Groundwater Geochemistry and Its Human Health Implications within the Lower Mouhoun River Sub-basin, Burkina Faso, West Africa

Groundwater is the primary source of drinking water in arid and semi-arid regions, especially in sub-Saharan Africa. This study aimed to assess groundwater’s contribution to the daily intake of macronutrients (Ca, Mg, Na, and K) and to evaluate health risks associated with nitrate (NO₃⁻) and arsenic (As) contamination in the Lower Mouhoun River Sub-basin, Burkina Faso, an area experiencing rapid land-use changes and increased anthropogenic pressure. We analysed 265 borehole water samples for physico-chemical parameters and major ions. The results reveal that groundwater is weakly mineralised and contributes modestly to macronutrient intake, approximately 10% for calcium, 8% for magnesium, 2% for sodium, and 0.5% for potassium, indicating that drinking water provides only a limited portion of daily nutritional needs. While natural water–rock interactions influence groundwater chemistry, anthropogenic activities have degraded water quality, with 11% and 0.02% of samples exceeding WHO guidelines for NO₃⁻ (50 mg/L) and As (10 µg/L), respectively. The health risk assessment identified children as the most vulnerable group, with a mean non-carcinogenic hazard index of 1.47 and a total carcinogenic risk of 2.02 × 10⁻⁴, both above the accepted safety standards. These results demonstrate that, although groundwater offers nutritional benefits, it also presents significant health risks due to contamination. Consequently, there is a critical need for continuous water-quality monitoring and targeted interventions to protect public health and guarantee access to safe drinking water.