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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][2004][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, 40 K and U series such as 214 Bi, and 212 Pb, and Th series) were measured in each food group, and artificial radionuclides, 90 Sr and 238 U, 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 137 Cs and 40 K intakes (mBq/ person · day) in the 13 cities were 12.5-<79.7 and 57309-95746, respectively. The 90 Sr 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 238 U 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 214 Bi and 212 Pb, and Th series were lower than the lower detection limits in many samples, their daily intakes were not calculated. Regarding the daily intake of 137 Cs from each food group, the intakes from fish and shellfish, milk, meat/eggs, and mushrooms/seaweed tended to be higher. The daily 40 K intake from each food group varied among the areas, but the total intake from the 14 food groups was similar in all 13 cities. 40 K from these foods accounted for most of the annual effective dose (µSv/person · year) of γ-ray emitting nuclides, and the doses of 40 K, 90 Sr, and 238 U were 130-217, 0.21-0.55, and 0.10-0.51, respectively.Key words --radionuclide, intake, dose estimation, diet, cesium INTRODUCTIONClarification of the contents and distribution of toxic substances in foods, and estimation and evaluation of their intakes by the public are important to secure food safety. For this purpose, studies concerning dietary intakes of chemical substances, such as Polychlorinated Biphenyl (PCB) and dioxin, and toxic elements, such as Cd, Pb, and As, have been * To whom correspondence should be addressed: Department of Environmental Health, National Institute of Public Health, 2-3-6, Minami, Wako-shi, Saitama 351-0197, Japan. Tel.: +81-48-458-6263; Fax: +81-48-458-6270; E-mail: sugiyama@niph.go.jp performed in Japan. [1][2][3][4] In addition to these substances, it is important to investigate the intakes of radionuclides, considering them to be toxic substances, and evaluate the dietary exposure doses based on the values obtained. Studies concerning the daily intakes of radionuclides by the public have been performed in many countries, [5]...

Concentrations of 137Cs, 134Cs and potassium were surveyed in 32 mushrooms and 24 substrates (upon which the mushrooms grow) obtained from fields in Japan. Radiocesium concentrations (137Cs+134Cs) in mushrooms and substrates in the forests of Mt. Fuji varied widely from 17 to 1083Bq/kg in fresh mushroom samples, and in dry substrate samples they were in the range of 66 to 531Bq/kg, whereas levels of potassium remained essentially constant. 134Cs released from the Chernobyl reactor was determined in some mushrooms and some substrates from the sub-alpine forest of Mt. Fuji. Mushroom-to-substrate concentration ratios of 137Cs were much higher than tree leaves-or mosses-to-substrates concentration ratios near the study locations, and were larger by 100-to 1000-fold than the reported transfer factors of 137Cs from soils to leaf vegetables, root crops or potatoes. Significant correlations between ignition loss of substrates and concentration of 137Cs in mushrooms, and between pH value in substrates and concentration of 137Cs in mushrooms or mushroom-to-soil concentration ratio of 137Cs were found, suggesting possible 137Cs uptake mechanisms. The effective dose equivalent received by the general public was calculated to be 57x10-6 Sv based on the annual intake of 3.7kg of mushrooms and the maximum concentration detected in this study, 1083Bq/kg. It is estimated that this value is less than 2.4% of the annual effective dose equivalent received from natural sources, 2.4x10-3 Sv.

We conducted a total diet study (TDS) of 137Cs, 134Cs, and 40K to assess their average dietary exposure levels in a Japanese adult population before and after the Fukushima Daiichi nuclear power plant (FDNPP) accident. Nineteen market baskets were evaluated in 2006–2011. In each basket, a TDS sample comprising tap water and 160–170 food items, which were combined into 13 groups, were collected for analysis by gamma-ray spectrometry. From 2006 to 2010, the 137Cs activity concentration in the “fish and shellfish” group was 0.099 Bq/kg, representing the highest value obtained, whereas the total committed effective dose (CED) of radiocesium isotopes (137Cs + 134Cs) was 0.69 μSv. In 2011, “milk and dairy products” from Sendai City had a Cs activity concentration of 12 Bq/kg, representing the highest values among all food groups studied. However, the annual CED of radioactive Cs in Fukushima City was 17 μSv after the FDNPP accident, which is 60-fold lower than the maximum permissible dose of 1 mSv/year. The mean CED obtained for 40K was 180 μSv, which is comparable to the global average. Our results reveal the average dietary exposure of 137Cs, 134Cs, and 40K, which can aid in estimating the radiological safety of foods.