Contaminant · PFAS
PFHxS in drinking water
Perfluorohexanesulfonic acid, a shorter-chain replacement for PFOS.
highest complete sampling-location average; sampled 2023–2025. Source: EPA records; Potrero Elementary School (CA3700963).
What the rules say
The April 2024 PFAS rule set a 10 ng/L (ppt) limit for PFHxS. In May 2026 EPA proposed rescinding that limit. Until a final decision, the 10 ng/L figure is shown for reference only.
What EPA's assessment says
EPA's 2024 rule cites health effects assessments associating PFHxS with thyroid, liver and immune effects.
Read the EPA source for PFHxS.
Across the country
EPA tested 10,307 water systems for PFHxS and found it in 1,037. Half of the systems that found it measured less than 4.6 ppt, and one in ten measured more than 11.8 ppt.
EPA's final UCMR 5 occurrence file contains 66,347 PFHxS results from 10,307 systems. 3,231 results were at or above the minimum reporting level, across 1,037 systems. Among detections, the median was 4.6 ppt and the 90th percentile was 11.8 ppt.
118 systems had a result at or above the reference on the page's stated comparison basis. For contaminants with a limit, that basis is the yearly average at the highest sampling location, not the highest single sample.
Systems with the highest recorded PFHxS results
| System | State | Population served | Recorded value | Records / periods |
|---|---|---|---|---|
| Potrero Elementary School CA3700963 | California | 300 | 222 ppt | 2 |
| Bayleaf Master NC0392373 | North Carolina | 16,715 | 140 ppt | 28 |
| Running Springs Water District CA3610062 | California | 5,268 | 68.6 ppt | 8 |
| Tempe City of AZ0407100 | Arizona | 165,000 | 67.8 ppt | 8 |
| Saukville Waterworks WI2460134 | Wisconsin | 4,268 | 62.5 ppt | 4 |
| Yeshiva Farm Settlement NY5903150 | New York | 300 | 47.2 ppt | 4 |
| Augusta-Richmond Co Ws GA2450000 | Georgia | 204,000 | 44.5 ppt | 4 |
| Great Bend, City of KS2000911 | Kansas | 14,580 | 44.0 ppt | 10 |
| Quistorff WA5370550 | Washington | 1,113 | 44.0 ppt | 2 |
| Ocala, City of (2 Wtps) FL3420922 | Florida | 66,449 | 41.5 ppt | 2 |
| Gwa Northern Water System GU0000006 | Guam | 139,207 | 40.0 ppt | 80 |
| Pewaukee City Water and Sewer Utility WI2680214 | Wisconsin | 8,671 | 34.5 ppt | 6 |
| Sauk Rapids MN1050004 | Minnesota | 13,835 | 32.3 ppt | 4 |
| Moses Lake City of WA5356300 | Washington | 32,428 | 31.8 ppt | 5 |
| Ruch Elementary Sd 549 OR4191508 | Oregon | 200 | 30.6 ppt | 2 |
| Sioux City Water Supply IA9778054 | Iowa | 85,791 | 30.3 ppt | 4 |
| Fort Campbell Water System TN0000820 | Kentucky | 43,270 | 30.1 ppt | 4 |
| Emerald Coast Utilities Authority (Ecua) FL1170525 | Florida | 242,172 | 30.0 ppt | 25 |
| City of Atwater CA2410001 | California | 29,479 | 29.5 ppt | 8 |
| Duxbury Water Department MA4082000 | Massachusetts | 16,387 | 29.3 ppt | 2 |
| City of Fresno CA1010007 | California | 545,716 | 29.0 ppt | 22 |
| Emmaus Borough Public Water PA3390032 | Pennsylvania | 14,000 | 28.9 ppt | 5 |
| Independence Township MI0003342 | Michigan | 11,790 | 28.0 ppt | 2 |
| Tanglewood on Texoma TX0910052 | Texas | 4,341 | 28.0 ppt | 3 |
| Widefield WSD CO0121900 | Colorado | 27,640 | 27.8 ppt | 6 |
Filters and testing
NSF/ANSI 53 or NSF/ANSI 58 with a PFAS reduction claim
A standard number by itself is not a contaminant claim. Check the product's current certification listing and performance data sheet for PFHxS or the specific contaminant you want to reduce. A utility-level record is not a test of your own faucet.