Assessment of radionuclide levels in soil, water and foodstuffs from selected gold mining areas in Uganda.

Abstract

This study assessed the levels of naturally occurring radioactive materials in soil, sediments, water and selected foodstuffs from artisanal and small-scale gold mining areas in Uganda, where local communities may be exposed to radionuclides, by measuring in-situ radiation dose rates using a portable Geiger counter and determining the activity concentrations of 238U, 232Th and 40K in collected environmental samples through Inductively Coupled Plasma Mass Spectrometry (ICPMS). The results obtained showed that the average radioactivity levels for soil and sediment samples ranged from 0.057 to 0.102 Bqkg-1 for 238U, 0.012 to 0.278 Bqkg-1 for 232Th, and 5.2E-06 to 8.5E-06 Bqkg-1 for 40K. These values were all below the world average values of 33 Bqkg-1, 45 Bqkg-1 and 420 Bqkg-1 for 238U, 232Th and 40K respectively. The average radioactivity levels in cassava tubers for 238U were 0.019 Bqkg-1, 0.0113 Bqkg-1, 0.0102 Bqkg-1, those of 232Th were 0.038 Bqkg-1, 0.037 Bqkg-1 and 0.039 Bqkg-1 while those of 40K were 8.9E-05 Bqkg-1, 8.1E-05 Bqkg-1 and 8.7E-05 Bqkg-1 respectively for Namayingo, Kassanda gold mining areas. These values were all below the world average values of 35 Bqkg-1, 30 Bqkg-1 and 400 Bqkg-1 for 238U, 232Th and 40K respectively. Whereas tea samples from Buhweju indicated ranges of 0.012 to 0.015 Bqkg1 , 0.035 to 0.037 Bqkg-1, 3.66E-09 to 9.27E-05 Bqkg-1 for U, Th, K respectively. The nnual effective dose of exposure by oral ingestion of cassava tubers and tea for adults with the mean values were approximately 0.0011mSvy-1 far lower than the recommended safe limits of 1 mSvy1 and also lower than the world average ingestion dose of 0.3 mSvy-1. The calculated average annual effective dose due to the ingestion of water was approximately 0.0018 mSvy-1 which was below the world average annual effective dose from ingestion of NORMs of approximately 0.002 mSvy-1. The excess life cancer risk (ELCR) was lower than their corresponding permissible values of 0.29 x 10-3. All average values were below international limits, indicating no significant health hazards for the local population. The study reveals that there are currently no potential health risks associated with the consumption of water and foodstuff from gold mining areas studied.