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, especially 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. (author)