By compound · EPA limit 10 ppt
Where HFPO-DA contamination is worst
Hexafluoropropylene oxide dimer acid (GenX) — 16 U.S. public water systems measured HFPO-DA above the EPA's 10 ppt limit during 2023–2025 UCMR 5 testing. They're ranked below by how far over the limit they tested.
EPA limit (MCL)
10 ppt Systems above the limit
16 Worst result
140.0 ppt (14×) — ABBEVILLE CITY OF, SC Systems exceeding the HFPO-DA limit
16 of 16| # | Water system | State | HFPO-DA measured | × limit |
|---|---|---|---|---|
| 1 | ABBEVILLE CITY OF | SC | 140.0 ppt | 14× |
| 2 | LAURENS COUNTY W&S COMM (SC3020001) | SC | 95.8 ppt | 9.6× |
| 3 | GREENWOOD CPW (2410001) | SC | 91.0 ppt | 9.1× |
| 4 | BELTON CITY OF (SC0410004) | SC | 82.9 ppt | 8.3× |
| 5 | HONEA PATH TOWN OF (0410003) | SC | 42.0 ppt | 4.2× |
| 6 | DONALDS-DUE WEST W&SA (SC0120001) | SC | 40.0 ppt | 4.0× |
| 7 | SALUDA CPW (4110001) | SC | 39.0 ppt | 3.9× |
| 8 | ROBESON COUNTY WATER SYSTEM | NC | 34.0 ppt | 3.4× |
| 9 | BIG SANDY WATER DISTRICT | KY | 25.0 ppt | 2.5× |
| 10 | WARE SHOALS TOWN OF (2410003) | SC | 22.0 ppt | 2.2× |
| 11 | CLINTON CITY OF (3010002) | SC | 14.3 ppt | 1.4× |
| 12 | PERTH AMBOY WATER DEPARTMENT | NJ | 14.0 ppt | 1.4× |
| 13 | BLADEN CO WTR DIST-EAST BLADEN | NC | 13.6 ppt | 1.4× |
| 14 | MILLTOWN W DEPT | NJ | 12.9 ppt | 1.3× |
| 15 | NEWBERRY CITY OF (3610001) | SC | 10.2 ppt | 1.0× |
| 16 | JOINT MUNICIPAL WSC (3220003) | SC | 10.1 ppt | 1.0× |
Being above the limit means the utility must reduce levels to comply by 2029 — not that the water is acutely unsafe today. A certified NSF/ANSI 53 or 58 filter reduces HFPO-DA at the tap. Source: EPA UCMR 5 (2023–2025). Methodology.