Measurements of Individual Radiation Doses in Residents Living Around the Fukushima Nuclear Power Plant

At the outset of the accident at Fukushima Daiichi NuclearPower Plant in March 2011, the radiation doses experiencedby residents were calculated from the readings at monitoringposts, with several assumptions being made from the point ofview of protection and safety. However, health effects shouldalso be estimated by obtaining measurements of theindividual radiation doses. The individual external radiation doses, determined by a behavior survey in the ‘‘evacuationand deliberate evacuation area’’ in the first 4 months, were,5 mSv in 97.4% of residents (maximum: 15 mSv). Doses inFukushima Prefecture were ,3 mSv in 99.3% of 386,572residents analyzed. External doses in Fukushima Citydetermined by personal dosimeters were ,1 mSv/3 months(September–November, 2011) in 99.7% of residents (maximum:2.7 mSv). Thyroid radiation doses, determined inMarch using a NaI (TI) scintillation survey meter in childrenin the evacuation and deliberate evacuation area, were ,10mSv in 95.7% of children (maximum: 35 mSv). Therefore, alldoses were less than the intervention level of 50 mSvproposed by international organizations. Internal radiationdoses determined by cesium-134 (134C) and cesium-137 (137C)whole-body counters (WBCs) were ,1 mSv in 99% of theresidents, and the maximum thyroid equivalent dose byiodine-131 WBCs was 20 mSv. The exploratory committee ofthe Fukushima Health Management Survey mentions on itswebsite that radiation from the accident is unlikely to be acause of adverse health effects in the future. In any event,sincere scientific efforts must continue to obtain individualradiation doses that are as accurate as possible. However,observation of the health effects of the radiation dosesdescribed above will require reevaluation of the protocol usedfor determining adverse health effects. The dose-responserelationship is crucial, and the aim of the survey should be tocollect sufficient data to confirm the presence or absence ofradiation health effects. In particular, the schedule ofdecontamination needs reconsideration. The decontaminationmap is determined based on the results of airbornemonitoring and the radiation dose calculated from readingstaken at the monitoring posts at the initial period of theaccident. The decontamination protocol should be reevaluatedbased on the individual doses of the people who desire tolive in those areas.journal articl