PFAS in tap water: Gifu 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 November 2020, Kakamigahara found 99 ng/L in raw water at the Mitsui water source (三井水源地, deep wells). Stopping the wells with the highest levels did not bring the raw water below 50, and there was no other water source available, so the city chose to remove PFAS at the treatment plant (MLIT case studies).
• In October 2023, treatment began in which the contents of an existing aeration tank (a tank that blows air into the water) were replaced with granular activated carbon. The case studies (November 2024) say that since then, treated water (at the treatment plant outlet and at taps) has stayed at or below the provisional target value (50 ng/L).
• For Kakamigahara, the “yearly maximum” in the national table also includes raw water values. The case studies say that from November 2020 “raw water has continued to exceed the provisional target value,” and the national table does not show whether values such as 550 are tap water values.
• Aiming for more stable treatment than activated carbon, Kakamigahara invited private companies and is testing granular activated carbon, ion exchange resin (resin that binds and removes PFAS) and other methods. It says it will decide its course after hearing from an expert “Water Quality Improvement Measures Committee,” including new water sources (river water, groundwater, or water bought from another bulk water supplier) (as of the case studies).
• Seki City (28–33 ng/L) and Gifu City (岐阜市) (7, FY2023) are “raw water only” suppliers in the table published in 2024. Of the 94 rows for the prefecture, 56 are “raw water only,” so check the testing point when you read a value. → How to read the national table
• Among private water supplies (for a facility), the one at the Japan Air Self-Defense Force Gifu Air Base (航空自衛隊岐阜基地), set up by the national government, had 86 ng/L in raw water (maximum from FY2020 through the end of August 2025). The national documents say it is “handled for now with water purifiers as an emergency measure; removal equipment is planned.” No other private water supply in the prefecture exceeded the provisional target value.
• In FY2024, 69 of the 74 rows with a value were nd (below the quantification limit); in FY2025, 78 of the 83 were nd.

Timeline

Rivers and groundwater (environmental monitoring)

These measure rivers or groundwater themselves, not tap water. The water is not necessarily used for drinking.

• The environment departments of Kakamigahara City and Gifu Prefecture are testing groundwater and river water in the city to identify the extent of contamination. They have also set up an expert panel of academics to consider the future direction for PFOS and PFOA in the environment (MLIT case studies, as of November 2024). This is environmental testing, separate from tap water values.
• The “guideline value” for rivers and groundwater (PFOS + PFOA 50 ng/L) is a benchmark for stepping up monitoring and plays a different role from the water quality standard for tap water. → High levels in rivers or groundwater = high levels in tap water?

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
• Do high PFAS values in rivers or groundwater mean high values in tap water? How guideline values differ from the tap water standard
• How do you check PFAS in your local tap water? Reading the national tables and working out “what percent of the TDI”
• 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 6: Kakamigahara City
• Same follow-up survey, attachment (status of private water supplies by prefecture; Table 6, private water supplies set up by the national government)

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
• Shizuoka Prefecture
• Aichi Prefecture