Futenma Daini Elementary School is just outside Marine Corps Air Station Futenma in Ginowan, Okinawa. (Keishi Koja/Stars and Stripes)

CAMP FOSTER, Okinawa — Okinawa prefecture again wants to sample soil and water on Marine Corps Air Station Futenma after detecting PFOS at a neighboring elementary school in December.

Tests by the prefecture’s Environmental Preservation Division found contamination at three sites in Ginowan, including Futenma Daini Elementary School, that was 16 times higher than at the Itoman control site where no U.S. base is nearby, the division said in a Feb. 15 statement.

The prefecture cannot rule out MCAS Futenma as a source of the pollution, according to the statement. Marine Corps Installations Pacific did not respond to an email Wednesday requesting comment.

The chemical compounds PFOS and PFOA are both subgroups of per-and polyfluoroalkyl substances, otherwise known as PFAS, and are used to make coatings and products that resist heat, oil, stains, grease and water, according to the Centers for Disease Control and Prevention. They are also found in firefighting foam commonly used on U.S. military bases.

Prefectural officials invited onto MCAS Futenma in July 2021 to collect treated wastewater samples found combined PFOS and PFOA levels below the safe drinking water standard of 50 nanograms per liter, according to an October 2021 statement by the prefecture.

The U.S. Environmental Protection Agency updated its health advisories in June to say no level of PFOS or PFOA in drinking water is safe. The synthetic compounds accumulate in the body over time, according to the agency.

Okinawa’s environmental division also tested two other sites in Ginowan, where MCAS Futenma is located, and a site in Kadena town, according to the Feb. 15 statement.

The PFOS levels detected in Ginowan were below the residential soil safety standard set by the U.S. Environmental Protection Agency, but much higher than the agency’s threshold for groundwater protection.

Okinawa citizens and local politicians requested the December tests after sampling by a private group last year revealed potential issues at Futenma Daini Elementary School, the division spokesman said. Some government officials are required to speak to the media only on condition of anonymity.

The sampling centered on the school due to its proximity to MCAS Futenma. It is just beyond the fence on the base’s northern boundary.

The school registered PFOS levels of 6.6 micrograms per kilogram and 0.7 micrograms for PFOA, far below the EPA’s noncarcinogenic residential screening level for a child, the environmental division statement said.

The EPA screening levels mark the threshold for potential health effects, according to the EPA website.

However, 6.6 micrograms per kilogram is 173 times the EPA’s screening level of 0.038 micrograms per kilogram for groundwater protection. The other Ginowan sites logged 0.6 and 0.7 micrograms per kilogram for PFOS and 0.4 and 0.4 for PFOA, according to the environmental division’s statement.

The EPA’s noncarcinogenic residential screening level for a child is 130 micrograms per kilogram for PFOS and 190 for PFOA. The control site in Itoman registered 0.4 micrograms per kilogram for PFOS and 0.5 micrograms for PFOA, according to the statement.

Futenma Daini Elementary School made headlines in December 2017 when a window from a Marine Corps CH-53E Super Stallion helicopter landed on a field where schoolchildren were playing. That incident was attributed to human error, according to the 1st Marine Aircraft Wing.