Okinawa Gov. Denny Tamaki, left, delivers a letter about PFAS to State Minister of Defense Masahisa Miyazaki at the ministry in Tokyo, Nov. 12, 2025. (Masahisa Miyazaki/X)

Japan’s Ministry of Defense has rejected as “ineligible” a request from Okinawa Gov. Denny Tamaki to fund new filters designed to remove “forever chemicals” from a major water purification plant in central Okinawa.

Tamaki delivered the request Wednesday in Tokyo to State Minister Masahisa Miyazaki, the ministry’s No. 2 official, a prefectural spokesman said by phone Friday.

The letter, addressed to Defense Minister Shinjiro Koizumi, sought “maximum support for the replacement and disposal costs” of granular activated carbon filters at the Chatan Water Purification Plant and urged the ministry to investigate the source of PFOS and PFOA contamination.

The filters now in use, which have a lifespan of about four years, were installed sometime between 2021 and 2023 and cost about $10 million, the spokesman said. The ministry footed most of the bill, he said, adding that the prefecture is still considering when to replace those filters and has yet to ask the ministry for a specific amount of money.

Miyazaki said the ministry cannot pay for plant maintenance, including filter replacement, under the current legal framework, according to a post he made Thursday on X.

Japanese law allows the government to subsidize portions of facilities built to address quality-of-life issues in municipalities that host U.S. or Japanese military bases.

However, Miyazaki wrote that it is difficult to use the subsidy program in this case because the source of PFAS contamination remains unclear.

PFOS and PFOA — two types of per- and polyfluoroalkyl substances, or PFAS — have been detected in levels above Japan’s national standard of 50 parts per trillion around Kadena Air Base in annual prefectural studies conducted since 2017.

PFAS are known was “forever chemicals” because they persist in the environment and the human body, according to the Environmental Protection Agency. Animal studies suggest they may increase the risk of tumors in the liver, breasts, testicles and pancreas, according to the American Cancer Society.

“Chatan town … and the cities that are supplied are my beloved hometown,” Miyazaki wrote on X. “However, forcing through subsidies that are not based on the system just because it’s my hometown is equivalent to fraud and absolutely unacceptable.”

Tamaki’s letter argues that evidence points clearly to the nearby U.S. air base.

“According to the results of investigations conducted by the Okinawa Prefectural Enterprise Bureau, it is highly likely that the main source of contamination is within Kadena Air Base,” he wrote.

The Chatan plant supplies water to seven municipalities south of the base, including the cities of Naha, Okinawa, Ginowan and Urasoe, along with Chatan town and the villages of Kitanakagusuku and Nakagusuku.

Some Japanese government officials speak to the press only on condition of anonymity.