Radioactivity levels of staple foodstuffs and dose estimates for most of the Tanzanian population

Abstract

Levels of natural radioactivity in staple food products (maize and rice) from various localities of Tanzania have been studied. The average activity concentrations of K-40, Th-232 and U-238 in maize were 48.79 +/- 0.11, 4.08 +/- 0.01 and 13.23 +/- 0.10 Bq kg(-1), respectively. In rice the concentrations of K-40, Th-232 and (238)Uwere 24.67 +/- 0.03, 3.82 +/- 0.02 and 5.02 +/- 0.02 Bq kg(-1), respectively. Cs-137 was detected in only one sample collected in Zanzibar. The sample, with activity concentration of 5.57 +/- 0.01 Bq kg(-1), had been imported from Thailand. The relatively high average concentrations of the radionuclides in maize compared to rice may be attributed to the extensive use of phosphate fertilizers in maize production in Tanzania. Total annual committed effective doses due to total 232Th and 238U intakes as a result of consumption of staple foodstuffs for infants, children and adults were 0.16, 0.29 and 0.36 mSv y(-1), respectively, which are lower than the annual dose guideline for the general public.