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Schoolyard Radiation Policy Brings a Backlash

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Science  20 May 2011:
Vol. 332, Issue 6032, pp. 909
DOI: 10.1126/science.332.6032.909

The Japanese government's most controversial misstep in response to the Fukushima nuclear power plant crisis may have been the release of guidelines on allowable radiological contamination in schoolyards.

TOKYO—The Japanese government has made a number of missteps during the 2-month-long Fukushima nuclear power plant crisis. But the most controversial may have been the release of guidelines from the education ministry on allowable radiological contamination in schoolyards. They seem to allow children to accumulate radiation exposures of 20 millisieverts (mSv) over the course of a year. By comparison, nuclear industry workers in Japan can absorb no more than 100 mSv per year; the limit for U.S. nuclear personnel is 50 mSv per year.

The 19 April announcement unleashed a torrent of criticism from civic groups and experts. “Setting [such radiation limits] for elementary schools is inexcusable,” Toshiso Kosako, a radiation health expert at the University of Tokyo, said on 30 April, when he resigned as an adviser to Prime Minister Naoto Kan on the nuclear crisis. Because children are known to be more susceptible than adults to risks of cancer from radiation, Physicians for Social Responsibility, a U.S. antinuclear proliferation group, condemned the exposure limit as “unconscionable.”

Dirty dirt.

Fukushima schools are stripping contaminated topsoil from playgrounds.


The ministry has backpedaled—but not fully retreated. On 11 May, it released suggestions for removing contaminated topsoil from schoolyards to reduce radiation exposures. But it did not change or retract the exposure guidelines.

In its “provisional idea” for acceptable levels of radiation in schoolyards, the education ministry cited a 2009 recommendation from the International Commission on Radiological Protection (ICRP), an Ottawa-based nongovernmental organization. During emergencies, ICRP Publication 109 states, populations can be exposed to 20 to 100 mSv per year. The education ministry calculated that children could spend 8 hours a day in a schoolyard exposed to as much as 3.8 microsieverts per hour, and 16 hours a day indoors exposed to 1.52 microsieverts per hour, and not exceed the 20-mSv limit. Civic groups contend that the education ministry should follow another ICRP recommendation, which states that exposure limits for long-term residence in contaminated areas after an accident should be kept “in the lower part of the 1-20 mSv/year” range.

In the past few weeks, several schools took matters into their own hands and stripped topsoil from their grounds. On 11 May, the ministry jumped on that bandwagon, announcing test results showing that swapping the top 10 centimeters of topsoil with dirt from deeper down cut surface radiation 90%. Stripping and burying the topsoil in a deep hole reduces surface radiation 99%. The ministry is leaving final decisions on what to do in the hands of local officials.

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