FUKUSHIMA--Two women were likely exposed to radiation exceeding the government’s annual ceiling in the four months after the accident started at the Fukushima No. 1 nuclear power plant, prefectural officials said Feb. 20.
FUKUSHIMA--Two women were likely exposed to radiation exceeding the government’s annual ceiling in the four months after the accident started at the Fukushima No. 1 nuclear power plant, prefectural officials said Feb. 20.
The central government last year decided to allow residents to return home in stages in areas surrounding the crippled nuclear plant if the accumulated radiation 1 meter above ground is less than 20 millisieverts annually.
A study of radiation exposure on about 9,750 people in Fukushima Prefecture, excluding those who had worked previously at the plant, found that two adult women were exposed to more than 20 millisieverts over four months. One was exposed to 23 millisieverts during that period.
Although they fled after the nuclear accident started on March 11, they moved to areas where evacuation was recommended but not mandatory. Radiation levels could top 20 millisieverts a year in such areas.
In the study, estimates of radiation exposure were made based on individuals’ reports about their daily activities over the four months. The figures exclude natural radiation.
In a previous study, the highest exposure level for people in the prefecture was 14.5 millisieverts over the four months.
Kenji Kamiya, vice president of Fukushima Medical University, said the latest radiation figures are not surprising.
“Given the extent of the nuclear accident, I thought it was a matter of time for readings for some people in the prefecture to exceed 20 millisieverts,” he said. “We have to take the findings of the study seriously.”
Experts on the health risks of radiation say monitoring should continue, but they stressed that accumulated exposure of more than 20 millisieverts will not necessarily lead to immediate health problems.
“The yardstick of 20 millisieverts is a figure with more political and social implications, not scientific ones,” one of the experts said.
A government panel of experts compiled a report in December that said accumulated annual exposure of 20 millisieverts constitutes a “low risk” in terms of developing cancer, compared with other factors. The report was used to determine the central government’s ceiling.
One member of the panel, Kazuhiko Maekawa, professor emeritus at the University of Tokyo researching the health effects of radiation exposure, played down the dangers at this exposure level.
“There is not much difference in the health risks between 14.5 millisieverts and 23 millisieverts from a scientific viewpoint,” he said. “Twenty millisieverts is not a small number, but people should not worry about it too much because it is not likely that they will continue to be exposed to 20 millisieverts year after year.”
The latest study covered 10,468 of about 29,000 people from Iitate, a district in Kawamata and Namie close to the nuclear plant. The area was selected for the study before other districts due to its relatively high radiation levels.
About 720 others, mostly people who had formerly worked at the crippled plant, were also surveyed. The highest annual radiation exposure level for this group was 47.2 millisieverts.
The results of the study will be used as reference material for a similar survey on about 2 million people in the prefecture for the coming 30 years about the health effects of radiation exposure.
(This article was written by Yoshinori Hayashi and Yuri Ozawa.)