PFAS in tap water database (Japan)ChubuChecked 2026.10.04
PFAS in tap water: Niigata Prefecture
Highest, FY2020–202510 ng/L十日町市（2025）
Highest, FY2025 (to Aug)10 ng/L
Utilities with a year above 50 ng/L0
Utilities with values108 / 116
In Niigata Prefecture’s water supplies, the highest combined PFOS and PFOA value for FY2020–FY2025 (FY2025 through the end of August) was 10 ng/L in Tokamachi City (十日町市) (FY2025). It was measured at the tap, and FY2020–FY2024 were nd (below the detection or quantification limit). No utility exceeded 50 ng/L.
Levels by utility (PFOS + PFOA combined, ng/L)
| Utility | FY2020 | FY2021 | FY2022 | FY2023 | FY2024 | FY2025* | Sampled at |
|---|---|---|---|---|---|---|---|
| 新潟市水道事業Water supply · 新潟市 | 8 | 5 | nd | nd | nd | nd | tap and raw |
| 長岡市水道事業Water supply · 長岡市 | — | nd | nd | nd | nd | nd | — |
| 見附市水道事業Water supply · 見附市 | — | nd | nd | nd | nd | nd | tap, plant outlet and raw |
| 上越市水道事業Water supply · 上越市 | nd | nd | nd | nd | nd | nd | raw water only |
| 柏崎市水道事業Water supply · 柏崎市 | — | nd | nd | nd | nd | nd | plant outlet and raw |
| 佐渡市水道事業Water supply · 佐渡市 | — | — | — | — | nd | 5 | tap only |
| 燕・弥彦総合事務組合水道事業Water supply | — | nd | nd | nd | nd | nd | tap only |
| 新発田市水道事業Water supply · 新発田市 | — | — | — | nd | nd | nd | tap only |
| 南魚沼市水道事業Water supply · 南魚沼市 | — | — | — | — | nd | nd | raw water only |
| 阿賀野市水道事業Water supply · 阿賀野市 | — | 3 | 2 | 5 | nd | nd | raw water only |
| 三条市水道事業Water supply · 三条市 | nd | nd | nd | nd | nd | — | tap only |
| 田上町水道事業Water supply · 田上町 | — | — | — | — | nd | nd | tap only |
| 五泉水道事業Water supply · 五泉市 | nd | nd | nd | nd | nd | nd | tap only |
| 小千谷市水道事業Water supply · 小千谷市 | — | — | — | — | nd | nd | tap and plant outlet |
| 村上市上水道事業Water supply · 村上市 | — | — | nd | — | nd | nd | raw water only |
| 湯沢町水道事業Water supply · 湯沢町 | — | — | — | — | nd | nd | raw water only |
| 加茂市水道事業Water supply · 加茂市 | — | — | — | — | nd | nd | tap only |
| 胎内市水道事業Water supply · 胎内市 | — | — | — | nd | nd | — | raw water only |
| 糸魚川市上水道事業Water supply · 糸魚川市 | nd | nd | nd | nd | nd | nd | raw water only |
| 阿賀町水道事業Water supply · 阿賀町 | — | — | — | — | nd | nd | tap only |
| 十日町市Water supply · 十日町市 | nd | nd | nd | nd | nd | 10 | tap only |
| 魚沼市上水道Water supply · 魚沼市 | — | — | — | — | nd | — | tap only |
| 聖籠町水道事業Water supply · 聖籠町buys all its water — Buys from 新潟東港地域水道用水供給企業団 | — | — | — | — | — | — | — |
| 新井上水道Water supply | — | — | — | nd | nd | nd | raw water only |
| 妙高高原上水道Water supply | — | — | — | — | nd | — | raw water only |
| 三条地域水道用水供給企業団水道用水供給事業Bulk supplier · 三条市Supplies: 三条市、加茂市、田上町 | — | — | — | nd | nd | nd | plant outlet and raw |
| 新潟東港地域水道用水供給企業団Bulk supplierSupplies: 新潟市、新発田市、聖籠町、明和工業株式会社 | — | 6 | 5 | 3 | nd | 3 | plant outlet and raw |
| 上越市水道用水事業Bulk supplier · 上越市Supplies: 妙高市 | — | — | nd | — | — | nd | raw water only |
| 法末簡易水道Small water supply | — | — | — | — | nd | — | raw water only |
| 虫亀簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 山古志簡易水道Small water supplybuys all its water — Buys from 長岡市水道事業 | — | — | — | — | — | — | — |
| 一之貝簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 新山簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| まんさく簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 明道簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 中野俣地区簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 入東地区簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 山葵谷簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 川口中央簡易水道Small water supply | — | — | — | — | 6 | nd | raw water only |
| 西倉簡易水道Small water supply | — | — | — | — | nd | nd | raw water only |
| 新潟東港簡易水道事業Small water supplybuys all its water — Buys from 新潟東港地域水道用水供給企業団 | — | — | — | — | — | — | — |
| 中央簡易水道事業Small water supply | — | — | — | — | nd | nd | tap only |
| 城原簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 津南原簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 三箇簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 貝坂簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 大井平簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 太田新田簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 卯之木簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 所平簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 芦ヶ崎簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 竜ヶ窪簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 羽倉簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 駒返り簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 相吉簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 寺石簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 宮野原簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 中子簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 小下里簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 神山簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 田中簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 上野簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 逆巻簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 小規模簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 内浦簡易水道事業Small water supply | — | — | — | — | nd | nd | raw water only |
| 釜谷簡易水道事業Small water supply | — | — | — | — | nd | nd | raw water only |
| 猫又簡易水道組合Small water supply | — | — | — | — | — | nd | — |
| 出雲崎町簡易水道事業Small water supply · 出雲崎町 | — | — | — | — | nd | nd | — |
| 村上市簡易水道事業Small water supply · 村上市 · 19 systems | — | — | — | — | nd | nd | raw water only |
| 関川村簡易水道事業Small water supply · 関川村 | — | — | — | — | nd | nd | raw water only |
| 胎内市第一簡易水道事業Small water supply · 胎内市 | — | — | — | — | nd | — | — |
| 胎内市第二簡易水道事業Small water supply · 胎内市 | — | — | — | — | nd | — | — |
| 荒井浜区簡易水道組合Small water supply | — | — | — | — | nd | nd | — |
| 姫川簡易水道事業Small water supply | nd | nd | nd | nd | nd | nd | raw water only |
| 小滝簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 白馬簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 西海簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 早川簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 能生谷簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 大洞簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 中尾新戸簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 高倉簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 徳合簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 歌外波簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 市振簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 上路簡易水道事業Small water supply | — | — | — | — | — | nd | — |
| 津南町秋成反里口簡易水道Small water supply · 津南町 | — | — | — | — | — | planned | — |
| 津南町見玉地区Small water supply · 津南町 | — | — | — | — | — | planned | — |
| 津南町出浦地区簡易水道Small water supply · 津南町 | — | — | — | — | — | — | — |
| 津南町加用地区簡易水道Small water supply · 津南町 | — | — | — | — | nd | — | tap only |
| 津南町亀岡子種地区簡易水道Small water supply · 津南町 | — | — | — | — | nd | — | tap only |
| 十日町市Small water supply · 十日町市 · 36 systems | nd | nd | nd | nd | nd | nd | tap only |
| 伊米ヶ崎簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 干溝簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 湯之谷簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 大湯簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 銀山平簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 川西地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 滝之又地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 貫谷地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 芋川地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 川東地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 三ツ又地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 須原簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 上条地区簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 福山簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 入広瀬地域簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 横根地域簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 大白川地域簡易水道Small water supply | — | — | — | — | nd | — | tap only |
| 平丸簡易水道Small water supply | — | — | — | — | — | nd | — |
| 長沢簡易水道Small water supply | — | — | — | — | — | nd | — |
| 妙高簡易水道Small water supply · 妙高市 | — | — | — | nd | nd | nd | raw water only |
| 関地区簡易水道Small water supply | — | — | — | — | — | nd | — |
| 上折立簡易水道Small water supply | — | — | — | — | — | planned | — |
| 下折立簡易水道Small water supply | — | — | — | — | — | planned | — |
| 宇津野簡易水道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 Niigata City water utility (新潟市水道事業) was 8 (FY2020) and 5 (FY2021), and has been nd since FY2022. The bulk water supplier Niigata Higashi-ko Area Bulk Water Supply Authority (新潟東港地域水道用水供給企業団) was nd–6.
- Of the 116 rows in the table, 88 are small water supply systems. The FY2024 maximum was 6 at the Kawaguchi Chuo small water supply system (川口中央簡易水道) (a raw water value, i.e. water before treatment at the plant). → How to read the national table
- Private water supplies (for a facility) were tested at 25 of the 66 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.
This page lists levels published by national and local government bodies and facts from standards, assessments and papers. It does not judge whether tap water is good or bad or whether it affects health. Check the latest values and measures with your local water utility.