Human health risk assessment of nitrate and heavy metals in urban groundwater in Southeast Nigeria

Abstract

Groundwater contamination by nitrate and heavy metals is a growing global concern due to its detrimental effects on human health through ingestion and dermal exposure. This study aimed to assess the concentrations of nitrate and heavy metals (Pb, Cu, Cd, and Fe) in groundwater and evaluate the associated health risks among different age groups (females, males, and children) in the Nnewi and Awka regions of southeast Nigeria. Standard methods were followed. Ten groundwater samples were collected from each study locality, and their physicochemical parameters were analyzed. The evaluation of heavy metal levels in groundwater was conducted using the risks of cancer and health hazard index as indicators of public health impact. The results showed that while nitrate levels were within acceptable limits, heavy metal concentrations exceeded permissible levels in all samples. Carcinogenic risk (CR) analysis revealed that approximately 40% of Nnewi samples and 80% of Awka samples exceeded the permitted range of ≤1 × 10 −6–1 × 10 −4. In the Nnewi region, the order of heavy metal toxicity was Cd > Pb > Cu > Fe, while in Awka, it was Pb > Cd > Cu > Fe, resulting in severe non-carcinogenic health hazards for users. Cd and Pb were identified as the most significant contaminants impacting water quality in both regions. Children exhibited greater vulnerability to health risks compared to adults in both areas. These findings contribute to our understanding of localized nitrate and heavy metal contamination, highlight the vulnerability of children, and emphasize the importance of regular monitoring and management practices.