PFAS · Wisconsin
PFAS in Wisconsin drinking water: EPA’s final survey results
EPA’s national PFAS survey (UCMR 5) tested 196 of the community water systems that serve homes in Wisconsin. 52 found at least one of 29 PFAS above the laboratory reporting level, and 18 had a PFOA or PFOS sampling-location yearly average at or above EPA’s 4.0 ppt limit. Samples were collected from January 2023 to February 2026.
Data as of EPA UCMR 5 final release, August 2026 (file dated Aug 28, 2026) · EPA SDWIS 2026Q2 (file dated Jul 9, 2026). How we build these pages
PFHxS was the compound Wisconsin community systems found most often: 27 of 196 tested systems measured it above the reporting level. Across the country, 35% of surveyed community systems found at least one PFAS; in Wisconsin the share is 27%. The largest Wisconsin system with a detection, Madison Water Utility, serves 272,000 people and found 2 of the 29 compounds.
Which PFAS were found most often in Wisconsin
Each row counts the Wisconsin community water systems where that compound was measured above the reporting level at least once. A detection is a measurement, not a violation: most of these compounds have no federal limit.
| Compound | Systems where found | Systems tested | Share |
|---|---|---|---|
| PFHxS | 27 | 196 | 14% |
| PFBA | 26 | 196 | 13% |
| PFBS | 26 | 196 | 13% |
| PFPeA | 20 | 196 | 10% |
| PFHxA | 16 | 196 | 8% |
| PFOA | 15 | 196 | 8% |
| PFOS | 12 | 196 | 6% |
| PFHpA | 5 | 196 | 3% |
| 6:2 FTS | 2 | 196 | 1% |
| PFPeS | 2 | 196 | 1% |
Wisconsin systems with the most PFAS found
The 10 surveyed community water systems that found the most different PFAS, with PFOA and PFOS compared to EPA’s 4.0 ppt limits on the yearly average at the highest sampling location. Larger systems come first when counts tie.
| Water system | People served | PFAS found (of 29) | PFOA | PFOS |
|---|---|---|---|---|
| Pewaukee City Water and Sewer Utility WI2680214 | 8,671 | 10 | 4.3 ppt at or above the MCL | 6.0 ppt at or above the MCL |
| Saukville Waterworks WI2460134 | 4,268 | 9 | 2.1 ppt below the MCL | 30.5 ppt at or above the MCL |
| Weston Municipal Utilities WI7370163 | 16,000 | 8 | 5.5 ppt at or above the MCL | 10.8 ppt at or above the MCL |
| La Crosse Waterworks WI6320309 | 53,000 | 7 | 4.8 ppt at or above the MCL | 4.9 ppt at or above the MCL |
| Marshfield Utilities WI7720165 | 18,815 | 7 | — not detected above the reporting level | 13.0 ppt at or above the MCL |
| Hartland Waterworks WI2680205 | 9,212 | 7 | 4.4 ppt at or above the MCL | 4.4 ppt at or above the MCL |
| Rib Mountain Water Utility WI7370660 | 6,398 | 7 | 4.8 ppt at or above the MCL | 8.5 ppt at or above the MCL |
| Prescott Waterworks WI6480243 | 4,258 | 6 | 9.4 ppt at or above the MCL | — not detected above the reporting level |
| Schofield Waterworks WI7370162 | 2,205 | 6 | 4.4 ppt at or above the MCL | — not detected above the reporting level |
| Monona Waterworks WI1130245 | 8,624 | 5 | — not detected above the reporting level | — not detected above the reporting level |
Counties with the most systems that found PFAS
- Dane County 6 of 15 surveyed systems
- Waukesha County 6 of 12 surveyed systems
- Marathon County 4 of 5 surveyed systems
- Washington County 4 of 6 surveyed systems
- La Crosse County 3 of 4 surveyed systems
- Walworth County 2 of 6 surveyed systems
- St. Croix County 2 of 3 surveyed systems
- Pierce County 2 of 3 surveyed systems