Sex-Specific per capita Dose due to Background Radiation in Japan

概要

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The collective dose due to the background radiation outdoors in Japan was analyzed, and the influence of the time trend of the population movement on the per capita dose was estimated. Only the external dose was considered. It was previously shown that the per capita dose calculated for each year between 1952 and 1980 by the use of the surveyed background levels along with the registered population data has been decreasing continuously. In this work, the latest data in 1981 was added, and male and female statistics were pro-cessed separately. The result showed that the male values of the per capita dose have been always lower than the female values, if the deficit is small. It was also shown pre-viously that the prevailing population movement from countryside toward urban areas (often plains of volcanic ash) would be the cause which have changed the per capita dose, <I>i</I>.<I>e</I>. population-weighted mean dose of the whole country. In this work, it was anticipated that the gross population movement from the South-West toward the North-East Japan would be another cause of the decrease.