Dietary exposure levels to 134Cs, 137Cs, 90Sr, and 239+240Pu in Japan after the Fukushima Daiichi Nuclear Power Plant accident: a duplicate portion study for fiscal years 2012-2014.

Background: Since the accident at Fukushima Daiichi Nuclear Power Plant (FDNPP), concerns have arisen in Japan regarding the presence of radionuclides in food. Moreover, exposure levels to ⁹⁰Sr and Pu isotopes in adults and those to ¹³⁴Cs+¹³⁷Cs, ⁹⁰Sr, and Pu (where Cs, Sr, and Pu are cesium, strontium, and plutonium, respectively) in children have not been examined. Therefore, this study employed a duplicate portion approach to examine dietary exposure levels of radionuclides in adults and children following the FDNPP accident.

Methods: The study spanned fiscal years 2012-2014 and was conducted in 10 prefectures: Hokkaido, Iwate, Miyagi, Fukushima, Ibaraki, Saitama, Tokyo, Kanagawa, Osaka, and Kochi. The participants provided portions of their meals for two non-consecutive days and completed questionnaires on the meal items. The activity concentrations of ¹³⁴Cs, ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu, which are targets of standard limits for radionuclides in foods in Japan, were determined according to the Radioactivity Measurement Series. The daily intake was calculated based on the radionuclide activity concentrations in the duplicate portion samples, and the committed effective doses were estimated using dose coefficients for the ingestion of each radionuclide provided by the International Commission on Radiological Protection.

Results: Approximately 80 duplicate samples were obtained in each fiscal year, and 242 samples were collected. The highest summed activity concentration of ¹³⁴Cs and ¹³⁷Cs was 11 Bq/kg, which was recorded in Date City (child) in 2013; this level was approximately one-ninth of the standard limit for general foods (100 Bq/kg). The committed effective dose from annual ingestion of the sample described above was 74 µSv, approximately 14 times lower than the maximum permissible level of 1 mSv/y. Pu was not detected and the ⁹⁰Sr activity concentrations were similar to those before the FDNPP accident.

Conclusions: For the samples examined in the present study, the ¹³⁴Cs, ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu dietary exposure levels were considerably lower than the regulatory levels and may not pose a health risk.