PFAS Detection and Exceedance Rates
Source period August 2026. Recomputed by ZipCheckup from the cited federal source.
Per ZipCheckup's reading of EPA UCMR5, 34.9% of PFAS-tested systems had a detection and 16.8% exceeded an EPA limit, as of August 2026.
Among the 10,312 water systems EPA tested for PFAS under UCMR5, 34.9% had a detection and 16.8% exceeded an EPA maximum contaminant level, as of August 2026.
By state
| metric | value |
|---|---|
| pwsids_tested | 10,312 |
| pwsids_with_any_detection | 3,595 |
| pwsids_with_mcl_exceedance | 1,734 |
Open data, licensed CC BY 4.0 · DOI: 10.5281/zenodo.19427201
How we compute this
We read EPA's UCMR5 occurrence data and compute, among systems with at least one PFAS result, the share with any detection and the share with at least one result above an EPA maximum contaminant level.
Detection is not the same as exceedance. A detection means PFAS were measurable; an exceedance means a result was above a federal limit. We report both rates separately.
These rates describe tested systems only. They are not a national prevalence estimate, because the set of tested systems is defined by UCMR5 monitoring rules.
Frequently asked questions
What share of tested U.S. water systems had PFAS detections?
Per ZipCheckup's reading of EPA UCMR5, 34.9% of the 10,312 tested systems had a PFAS detection (3,595 systems) and 16.8% exceeded an EPA limit (1,734 systems), as of August 2026. according to ZipCheckup's reading of the cited federal source period, August 2026.
How to cite this page
ZipCheckup. (2026). PFAS Detection and Exceedance Rates. https://zipcheckup.com/findings/pfas-detection-and-exceedance-rate/
@misc{zipcheckup-findings-pfas-detection-and-exceedance-rate,
author = {{ZipCheckup}},
title = {{PFAS Detection and Exceedance Rates}},
year = {2026},
url = {https://zipcheckup.com/findings/pfas-detection-and-exceedance-rate/}
}
Page version: August 2026.