Objective To measure the contents of natural uranium and thorium in retail food in Beijing and public dietary intake levels of these two elements, to estimate their internal irradiation doses, and to comprehensively understand and evaluate the safety of public diet.
Method Five main retail foods (meat, vegetables, potatoes, cereals, and milk) were chosen to determine the uranium and thorium contents by tri-n-octylamine extraction-spectrophotometry. Then based on the method reported in 2008 by the United States Effects of Atomic Radiation Scientific Committee, the internal irradiation effective doses were estimated.
Result In the five kinds of food samples, the highest content of uranium was found in cereals samples (1.86×10-6 g/kg), while the highest content of thorium was found in meat (2.28×10-6 g/kg), and both were lower than the limits according to the Limited Concentrations of Radioactive Materials in Foods (GB 14882-1994). The internal irradiation effective dose from uranium and thorium radionuclide for adults was 0.951 μSv/a, in which uranium contributed 0.318 μSv/a and thorium contributed 0.633 μSv/a; the internal irradiation effective dose for children was 0.666 μSv/a, in which uranium was 0.243 μSv/a and thorium was 0.423 μSv/a.
Conclusion The uranium and thorium contents detected in the five kinds of foods are under the limits of the Limited Concentrations of Radioactive Materials in Foods (GB 14882-1994). The internal irradiation effective doses of uranium and thorium for adults is higher than those for children, and the contribution of uranium is greater than that of thorium.
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