*2.2. Determination of 137Cs, 134Cs, and 40K*

Cs-137, Cs-134, and K-40 in the TDS samples were detected for a minimum of 80,000 s using high-purity Ge semiconductor detectors (2519 and GC2018 of CANBERRA Co., Meriden, CT, USA; EGPC 20-190-R of EURYSIS Co., Lingolsheim, Cedex-France; CNVD30-35195 of OXFORD Co., Oxon, Oxford, UK; and IGC40200 and IGC25190SD of PGT Co., Princeton, NJ, USA). Activity concentrations of the three radionuclides were corrected as of the end of the sampling period and expressed in Bq/kg of fresh weight. Energy and efficiency calibrations were performed using γ-ray volume sources (MX033U8PP and MX033MR, Japan Radioisotope Association, Tokyo, Japan). The limits of detection (LODs) for 137Cs and 134Cs were approximately 0.05 Bq/kg for all food groups, except for "fats and oils" and "seasonings".

#### *2.3. Calculation of Dietary Intake and the Committed E*ff*ective Dose (CED) Values*

The daily dietary intake of radioactive Cs and 40K for adults was calculated from the activity concentrations of the three radionuclides in the samples, as described above. The radionuclide

activity concentration was multiplied by the average food consumption value for the adult population, as determined by the NHNS, in each regional block to provide the radionuclide intake for each radionuclide and food group. Next, the calculated intake for each food group was summed to estimate the total dietary intake of a given radionuclide in each MB. The dietary intake of radioactive Cs was obtained by summation of 137Cs and 134Cs intake values. If a target radionuclide was not detected in a sample, the activity concentration of the non-detected (ND) radionuclide was assumed to be zero or the LOD value. The lower and upper limits of the total radionuclide intake values were estimated by assuming the ND value as zero and the LOD, respectively.

The CED values associated with Cs and 40K for adults were estimated under the assumption of a one-year intake of the TDS samples, and were obtained by applying the dietary radionuclide intake values and dose coefficients for ingestion of each radionuclide, given by the International Commission on Radiological Protection (ICRP), to be 1.3 <sup>×</sup> <sup>10</sup>−<sup>8</sup> Sv/Bq for 137Cs, 1.9 <sup>×</sup> <sup>10</sup>−<sup>8</sup> Sv/Bq for 134Cs, and 4.6 <sup>×</sup> <sup>10</sup>−<sup>9</sup> Sv/Bq for 40K [20]. The CED of radioactive Cs was calculated by summing those of 137Cs and 134Cs. The ND radionuclides were given a value of zero and the LOD for estimating the lower and upper limits of the CED values, respectively.
