Annual effective dose and radiological risk assessment from selected salt pans from the lagoon of Erongo region, Namibia

Radioactivity levels in salt pans from the Erongo region of Namibia have been investigated. Ten composite salt samples, collected from salt pans of the Walvis Bay lagoon were analyzed for activity concentrations of 2226Ra, 232Th and 40K. This was done using a high-resolution gamma-ray spectrometer. The average activity concentrations in (Bq.kg-1) of 226Ra, 232Th and 40K were found to be 2.17 ± 0.19, 0.20 ± 0.02 and 2.28 ± 0.39, respectively. These activity concentrations were used to calculate the annual effective dose and radiological health risk from the ingestion of salt for the different age groups. The average annual effective dose in (μSv/yr) for the age ranges (2-7 years), (7- 12 years), (12-17 years) and ≥ 17 years were found to be 2.67 ± 0.22, 3.33 ± 0.28, 6.08 ± 0.53 and 1.22 ± 0.10, respectively. All these were lower than the worldwide average of 0.29 mSv/yr as reported by UNSCEAR in 2000. The total average radiological risk (unitless x 10-8) for the age ranges (2-7 years), (7-12 years), (12-17 years) and ≥ 17 years were found to be 30.15 ± 2.48, 60.30 ± 4.96, 89.8 ± 7.44 and 422.09 ± 34.75, respectively. All these were lower than the recommended limit of between 1x10-6 to 1x10-4 as reported by USEPA in 1991. Therefore, the results from this study indicated that the salt samples do not pose a radiological risk to members of the public.