PFAS in tap water: Saga Prefecture
In the national survey table, no water utility in Saga Prefecture exceeded 50 ng/L (PFOS and PFOA combined) in FY2020–FY2025. The highest value in the prefecture was 15 ng/L (FY2023, measured at the tap and in raw water) for the Genkai Town Water and Sewer Service (玄海町上下水道事業). The highest value in the prefecture was 11 in FY2024, also in Genkai Town, and 13 in FY2025 (through the end of August) for the Hasenoura District Small Water Supply Association (波瀬ノ浦地区簡易水道組合).
Levels by utility (PFOS + PFOA combined, ng/L)
| Utility | FY2020 | FY2021 | FY2022 | FY2023 | FY2024 | FY2025* | Sampled at |
|---|---|---|---|---|---|---|---|
| 佐賀市水道事業Water supply · 佐賀市Also buys from: 佐賀東部水道企業団, 佐賀西部広域水道企業団・水道用水供給事業 | 5 | nd | nd | nd | 7 | nd | tap, plant outlet and raw |
| 唐津市水道事業Water supply · 唐津市 | nd | nd | nd | nd | nd | nd | plant outlet and raw |
| 伊万里市水道事業Water supply · 伊万里市 | nd | nd | nd | nd | nd | nd | tap and raw |
| 鹿島市水道事業Water supply · 鹿島市 | — | — | — | nd | nd | nd | tap and raw |
| 有田町水道事業Water supply · 有田町 | — | — | — | — | nd | nd | plant outlet and raw |
| 鳥栖市上下水道局Water supply · 鳥栖市 | nd | nd | nd | nd | nd | nd | plant outlet and raw |
| 小城市水道事業Water supply · 小城市 | nd | nd | nd | nd | nd | — | — |
| 太良町水道事業Water supply · 太良町 | — | — | — | — | nd | nd | tap only |
| 佐賀東部水道企業団Water supplybuys all its water — Buys from 佐賀東部水道企業団 | — | — | — | — | — | nd | — |
| 玄海町上下水道事業Water supply · 玄海町 | — | — | — | 15 | 11 | nd | tap and raw |
| 佐賀西部広域水道企業団・水道事業Water supply | nd | nd | nd | nd | nd | nd | tap and plant outlet |
| 佐賀東部水道企業団Bulk supplierSupplies: 佐賀東部水道企業団（水道事業：神埼市・吉野ヶ里町・上峰町・みやき町・基山町・佐賀市の旧諸富/川副/東与賀町）、佐賀市 | — | nd | nd | nd | nd | nd | plant outlet and raw |
| 佐賀西部広域水道企業団・水道用水供給事業Bulk supplierSupplies: 佐賀西部広域水道企業団・水道事業、佐賀市、小城市 | nd | nd | nd | nd | nd | nd | plant outlet only |
| 久池井簡易水道組合Small water supply | — | — | — | — | — | 6 | — |
| 惣座簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 平田簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 田手宿簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 渕上簡易水道Small water supply | — | — | — | — | nd | nd | tap only |
| 蕨野簡易水道Small water supply | — | — | — | — | — | nd | — |
| 久原一区水道組合Small water supply | — | — | — | — | nd | nd | — |
| 久原二区水道組合Small water supply | — | — | — | — | — | nd | — |
| 波瀬水道組合Small water supply | — | — | — | — | — | nd | — |
| 東分簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 城簡易水道組合Small water supply | — | — | — | — | — | planned | — |
| 大久保水道組合Small water supply | — | — | — | — | — | nd | — |
| 中尾簡易水道Small water supply | — | — | — | — | — | nd | — |
| 飯田新地簡易水道Small water supply | — | — | — | — | — | nd | — |
| 槿廟簡易水道Small water supply | — | — | — | — | — | nd | — |
| 山浦簡易水道Small water supply | — | — | — | — | — | nd | — |
| 掛橋・平原簡易水道Small water supply | — | — | — | — | — | nd | — |
| 奥山簡易水道Small water supply | — | — | — | — | — | nd | — |
| 本城地区簡易水道Small water supply | — | — | — | — | — | nd | — |
| 東木庭簡易水道Small water supply | — | — | — | — | — | nd | — |
| 七開簡易水道組合Small water supply | — | — | — | — | — | planned | — |
| 飯田橋西簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 貝瀬簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 音成簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 大木庭簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 大宮田尾簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 上古枝簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 上中尾簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 大野簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 波瀬ノ浦地区簡易水道組合Small water supply | — | — | — | — | — | 13 | — |
| 大浦地区簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 蕪田地区簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 里地区簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 伊福地区簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 喰場地区簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 中尾地区簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 風配地区簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 郷野簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 土穴簡易水道組合Small water supply | — | — | — | — | — | nd | — |
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 national table has 52 rows for Saga Prefecture (including small water supply systems), and 50 of them have testing records. The Saga City water service (佐賀市水道事業) was nd (below the detection or quantification limit) to 7 in FY2020–FY2025.
- The Hasenoura District Small Water Supply Association is a row whose value first appeared in the December 2025 table. The table does not list the testing point.
- There are 76 private water supplies (for a facility: in-house water systems for company housing, hospitals and so on). None of the 53 that were tested exceeded 50 (FY2020 to August 2025).
Put it in terms of your own intake
- Intake from water
- — ng/kg/day
- Compared with Japan’s tolerable daily intake (PFOS and PFOA, 20 ng/kg bw/day each)
- —
- Compared with EFSA’s tolerable weekly intake (4 PFAS combined, 4.4 ng/kg bw/week ≈ 0.63 a day)
- —
- Compared with intake from 37 foods (MAFF estimate: PFOS 0.13 + PFOA 0.09 = 0.22 ng/kg bw/day; the 37 foods make up about half of what people eat by amount)
- —
The combined value is treated as a single substance (in reality it is split between PFOS and PFOA, so the share of Japan’s TDI would be smaller). EFSA’s value is for the sum of PFOA, PFNA, PFHxS and PFOS; tap-water values here do not include PFNA or PFHxS. This calculation shows how the same intake reads differently against different yardsticks; it does not judge health effects.
Related explainers
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 (December 25, 2025)
- Ministry of the Environment and MLIT: List of survey results (published November 29, 2024)
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.