Measures against impacts of nuclear disaster on drinking water supply systems in Japan

On 11 March 2011, the Great East Japan Earthquake occurred and then the Japanese Prime Minister declared the state of nuclear emergency. The earthquake followed by tsunami and several accidents caused a nuclear power plant in Fukushima Prefecture to release radioactive materials into the environment. Ministry of Health, Labour and Welfare, Japan (MHLW) established a new review meeting to investigate subjects relating to radioactive materials in tap water such as the mechanism of influence of radioactive materials on tap water, measures to reduce the level of radioactive materials contaminated in tap water and medium- and long-term measures based on the results of monitoring. The review meeting published its interim report on 21 June 2011. The report analyzed future prospects as follows: (i) unless a large amount of radioactive materials is released again from the nuclear power plant, tap water has low probability to require measures such as intake restriction and (ii) groundwater that is not affected by surface water has low probability to be affected from radioactive materials. Based on the report, MHLW announced measures to reduce radioactive materials in tap water and also revised the future monitoring policy for more rational and effective implementation. Whilst radioactivity in tap water has not been detected or has been minute if detected since April 2011, the monitoring of tap water and announcement of results will be further continued in Japan.