Balance of Cobalt in Japanese People and Diet

Measurements were made of the stable cobalt in total diet samples collected from a number of sites to know the normal daily ingestion of this element by average Japanese. Two thirds of Japanese adults should take 11-28 μg of cobalt daily and rural children, a half or less amount. The main contributors of cobalt in Japanese diet are plant products. Their contribution as a whole was estimated up to 88.2% of the total intake. Biological half-life of radiocobalt was estimated as 106 days (fw : 0.3) or 29.3 days (fw : 0.92) for Japanese on the basis of assumed existence of an equilibrium condition between the stable element and radiocobalt. Finally, estimation of the daily intakes by Japanese of 60Co through marine and land products was also attempted in the assumed situation of environmental contamination of sea-water and soils.