Fearing contamination of Tokyo water supply, group says PFAS

TOKYO Kyodo citizens' group said Monday it had detected high concentrations of potentially harmful substances known as PFAS in some western Tokyo residents' blood, suggesting it could be due to contamination of the local water supply by U.S. military base activity.

Despite the discovery of high levels of PFAS, or per- and polyfluoroalkyl substances, Koji Harada, an associate professor of public health at Kyoto University, said it was highly unlikely to cause acute health effects. PFAS is a general term for a group of artificial chemicals, such as PFOS or perfluorooctanesulfonic acid, and PFOA or perfluorooctanoic acid. Harada said residents were tested under German standards because Japan has no guidelines for measuring their concentration in blood.

The group said PFAS can be found in foam extinguishers used on U.S. military bases, but said it was not clear if the findings have any relation to Yokota Air Base, a U.S. Air Force installation in the Tama area of western Tokyo.

The group began carrying out tests in November to determine the source of the contamination. The tests involved 87 people, mostly residents of Kokubunji and some from other cities, such as Kodaira, Koganei and Musashino.

21 of them were found to have exceeded acceptable levels of PFOS in their bloodstream, according to interim results. Six of the 21 had unacceptable levels of PFOA.

The highest detected concentration of PFOS was 35.8 nanograms and 18.6 nanograms for PFOA. The German standard per milliliter for each chemical is 20 nanograms and 10 nanograms.

The concentration is evidently high for some residents, Harada said. That leads one to think that potable water is the main cause of it. Harada had previously detected PFAS in residents' bloodstreams in the vicinity of a U.S. base in Okinawa Prefecture in Japan's south.

Of 387 people tested, Harada found that 27 exceeded the German standard, with the highest example being 41.6 nanograms of PFOS in a person.

Harada told reporters the state and local governments must deal with the issue from the perspective of what to do with the source of contamination.

In the past, the Tokyo metropolitan government has detected high levels of PFOS and PFOA in wells in parts of the Tama area, leading some purification facilities in Kokubunji and Fuchu to stop drawing water from affected wells.