Residents living near a U.S. military base in western Tokyo have been having deepening concerns about their health after a recent local study found many of them have excessive amounts of harmful substances, dubbed "forever chemicals," in their bloodstream.

After the government revealed last month that leakages had occurred from foam extinguishers containing polyfluoroalkyl substances, known as PFAS, over a decade ago at Yokota Air Base, locals have grown increasingly suspicious that the incident could be related to their blood test results.

Photo taken on Feb. 21, 2023, shows a woman (R) undergoing a blood test in Fuchu, Tokyo, for research on the impact of per- and polyfluoroalkyl substances. (Kyodo)

Yukio Negiyama, who lives in Hino in western Tokyo's Tama area, where the military facilities are located, is one of the many locals demanding detailed inspections and more information.

"Although I cannot swear by it, I strongly suspect that the Yokota base has a connection to the outcomes of the blood tests," he said.

PFAS is a general term for a group of artificial chemicals that include PFOS, or perfluorooctanesulfonic acid, and PFOA, or perfluorooctanoic acid. They are described as persistent organic pollutants, or forever chemicals, because they are nearly indestructible.

File photo taken in April 2020 shows foam extinguishers believed to contain perfluorooctanesulfonic acid being leaked into a river from the U.S. Marine Corps Air Station Futenma in Ginowan, Okinawa. (Photo courtesy of Ginowan City)(Kyodo)

Resistant to oil and water while tolerant of heat, PFAS chemicals have been used for a wide range of applications, including nonstick frying pans, fire extinguishers and the production of semiconductors.

But given they do not degrade over time unlike most other chemicals, they can accumulate in the environment and the human body, with American and European researchers pointing out in recent years that high exposure to PFAS chemicals increases the risk of developing kidney and testicular cancers and high cholesterol.

International efforts, such as those made by the European Union, have been underway to prohibit or limit the usage and production of the chemicals, and rules have been tightened regarding their management and disposal.

Japan banned the manufacture and import of PFOS substances across the board in 2018, as well as those categorized as PFOA in 2021.

Meanwhile, following the detection of a high concentration of PFOS and PFOA substances in water sources in the Tama area such as wells, a local civil group began conducting blood tests on 650 residents from 27 municipalities in November last year.

The results, released in June, found high PFAS levels, defined as surpassing 20 nanograms per milliliter in someone's blood sample, in 335 people, with the highest at 124.5 ng/ml.

The guideline comes from the U.S. National Academies of Sciences, Engineering, and Medicine, as Japan does not have an equivalent system for measuring PFAS concentration levels in the blood.

Negiyama, 76, a co-head of the Tama civil group, was among the 650 tested residents. His PFAS bloodstream concentration level was 17.7 ng/ml, prompting him to want to visit a doctor as a precaution.

Koji Harada, an associate professor at Kyoto University who is in charge of analyzing the test results, said that while the figures indicate no risk of developing acute symptoms, the likelihood of people suffering from diseases in the long run increases.

Photo taken on March 11, 2022, shows Yukio Negiyama, co-head of a civil group in western Tokyo. (Photo courtesy of Yukio Negiyama)(Kyodo)

In July, the Tokyo metropolitan government said the Defense Ministry explained that there were three instances of foam extinguishers containing PFAS chemicals leaking at the Yokota base from storage sites between 2010 and 2012.

Additionally, later that month, the Defense Ministry said that U.S. forces had informed them that there were four other cases of leakages at the base in 2020 and 2022 but added that those extinguishers did not contain any PFAS chemicals, unlike in the three previous incidents.

According to the ministry, U.S. forces confirmed that the leakage from the extinguishers was confined to the facility, meaning the chemicals did not flow outside the base on any of the seven occasions.

Harada argues, however, that in each case the PFAS chemicals were likely absorbed into the soil, contaminating the local area's groundwater.

"There might be other major sources of pollution, such as factories, for instance, but I can say for sure that the extinguisher leakages at the U.S. base are one of the contributing factors," he said.

The health and environmental sciences expert added that it is likely daily activities at the base, such as firefighter training, will have also polluted the area.

U.S. forces began using extinguishers containing PFAS substances in the 1960s, and the chemicals "may have been contaminating underground water throughout the Tama area over decades," Harada suggested.

Besides Tama, other parts of the country hosting U.S. bases have also detected high PFAS concentrations at rivers and other water sources, prompting local governments and residents to demand on-site inspections by the central government and the further disclosure of information.

Those include the neighborhoods surrounding U.S. Marine Corps Air Station Futenma in the southern prefecture of Okinawa and the U.S. Navy base in Yokosuka, southwest of Tokyo.

At a press conference last month, Chief Cabinet Secretary Hirokazu Matsuno said the Yokota base PFAS leakage was "an accident that should never have happened," highlighting that the government has repeatedly requested the U.S. "thoroughly implements safety management" at military facilities.

Still, Matsuno stopped short of providing detailed answers when reporters asked if the national government intends to carry out on-site inspections, saying only that it will "respond to local government requests."

Locals have also criticized the central government for its slow response to the incident and its failure to disclose information on the issue when it occurred.

The Defense Ministry says it first got hold of the reports on the 2010-2012 PFAS leakage in January 2019, four and a half years before the public announcement about the leakage.

"Given the high public interest in recent years in PFOS and other chemicals, I think we should have informed people about what we had obtained as quickly as possible," Defense Minister Yasukazu Hamada told a press conference in late July.

Speaking on the importance of maintaining a good relationship between the operators of military facilities in Japan and local residents, Negiyama said, "It doesn't seem like U.S. forces are trying to build trust with us."

Seeking to eventually cover the whole Tama area, the civic group has already conducted blood tests on, roughly, an additional 200 residents, with the results expected to be released in September, according to Negiyama.

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