PFAS in tap water: Toyama Prefecture
In Toyama Prefecture’s water supplies, the highest combined PFOS and PFOA value for FY2020–FY2025 (FY2025 through the end of August) was 7 ng/L at the Takaoka City water utility (高岡市水道事業) (FY2023, tap). This is the only time a number appeared, and in FY2024 and FY2025 all values in the prefecture were nd (below the detection or quantification limit).
Levels by utility (PFOS + PFOA combined, ng/L)
| Utility | FY2020 | FY2021 | FY2022 | FY2023 | FY2024 | FY2025* | Sampled at |
|---|---|---|---|---|---|---|---|
| 射水市水道事業Water supply · 射水市 | — | — | — | nd | nd | — | raw water only |
| 高岡市水道事業Water supply · 高岡市 | nd | nd | nd | 7 | nd | nd | tap only |
| 南砺市水道事業Water supply · 南砺市 | — | — | — | — | nd | — | — |
| 富山市上下水道局Water supply · 富山市 | nd | nd | nd | nd | nd | nd | tap, plant outlet and raw |
| 魚津市上水道事業Water supply · 魚津市 | — | — | — | nd | — | nd | raw water only |
| 氷見市水道事業Water supply · 氷見市 | — | — | — | — | nd | nd | raw water only |
| 滑川市水道事業Water supply · 滑川市 | — | — | — | — | nd | nd | — |
| 黒部市水道事業Water supply · 黒部市 | — | — | — | — | nd | nd | tap only |
| 砺波市水道事業Water supply · 砺波市 | — | — | — | — | nd | nd | — |
| 小矢部市水道事業Water supply · 小矢部市 | — | — | — | — | nd | nd | — |
| 上市町水道事業Water supply · 上市町 | — | — | — | — | nd | nd | tap only |
| 立山町水道事業Water supply · 立山町 | — | — | — | — | nd | nd | — |
| 西部水道用水供給事業Bulk supplierSupplies: 高岡市、射水市、氷見市、小矢部市 | — | nd | nd | nd | nd | — | plant outlet and raw |
| 砺波広域圏事務組合水道事業所Bulk supplierSupplies: 砺波市、南砺市 | nd | nd | nd | nd | nd | — | plant outlet only |
| 魚津市日尾簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市黒沢簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市東城簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市島尻簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市東蔵簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市小菅沼簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市鉢簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市升方簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 魚津市長引野簡易水道事業Small water supply · 魚津市 | — | — | — | — | — | nd | — |
| 黒部市宇奈月簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | nd | — |
| 黒部市愛本簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | nd | — |
| 黒部市内山簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | nd | — |
| 黒部市音沢東山簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | nd | — |
| 黒部市布施山簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | nd | — |
| 黒部市田籾簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | — | — |
| 黒部市朴谷簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | — | — |
| 黒部市福平簡易水道事業Small water supply · 黒部市 | — | — | — | — | nd | — | — |
| 舟橋村簡易水道事業Small water supply · 舟橋村 | — | — | — | — | nd | nd | — |
| 入善町野中簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町舟見簡易水道事業Small water supply · 入善町 | — | — | — | — | nd | — | tap only |
| 入善町青木簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町椚山簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町西部簡易水道事業Small water supply · 入善町 | — | — | — | — | nd | — | tap only |
| 入善町新屋簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町小摺戸簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町横山簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳９区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳１０区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳１１区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳１３区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳１４区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳１５区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町入膳１７区簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 入善町上野簡易水道事業Small water supply · 入善町 | — | — | — | — | — | planned | — |
| 朝日町大平簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町境簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町宮崎簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町笹川簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町横尾簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町泊簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町五箇庄簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町南保簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町蛭谷簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町山崎簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | nd | — |
| 朝日町大家庄簡易水道事業Small water supply · 朝日町 | — | — | — | — | — | 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 Toyama City Water and Sewerage Bureau (富山市上下水道局) was nd for all six years. The bulk water suppliers Western Bulk Water Supply (西部水道用水供給事業) and the Tonami Regional Association (砺波広域圏事務組合) were also nd.
- Of the 59 rows in the table, 45 have a testing record; many small water supply systems remain untested. Imizu City (射水市), Uozu City (魚津市), Himi City (氷見市) and others measure in raw water (water before treatment at the plant). → How to read the national table
- Private water supplies (for a facility) were tested at 130 of the 156 operators, and no exceedance has been confirmed (through the end of 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, “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)
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.