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

Abstract

Following Japan’s 2011 Fukushima nuclear incident, voluntary participation, rather than mandatory, was adopted as the default scenario for individual radiation monitoring. We evaluated the representativeness of the internal monitoring results from voluntary participants in Minamisoma City, which is located 10–40 km from the Fukushima nuclear plant. Of approximately 70,000 individuals who were residing in Minamisoma City before the incident, a total of 19,263 residents (aged ≥21 years) participated in the monitoring from 1 October 2011 to 31 March 2015. Based on regression projection techniques with the available data obtained from the voluntary participants, the modeled probabilities of radiocesium (Cs) detection in October 2011 for Cs-137 and Cs-134 were 66.9% and 52.9%, respectively, which declined dramatically within a year following the incident. The rate of decline had stagnated since mid-2012, and the probability was close to zero after mid-2014. Sufficient agreement between the modeled probabilities of Cs detection (for the whole population) versus the measured Cs levels (for voluntary participants) was observed, except for Cs-134 in October 2011, indicating that the voluntary monitoring participant group was a good representative sample. Our findings affirmed the clinical importance of voluntary-based monitoring as a screening and dose-assessment tool in a post-nuclear incident. Our study informs societal decision-making regarding the long-term maintenance of the monitoring program under the current low exposure levels.

Usefulness of the whole-body counter for infants and small children (BABYSCAN) as a risk communication tool after the Fukushima Daiichi nuclear power plant incident

“…This finding is comparable with the previously reported results for adults and children in Minamisoma City. 29) Although additional doses from foods were reported to be negligible (50.002 mSv/y in 2014) in market basket and duplicate portion studies, 30) the present results also showed that chronic internal exposure is wellmanaged through food contamination control and that internal exposure has a negligible health risk for children aged 0-6 years. Although infants/small children might have different dietary patterns from adults, internal contamination is still well-controlled.…”

Effect of Radiological Countermeasures on Subjective Well-Being and Radiation Anxiety after the 2011 Disaster: The Fukushima Health Management Survey

“…The radiological countermeasures assessed in this study included WBC, food inspection, air dose monitoring, individual dose monitoring, basic survey, thyroid examination (specific to the examination under the FHMS), and explanatory meetings. WBC is the monitoring of internal radiation exposure and provides opportunities for the experts and examinees to exchange the individual dose information [ 20 , 25 ]. Food inspection is the measurements of radionuclide concentrations in foods.…”

“…These activities identified radiation risks and they also addressed radiation anxiety, comprehensive health risks to individuals, and well-being [ 20 ] and were well in accordance with the concept of risk communication, which has been defined by the National Research Council as “an interactive process of exchange of information and opinion among individuals” [ 24 ]. For example, whole body counter (WBC), i.e., the monitoring of internal radiation exposure, was first used to measure levels of internal radiation doses for medical interventions but then became a tool for risk communication: the WBC creates the opportunity for experts to discuss radiation directly with individuals and address their concerns [ 20 , 25 ]. In addition to radiation monitoring of foods and air dosages, “individual” dose monitoring has been performed by collecting and providing external radiation exposure data using devices such as glass badges [ 4 , 26 , 27 ].…”

Individual Doses to the Public after the Fukushima Nuclear Accident

“…They were compared with 134 Cs and 137 Cs levels measured from October 2011 to March 2015 for voluntary participants. They found sufficient agreement between simulated and measured 134 Cs and 137 Cs levels except for 134 Cs in October 2011 and concluded that the voluntary monitoring participant group was a good representative sample [72].…”

“…As mentioned in previous subsection, "interpretation of personal dose measurement results", representativeness of subjects is one of the concerns about volunteer-based monitoring. Representativeness of WBC subjects was investigated by Nomura et al [72]. Based on regression projection techniques, separate probabilities for 137 Cs and 134 Cs detection for a whole population were simulated.…”