Change in the Measurement Frequency of Indoor Radiation Levels

Since the occurrence of the Great East Japan Earthquake, the city has been conducting fixed-point measurements of ambient radiation levels at a height of 5 cm and 100 cm in Elementary and Junior High Schools, Nursery Schools, and Kindergartens within the city since June 2011. In fiscal year 2016, measurements were conducted once a month at 40 locations.
Additionally, starting from February 2012, locations prone to accumulation of rainwater, dust, and dirt, such as under rain gutters and rainwater catch basins in Public Facilities, were selected for annual local measurements of ambient radiation levels at a height of 1 cm from the ground. In fiscal year 2016, measurements were conducted at 235 facilities and 729 locations.
In this context, the measurement results from 2011 to the present have shown stable values, remaining below the standard value indicated by the Ministry of the Environment (0.23 microsieverts per hour). Furthermore, the values from the radiation monitoring posts in Shinjuku Ward, which were established before the Great East Japan Earthquake, have decreased to levels lower than those before the disaster. Therefore, the city will suspend measurements of ambient radiation levels within the city from fiscal year 2021 onwards. However, if any concerns arise, measurements will be resumed immediately.

• Change in Frequency of Ambient Radiation Measurement (PDF 283.9KB)