Guam PFAS results from EPA's final data
Report published Nov 14, 2026 · EPA UCMR 5 final data file of Oct 15, 2026 (samples collected 2023–2025) · Method · National results →
1 Guam water system serving 139,207 people had PFAS above a 2024 federal limit in EPA's final round of nationwide PFAS testing: 20% of the 5 Guam systems tested, compared with 11% nationally.
Highest PFOA or PFOS averages in Guam
- Guam Waterworks Authority – Northern Water System Mangilao · PFOS67.5 ppt
Chart data as a table
| System | ppt |
|---|---|
| Guam Waterworks Authority – Northern Water System · Mangilao · PFOS | 67.5 |
Largest systems above a limit
| # | System | People served |
|---|---|---|
| 1 | Guam Waterworks Authority – Northern Water System Mangilao Above: PFOA, PFOS, PFHxS, Hazard Index | 139,207 |
Which limits were exceeded
| PFAS | Federal limit | Systems above it |
|---|---|---|
| PFOA 139,207 people | 4 ppt | 1 |
| PFOS 139,207 people | 4 ppt | 1 |
| PFHxS 139,207 people | 10 ppt | 1 |
| PFNA | 10 ppt | 0 |
| GenX (HFPO-DA) | 10 ppt | 0 |
| Hazard Index 139,207 people | 1 | 1 |
"–" in the table above means not detected. A system can be above more than one limit. EPA proposed in May 2026 to rescind the PFHxS, PFNA, GenX and Hazard Index limits. That proposal is not final.
Data and how to cite it
- Download every Guam water system as CSV (PFOA and PFOS averages, systems above a limit, lead, violations).
- EPA's source file: UCMR 5 occurrence data.
Suggested citation:
Tap Water Results, "Guam PFAS results from EPA's final UCMR 5 data" (published Nov 14, 2026, EPA data file of Oct 15, 2026). https://tapwaterresults.com/pfas/guam/
You're welcome to quote and republish these figures with a link back. Questions from reporters: see contact.
Method
For each system we average each entry point's UCMR 5 results (non-detects count as zero, complete sets of samples only) and compare the highest entry-point average with the 2024 federal limit, using EPA's rounding. This is how EPA compares UCMR 5 results to the limits in its own data summary, and our national counts match EPA's published table within 2% (how we check). Results are monitoring data from 2023–2025, not compliance determinations, and treatment installed since then is not reflected. Full method.
Questions
How many Guam water systems have PFAS above the limit?
1 of the 5 Guam community water systems EPA tested in 2023–2025 (20%) had at least one entry-point average above a 2024 federal PFAS limit. They serve 139,207 people. Nationally the share is 11%.
Are these systems violating the law?
Not yet. Systems have until 2029 to meet the 2024 limits, and EPA has proposed moving the PFOA and PFOS deadline to 2031 and rescinding the other limits. EPA's UCMR 5 results are monitoring data and do not determine compliance.
Which systems were tested?
EPA's UCMR 5 tested every community water system serving more than 3,300 people and a representative sample of smaller ones. Systems that were not tested have no federal result, which is not the same as having no PFAS.
All Guam water systems → · National results → · PFAS results for every state →
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.