Natural Radioactivity in Vegetables from Selected Areas of Manyoni District in Central Tanzania

The study determined the mean concentrations of natural radionuclides, the annual intake of radionuclides and annual effective dose due to the ingestion of Vegetables from selected areas of Manyoni in Tanzania. Thirty (30) bunches of leafy vegetable samples grouped into five categories were collected randomly from different locations of the study area. The activity concentration levels of U-238, Th-232, and K-40 were measured by direct γ‐ray spectrometry using HPGe detector by Compton suppression method. The radioactivity in vegetables ranged from 2.2 Bq/kg – 36.8 Bq/kg for U-238, 4.1 Bq/kg – 30.1 Bq/kg for Th-232 and 700.0 Bq/kg – 2520.0 Bq/kg for K-40, respectively. Except for K-40, the activity levels reported into this study were lower than the activity levels of vegetables reported from various parts of Tanzania. However, the concentrations of radionuclides in the vegetables samples found in this study were higher than the world average values suggested by the UNSCEAR. The annual effective dose due to intake of vegetables was 2.73 mSv/year. This dose value was found 9.4 times higher than total exposure per person resulting from the ingestion of terrestrial radionuclides as proposed by UNSCEAR. Also the dose was higher than the annual dose limit of 1 mSv/year recommended by the ICRP for the general public. The annual intakes of U-238 and Th-232 in vegetables were much higher than the world reference value in diets. Hence a conclusion could be made that vegetables cultivated in Manyoni might expose the population to high radiation dose which might be detrimental to their health.