Data investigation · EPA UCMR 5
The most PFAS-contaminated water systems in America
Between 2023 and 2025, the EPA required large U.S. water utilities to test for PFAS for the first time. 1,717 public water systems came back above the federal limits the EPA finalized in 2024 — the worst at 123× the limit. These are those systems, ranked by severity.
How to read this
What "above the limit" means — and doesn't
The EPA's Maximum Contaminant Levels (MCLs) for PFOA and PFOS are 4 parts per trillion — roughly four drops in an Olympic swimming pool. A system listed here measured at least one compound above its MCL during 2023–2025 testing. A result of "123× the limit" means the measured concentration was that many times the MCL.
Being above the limit does not mean the water is acutely unsafe to drink today. The MCLs are set to limit lifetime exposure risk. It does mean the utility is legally required to reduce levels and come into compliance by 2029. If your system is listed, an NSF/ANSI 53 or 58 certified filter reduces PFAS at the tap in the meantime — see your ZIP's page for specifics.
Source: EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR 5), sampled 2023–2025. Rankings reflect the highest single sample reported at each system's entry point. Figures update when the EPA releases new data. Full methodology.
01The 100 most contaminated systems
by × of EPA limitShowing the 100 most severe of 1,717 systems above EPA limits. Select any system for its full results and guidance.
02Worst by compound
Five PFAS compounds carry enforceable EPA limits. PFOA and PFOS — the two most studied and most widespread — drive the overwhelming majority of exceedances.
Perfluorooctane sulfonic acid
Worst: 123× — NASHVILLE, TOWN OF, NC
See all PFOS rankings →Perfluorooctanoic acid
Worst: 59× — COLLEGEVILLE TRAPPE JOINT PWD, PA
See all PFOA rankings →Perfluorohexane sulfonic acid
Worst: 25× — POTRERO ELEMENTARY SCHOOL, CA
See all PFHxS rankings →Perfluorononanoic acid
Worst: 10.0× — EMMAUS BOROUGH PUBLIC WATER, PA
See all PFNA rankings →Hexafluoropropylene oxide dimer acid (GenX)
Worst: 14× — ABBEVILLE CITY OF, SC
See all HFPO-DA rankings →03Most affected states
by systems above limit| # | State | Systems above limit | Worst system |
|---|---|---|---|
| 1 | California | 167 | RUNNING SPRINGS WATER DISTRICT 59× |
| 2 | Florida | 157 | ORANGEWOOD WATER SYSTEM 20× |
| 3 | New Jersey | 156 | LIVINGSTON TWP DIV OF WATER 11× |
| 4 | Pennsylvania | 119 | COLLEGEVILLE TRAPPE JOINT PWD 59× |
| 5 | North Carolina | 115 | NASHVILLE, TOWN OF 123× |
| 6 | Massachusetts | 106 | RAYNHAM CENTER WATER DISTRICT 23× |
| 7 | Texas | 103 | CITY OF GRAND PRAIRIE 21× |
| 8 | Alabama | 79 | IRONDALE WATER SYSTEM 15× |
| 9 | South Carolina | 68 | ABBEVILLE CITY OF 14× |
| 10 | Ohio | 59 | KINGS ISLAND PWS 7.2× |
| 11 | New York | 52 | PEQUENAKONCK ELEMENTARY SCHOOL 28× |
| 12 | Georgia | 42 | LAFAYETTE 14× |
| 13 | Tennessee | 37 | SAVANNAH VALLEY U. D. 8.8× |
| 14 | Connecticut | 36 | NORWICH PUBLIC UTILITIES 4.0× |
| 15 | Washington | 34 | ARTONDALE WATER SYSTEM 38× |
| 16 | Kentucky | 32 | HARRISON CO WATER ASSOC 12× |
| 17 | Illinois | 27 | COLLINSVILLE, IL 4.5× |
| 18 | Arizona | 25 | TEMPE CITY OF 14× |
| 19 | Wisconsin | 23 | SAUKVILLE WATERWORKS 7.8× |
| 20 | West Virginia | 21 | LUBECK PSD 45× |
| 21 | Virginia | 20 | BEALETON REGIONAL 11× |
| 22 | Indiana | 19 | MARYSVILLE OTISCO NABB WATER CORP. 3.6× |
| 23 | Minnesota | 17 | Hastings, MN 5.9× |
| 24 | Maryland | 16 | TOWN OF THURMONT 12× |
| 25 | New Hampshire | 16 | HUDSON WATER DEPT 2.3× |
Top 25 states shown. Browse all states →
If your system is listed
04What you can do
01
Look up your ZIP for the exact utility serving your home and its full results.
02
Install a certified filter — NSF/ANSI 53 or 58 — to reduce PFAS at the tap now.
03
Read your utility's CCR for its compliance plan and timeline to 2029.