Comparison between Direct Measurements and Modeled Estimates of External Radiation Exposure among School Children 18 to 30 Months after the Fukushima Nuclear Accident in Japan

Abstract

After a major radioactive incident, accurate dose reconstruction is important for evaluating health risks and appropriate radiation protection policies. After the 2011 Japan Fukushima nuclear incident, we assessed the level of agreement between the modeled and directly measured dose and estimated the uncertainties. The study population comprised 520 school children from Minamisoma city, located 20 km north of the nuclear plant. The annual dose 18–30 months after the incident was assessed using two approaches: estimation using the model proposed by the Japanese government and direct measurement by radiation dosemeters. The ratio of the average of modeled and measured doses was 3.0 (standard deviation (SD): 2.0). The reduction coefficient, an index for radiation attenuation properties, was 0.3 (SD: 0.1) on average, whereas the value used in the government model was 0.6. After adjusting for covariates, the coefficient had a significant negative correlation with the air dose rate in the dwelling location (p < 0.001), indicating that stronger building shielding effects are valuable in areas with higher air contamination levels. The present study demonstrated that some overestimation may have been related to uncertainties in radiation reduction effects, and that the air contamination level might provide a more important indicator of these effects.

Individual external dose monitoring of all citizens of Date City by passive dosimeter 5 to 51 months after the Fukushima NPP accident (series): 1. Comparison of individual dose with ambient dose rate monitored by aircraft surveys

“…In order to evaluate the additional dose due to the radioactive cesium released by the accident, it is necessary to subtract the background contribution. In generating the glass badge readout report for Fukushima Prefecture residents, the glass-badge supplier, Chiyoda Technol, subtracts a value equivalent to 0.54 mSv y −1 as the background, measured at Oarai Town, Ibaraki Prefecture (130 km south of FDNPP), where the contamination due to the FDNPP accident was low [18]. Date City then mails the results to each monitoring survey participant.…”

Towards a Long-Term Strategy for Voluntary-Based Internal Radiation Contamination Monitoring: Representativeness of the Monitoring Results in Fukushima, Japan

“…Except for dose reconstruction estimation with scientific assumptions [12,13], most of these evaluations were based on voluntary-based radiation monitoring administered by local authorities, using an individual radiation dosimeter for determining the external exposure level [3,14,15] or anthropogammametry (i.e., whole body counting (WBC) for determining the amount of radionuclides within the body at the time of monitoring) [16,17,18,19]. In summary, as a result of the counter-dose measures as well as natural removal phenomena such as weather and radioactive decay [6], the current exposure risks from radiation in the environment (attributable to the Fukushima incident) is considerably low or at undetectable levels [20], implying a marginal risk of radiation-associated physical health consequences of the incident [12,13].…”

Effectiveness of landscape decontamination following the Fukushima nuclear accident: a review

“…Furthermore, the low permissible levels for radiocesium contamination in wood (e.g. 40 Bq kg −1 in wood for cooking or eating) will restrict the use of this commodity for at least several decades in the region (Ohashi et al, 2017). In addition, approximately 1800 workers are employed by the forest industry in the region (Yasutaka and Naito, 2016).…”