Whole-body retention of 137Cs emitted in the environment

Two methods of estimating environmental doses of 137Cs, which are absorbed by the whole Japanese population for a long period of time, are presented. One method (method I) is based on measurement data on whole-body retention of 137Cs in adult male populations aged 20 - 49 yr (population A); and another method (method II) is based on measurement of uptake values and metabolic models of 137Cs. The sum of environmental doses from 1964 to 1974 using method I was 6.1 x 105 man-rad. Furthermore, dose commitments from 1964 to 2000 were estimated to be 8.15 x 105 man-rad when the uptake tendency in the population A from 1968 to 1974 continues up to 2000 (Case I), and 1.2 x 106 man-rad when environmental doses from 1970 to 1974 are not changed up to 2000 (Case II). The measured uptake dose of 137Cs in the population A was approximately 1.4 times higher than the estimated dose when compared among the same age group. The sum of environmental doses from 1964 to 1974 using method II was 3.3 x 105 man-rad, and dose commitments from 1964 to 2000 was 5.2 x 105 man-rad in Case I and 7.4 x 105 man-rad in Case II. The environmental dose commitment of 137Cs from 1964 to 2000 was thus estimated to be approximately 1.2 x 106 man-rad, corresponding to approximately 60 % of annual environmental doses of naturally occurring 40K in the body. (Namekawa, K.)