Estimation of Effect of Radiation Dose Reduction for Internal Exposure by Food Regulations under the Current Criteria for Radionuclides in Foodstuff in Japan Using Monitoring Results.

Minoru Osanai,Kazuki Iwaoka,Megumi Tsushima,Yoko Saito,Shota Hosokawa,Daisuke Hirano,Kohsei Kudo,Yoichiro Hosokawa,Masahiro Hosoda,Shiori Mitsuhashi,Ichiro Yamaguchi,Takakiyo Tsujiguchi

doi:10.3390/foods10040691

Abstract

This study examined the effect of food regulations under the current criteria (e.g., 100 Bq/kg for general foods) established approximately a year after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Foods are monitored to ensure that foods exceeding the standard limit are not distributed; ~300,000 examinations per year have been performed especially since FY2014. This study comprehensively estimated the internal exposure dose resulting from the ingestion of foods containing radioactive cesium using the accumulated monitoring results. Committed effective dose was conservatively calculated as the product of the radioactive concentration randomly sampled from test results, food intake, and dose coefficient. The median, 95th, and 99th percentile of the dose were 0.0479, 0.207, and 10.6 mSv/y, respectively, in the estimation with all test results (without regulation), and 0.0430, 0.0790, and 0.233 mSv/y, respectively, in the estimation with results within the standard limits (with regulation) in FY2012. In FY2016, the dose with and without regulation were similar, except for high percentile, and those doses were significantly smaller than 1 mSv/y, which was adopted as the basis for the current criteria. The food regulation measures implemented in Japan after the FDNPP accident have been beneficial, and food safety against radionuclides has been ensured.

Highlights

The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident was caused by the11 March 2011 Great East Japan Earthquake and tsunami
Because the new standard limits are aimed at long-term application, radionuclides whose halflives are longer than one year were selected as the regulation target
When the not detected (ND) ratio was less than 60% in a category, the radioactivity concentration was set to the value of limit of detection (LOD)

Summary

Introduction

The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident was caused by the11 March 2011 Great East Japan Earthquake and tsunami. The provisional regulation values were established as radionuclide concentration based on an effective dose of 5 mSv/y for radioactive cesium. The value for radioactive cesium in drinking water and milk/dairy products was 200 Bq/kg, and that in vegetables, grains, meat, eggs, and fish was 500 Bq/kg These values of radioactivity concentration were set including the contribution of radioactive strontium to the radiation dose. The standard limits for radioactive cesium were calculated based on the estimated concentration ratio of each radionuclide in foods [12,17] so that the effective dose from all regulated radionuclides would not exceed 1 mSv/y. Unless the radioactive cesium in foods exceeds the standard limits (e.g., 100 Bq/kg for general food), the radiation dose from all regulated radionuclides such as strontium-90 does not exceed 1 mSv/y. The dominant radionuclide in the long term was radioactive cesium, and the contribution of other radionuclides to the radiation dose from foodstuffs was estimated as 12% for age 19 and older when the current limits were derived [17]

Objectives

Results

Discussion

Conclusion