The Japanese government is considering treating its provisional drinking water target as a benchmark for the level of potentially harmful PFAS chemicals in discharged water.



This comes as the US military's Yokota Air Base in western Tokyo informed Japanese authorities of its plan to release water containing the chemicals after decontaminating it.



PFAS is a group of organic fluorine compounds. Last year, it was found that water containing PFAS chemicals, including PFOS and PFOA, which are considered potentially harmful, had likely leaked from the air base.



Officials of the Tokyo Metropolitan Government and surrounding cities and towns called on the air base to indicate when it would dispose of the remaining water containing the chemicals.



On Wednesday, the US side informed the Japanese Defense Ministry that it planned to use activated carbon filters to remove PFOS and other chemicals from the water remaining in a reservoir. They said the treated water would then be released into drains.



Japan does not have a legal standard for PFAS levels in discharged water, but the government's provisional limit for PFAS in tap water is set at 50 nanograms per liter.



The Environment Ministry has indicated that the Yokota Air Base's water release would be permissible if PFAS levels are below that threshold.



Environment Minister Asao Keiichiro told reporters on Friday, "The government is considering this level as a general benchmark for treating water containing PFOS and PFOA. At that concentration, we believe there will be no adverse effects on human health."