2.2 ng/L |
| Greenfield, WI 2024 annual report | 2.2 ng/L |
| Hales Corners, WI 2024 annual report | 2.2 ng/L |
| Menomonee Falls, WI 2024 annual report | 2.2 ng/L |
| Mequon, WI 2024 annual report | 2.2 ng/L |
| Milwaukee, WI 2024 annual report | 2.2 ng/L |
| New Berlin, WI 2024 annual report | 2.2 ng/L |
| Shorewood, WI 2024 annual report | 2.2 ng/L |
| St. Francis, WI 2024 annual report | 2.2 ng/L |
| Thiensville, WI 2024 annual report | 2.2 ng/L |
| Waukesha, WI 2024 annual report | 2.2 ng/L |
| Wauwatosa, WI 2024 annual report | 2.2 ng/L |
| West Allis, WI 2024 annual report | 2.2 ng/L |
| Tempe, AZ 2024 annual report | 0.3 ng/L |
| Colorado Springs, CO 2024 annual report | 0.81–0.93 ng/L |
| Albuquerque, NM 2024 annual report | Not detected |
| Anchorage, AK 2024 annual report | Not detected ng/L |
| Bakersfield, CA 2024 annual report | Not detected ng/L |
| Calvert Manor, MD 2024 annual report | Not detected |
| Cary, NC 2025 annual report | Not detected |
| Chandler, AZ 2024 annual report | 0 ng/L |
| Chico, CA 2024 annual report | Not detected ng/L |
| Dearborn, MI 2024 annual report | Not detected ug/L |
| El Cajon, CA 2024 annual report | Not detected ng/L |
| El Monte, CA 2024 annual report | Not detected ng/L |
| Freedom District, MD 2024 annual report | Not detected ng/L |
| Glendale, AZ 2024 annual report | Not detected ng/L |
| Louisville, KY 2024 annual report | 0 |
| Lubbock, TX 2024 annual report | Not detected ng/L |
| Madison, WI 2024 annual report | Not detected ng/L |
| Mobile, AL 2024 annual report | Not detected |
Showing 50 of 61. The full list is in the JSON API.
Frequently asked
+What is PFOS?
Perfluorooctanesulfonic acid, a PFAS 'forever chemical' once used in firefighting foam and coatings. Linked to cancer, thyroid disease, and immune effects; the EPA set an enforceable limit of 4 parts per trillion.
+What is the federal limit for PFOS in drinking water?
The federal MCL for PFOS is 4 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 PFOS over the federal limit?
48 of the 147 public water systems on The Water Map report PFOS at or above its federal limit, spanning 30 U.S. states. The full list is on this page.
+How can I check if PFOS 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 PFOS.