Red circles on this graphic mark the locations of recent Japanese government PFAS surveys near Yokota Air Base, outlined in yellow. (Japan's Ministry of Defense)
YOKOTA AIR BASE, Japan — Levels of chemicals in treated water discharged from two sites outside this U.S. airlift hub in western Tokyo spiked recently but remained within safe limits, according to Japanese government surveys.
The findings were announced July 14 by Japan’s Ministry of Defense and the Tokyo Metropolitan Government following multistage surveys near Yokota. They followed the discharge of approximately 400,000 gallons of treated water between May 30 and June 17.
The water, previously contaminated with PFOS and PFOA — chemicals once found in firefighting foam used at the base — was treated using activated carbon filters and tested before being released into storm drains.
PFOS and PFOA are part of a broader group of synthetic compounds known as PFAS, or forever chemicals, because they persist in the environment and the human body for extended periods.
U.S. Forces Japan announced in November it had destroyed its final stockpile of PFAS-based firefighting foam.
The North Kanto Defense Bureau — an arm of the Defense Ministry — and the metropolitan government collected water samples between May 29 and June 17 from two spots: a storm drain near Yokota’s southwest corner and another near Fussa Minami Park, less than a mile away, according to two news releases issued July 14.
The bureau’s initial testing on May 29 found PFAS concentrations at 13 nanograms per liter near the base and 11 nanograms per liter near the park, according to the defense bureau’s release. By June 10, levels near the base rose to 30 nanograms per liter, while those near the park increased slightly to 12.
On June 26, concentrations remained stable at 28 nanograms and 10 nanograms per liter, respectively, the release said.
“It is difficult to give a general answer to the factors related to each survey result,” a defense bureau spokesman told Stars and Stripes by phone on July 16.
The metro government conducted its own survey only near the park and reported lower values, according to its release. The highest level detected was 11 nanograms per liter on June 11; the lowest was 6.3 nanograms per liter on June 27.
Japan maintains a provisional guideline of 50 nanograms per liter for PFOS and PFOA in public water supplies — levels considered unlikely to pose health risks. Permanent standards for tap water are expected to be finalized by April.
The independent study aimed to “eliminate the anxiety” of local residents, the metro government said in its release. It plans to monitor the situation and ensure the base properly handles the reservoir and disposes of its filtration equipment, a metro government official told Stars and Stripes by phone on July 16.
Some Japanese government officials speak to the media only on condition of anonymity.
USFJ said it “remains committed to protecting the health of our personnel, their families, and the surrounding communities in which we live and serve,” and plans to continue cooperating with Japan on environmental issues, a command spokesperson said in an unsigned email to Stars and Stripes on July 18.
