The radioactive dusts floating in the sky over Japan at the altitude of between 10 and 12 km were collected by the use of an airborne sampler mounted on aircraft separately at the time when a nuclear test was carried out somewhere and at a normal time, and subjected to the measurement of radioactivity and ordinary chemical analysis to make a comparative study as to whether there exists any difference between the radioactive dusts collected at two different times. As a result of this study, it was found that the density of radioactivity in the air at the time of a nuclear test was about 500 times as high as at a normal time, whereas the density of the dusts in the air was the same at about 10μg/m3 at both times and the component elements of the dusts were Si, Fe, Al, Mg, etc., with no much difference discovered.
Mice of NA-2 strain were administered continuously and through generations with 90Sr and 137Cs contained in drinking water. Concentration of the isotopes was divided into three levels; Group I: (90Sr 0.1μCi and 137Cs 0.4μCi) /ml, GroupII: (0.01and 0.04μCi) /ml, Group III: (0.001and 0.004μCi) /ml, and Group IV (Control) was fed with noncontaminated water. Abnormality of growth, life-span and reproduction in these groups were summed up till 10th generation. Group I showed shortening of life-span and lost reproductive function already in 2nd generation. Group II showed injury of growth and reproduction and shortening of life-span, but kept proceeding of the generations. In Group III we could not observe such injury as seen in GrouprI and II, but there appeared increase in reproductive function and lengthening of life-span. It can be concluded that Group I and II were obviously in state of radiation injury, but Group III was in some excited state by 90Sr and 137Cs. Another remarkable character of Group III is that tolerance against whole body irradiation of 700 R was aquired not by genetic mutation or selection but by effect of the isotopes after birth and that the tolerance was more intence in female than in male mice. This tendency was found also in Group II, but the tolerance was weaker.
The authors emphasized in the former paper that the measured values in the field of radiological protection are inevitably concerned with the uncertain factors which can never be dissolved by mere improvement of measurement techniques. A single value measured by an external personnel monitor attached on a certain position on the surface of human body does not carry the informations of incident direction of the exposed radiation, and therefore the organ dose can not be estimated correctly by a single measured value of the personnel monitor unless we get informations of irradiation pattern or special distribution of the incident radiation. The authors gave a basic matrix expression of the relationship between the measured value and the organ dose. In case as shown in Fig. 2 in the text, organ dose is given as follows; Where D; organ dose fi; a measured value of the personnel monitor facing i-th direction. (In usual situation only one value of f1……fn is given as a measured value). aij; contribution coefficient of the exposure from j-th direction to the measured value of the i-th monitor bj; contribution coefficient of the exposure from j-th direction to the organ dose On the basis of this fundamental equation the authors developed a probabilistic investigation in estimating the organ dose from a single measured value and gave a quantitative expression of the uncertainty in dose estimation, introducing a concept of“Entropy”which is popularly used in information theory. The authors also made some discussions on the elimination of uncertainty when more than one measured values are obtained or some qualitative informations are additionally given about the spacial distribution of incident radiation