Shaping global health protection policy following nuclear disasters: learning from Japan’s 2011 Fukushima Dai-ichi Nuclear Power Plant Incident

Abstract

Japan's 2011 Fukushima Dai-ichi Nuclear Power Plant Incident displaced more than 150 thousand people due to a release of radioactive material, highlighting the challenges facing us regarding radiation dose assessment and effective countermeasures (especially evacuation) when responding to a major incident.

The overall aim of my PhD project was to inform the design, preparation, and delivery of measures to manage health risks of a major nuclear disaster, by adding evidence to fill knowledge gaps using data collected following the Fukushima nuclear incident. The emergency phase of the incident (i.e. within the first few hours/days) has been assessed elsewhere, so my focus was the post-emergency phase (i.e. in the days/months/years following the incident).

To meet this aim, and building on a review of the relevant literature, I identified key research questions linked to the radiological and non-radiological health protection aspects in the context of the Fukushima incident. I was primarily interested in understanding 1) the potential challenges concerning the assessment of levels of external radiation exposure (the dominant exposure pathway) in children in the post-emergency phase following the Fukushima incident, and 2) the potential benefits and health risks of the post-incident evacuation in adults.

The study areas are Minamisoma City and Soma City in Fukushima Prefecture, Japan, located 14–38 and 35–50 km from the Fukushima nuclear plant, respectively. Various primary and secondary datasets were used in my PhD project, including: measured levels of external radiation exposure; data on post-incident daily behaviour patterns; air dose rate data; measured levels of internal/body radio-contamination; early incident response patterns; nursing home data with evacuation records; and public health check-up data. A variety of statistical approaches to analyse these data were applied.

Key findings concerning the evaluation of external radiation exposure in children included: (a) an average three-fold disagreement between the measured dose and that estimated from Japan's government dose reconstruction model, with the model overestimating it; (b) air dose rates at places where children spend most of the day being the significant predictors of the dose; and (c) poor compliance with radiation dosimeters among children (only 7.3% used the dosimeters properly). With respect to the potential benefits and health risks of early evacuation of adults, findings included: (d) limited effectiveness of early evacuation on reducing internal exposure risk; (e) a substantial mortality impact of initial evacuation (vs. non-evacuation); and (f) increased risk of long-term hyperlipidemia associated with evacuation.

Overall, these findings indicate that the latitude for improving the evaluation of external radiation exposure in children in the post-emergency phase of a major nuclear incident is wide; dose reconstruction models should be developed that ensure a more realistic representation of external exposure risk factors, and factors influencing the proper use of direct measurements (using an individual radiation dosimeter) must be better understood. In addition, there is scope for reducing post-incident evacuation-related health risks; disaster planning must emphasise well-planned evacuation, with satisfactory arrangements for appropriate transportation, places to evacuate to safely, and include the long-term strategies for mitigating the evacuation-related health risks.

The evidence presented in this PhD thesis will help the government, local authorities, health planners, and disaster coordinators to develop better optimized radiological and non-radiological protection policies to minimise health risks of future nuclear incidents.