According to Japanese media reports, the blood test results of some residents in the Tama area of Tokyo showed that organic fluorine compounds exceeded the standard. The most suspected source of pollution is the Yokota base of the US military in the western suburbs of Tokyo.

According to the "Tokyo Shimbun" report on the 15th, a citizen group called "Exposure of PFAS Pollution in Tama Area" organized blood tests for local residents around the issue of suspected contamination of tap water in Tama area by organic fluorine compounds (PFAS). Part of the results released so far show that for the total values of four representative organic fluorine compounds in the blood, including perfluorooctanesulfonyl acid (PFOS) and perfluorooctanoic acid (PFOA), the average values of 16 cities and towns with more than 10 subjects all exceed the national average. Among them, the highest average for residents of Kokubunji City reached 44.9 nanograms per milliliter of blood, more than five times the national average. The group will announce the test results of all those tested by the end of May.

Koji Harada, an associate professor of environmental health at Kyoto University who conducted the analysis, said the test results supported the idea that residents were ingesting PFAS due to contaminated tap water.

According to reports, the most suspected source of pollution is the Yokota base of the US military in the western suburbs of Tokyo. A British reporter once reported that from 2010 to 2017, a large amount of foam fire extinguishing agent containing PFAS leaked into the soil at the Yokota Base. In addition, in a survey in 2018, a well water located in Tachikawa City, east of the Yokota base, was detected to contain 1,340 nanograms of PFAS per liter of water, while the Japanese national standard is no more than 50 nanograms of PFAS per liter of water. The concentration of PFAS in the well water of Musashimurayama City, Kokubunji City, and Kunitachi City, which are also located on the east side of the base, also exceeded 500 nanograms per liter. On the west side of the base, this value is relatively low in Fussa City, Hamura City and Mizuho Town.

The report quoted staff from the Water Environment Division of the Tokyo Metropolitan Environmental Bureau as saying that the flow of groundwater in Tokyo is roughly from west to east. Harada Koji said that apart from the fact that the Yokota Base is the source of pollution, there is currently no other explanation.

PFAS is a general term for various organic fluorine compounds such as perfluoroalkyl and polyfluoroalkyl compounds, which are widely used in various industrial products. PFAS do not break down easily, and some of them have been shown to accumulate in the environment and in humans, causing health problems.