PFAS in tap water: Hiroshima 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

• Each value in the national table is “the highest value for that utility in that fiscal year.” The Akitakata City water service had 37 in FY2023, 40 in FY2024 and 23 in FY2025. When the table was published in November 2024, the FY2024 column was still blank; the 40 was added in the December 2025 table.
• In the national table, the water services of many cities and towns in the prefecture are listed under names like “Hiroshima Prefecture Water Supply Regional Union Authority, ___ City water service.” Their values for FY2020–FY2025 were 8–19 ng/L for Higashihiroshima City (東広島市), 4–22 for Hatsukaichi City (廿日市市) and 5–15 for Mihara City (三原市). The Hiroshima City Waterworks Bureau (広島市水道局) was nd (below the detection or quantification limit) in all six years, and Kure City (呉市) was 2–5 (in the November 2024 table, both were tested at the treatment plant outlet and in raw water, meaning water before treatment).
• Two services “buy all their water” (they have no water source of their own and buy water from another utility): Kumano Town (熊野町) and Osakikamijima Town (大崎上島町). The prefecture’s three bulk water suppliers (which sell water wholesale to cities and towns), Hiroshima (広島), Hiroshima Western Region (広島西部地域) and Nutagawa (沼田川), had values of nd–6 ng/L in FY2020–FY2025.
• Higashihiroshima is a frequently searched place name. The high values in the city come from measurements of rivers (such as the Seno River (瀬野川)) and groundwater (wells), which are separate from tap water values. Higashihiroshima City says that for homes connected to the public water supply, “safety has been confirmed in each fiscal year’s testing.” → High levels in rivers or groundwater = high levels in tap water?
• On May 31, 2024, Higashihiroshima City set up a committee to evaluate the health effects of organic fluorine compounds (“有機フッ素化合物健康影響評価検討委員会”), which issued a report in March 2025. As a response to residents’ health concerns, the committee also considered whether to measure blood levels. → How does PFAS affect the body?
• There are 165 private water supplies (for a facility: in-house water systems for company housing, hospitals, schools and so on) in the prefecture. Of the 69 that were tested, 1 exceeded 50 between FY2020 and August 2025 (a facility not set up by the national government; its name has not been made public).
• From April 1, 2026, 50 ng/L became a “water quality standard,” and water utilities are now required to test at least once every three months and to meet the standard. Values by utility for FY2026 do not yet appear in the national table (as of October 2026).

Rivers and groundwater (environmental monitoring)

These measure rivers or groundwater themselves, not tap water. The water is not necessarily used for drinking.

• When Higashihiroshima City and Hiroshima City surveyed 9 points on the Seno River and its tributaries on November 20, 2023, 2 points (1 in Higashihiroshima and 1 in Hiroshima City at the city border) exceeded the guideline value for rivers and groundwater (provisional; 50 ng/L for PFOS and PFOA combined). These are river water measurements, not tap water values.
• Higashihiroshima City has a program that helps households in the contaminated area designated by the city that are not connected to the public water supply to install water supply pipes. The city also says that, in a follow-up survey that retested groundwater at 7 business sites (8 points) along the Seno River, it confirmed that groundwater was not being used for drinking at the points that exceeded the guideline value. The city also says that values above the provisional guideline value were detected in groundwater that is being used for drinking in the river basin.
• The city’s page (updated September 8, 2026) does not say that the cause has been identified. According to the same page, in a reply dated September 6, 2024, the Chugoku-Shikoku Defense Bureau told the city that it had obtained from the U.S. side a usage history showing that inspections and training of fire trucks using PFOS-containing firefighting foam were carried out at the U.S. forces’ Kawakami Ammunition Depot (米軍川上弾薬庫) from 1991 to 2009. However, on the city’s page, neither the city nor the national government links this usage history to the detections. Together with the prefecture, the city has asked the national government (the Minister of Defense) for measures such as water and soil surveys inside the depot and publication of the results.

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
• How does PFAS affect the body? Assessments by different bodies, and what a blood test can tell you
• 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: List of results of the follow-up survey of PFOS and PFOA in water supplies (published December 25, 2025)
• Ministry of the Environment and MLIT: Results of the follow-up survey (including private water supplies by prefecture, December 25, 2025)
• Ministry of the Environment and MLIT: List of survey results (published November 29, 2024)
• Higashihiroshima City: “Survey results and response regarding organic fluorine compounds (PFOS and PFOA) in the Seno River system” (updated September 8, 2026)
• Higashihiroshima City Committee to Evaluate the Health Effects of Organic Fluorine Compounds: Report (March 2025)
• Ministry of the Environment: Notice on the enforcement of the partial revision of the Ministerial Ordinance on Water Quality Standards (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

• Tottori Prefecture
• Shimane Prefecture
• Okayama Prefecture
• Yamaguchi Prefecture