PFAS in tap water: Ishikawa 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

• The Fukudome Green City small water supply system is a row whose value appeared for the first time in the 2025 table, and the table does not say where it was sampled (tap or raw water). Other small water supply systems also appeared for the first time in FY2025, including Naka-Aikawa (中相川簡易水道) at 17, Ishidate-machi (石立町簡易水道) at 16, the Kurabe housing estate (倉部住宅団地簡易水道) at 13 and Aikawa-shinmachi (相川新町簡易水道) at 12.
• Hakui City was 11–17 in all six years, measured only in raw water. The Hakusan City water utility (白山市水道事業) was 5–11 (raw water only).
• The Kanazawa City Public Enterprise Bureau (金沢市企業局) and the Ishikawa Prefecture Bulk Water Supply (石川県水道用水供給事業) (which sells water wholesale to cities and towns) were nd (below the detection or quantification limit) for all six years. → How to read the national table
• Private water supplies (for facilities such as company housing and hospitals) were tested at 72 of the 100 operators, and 3 exceedances have been confirmed (none national-government, FY2020 to the end of August 2025). The operators’ names are not given in the national documents.
• The national table shows “the highest value for each utility in that fiscal year.” From April 2026 this becomes a water quality standard, and periodic testing is required, including for small water supply systems. → How was the “50 ng/L” standard decided?

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)
• Ministry of the Environment, notice on the enforcement of the partial revision of the Ministerial Ordinance on Water Quality Standards, etc. (No. 2506301, June 30, 2025)

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

• Niigata Prefecture
• Toyama Prefecture
• Fukui Prefecture
• Yamanashi Prefecture
• Nagano Prefecture
• Gifu Prefecture
• Shizuoka Prefecture
• Aichi Prefecture