Total Diet Study to Assess Radioactive Cs and (40)K Levels in the Japanese Population before and after the Fukushima Daiichi Nuclear Power Plant Accident

We conducted a total diet study (TDS) of (137)Cs, (134)Cs, and (40)K 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 (137)Cs 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 ((137)Cs + (134)Cs) 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 (40)K was 180 μSv, which is comparable to the global average. Our results reveal the average dietary exposure of (137)Cs, (134)Cs, and (40)K, which can aid in estimating the radiological safety of foods.