After the 2011 accident at the Fukushima Daiichi nuclear power plant, nursing-home residents and staff were evacuated voluntarily from damaged areas to avoid radiation exposure. Unfortunately, the evacuation resulted in increased mortalities among nursing home residents. We assessed the risk trade-off between evacuation and radiation for 191 residents and 184 staff at three nursing homes by using the same detriment indicator, namely loss of life expectancy (LLE), under four scenarios, i.e. “rapid evacuation (in accordance with the actual situation; i.e. evacuation on 22 March),” “deliberate evacuation (i.e. evacuation on 20 June),” “20-mSv exposure,” and “100-mSv exposure.” The LLE from evacuation-related mortality among nursing home residents was assessed with survival probability data from nursing homes in the city of Minamisoma and the city of Soma. The LLE from radiation mortality was calculated from the estimated age-specific mortality rates from leukemia and all solid cancers based on the additional effective doses and the survival probabilities. The total LLE of residents due to evacuation-related risks in rapid evacuation was 11,000 persons-d—much higher than the total LLEs of residents and staff due to radiation in the other scenarios (27, 1100, and 5800 persons-d for deliberate evacuation, 20 mSv-exposure, and 100 mSv-exposure, respectively). The latitude for reducing evacuation risks among nursing home residents is surprisingly large. Evacuation regulation and planning should therefore be well balanced with the trade-offs against radiation risks. This is the first quantitative assessment of the risk trade-off between radiation exposure and evacuation after a nuclear power plant accident.

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It is examined how and to what extent cost-bene t analysis can be used in the decision-making concerning the regulation of foodstuffs contaminated with radioactive substances released from the accident of the Fukushima Daiichi Nuclear Power Plants. Cost per life-year saved is calculated for the ban of the distribution of the vegetables harvested in March and April 2012 just after the accident. It is estimated at 20 million yen. Cost per life-year saved is also estimated for the stop of the distribution of the rice harvested in autumn in some parts of the three municipalities at 1.0 billion yen. The former is smaller and the latter is larger than the values for the cost per life-year saved for the past regulation of toxic chemicals. The former is as large as the value of a life-year based on willingness to pay for risk-reduction, but the latter is much larger than that. Limit values for foodstuffs are proposed which would make the cost of regulation never exceed its bene t. The limitations of costbene t analysis are discussed, and what is necessary for the future regulation is suggested.KEY WORDS: cost-benefit analysis, Fukushima Daiichi Nuclear Power Plants, radioactive contamination of foodstuffs, regulation of foodstuffs, cost-per life-year saved, value of a life-year, willingness to pay.

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