Natural radioactivity measurements in drinking water and ingestion dose assessment: case of the uranium bearing region of Poli, Cameroon

Abstract

This study aimed at measuring radioactivity in drinking water and to assess corresponding ingestion dose to the public and the uranium toxicity. Twenty samples were collected in the uranium bearing region of Poli, Cameroon. α- and γ-spectrometry were used for radioactivity measurements. The range of activity concentrations for each radionuclide is 0.7 ± 0.3-3.5 ± 0.5 mBq.l−1 for 238U, 0.07 ± 0.03-2.1 ± 0.9 mBq.l−1 for 235U, 0.6 ± 0.2-5.1 ± 0.6 mBq.l−1 for 234U, 10 ± 1 mBq.l−1 for 226Ra, 10 ± 2-16.8 ± 2.2 mBq.l−1 for 210Po. Ingestion dose due to intake of 238U, 235U, 234U, 226Ra and 210Po in water was assessed for six age groups. The mean ingestion dose ranges from 8.8 μSv.yr−1 for adult to 123 μSv.yr−1 for infant, higher than the reference level of the committed effective dose (100 μSv.yr−1) recommended by the World Health Organisation (WHO). The uranium mass ranges between 0.014 μg.l−1 and 0.18 μg.l−1, below the reference mass which is 30 μg.l−1 showing that the uranium toxicity is low. 234U/238U isotopic ratio in water was observed with values near the equilibrium on 70% of collected samples and far from equilibrium reaching 3.09 in a borehole.