PFAS (“forever chemicals”) are among the most common concerns in large US water systems on our site. Of the 1,000 systems we grade, 411 (41%) list PFAS among their top three concerns. Together they serve about 78.6 million people, roughly 39% of the 199 million people covered by our data. Ten of the 27 systems serving a million or more people are on that list. These are detections compared with health guidelines, not EPA violations. Federal PFAS limits are not enforceable yet.
Below is how we counted, which large systems are affected, how PFAS shapes grades, and what you can do.
Where this data comes from
This post is not based on EPA violation records. It uses the contaminant data behind our grades, which comes mainly from the EWG Tap Water Database and utility Consumer Confidence Reports (see our methodology). That data compares the PFAS levels a utility reported in testing with EWG’s health-based guidelines, which are far stricter than EPA’s legal limits.
Each system page lists its top three concerns. We counted a system if any of those three named PFAS. Two kinds of entries appear:
- “PFAS contamination”: a flag that PFAS were detected in the system’s data. 392 systems have it.
- A specific PFAS “significantly above health guideline”: 244 systems, serving about 42.7 million people. The compound named most often is PFHxS (230 systems). Others are total PFOS and PFOA (24), PFOA (3), PFUnA (2), PFHpS (1) and PFDA (1).
Most systems with a specific compound (225 of 244) also have the general flag.
Important limits
- This is a detection count, not a violation count. EPA’s April 2024 rule set limits of 4.0 parts per trillion (ppt) for PFOA and PFOS, but compliance is not required until April 2029, and EPA has proposed extending PFOA and PFOS compliance to 2031 (not final as of October 2026). No system can have a federal PFAS violation yet. Our EPA PFAS rule explainer covers the details.
- Detections can be far below legal limits. For example, the MWRA page shows PFOA at 0.832 ppt, well under EPA’s 4.0 ppt limit but above EWG’s guideline.
- Only the top three concerns are counted. A system without PFAS in its top three may still have detected PFAS at lower levels, so this is likely an undercount.
- Test dates vary. The underlying results come from different years, and a utility may have added treatment since. Check your utility’s latest report.
- Only large systems. Every system here serves more than 50,000 people. Smaller systems and private wells are not included.
The largest systems with PFAS as a top concern
| System | State | People served | Grade (score) | PFAS concern listed |
|---|---|---|---|---|
| MWRA | MA | 2,660,000 | C (72) | PFAS detected |
| Miami-Dade WASA Main System | FL | 2,377,460 | F (46) | PFAS detected; PFHxS |
| Philadelphia Water Department | PA | 1,600,000 | F (50) | PFAS detected |
| City of San Diego | CA | 1,385,379 | D (60) | PFAS detected |
| Dallas Water Utility | TX | 1,356,479 | D (61) | PFAS detected; PFHxS |
| Charlotte Water | NC | 1,163,701 | C (65) | PFAS detected |
| Fairfax County Water Authority | VA | 1,121,613 | D (63) | PFAS detected |
| Austin Water | TX | 1,115,323 | C (67) | PFAS detected; PFHxS |
| Suffolk County Water Authority | NY | 1,100,000 | C (72) | PFAS detected; PFHxS |
| San Jose Water | CA | 1,039,920 | F (45) | PFAS detected; PFHxS |
| City of Fort Worth | TX | 955,900 | D (58) | PFAS detected; PFHxS |
| Aqua PA Main System | PA | 822,600 | F (43) | PFAS detected; PFHxS |
| Veolia Water New Jersey Hackensack | NJ | 792,713 | F (50) | PFAS detected; PFHxS |
| MCWA | NY | 768,458 | F (54) | PFAS detected |
| Louisville Water Company | KY | 764,769 | C (74) | PFAS detected |
The largest system where total PFOS and PFOA is listed above the health guideline is Milwaukee Water Works (626,000 people, grade C).
PFAS by state
States with the most large systems listing PFAS as a top concern:
| State | Systems with PFAS concern | Systems in our data | Share |
|---|---|---|---|
| California | 87 | 176 | 49% |
| Florida | 40 | 93 | 43% |
| Massachusetts | 28 | 30 | 93% |
| Texas | 26 | 76 | 34% |
| North Carolina | 24 | 29 | 83% |
| New Jersey | 22 | 25 | 88% |
| New York | 18 | 29 | 62% |
| Washington | 15 | 36 | 42% |
| Minnesota | 13 | 18 | 72% |
| Alabama | 12 | 16 | 75% |
| Wisconsin | 11 | 11 | 100% |
| Pennsylvania | 11 | 30 | 37% |
California has the most by count. Wisconsin, Massachusetts, New Jersey and North Carolina have the highest shares among states with at least 10 systems. These shares partly reflect how much PFAS testing each state’s utilities have reported, so a lower share does not prove less PFAS. For state detail, see our posts on California and Texas.
PFAS showed up about equally in groundwater and surface water systems: 94 of 224 groundwater systems (42%), 195 of 474 surface water systems (41%), and 116 of 290 systems that buy surface water from another utility (40%).
How PFAS affects grades
PFAS weighs heavily in our grades. Detections above health guidelines reduce the largest scoring component, and any PFAS detection counts in the “high-risk contaminant presence” component. The effect is clear in the data:
| Systems with PFAS concern | Systems without | |
|---|---|---|
| Number of systems | 411 | 589 |
| Average score | 59.7 | 74.3 |
| Graded A | 2 | 75 |
| Graded F | 123 | 11 |
Of the 134 systems graded F nationally, 123 list PFAS as a top concern. That is why a system with a clean EPA record can still get a low grade. Our lowest-graded big cities list shows this pattern too.
Why PFAS matter
PFAS are a large family of human-made chemicals that break down very slowly. EPA says lowering PFAS exposure in drinking water is expected to prevent certain cancers and liver and heart effects in adults, and immune and developmental effects in infants and children. EPA set its health goal for PFOA and PFOS at zero, meaning it did not identify a safe level of exposure.
PFHxS, the compound most often flagged on our site, is one of the four PFAS whose federal limits EPA proposed to repeal in May 2026. As of October 2026 that proposal is not final. California’s notification level for PFHxS is 3 ppt.
What you can do
- Find your system. Use our search page to see whether PFAS is listed for your utility, and which compounds.
- Get recent results. Your Consumer Confidence Report, or results your utility posted from EPA’s fifth Unregulated Contaminant Monitoring Rule (UCMR 5), may show newer PFAS numbers than our data.
- Compare against 4 ppt. A utility can be above 4 ppt for PFOA or PFOS without a violation until 2029.
- Do not boil water for PFAS. EPA says boiling does not remove PFOA or PFOS.
- Consider a certified filter. Look for certification to NSF/ANSI 53 or 58 with a specific PFOA/PFOS reduction claim, and confirm the exact model in the certifier’s online listing. Our guide to the best water filters for PFAS removal explains what to look for.
- Ask a doctor if you are pregnant, feeding an infant with formula, or have specific health concerns.
Note: utilities may have resolved issues or added treatment since these results were reported. Check your utility’s latest Consumer Confidence Report and its page on our site for current information.
Sources
- EPA: PFAS National Primary Drinking Water Regulation
- EPA: Proposed PFOA and PFOS Compliance Extension Rule
- Federal Register, May 20, 2026: Rescission of Regulatory Determinations for Four PFAS
- EPA: PFAS NPDWR Questions and Answers (April 2024)
- California State Water Resources Control Board: PFAS
- EWG Tap Water Database
- TapWaterSafety.org methodology