Abstract

This study presents a comprehensive ecotoxicological assessment of heavy metal contamination in surface water samples from Mayo-Sinna (Nguroje), a prominent artisanal and small-scale mining (ASM) community in Taraba State, Nigeria. The concentrations of cadmium (Cd), lead (Pb), cobalt (Co), copper (Cu), chromium (Cr), zinc (Zn), nickel (Ni), manganese (Mn), and iron (Fe) were quantified using atomic absorption spectrophotometry (AAS). Measured values were evaluated against benchmark limits established by the World Health Organization (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ). Risk characterization was conducted using the Hazard Quotient (HQ) model, a ratio-based approach that compares exposure levels to toxicological reference values. The HQ for lead (Pb) was 2.20, exceeding safety thresholds by 120%, while iron (Fe) recorded an HQ of 3.74, corresponding to a 274.4% exceedance, both indicating significant ecotoxicological and public health threats. Conversely, HQ values for Cd, Co, Cu, Cr, Zn, Ni, and Mn remained below unity, with exceedances ranging from –98.2% to –45.5%, suggesting negligible current risk. These findings underscore the environmental consequences of poorly regulated ASM operations and highlight the urgent need for routine water quality monitoring, enforcement of environmental standards, and implementation of site-specific remediation strategies to safeguard both ecosystem and human health.