Global Fallout Strontium-90 and Its Dietary Intake by Japanese

Japan imports 70% of her grain needed. Therefore not only 90Sr level in Japanese food but also concentration in imported grains should be taken into account for the estimation of 90Sr intake by Japanese. Mathematical model is developed and examined by the data of Japanese dietary 90Sr intake for past 30 years. The main results obtained in this study under the limited assumptions are as follows: (1) The proposed model is promising for evaluating the Japanese dietary intake of global radioactive fallout 90Sr. (2) Uptake of 90Sr by ingestion depends mainly on agricultural products, especialy on leaf vegetables during high deposition periods of 90Sr and on wheats during low deposition periods. Almost 60% of Japanese dietary 90Sr intake now comes from foreign countries through foods imported. (3) The Japanese dietary intake of 90Sr depends largely on the direct deposition coefficient of 90Sr on crops for high deposition periods, also on the environmental decay coefficient for low deposition. periods, and the root transfer factor of 90Sr for both periods.