RADIOISOTOPES

Changes in numbers of food materials that exceeded the standard limits of radiocaesium (¹³⁴Cs+¹³⁷Cs) with time were examined for the last decade after the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant using the food monitoring data collated by the Ministry of Health, Labour and Welfare. The food standard limits that set from April 1, 2012, were used throughout the study to elucidate changes in exceeding ratios of radiocaesium. For this analysis, we did not use the data for beef, because number of all beef cattle inspection occupied more than 60％ of total numbers of food monitoring until March 2020. It was found that the ratio exceeding the limit has been less than 1％ since 2014. After 2018, most food items have never exceeded the standard value except for wild animal meat, wild plants and mushrooms. These uncontrollable wild foods may need to be monitored their radiocaesium activity concentrations for a longer time period; however, public people do not use these foods frequently. Thus, it was assumed that the internal dose by ingestion of these food materials would provide only a limited contribution to the total radiation from the environment.