Activity concentrations of 226^Ra, 232^Th, and 40^K in common maize meal consumed in Namibia and their potential radiation hazards

Abstract

Gamma spectroscopy was performed to determine the concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in maize meal samples collected from shop outlets and open markets in Namibia. The activity concentrations and Excess Lifetime Cancer Risk were determined using a high purity germanium (HPGe) detector. The average activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th were found to be 29.98 ± 4.05, 0.99 ± 0.40 and 0.35 ± 0.08 Bq.kg ^{– 1} in the maize meal samples. The result showed the activity concentrations of ⁴⁰K significantly higher than the other radionuclides in all the maize meal samples. The average excess life cancer risk varies from 1.33 x 10 ^{– 13} to 6.05 x 10 ^{– 13} for ⁴⁰K, 8.76 x 10 ^-13 to 1.19 x 10 ^{– 12} for ²³²Th and 2.43 x 10 ^-11 to 2.83 x 10 ^{– 11} for ²²⁶Ra. Hence, when compared with internationally acceptable limits, all values fall within the safety limits. Thus, the study concludes that the maize meals consumed in Namibia are radiologically safe for consumption.