Radioactivity Levels in Maize from High Background Radiation Areas and Dose Estimates for the Public in Tanzania

Natural radioactivity levels in maize which is one of the staple foods in various regions in Tanzania have been studied. The radioactivity concentration of 238U, 232Th and 40K were determined using γ ray spectrometry employing HPGe detector of relative efficiency of 51%. The average radioactivity concentrations in maize from five regions were ranged from 1.8 ± 0.2 to 23.6 ± 0.7 Bq/kg for 238U, 2.2 ± 0.1 to 38.9 ± 1.0 Bq/kg for 232Th and 42.0 ± 0.4 to 434.6 ± 18.7 Bq/kg for 40K respectively. Total annual committed effective dose due to total 238U and 232Th intakes as a result of consumption of maize in five Regions were as follows; Manyara (1.46 mSv/y), Mbeya (0.31 mSv/y), Dodoma (0.21 mSv/y), Ruvuma (0.19 mSv/y) and Dar es Salaam (0.08 mSv/y). The dose value from Manyara was almost the same to the annual dose guideline for the general public which is 1 mSv/y, where as for other regions the doses are low. Hence a conclusion could be made that food crops cultivated at Minjingu village might expose the population to high radiation dose which might be detrimental to their health.