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Water Quality and Water Resources

Q&A about Radioactive Materials

< Testing of radioactive materials >

Q1  Where does the water that the Bureau of Waterworks tests come from?
A1  Bureau of Waterworks Tokyo Metropolitan Government tests at all purification plants. For details of testing please check here.
Q2  Does the Bureau of Waterworks publish the results of its tests?
A2  We publish the results on our website on the next business day after the sample was taken.
Q3  Is the amount of radioactive materials in tap water in the Tokyo Metropolitan area tested by any organizations other than the Bureau of Waterworks?
A3  The Tokyo Metropolitan Institute of Public Health tests samples of tap water taken from a tap in Hyakunincho, Shinjuku-ku every day. The results of those tests are published on the Institute’s website.

< Results of Testing radioactive materials >

Q4  Does water in Tokyo include radioactive materials?
A4  Radioactive cesium has never been detected in the period since testing began on March 22, 2011. Radioactive iodine was initially detected in the immediate aftermath of the accident at the Fukushima Dai-ichi Nuclear Power Plant, but the short half life (around 8 days) of this material means that it has not been detected since mid-April 2011.
Q5  How many Bq/kg is the maximum permissible amount of radioactive cesium in water?
A5  Since April 2012, the maximum amount of radioactive cesium permissible in drinking water has been set at 10Bq/kg, based on the Food Hygiene Law. This 10Bq/kg figure has been set as a target for the management of radioactive cesium in tap water.

< Water Treatment Measures >

Q6  What treatment measures are being taken to remove radioactive materials?
A6  Radioactive cesium is easily absorbed in suspended substances, and so, in almost all cases it is present in untreated water is absorbed in the suspended substances. At the purification plants, the suspended substances can be removed, together with the radioactive cesium, through a process of coagulation-sedimentation and sand filtration.
    Radioactive Iodine can be effectively removed through a combination of powdered activated carbon and chlorine (disinfectant).
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