Continuous Estimation of Annual Committed Effective Dose of Radioactive Cesium by Market Basket Study in Japan from 2013 to 2019 after Fukushima Daiichi Nuclear Power Plant Accident

Hiromi Nabeshi; Tomoaki Tsutsumi; Masataka Imamura; Yoshinori Uekusa; Akiko Hachisuka; Rieko Matsuda; Reiko Teshima; Hiroshi Akiyama

doi:10.14252/foodsafetyfscj.D-20-00017

Continuous Estimation of Annual Committed Effective Dose of Radioactive Cesium by Market Basket Study in Japan from 2013 to 2019 after Fukushima Daiichi Nuclear Power Plant Accident

Food Saf (Tokyo). 2020 Dec 25;8(4):97-114. doi: 10.14252/foodsafetyfscj.D-20-00017. eCollection 2020 Dec.

Authors

Hiromi Nabeshi¹, Tomoaki Tsutsumi¹, Masataka Imamura¹, Yoshinori Uekusa^{1

2}, Akiko Hachisuka³, Rieko Matsuda^{1

4}, Reiko Teshima^{1

5}, Hiroshi Akiyama¹

Affiliations

¹ Division of Foods, National Institute of Health Sciences, Kanagawa, Japan 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan.
² Division of Natural Medicines, Faculty of Pharmacy, Keio University, Tokyo, Japan 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan.
³ Division of Biochemistry, National Institute of Health Sciences, Kanagawa, Japan 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan.
⁴ Division of Food Safety Information, National Institute of Health Sciences, Kanagawa, Japan 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan.
⁵ Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan 1-3 Ikoinooka, Imabari, Ehime 794-8555, Japan.

Abstract

Radionuclide contamination in foods has been a great concern after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. To estimate time trends of daily intake and annual committed effective dose of radionuclides after the accident, radioactive cesium (r-Cs; ¹³⁴Cs and ¹³⁷Cs) and potassium-40 (⁴⁰K) in market basket (MB) samples prepared at 6-month intervals in periods from September 2013 to March 2019 in 15 regions of Japan were analyzed using γ-ray spectrometry. The annual committed effective dose of r-Cs, calculated at non-detected radionuclide levels assumed to be half the limit of detection (LOD), appeared to decrease gradually in 11 regions close to the FDNPP that were more likely to be affected by the accident. Differences in doses among the 15 regions were large just after the accident, but gradually decreased. In particular, ¹³⁴Cs has not been detected in any MB sample in any region since September 2018, and annual committed effective dose from ¹³⁴Cs in all regions was mostly constant at around 0.3 μSv/year (given the respective LODs). The maximum annual committed effective dose of r-Cs in this study was decreased from 2.7 μSv/year in September 2013 to 1.0 μSv/year in March 2019. In contrast, the range of annual committed effective dose of ⁴⁰K varied from approximately 150 to 200 μSv/year during that time frame and did not change much throughout the period of this study. Although annual committed effective doses of r-Cs in regions close to the FDNPP appeared to be higher than in regions far from the FDNPP, doses in all regions are remaining at a much lower levels than the intervention exemption level, 1 mSv/year, in foods in Japan.

Keywords: Fukushima Daiichi Nuclear Power Plant accident; Key word annual committed effective dose; daily intake; market basket; radioactive cesium.