Total Diet Study to Assess Radioactive Cs and ⁴⁰K Levels in the Japanese Population before and after the Fukushima...

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.