抄録
Radioactive materials were released into the environment, and contaminated food due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In response to this situation, regulations on radionuclides in food came into effect immediately after the accident, and food regulations based on standard values are still in place. In order to estimate the intake of radioactive materials in food after the Fukushima nuclear power plant accident, a total diet study (TDS) was conducted. The market basket (MB) method, which estimates the average intake by analyzing samples prepared based on the average food consumption data of Japanese people, and the duplicate diet (DD) method, which analyzes samples mixed with the daily meals of survey subjects and investigates the distribution of intake, were used to estimate the daily dietary intake and the annual committed effective dose of radioactive cesium (Cs) (Cs-134 and Cs-137) and the natural radionuclide potassium 40 (K-40). The maximum annual committed effective dose estimated by the MB method conducted twice a year from September 2011 to March 2019 was 0.0010-0.019 mSv/year, and the maximum annual committed effective dose estimated by the DD method conducted in 2012 was 0.027 mSv/year. The MB data for each period was collected across different regions. Although the detection rate and annual committed effective dose of radioactive Cs were somewhat higher in Fukushima and the surrounding regions than in other regions, regional differences tended to become smaller with time since the accident. In addition, the annual committed effective dose in each region tended to decrease with time since the accident. In Fukushima and the surrounding areas, in particular, the annual committed effective dose of radioactive Cs decreased significantly 2 years after the accident. It was considered that this was caused by the decrease in the concentration of radioactive Cs in food due to the effect of administrative measures such as food regulations based on the standard value in addition to the attenuation of radioactive Cs, mainly Cs-134. In the DD method, the histogram of the annual committed effective dose in Fukushima and the surrounding regions showed a wide distribution with a slightly higher dose side, however, most of the survey subjects from those regions had an annual committed effective dose of radioactive Cs through food which was similar to that in other regions. In both the MB and DD methods, the estimated maximum annual committed effective dose was sufficiently smaller than the maximum permissible dose (1 mSv/year) in food. In addition, it was confirmed that the annual committed effective dose of radioactive Cs was much smaller than the annual committed effective dose from K-40, a natural radionuclide, using both the MB and DD methods. These results suggest that the health risk of ingestion radioactive Cs is extremely low when consuming normal diets that include commercial foods on the Japanese market. Nevertheless, to ensure food safety from the viewpoint of risk communication, it should be necessary to continue to monitor and disclose the daily dietary intake and annual committed effective dose of radioactive Cs.
