PFAS in tap water, St. Lawrence County, New York
None of the 5 water systems had a PFAS-4 compound above the 3 to 4 ng/L reporting limits at the latest sample. That's below the lab limit, not zero.
5 community water systems · 46,423 people served · newest sample December 4, 2025
Water systems in St. Lawrence County
| Water system | People served | PFAS-4 at the latest sample | Entry points | Latest sample |
|---|---|---|---|---|
| Massena Village | 16,729 | below the 3 to 4 ng/L reporting limit | 1 | September 18, 2024 |
| Ogdensburg City | 10,064 | below the 3 to 4 ng/L reporting limit | 1 | December 4, 2025 |
| Potsdam Village | 8,312 | below the 3 to 4 ng/L reporting limit | 1 | December 12, 2023 |
| Canton Village | 7,055 | below the 3 to 4 ng/L reporting limit | 5 | December 11, 2024 |
| Gouverneur | 4,263 | below the 3 to 4 ng/L reporting limit | 2 | November 14, 2023 |
Not sure which one is yours? The systems report their own service areas to EPA. Check your water bill or your utility's Consumer Confidence Report.
Cities and towns
ZIP codes in St. Lawrence County
Census ZIP code tabulation areas that overlap the county. A ZIP served by one system opens that system's page; a ZIP shared by several systems lists them.
How to read these numbers
We compare PFAS-4 (PFOA + PFOS + PFNA + PFHxS) with this site's 0.5 ng/L benchmark, the same line as on the European pages. UCMR 5 reporting limits are 3 to 4 ng/L. So any quantified PFAS-4 compound is above the benchmark, and a clean result reads "below the 3 to 4 ng/L reporting limit", never zero. The US legal limit is the 4 ng/L federal MCL for PFOA and PFOS, which systems must meet from April 26, 2029 ("above the 2029 federal MCL").
EPA: "UCMR 5 results do not indicate compliance or noncompliance with the PFAS drinking water standards". Samples are taken where water enters the distribution system, not at your tap. A system may have changed sources or added treatment since. Source: U.S. Environmental Protection Agency (EPA), Office of Water, PFAS National Primary Drinking Water Regulation (NPDWR). Regulation details retrieved September 19, 2026. Every system page tracks the 2029 compliance date and the proposed rescission of the PFHxS, PFNA, HFPO-DA and Hazard Index limits.
This site is a data project, not an official source. If in doubt, check with your water supplier or local authority.