City in Saitama Prefecture (Near Tokyo) Sets Independent Maximum Radiation Dose For Children

City in Saitama Prefecture sets independent maximum radiation dose for children (Mainichi, June 21, 2011):

KAWAGUCHI, Saitama — The city government here has set the maximum radiation dose for children at 1.64 millisieverts per year, making it the first local government in Japan to implement its own radiation exposure standard.

The tentative figure announced on June 20 is based on the International Commission on Radiological Protection (ICRP)’s 1 millisievert recommended maximum exposure to man-made radiation sources, plus Japan’s average background radiation dose of 0.34 millisieverts and the average 0.3 millisieverts of annual exposure to cosmic radiation.

According to the Kawaguchi city government, the new annual exposure limit breaks down to a maximum hourly dose of 0.31 microsieverts, assuming a child spent eight hours a day outside. Officials will take radiation measurements at 10 sites in the city once a week, starting in mid-July. If they find radiation levels at a site have exceeded the new municipal maximum, the city will restrict outdoor activities at surrounding nursery schools, kindergartens, primary and junior high schools to three hours a day.

The Kawaguchi city government has already taken radiation measurements twice at the 10 sites, recording a top hourly dose of 0.16 microsieverts.

The new maximum dosage was set after the city received inquires from worried parents and guardians, asking what they should do about their children should radiation exposure rise.

Asked if the city’s move wouldn’t spark confusion in other local governments, Kawaguchi Mayor Koshiro Okamura replied, “We shouldn’t all have different regulations. The central government really needs to set a national radiation dose standard.”

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