Contaminant · PFAS
PFHxA in drinking water
Perfluorohexanoic acid, a short-chain PFAS and common breakdown product of newer fluorotelomer chemistries.
highest recorded single-sample basis; sampled 2023–2025. Source: EPA records; Experimental (PR0004604).
What the rules say
PFHxA has no federal limit. The USGS health-based screening level of 3,000 ng/L (from EPA's IRIS reference dose) is shown for scale only.
What EPA's assessment says
EPA's 2023 IRIS assessment for PFHxA cites developmental, liver and blood effects in animal studies.
Read the EPA source for PFHxA.
Across the country
EPA tested 10,307 water systems for PFHxA and found it in 1,807. Half of the systems that found it measured less than 4.6 ppt, and one in ten measured more than 10.1 ppt.
EPA's final UCMR 5 occurrence file contains 66,357 PFHxA results from 10,307 systems. 6,060 results were at or above the minimum reporting level, across 1,807 systems. Among detections, the median was 4.6 ppt and the 90th percentile was 10.1 ppt.
0 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 PFHxA results
| System | State | Population served | Recorded value | Records / periods |
|---|---|---|---|---|
| Experimental PR0004604 | Puerto Rico | 6,445 | 260 ppt | 2 |
| Widefield WSD CO0121900 | Colorado | 27,640 | 141 ppt | 12 |
| Northrop Grumman Corp. CA1910097 | California | 6,214 | 137 ppt | 4 |
| Telford Borough Authority PA1460050 | Pennsylvania | 7,700 | 94.6 ppt | 10 |
| Caernarvon TWP Auth PA3060052 | Pennsylvania | 4,245 | 92.0 ppt | 3 |
| Pequenakonck Elementary School NY5907717 | New York | 700 | 160 ppt | 1 |
| Potrero Elementary School CA3700963 | California | 300 | 95.2 ppt | 2 |
| Yeshiva Farm Settlement NY5903150 | New York | 300 | 69.0 ppt | 4 |
| Mdwasa - Main System FL4130871 | Florida | 2,377,460 | 58.0 ppt | 6 |
| Emerald Coast Utilities Authority (Ecua) FL1170525 | Florida | 242,172 | 111 ppt | 19 |
| Bayleaf Master NC0392373 | North Carolina | 16,715 | 57.3 ppt | 50 |
| Great Bend, City of KS2000911 | Kansas | 14,580 | 69.0 ppt | 4 |
| Valley Utilities Water Company Glendale AZ0407079 | Arizona | 5,940 | 52.0 ppt | 4 |
| Hatfield Water Dept MA1127000 | Massachusetts | 3,164 | 60.8 ppt | 4 |
| Artesian Water Company DE0000552 | Delaware | 231,114 | 72.2 ppt | 14 |
| Stratmoor Hills WSD CO0121800 | Colorado | 6,500 | 42.0 ppt | 4 |
| Suffolk County Water Authority NY5110526 | New York | 1,100,000 | 43.5 ppt | 45 |
| North Bay Village, City of FL4130970 | Florida | 8,317 | 52.9 ppt | 2 |
| Georgetown Water Department DE0000592 | Delaware | 7,259 | 68.0 ppt | 3 |
| Fountain City of CO0121275 | Colorado | 25,130 | 50.8 ppt | 10 |
| Emmaus Borough Public Water PA3390032 | Pennsylvania | 14,000 | 41.5 ppt | 8 |
| Hialeah, City of FL4130604 | Florida | 238,000 | 35.2 ppt | 4 |
| Pennsville Twsp. Water Depart. NJ1708001 | New Jersey | 13,500 | 37.0 ppt | 6 |
| Raynham Center Water District MA4245000 | Massachusetts | 10,964 | 58.8 ppt | 4 |
| Ottawa Village OH6900711 | Ohio | 4,393 | 51.8 ppt | 4 |
Filters and testing
NSF/ANSI 58 (reverse osmosis); carbon filters vary for short-chain PFAS
A standard number by itself is not a contaminant claim. Check the product's current certification listing and performance data sheet for PFHxA or the specific contaminant you want to reduce. A utility-level record is not a test of your own faucet.