3.1.1. 137Cs Levels before the FDNPP Accident

We collected 16 MBs from 13 cities between 2006 and 2010, resulting in a total of 224 TDS samples. Cesium-137 was the only anthropogenic radionuclide observed in these samples, as 134Cs, which was released from the Chernobyl disaster, was not detected at all. Table 1 summarizes the 137Cs activity concentrations in TDS samples from 2006 to 2010. The activity concentrations of 137Cs in TDS samples were all below 0.1 Bq/kg during this period. The food group "fish and shellfish" had a 137Cs activity concentration of 0.099 Bq/kg, representing the highest value measured, followed by "other vegetables, mushrooms and seaweeds" (0.092 Bq/kg), "meat and eggs" (0.083 Bq/kg), and "milk and dairy products" (0.057 Bq/kg). The highest mean 137Cs activity concentrations were found in "fish and shellfish" (0.072 Bq/kg) followed by "other vegetables, mushrooms and seaweeds" (0.024 Bq/kg), "meat and eggs" (0.024 Bq/kg), and "milk and dairy products" (0.022 Bq/kg). These results are similar to the TDS carried out between 2003 and 2005 [13]. Cesium-137 was detected in all "fish and shellfish" samples, whereas it was not found in any samples of "fats and oils", "seasonings", and "drinking water". The detection rate of 137Cs was about 30%, and was the highest in "fish and shellfish" (100%), followed by "milk and dairy products" (68.8%), "meat and eggs" (62.5%), and "other vegetables, mushrooms and seaweeds" (50.0%).
