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External radiation doses in Fukushima comparable to those of Europe: study

by Mizuho Aoki

Staff Writer

The external radiation exposure levels of high school students in Fukushima Prefecture are within the same range of those living in France, Poland and Belarus, a scientist and a high school student said Monday in Tokyo.

Both were among members of a research group that conducted a study on individual radiation levels.

Speaking at the Foreign Correspondents’ Club of Japan, Ryugo Hayano, a professor in the University of Tokyo’s physics department, said that while the effect of the 2011 meltdowns at the Fukushima No. 1 nuclear plant definitely remains, radiation levels have fortunately lowered over the past five years.

Because natural background radiation levels in Fukushima are lower than the world’s average, even when the extra radiation dose from the nuclear disaster is added, the external exposure of Fukushima residents did not differ significantly from those measured in other parts of the world, they said.

The study does not include the evacuation zone around the crippled plant.

Initiated by a group of students at Fukushima High School, the study examined 216 students and teachers in 12 high schools — six in Fukushima and six in other prefectures such as Kanagawa and Nara — and compared the results with eight schools in Poland, four in France and two in Belarus for two weeks in 2014.

Each participant wore a personal electronic dosimeter and kept a journal of their activities.

According to the study, published in the Journal of Radiological Protection last November, the external doses received by participants in Fukushima during the two-week period were “well within the terrestrial background radiation levels of other regions or countries.”

The median annual external radiation exposure of students in Fukushima was estimated to be 0.63 to 0.97 millisieverts, compared with 0.51 to 1.10 in Poland, France and Belarus, according to the study.

“I wanted to know how high my exposure dose was and wanted to compare that with people in other places,” said Haruka Onodera, a student at Fukushima High School.

Although she knew nothing about external radiation at the start of the examination, through analyzing and collecting data, Onodera said she was able to deepen her understanding and realized the importance of evaluating risk based on objective scientific facts.

The International Commission on Radiological Protection (ICRP) sets recommended annual radiation exposure limits under normal situations at 1 millisievert. A cumulative dose of 100 millisieverts over a lifetime would increase the chance of developing cancer by 0.5 percent, according to the ICRP.

The average terrestrial natural radiation level in Japan is around 0.33 millisieverts per year, the report said, which is lower than the world average of 0.48 millisieverts.

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