PFAS in tap water: Tokyo

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

Values published by local governments and utilities

Good to know

• The Tokyo Metropolitan Waterworks Bureau’s annual maximums were 64, 39, 20, 14, 14 and 11 (FY2020–FY2025). The bureau has many treatment plants, and the national table lists only the single highest value among them. It is not necessarily the value at your own tap. → How to read the national table
• The bureau publishes quarterly results for taps at 131 locations across Tokyo (84 in Tama and 47 in the 23 wards) and for raw and treated water at its treatment facilities. In FY2025, 81 of the 84 Tama sites were below 5 in every quarter; the maximum was 14 at Hakonegasaki, Mizuho Town (瑞穂町 箱根ヶ崎), followed by 10 at Tamadaira 4-chome, Hino City (日野市 多摩平四丁目). In the 23 wards, 46 of the 47 sites were below 5 in April–June, and only Nozawa 1-chome, Setagaya Ward (世田谷区 野沢一丁目) was 8.
• By treatment plant, in April–June 2025 the treated water was 27 at the Kinutashimo treatment station (砧下浄水所) (raw water 35) and 18 at the Kinuta treatment plant (砧浄水場) (raw water 25). These are higher than the FY2025 value in the national table (11), but the table does not say which sites its value summarizes.
• Musashino City, Akishima City (昭島市) and Hamura City (羽村市) have their own city water supplies, separate from the Tokyo Metropolitan Waterworks Bureau. Musashino City was 12–22 (tap), Akishima City 7–8.5, and Hamura City 1.34–2.3 (raw water only). The water supplies of the towns and villages on the islands were nd–11.
• In the Tama documents, many treatment facilities are marked “suspended,” and the systems they served are mainly supplied with water from the Higashimurayama treatment plant (東村山浄水場) and the Ozaku treatment plant (小作浄水場). Not every suspension is due to PFAS.
• Among private water supplies (for facilities such as company housing, hospitals and bases), exceedances have been confirmed at 22 operators in Tokyo (FY2020 to the end of August 2025; 4 of them national-government). The national-government ones are Fuchu Prison (府中刑務所) at 204 ng/L (switched to the public water supply), Japan Ground Self-Defense Force (JGSDF) Camp Kodaira (陸上自衛隊小平駐屯地) at 200 (switched to the public water supply), JGSDF Camp Higashi-Tachikawa (陸上自衛隊東立川駐屯地) at 343 in raw water (switched to wells that do not exceed the target), and Japan Air Self-Defense Force (JASDF) Fuchu Air Base (航空自衛隊府中基地) at 245 in raw water (water filters as an emergency measure; planned to switch to the public water supply). Raw water values are not subject to the water quality standard.
• In a study, the median blood levels in 2023 of 17 women (aged 53–83) in the Tama area were PFOS 8.4, PFHxS 14.7 and PFOA 4.1 ng/mL, higher than the averages in a nationwide survey (PFOS 2.5, PFOA 1.5, PFHxS 0.4). It is a study of a small number of people and does not show effects on health. → How does PFAS affect the body?

Timeline

Put it in terms of your own intake

Related explainers

• What happened in areas where high PFAS values were found in tap water? A timeline of Kibichuo, Tama, Okinawa and more
• How do you check PFAS in your local tap water? Reading the national tables and working out “what percent of the TDI”
• How does PFAS affect the body? Assessments by different bodies, and what a blood test can tell you
• 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

• Tokyo Metropolitan Waterworks Bureau, “Detection of organic fluorine compounds (FY2020)”
• Tokyo Metropolitan Waterworks Bureau, “Detection of organic fluorine compounds in the Tama area (FY2025)”
• Tokyo Metropolitan Waterworks Bureau, “Detection of organic fluorine compounds in the 23 wards (FY2025)”
• 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)
• Same, follow-up survey annex (status of private water supplies by prefecture; national-government private water supplies above the provisional target value)
• Lyu Z et al. (2026). High serum PFAS levels in a population after exposure through drinking water in western Tokyo, Japan and their half-lives estimation. Environmental Health and Preventive Medicine（PMID 41548900）
• 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
• Kanagawa Prefecture