Scientists have confirmed a higher concentrations of PFAS, a group of potentially harmful chemicals, in the blood of some residents in western Tokyo. Levels were 2.7 times higher than Japan's national average, local media says, which survey results say could produce long-term adverse health effects. Local media says the main pollution source is likely the U.S. Yokota Air Base in the Tama region, where past use of firefighting foam containing PFAS has been confirmed.