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Background <p>This study assessed natural radionuclide concentrations and associated radiological health risks in borehole water from Benin City and Ogwa, Edo State, Nigeria, to determine compliance with international drinking water safety standards.</p> Methods <p>Thirty-five water samples were collected from both locations and analysed using gamma-ray spectroscopy with a NaI(Tl) detector to determine activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K. Radiological hazard indices, including annual effective doses, radium equivalent activity, and Excess Lifetime Cancer Risk (ELCR), were computed using standard dosimetric formulae. Correlation analysis examined relationships between radionuclides and hazard indices.</p> Results <p>Mean activity concentrations in Benin City were 56.1 ± 1.5&#xa0;Bq/L (⁴⁰K), 4.3 ± 0.8&#xa0;Bq/L (²³⁸U), and 9.3 ± 1.5&#xa0;Bq/L (²³²Th). In Ogwa, mean concentrations were 67.3 ± 1.8&#xa0;Bq/L (⁴⁰K), 2.5 ± 0.3&#xa0;Bq/L (²³⁸U), and 6.9 ± 0.6&#xa0;Bq/L (²³²Th). Both ²³²Th and ⁴⁰K exceeded WHO and UNSCEAR guidelines. Annual effective doses for all age groups in both locations significantly surpassed the 0.1 mSv/y limit, with infants most vulnerable. Radium equivalent and other radiological indices were below safety limits, but ELCR exceeded the global mean of 0.2 × 10⁻³. Notably, the correlation analyses revealed a radically different radiological association between the two locales. Benin City showed strong positive correlations among all radionuclides and hazard indices (<i>p</i> &lt; 0.01), characteristic of a homogeneous hydrogeochemical regime typical of sedimentary aquifers. In contrast, Ogwa exhibited a more complex pattern, including a negative correlation between ⁴⁰K and ²³²Th (<i>r</i> = − 0.79), indicating different source terms and mobilisation pathways within the basement complex aquifer.</p> Conclusions <p>The results underscore the importance of continuous monitoring of drinking water sources in the area, particularly boreholes, to mitigate long-term radiological health risks. Urgent regulatory and public health interventions may be necessary to reduce exposure, especially for infants.</p> Clinical trial registration <p>Not applicable.</p>

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Assessment of natural radionuclides and radiation hazard indices of borehole water samples collected from selected locations in Benin City and Ogwa, Edo State, Nigeria

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  • 发表日期：

    2026年5月18日

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  • Felix A. Popoola,
  • Okhuomaruyi D. Osahon

摘要

Background

This study assessed natural radionuclide concentrations and associated radiological health risks in borehole water from Benin City and Ogwa, Edo State, Nigeria, to determine compliance with international drinking water safety standards.

Methods

Thirty-five water samples were collected from both locations and analysed using gamma-ray spectroscopy with a NaI(Tl) detector to determine activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K. Radiological hazard indices, including annual effective doses, radium equivalent activity, and Excess Lifetime Cancer Risk (ELCR), were computed using standard dosimetric formulae. Correlation analysis examined relationships between radionuclides and hazard indices.

Results

Mean activity concentrations in Benin City were 56.1 ± 1.5 Bq/L (⁴⁰K), 4.3 ± 0.8 Bq/L (²³⁸U), and 9.3 ± 1.5 Bq/L (²³²Th). In Ogwa, mean concentrations were 67.3 ± 1.8 Bq/L (⁴⁰K), 2.5 ± 0.3 Bq/L (²³⁸U), and 6.9 ± 0.6 Bq/L (²³²Th). Both ²³²Th and ⁴⁰K exceeded WHO and UNSCEAR guidelines. Annual effective doses for all age groups in both locations significantly surpassed the 0.1 mSv/y limit, with infants most vulnerable. Radium equivalent and other radiological indices were below safety limits, but ELCR exceeded the global mean of 0.2 × 10⁻³. Notably, the correlation analyses revealed a radically different radiological association between the two locales. Benin City showed strong positive correlations among all radionuclides and hazard indices (p < 0.01), characteristic of a homogeneous hydrogeochemical regime typical of sedimentary aquifers. In contrast, Ogwa exhibited a more complex pattern, including a negative correlation between ⁴⁰K and ²³²Th (r = − 0.79), indicating different source terms and mobilisation pathways within the basement complex aquifer.

Conclusions

The results underscore the importance of continuous monitoring of drinking water sources in the area, particularly boreholes, to mitigate long-term radiological health risks. Urgent regulatory and public health interventions may be necessary to reduce exposure, especially for infants.

Clinical trial registration

Not applicable.