PFAS in tap water: Tottori Prefecture
For tap water in Tottori Prefecture, the highest combined PFOS and PFOA value in FY2020–FY2025 (FY2025 through the end of August) was 24 ng/L at Yonago City Waterworks (米子市水道事業) in FY2020 and FY2022. No supplier exceeded 50 ng/L. The highest value was 15 in Yonago in FY2024 and 19 ng/L in Daisen Town (大山町) in FY2025.
Levels by utility (PFOS + PFOA combined, ng/L)
| Utility | FY2020 | FY2021 | FY2022 | FY2023 | FY2024 | FY2025* | Sampled at |
|---|---|---|---|---|---|---|---|
| 倉吉市上下水道局Water supply · 倉吉市 | — | — | — | nd | nd | nd | tap only |
| 琴浦町水道事業Water supply · 琴浦町 | — | — | — | nd | — | nd | tap only |
| 岩美町水道事業Water supply · 岩美町 | — | — | — | — | nd | nd | tap only |
| 南部町上水道Water supply · 南部町 | — | — | — | nd | — | — | tap only |
| 伯耆町水道事業Water supply · 伯耆町 | — | — | — | nd | — | — | tap only |
| 湯梨浜町水道事業Water supply · 湯梨浜町 | — | — | — | nd | — | — | tap only |
| 大山町水道事業Water supply · 大山町 | — | — | — | 11 | — | 19 | tap only |
| 智頭町上水道事業Water supply · 智頭町 | — | — | — | — | nd | nd | tap only |
| 三朝町水道事業Water supply · 三朝町 | — | — | — | — | nd | — | raw water only |
| 北栄町水道事業Water supply · 北栄町 | — | — | — | — | nd | — | tap only |
| 鳥取市水道事業Water supply · 鳥取市 | nd | nd | nd | nd | nd | nd | — |
| 米子市水道事業Water supply · 米子市 | 24 | 11 | 24 | 15 | 15 | 15 | tap, plant outlet and raw |
| 倉吉市上下水道局Small water supply · 倉吉市 · 6 systems | — | — | — | nd | nd | nd | tap only |
| 智頭町簡易水道事業Small water supply · 智頭町 · 15 systems | — | — | — | — | — | planned | — |
| 湯梨浜町簡易水道事業Small water supply · 湯梨浜町 · 6 systems | — | — | — | nd | — | nd | tap only |
| 若桜簡易水道Small water supply · 若桜町 | — | — | — | — | nd | nd | raw water only |
| 八頭町簡易水道事業Small water supply · 八頭町 · 17 systems | — | — | — | — | nd | nd | raw water only |
| 日南町簡易水道Small water supply · 日南町 · 11 systems | — | — | — | nd | — | — | tap only |
| 日野町簡易水道Small water supply · 日野町 · 7 systems | — | — | — | nd | — | — | tap only |
| 江府町簡易水道事業Small water supply · 江府町 | — | — | — | — | nd | — | tap only |
| 三朝町簡易水道事業Small water supply · 三朝町 · 18 systems | — | — | — | — | nd | — | tap only |
| 小別所地区 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
- Yonago City Waterworks reported 11–24 ng/L, with testing points that mix the tap, the treatment plant outlet and raw water (before treatment). Tottori City Waterworks (鳥取市水道事業) was nd (below the quantification limit) in every year from FY2020 to FY2025.
- Daisen Town Waterworks reported 11 (FY2023) and 19 (FY2025), with the tap as the testing point.
- Among private water supplies (for a facility, such as company housing or hospitals), none of the 9 tested in the prefecture was found to exceed the provisional target value (50 ng/L) (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, “Survey on PFOS and PFOA in Water Supply,” follow-up survey: list of results (published December 25, 2025)
- Ministry of the Environment and MLIT, list of results (published November 29, 2024; testing point column)
- Same follow-up survey, attachment (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.