Estimation of internal radiation exposure during 9 years after Fukushima nuclear accident using National food-monitoring data in Japan

Abstract

Purpose: To clarify public health mitigations to reduce ingestion dose after the nuclear accident by demonstrating the trends in official radiological food monitoring data from the national food surveillance program during the first nine years after the Fukushima nuclear accident.Methods: 2,524,369 food samples have been officially submitted to the Ministry of Health, Labour and Welfare for monitoring during the first nine years after the Fukushima Nuclear Accident as of 25 December 2019 since March 2011. Among them exceeded samples were 6,577. Radiation doses were estimated using ingestion rates based on the Japanese National Food Consumption Survey dataset (N = 6,962) using a Monte Carlo method.Results: Assuming that food restrictions were fully implemented and using the national mean food consumption data, the 95 percentile of the effective doses to adult males from dietary exposures was 110 µSv reducing 108 µSv in 2011 and 36 µSv reducing 1 µSv in 2019. The 99.99 percentile of the effective doses to adult males from dietary exposures was 943 µSv reducing 3,608 µSv in 2011 and 206 µSv reducing 54 µSv in 2018.Discussion: The effect of public health mitigation on radiation food safety has been changing during the first nine years after the Fukushima accident. The 99.99 percentile of the effective doses was below the standard limit even if the regulation was not applied in 2019.Conclusions: We confirmed the improving internal radiation dose trend with the official national food surveillance system data from the first nine years after the Fukushima nuclear accident. We expect that the food contamination levels will continue to decrease over time.