Photo/Illutration The U.S. Yokota Air Base in western Tokyo (Takeshi Iwashita)

Health concerns for residents in western Tokyo heightened after a potential leak of toxic chemicals from the U.S. Yokota Air Base was reported earlier this month.

Approximately 48,000 liters of water contaminated with PFAS synthetic chemicals overflowed from a firefighting training area at the base during heavy rainfall on Aug. 30, according to the Tokyo metropolitan government.

Tokyo officials received the report on Oct. 3 from the U.S. military through the Defense Ministry. 

PFAS stands for perfluoroalkyl and polyfluoroalkyl substances. This group of synthetic chemicals is used in a variety of products ranging from nonstick cookware and water-repellent clothing to firefighting foam.

They are also linked to cancer and other health problems.

Although the risk of chemical release into the environment has long been a concern in areas surrounding the base, this marks the first time that U.S. officials have acknowledged a potential PFAS leak outside the facility.

The Yokota base overlaps with Fussa and five other municipalities in the western suburb of the capital.

On Oct. 4, a council composed of officials from the metropolitan government and affected municipalities told Defense Minister Gen Nakatani that the significant delay in reporting the incident was deeply regrettable.

The council requested that the Japanese government take responsibility for investigating and analyzing the leak’s potential impact on groundwater and other environmental resources.

Previously, Tokyo officials received reports from the U.S. military of three incidents that occurred between 2010 and 2012 at Yokota Air Base involving leaked firefighting foam, which contains PFAS.

However, in those instances, the U.S. side assured the metropolitan government that no substances spilled beyond the base premises.

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