Natural Radioactivity and Radiological Risk Estimation of Drinking Water from Okposi and Uburu Salt Lake Area, Ebonyi State, Nigeria

Aim: The objectives of this study was to measure the activity concentration of natural radionuclides in different drinking water sources in order to access the associated radiological health risk due to ingestion of such water.

Study Design: The design of this study is purely experimental.

Place and Duration: This study was carried out on drinking water sources around Uburu and Okposi salt lakes areas of Ebony state between April and September, 2016.

Methodology: Sachet waters, borehole water, stream and river waters were collected and chemically treated by adding few drops of nitric acid to each of the samples and then pre-concentrated and kept in a marinelli container for four weeks. The activity concentration of 226Ra, 232Th and 40K in all the water samples was measured using the High- Purity Germanium detector. Results: The specific activity concentration of 226Ra, 232Th and 40K ranged from BDL to 3.66± 0.78 Bql-1, BDL to 7.56 ± 0.0.59 Bql-1 and BDL to 23.31 ± 1.65 Bql-1 respectively in sachet water. The activity concentration of 226Ra, 232Th and 40K in borehole water ranges from BDL to 5.65±1.25, 0.45±0.09 to 13.00±0.97 and BDL to 26.45±1.83 Bql-1 respectively. Furthermore the activity concentration of 226Ra, 232Th and 40K in stream water ranges from BDL to 2.88±1.32 Bql-1, BDL to 8.93±0.66 Bql-1 and BDL to 33.32±2.18 Bql-1 respectively, while that for river water ranges from 0.03±0.01 to 4.48±1.13 Bql-1, 0.55±0.10 to 8.60±0.65Bql-1 and BDL to 13.85 ±0.98 Bql-1 respectively. The mean values of annual effective dose obtained for infants, children and adults are within the ICRP and WHO recommended reference values. The life-long cancer risk and hereditary effects due to ingestion of radionuclides by adults show that 16 out of 100,000 may suffer some form of cancer fatality and 9 out of 100,000 may suffer some hereditary effects. Statistical analysis of the data revealed a positively skewed and platokurtic distribution of radionuclides in all the drinking water sources.

Conclusion: All the radiological health risk parameters obtained were within their safe values. Therefore, all the sampled drinking water are radiologically safe for domestic use but infant should not be given any of the studied drinking water since the annual total effective dose for infant exceeded the safe value.