人体における?Q１３７?RＣｓ

Abstract

Body burden of 137Cs has changed with time relating to its amount in the environment. Therefore, in order to estimate the radiation dose due to internally depositted 137Cs originating from nuclear tests, it is important to understand both its metabolism in man and its behavior in his environment.This short report summarizes the change of level in body burden and dose commitment of 137Cs originating from fall-out in the section 1. In the section 2, two categories of people with relatively higher body burden of or exposed to relatively huge internal radiation dose from 137Cs, are explained. One of them is the population living in or near the arctic regions and eating caribou or reindeer meat. This is a good example to understand that body burden of 137Cs deeply relates to 137Cs in the ecosystems around the people. The other is bottle-fed babies which should be taken as the critical group in Japan for the radiation dose from internally deposited 137Cs due to fall-out. The differences of body burden in the sexes and in the ages are in the section 3.Biological half-life is one of the most critical parameters relevant to the dose from internally deposited radionuclides. Therefore, some possible factors like the differences in the sex, age or temperature, limiting the length of 137Cs biological half-life, are fairly precisely discussed in the section 4. The biological half-life in average for Japanese is compared to those reported from another countries.The section 5 contains the estimation method of 137Cs body burden following continuous ingestion of 137Cs. An increase ratio method and a method by compartmental model are introduced.Some examples of occupational accident due to 137Cs which were inhaled or ingested are indicated in the section 6.From the standpoint of radiation protection against internally deposited radioactive cesium, some methods to enhance the excretion of the nuclide from body, are explained in the last section.