PFAS in tap water: Kanagawa 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

• Zama City’s annual maximums were 63, 38, 41, 34, 21 and 18 (FY2020–FY2025). It measures at the tap, at the treatment plant outlet and in raw water, and the table does not say which site the FY2020 value of 63 came from.
• According to MLIT’s case collection, in October 2021 Zama City found 100 ng/L in the raw water (water before treatment at the plant) of its Source No. 3 (第3水源), suspended intake from it in November, and increased the water it buys from the Kanagawa Prefectural Waterworks (神奈川県営水道). By raising the share of other sources, it manages the water so that it stays below the provisional target value at the distribution reservoir outlets and at taps. Zama City’s treatment is chlorine disinfection only, and it is said to be considering improvements to the treatment method.
• Zama City’s FY2021 value in the national table is 38, and the 100 in raw water is not included. The national table is, in principle, based on tap values, and raw water values are not subject to the water supply standard. → How to read the national table
• The Yokohama City Waterworks Bureau (横浜市水道局), the Kawasaki City Water and Sewerage Bureau (川崎市上下水道局), the Yokosuka City Water and Sewerage Bureau (横須賀市上下水道局), the Kanagawa Prefecture water utility (神奈川県水道事業) (prefectural waterworks) and the Kanagawa Regional Water Supply Authority (神奈川県内広域水道企業団) (a bulk water supplier) were nd (below the detection or quantification limit) for all six years. Yokohama City and Kawasaki City measure at the treatment plant outlet and in raw water.
• Besides Zama City, values appeared for Hadano City (秦野市) at nd–20 (20 in FY2022 and FY2024), Aikawa Town (愛川町) at nd–7 (raw water only), Minamiashigara City (南足柄市) at 6 (FY2024), and Manazuru Town (真鶴町) at 5 (raw water only), among others.
• Cities without a utility under their own name in the table are supplied by another utility, such as the prefectural waterworks. Check your city’s water supply information to see which utility’s water you receive. → How do I look up PFAS in my local tap water?
• Private water supplies (for facilities such as company housing and hospitals) were tested at 280 of the 481 operators, and 5 exceedances have been confirmed (none national-government, through the end of August 2025).

Timeline

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”
• What happened in areas where high PFAS values were found in tap water? A timeline of Kibichuo, Tama, Okinawa and more
• 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?
• Do high PFAS values in rivers or groundwater mean high values in tap water? How guideline values differ from the tap water standard
• Water filters and PFAS

Sources

• MLIT, “Case examples of PFOS and PFOA responses by water utilities to date” (November 29, 2024)
• 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

• Ibaraki Prefecture
• Tochigi Prefecture
• Gunma Prefecture
• Saitama Prefecture
• Chiba Prefecture
• Tokyo