PFAS in tap water: Yamagata Prefecture

Levels by utility (PFOS + PFOA combined, ng/L)

These are the highest values in each fiscal year reported by each utility to the national government (MLIT and the Ministry of the Environment). A utility with several sources or treatment plants can have different levels in different parts of its area. Samples are taken at the tap in principle, but some utilities only measured raw water (water before treatment), and raw-water values are not covered by the tap-water standard. nd = below the detection or quantification limit; — = no value reported. *FY2025 covers results up to the end of August 2025. Utility names are left in Japanese as in the official table.

>50 a year above 50 ng/L (for utilities that also sampled raw water, the value may be from raw water)　raw above 50 ng/L, but measured in raw water only

Good to know

• Higashine City measures both at the tap and in raw water (water before treatment at the plant), and the table does not show which one the listed values come from.
• The next highest was 12 at the Kahoku Town water utility (河北町水道事業) (FY2024 and FY2025), measured only in raw water. The Yamagata City Water and Sewerage Department (山形市上下水道部) was nd–2.
• The four bulk water suppliers (utilities that sell water wholesale to cities and towns), Okitama (置賜), Mogami (最上), Murayama (村山) and Shonai (庄内), were nd for all six years. If your city or town buys water from them, check the supplier’s values as well. → How to read the national table
• Private water supplies (for a facility) were tested at 40 of the 52 operators, and no exceedance of the provisional target value has been confirmed (through the end of August 2025). Measurements of rivers and groundwater are a separate survey from the water supply. → High levels in rivers or groundwater = high levels in tap water?

Put it in terms of your own intake

Related explainers

• How do you check PFAS in your local tap water? Reading the national tables and working out “what percent of the TDI”
• Do high PFAS values in rivers or groundwater mean high values in tap water? How guideline values differ from the tap water standard
• Japan’s PFAS standard for tap water, “50 ng/L”: how was it set, and how does it differ from the U.S. and EU?
• Water filters and PFAS

Sources

• Ministry of the Environment and MLIT, “Results of the follow-up survey on PFOS and PFOA in water supplies” (December 25, 2025)
• Same, list of survey results (updated), Excel (annual maximums, FY2020–FY2025)
• Ministry of the Environment and MLIT, list of survey results, Excel (published November 29, 2024; sampling point column)
• Same, follow-up survey annex (status of private water supplies by prefecture)

Last checked 2026.10.04 (against the original government documents and papers, collected and cross-checked in Gemini Notebook). Utility values are as in the national table; Urayomi sorted and summarized them.

Other prefectures

• Aomori Prefecture
• Iwate Prefecture
• Miyagi Prefecture
• Akita Prefecture
• Fukushima Prefecture