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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]...

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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.

The present study was undertaken to investigate the amounts of artificial radionuclides ingested through the daily diet by inhabitants of Kanagawa Prefecture, Japan. To this end, the level of cesium-137 ( 137 Cs) contained in the daily diets of females (combined samples from 5 females) aged 40-69 living in urban and suburban districts of Kanagawa Prefecture was measured. Furthermore, 11 elements (Ca, Cl, Cr, Cs, Fe, K, Mn, Na, Rb, Sc, and Zn) in the diets were quantified by instrumental neutron activation analysis. The study revealed that the intake of 137 Cs increased markedly in 1986, the year the Chernobyl accident occurred, and it tended to decrease gradually thereafter. In recent years, the reduction in the dietary intake of 137 Cs has been slowing down. When the intake of nutrients ingested by inhabitants of the two survey areas was compared with the Dietary Reference Intakes for Japanese (2005), the amount ingested in each of the two survey areas approximately satisfied or was slightly lower than the reference levels. Among others, the amount of Ca and Fe ingested in the urban district was particularly low (52 and 64% of the national reference, respectively). For many elements, the amount ingested was greater in the suburban than in the urban district. When the ingredients of the subjects' meals were classified into food groups, the meals prepared by suburban inhabitants were found to be composed of more diverse ingredients, covering all food groups, compared to those prepared by urban inhabitants. The daily food intake was also greater in the suburban district. When the daily dietary samples from individual subjects were analyzed separately, without being combined, both the level of 137 Cs and the amount of stable elements contained in the separate samples showed greater variations from day to day than those in the combined samples. There was no correlation between the dietary intake of 137 Cs and that of Cs.