PFAS in tap water: Aichi 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

• In March 2021, the Kitanagoya Water Supply Authority found 175 ng/L in raw water and 150 ng/L in treated water on the Toyoyama distribution station (豊山配水場) supply line. It stopped drawing from that well and increased the water it buys from the bulk water supplier (the prefecture). The Toyoyama station supplied 3.87% of the authority’s total distribution (FY2020) (MLIT case studies). The national table then shows 6 (FY2021) and nd from FY2022.
• The same authority’s Shikatsu distribution station (師勝配水場) line had 76 ng/L in raw water in April 2021, but the treatment plant outlet was below the quantification limit. The case studies say that because this line already bought a large share of its water from the bulk water supplier, it kept supplying water without changing the share it drew itself.
• Iwakura City Waterworks reported 48, 43, 17, 49, 49 and 42 ng/L (FY2020–FY2025). It never exceeded 50, but it was the highest in the prefecture in FY2024 and FY2025. The testing point is the tap.
• Ichinomiya City (一宮市) (26–32 ng/L) and Konan City (江南市) (13–36) are “raw water only” suppliers in the table published in 2024. The Niwa Regional Administrative Association (丹羽広域事務組合) reported 22–48 (highest in FY2023), with testing points at the tap and raw water.
• The Nagoya City Waterworks and Sewerage Bureau (名古屋市上下水道局) was nd in every year from FY2020 to FY2025 (testing points: treatment plant outlet and raw water), and the Aichi Prefecture bulk water supply (愛知県水道用水供給事業) was nd except 8 in FY2021.
• Of the 48 rows for the prefecture, 19 are suppliers that buy all their water from a bulk supplier (they have no water source of their own). For these suppliers, it helps to look at the bulk supplier’s values as well. → How to check
• Among private water supplies (for a facility, such as company housing or hospitals), none of the 138 tested in the prefecture was found to exceed the provisional target value (50 ng/L) (through the end of August 2025).

Timeline

Put it in terms of your own intake

Related explainers

• What happened in areas where high PFAS values were found in tap water? A timeline of Kibichuo, Tama, Okinawa and more
• How do you check PFAS in your local tap water? Reading the national tables and working out “what percent of the TDI”
• 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, “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)
• MLIT, “Cases of PFOS and PFOA responses by water suppliers to date” (November 29, 2024), Case 7: Kitanagoya Water Supply Authority
• 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.

Other prefectures

• Niigata Prefecture
• Toyama Prefecture
• Ishikawa Prefecture
• Fukui Prefecture
• Yamanashi Prefecture
• Nagano Prefecture
• Gifu Prefecture
• Shizuoka Prefecture