TOKYO, June 8 (Xinhua) -- Scientists in western Tokyo have confirmed that concentrations of the potentially harmful per-and polyfluoroalkyl substances (PFAS) chemicals in the blood of a group of residents here were 2.7 times higher than Japan's national average, local media reported on Thursday.

The exposure was also at a level that may produce long-term health effects, according to survey results released on Thursday, which were based on blood samples of 650 residents in the area taken between last November and March.

The average exposure to the sum of four PFAS chemicals, PFOS, PFOA, PFHxS and PFNA, was 23.4 nanograms per milliliter (ng/ml), more than twice the average of 8.7 ng/ml among 119 people tested in a 2021 pilot study by Japan's environment ministry, the results showed.

Among the 650 people from 27 municipalities in western Tokyo, also known as the Tama region, PFAS levels were high especially among residents in the city of Kokubunji, whose blood concentrations averaged 45 ng/ml, followed by those in Tachikawa (28.6 ng/ml), Musashino (27.2 ng/ml) and Fuchu (23.9 ng/ml), the results showed.

The blood test was conducted following the detection of toxic chemical levels exceeding the government's provisional target levels in rivers and groundwater around the U.S. military base in Okinawa prefecture.

Higher-than-normal readings are likely attributable to past contamination of drinking water in the area, Koji Harada, an associate professor of environmental health at Kyoto University who was involved in the analysis of the blood, told a press conference in Tachikawa on Thursday.

"Considering that the levels of contamination are still high despite measures taken by the metropolitan government (to stop supplying polluted water), we need to monitor the health effects over the long term," Harada was quoted by the Japan Times as saying.

Harada told the press that more investigations are needed in high-risk communities known to or suspected to have used such firefighting foam or other PFAS-containing products, around U.S. military bases, Self-Defense Force bases, petroleum complexes and chrome-plating factories.

By the end of this month, the research team plans to check PFAS levels of 100 wells in areas surrounding Yokota Air Base in Japan, where the past use of PFAS-containing firefighting foam has been confirmed.

Known as "forever chemicals" that are extremely persistent in the environment and human bodies, PFAS could lead to health problems such as liver damage, thyroid disease, obesity, fertility issues and cancer. Enditem

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