Assessment of natural radioactivity and radiation risks in soil near the Manyoni uranium deposit, Tanzania

This study reports on natural radioactivity levels and radiation risk estimates from soil samples collected in five villages near the Manyoni Uranium Deposit in central Tanzania. The mean activity concentrations of 40K, 232Th, and 238U were 207 Bq kg-1, 78 Bq kg-1, and 302 Bq kg-1, respectively. While 40K levels were below the world average, the levels of 232Th and 238U were more than 1.7 and 9.2 times higher than world average values. The average absorbed dose rate for the area was 196 nSv h-1. Annual effective dose estimate values for outdoor and indoor exposure were 0.24 mSv and 0.96 mSv, respectively, exceeding global averages by 3.4 and 2.3 times. Based on the average external hazard index (Hex = 1.19) and excess lifetime cancer risk (ELCR = 0.46%), there is a potential risk of radiological effects from radiation exposure, with Mwanzi Village identified as a high background radiation area.