Recalculation of Age-specific Cancer Risk Due to Radiation Exposure Using the Recent Mortality Data of the Japanese Population

抄録

After the Fukushima Dai-ichi nuclear power plant accident, one of the main issues was that the level of the radiation risk due to exposure, such as nominal risk coefficient, was difficult to understand. On the other hand, in the ICRP 1990 recommendation Annex C, the conditional and unconditional death probability rates, which can consider a plausible additional risk, were used as one of the referral premises for the judgement of the effective dose limits for members of the public and radiation workers. These conditional and unconditional death probability rates were illustrated as a function of the attained age and appear to be easily understandable to people concerned about the “time” and “level” of risk increment due to radiation exposure. In this study the conditional and unconditional death probability rates were updated by using recent Japanese statistical data in line with the methodology of the ICRP 1990 recommendation. Uncertainties associated with the selection of the statistical data for the Japanese population from 1985 to 2010 were also estimated to reveal the hidden variation of the prospective risk estimation. Variations in the estimated risk up to 10% order were found owing to the recent increase in life expectancy; however, the range of the variation over time is comparable to that obtained from prefecture data as of 2010.