TOKYO (Kyodo) -- Potentially harmful PFAS chemicals have been detected at high levels in tap water at the Japanese Self-Defense Forces' facilities in the suburbs of Tokyo and elsewhere, a government survey showed Tuesday.

The five-year survey from fiscal 2020 looked into water systems dedicated to supplying hospitals, schools and other facilities, amid growing concerns over the health impact of the widely used and long-lasting substances already detected in water filtration plants and rivers across the country.

PFAS is a general term for a group of over 10,000 artificial chemicals that include PFOS, or perfluorooctanesulfonic acid, and PFOA, or perfluorooctanoic acid. The government currently sets a provisional cap of 50 nanograms per liter for PFOS and PFOA combined.

In the survey, facilities with higher PFAS levels included the Ground Self-Defense Force's Camp Higashitachikawa, which detected 343 nanograms, GSDF Camp Kodaira, which detected 200 nanograms -- both in Tokyo -- as well as Gifu Air Base in Gifu Prefecture, which saw a reading of 86 nanograms.

A separate water quality checkup conducted after the survey found 1,500 nanograms of PFAS in water at the Ashiya Air Base in Fukuoka Prefecture.

The Environment Ministry and the Ministry of Land, Infrastructure, Transport and Tourism conducted the survey targeting facilities that have more than 100 people per site, receiving 1,929 responses. Such locations often use water from wells.

Overall, levels of PFAS exceeded the provisional standards at 42 sites in 10 prefectures.

The survey only disclosed numerical data on some state-run facilities, with data on water available to private ones not made public.

PFAS is used in a wide variety of products including foam fire extinguishers and frying pan coatings. Exposure to certain levels of PFAS may lead to increased risk of cancers.

Since the provisional cap is currently nonbinding, the Environment Ministry intends to legally enforce the 50-nanogram cap from April 2026 and plans to require water quality tests and measures to address the issue when the PFAS levels exceed the standard.