Heavy Metal Contamination and Human Health Risk Assessment of Borehole Water at an Academic Campus in Ila-Orangun, Southwestern Nigeria

Abstract

This study assessed the hydrogeochemistry and health risks associated with groundwater from five existing boreholes sampled once in July, 2024, at Osun State College of Education, Ila-Orangun (OSCEILA), to determine their suitability for drinking and dermal use.  Physicochemical parameters and heavy metal concentrations were analyzed, alongside Water Quality Index (WQI) evaluations and human health risk assessments through ingestion and dermal exposure pathways.  Most water samples exhibited acceptable pH (7.05–7.89), turbidity (0.76–0.82 NTU), and salinity (0.48–0.97 mg/L), with four boreholes classified as “Excellent” by reflecting the quality of the physicochemical parameters incorporated into the WQI indices.  However, Borehole 2 (BH 2) showed elevated electrical conductivity, total dissolved solids, and heavy metal levels, likely influenced by atmospheric deposition and anthropogenic sources such as waste disposal and runoff.  Health risk analysis revealed non-carcinogenic and carcinogenic concerns, especially for children.  While most samples had hazard quotient (HQ) values below the safe threshold (HQ < 1), BH 2exceeded this limit for children (HQ = 1.45), suggesting potential adverse effects.  Carcinogenic risk values for both adults and children far exceeded the acceptable threshold (10⁻⁴), with children at BH 2 facing the highest risk (3.123189).  Although dermal exposure posed comparatively lower risks, values still exceeded safe levels.  Regular monitoring is recommended to mitigate long-term health effects.