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Toxic chemicals 172 times gov't criteria found in US naval base wastewater near Tokyo

The front gate of the U.S. naval base in Yokosuka is seen in Kanagawa Prefecture in this May 27, 2022, file photo. (Mainichi/Toshiaki Hashimoto)

YOKOSUKA, Kanagawa -- High levels of potentially cancer-causing chemical compounds, 172 times the Japanese government criteria, were detected in wastewater from a U.S. naval base here, it was learned on Sept. 30.

    According to the revelation, a combined total of 8,592 nanograms of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) per liter were detected in sewage discharged from a wastewater treatment plant at the Yokosuka naval base in the city of Yokosuka, Kanagawa Prefecture, after samples collected by the U.S. military in August were analyzed.

    The volume of the chemical compounds detected equals to 172 times the Japanese government-set provisional target value of a total of 50 nanograms per liter. Toru Yamano, head of the Japanese Ministry of Defense's South Kanto Defense Bureau, reported the findings to Yokosuka Mayor Katsuaki Kamiji during his visit to the city hall. The cause of the toxic chemicals' discharge is reportedly unknown.

    According to Yamano, 8,592 nanograms per liter of the chemicals, or 172 times the government's target value, were detected in domestic wastewater discharged from the base's treatment plant on Aug. 29, and 5,450 nanograms per liter of the chemical toxin, or 109 times the target value, were detected from industrial drainage.

    While the U.S. military's previous surveys conducted in May and July had found up to 112 nanograms of the chemicals in wastewater from the treatment facility, the latest findings largely exceeded values detected in the two earlier surveys.

    "I can't help but feel anger. I can no longer trust (the U.S. military)," Mayor Kamiji said, demanding that the Japanese government conduct an on-site inspection at the base.

    As the discharged water flows into Tokyo Bay, the U.S. military said it will set up filters to absorb the two chemical compounds by Nov. 1. The mayor told Yamano, "I want the wastewater to be stopped more quickly, before that date." In response, the defense bureau chief stated, "It is quite difficult, but we'll file a request with the U.S."

    (Japanese original by Toshiaki Hashimoto, Yokosuka Local Bureau)

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