Contents and Daily Intakes of Gamma-Ray Emitting Nuclides, ⁹⁰Sr, and ²³⁸U using Market-Basket Studies in Japan

Abstract

To investigate the contents of radionuclides in foods marketed in Japan and their daily intakes and exposure doses in adults, we performed market-basket studies concerning radionuclide intakes. The study period was 2003-2005, and the studies were performed in 13 cities in Japan. Foods including drinking water were divided into 14 food groups, and samples were prepared by common cooking procedures. γ-ray emitting nuclides (an artificial radionuclide, radioactive Cs, and natural radionuclides, ⁴⁰K and U series such as ²¹⁴Bi, and ²¹²Pb, and Th series) were measured in each food group, and artificial radionuclides, ⁹⁰Sr and ²³⁸U, were measured in a mixed sample of 13 food groups excluding drinking water. The daily intakes in adults were calculated from the concentrations of the radionuclides and mean daily consumption of foods and drinking water. The daily ¹³⁷Cs and ⁴⁰K intakes (mBq/person·day) in the 13 cities were 12.5-<79.7 and 57309-95746, respectively. The ⁹⁰Sr intake from the food groups excluding drinking water was 20.8-53.6, with a mean of 39.2 (mBq/person·day) (deviation of the mean: 23%). Similarly, the daily ²³⁸U intake was 5.9-31.1, with a mean of 12.6 (mBq/person·day) (deviation: 60%), showing a more than 5-fold difference between the minimum and maximum values, and there were regional differences. Since the contents of the U series, such as ²¹⁴Bi and ²¹²Pb, and Th series were lower than the lower detection limits in many samples, their daily intakes were not calculated. Regarding the daily intake of ¹³⁷Cs from each food group, the intakes from fish and shellfish, milk, meat/eggs, and mushrooms/seaweed tended to be higher. The daily ⁴⁰K intake from each food group varied among the areas, but the total intake from the 14 food groups was similar in all 13 cities. ⁴⁰K from these foods accounted for most of the annual effective dose (μSv/person·year) of γ-ray emitting nuclides, and the doses of ⁴⁰K, ⁹⁰Sr, and ²³⁸U were 130-217, 0.21-0.55, and 0.10-0.51, respectively.