Assessment of The Heavy Metal Concentrations, Sources and Health Risks in Well Water Around Karu Dumpsite, Federal Capital Teritory, Abuja, Nigeria

Groundwater contamination from open dumpsites poses serious public health and environmental risks, particularly in rapidly urbanizing areas of Nigeria. This study assessed the concentration of heavy metals in well water sources within a 5-kilometer radius of the Karu dumpsite in FCT, Abuja, and evaluated associated non-carcinogenic health risks for children and adults consuming this water. A descriptive cross-sectional design was adopted using a positivist research approach. Water samples were collected from one borehole and two wells. Heavy metals—manganese (Mn), copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), and arsenic (As)—were analyzed using atomic absorption spectroscopy. Structured questionnaires were also administered to 100 households. Chronic Daily Intake (CDI), Hazard Quotient (HQ), and Hazard Index (HI) were calculated for children and adults. Pearson correlation and hierarchical clustering were performed using SPSS v25. Heavy metal concentrations (mg/L) exceeded FMEnv limits in most sources except for arsenic. Manganese ranged from 0.415 (Well 2) to 0.94 (Well 1), copper from 0.505 (Well 2) to 0.986 (Well 1), cadmium from 0.102 (Well 2) to 0.224 (Well 1), zinc from 0.493 (Well 2) to 0.923 (Well 1), lead from 0.049 (Borehole) to 0.288 (Well 1), nickel from 0.043 (Borehole) to 0.213 (Well 1), chromium from 0.042 (Borehole) to 0.432 (Well 1), and arsenic from 0.014 (Borehole) to 0.032 (Well 2). Hazard Index (HI) values for children were highest in Well 1 (HI = 0.3117), followed by Borehole (HI = 0.1717), and Well 2 (HI = 0.1429). Adults had lower HIs, with Well 1 at 0.0673, Borehole at 0.0381, and Well 2 at 0.032. All HQs were below 1, indicating no immediate non-carcinogenic risk; however, cumulative effects may be significant for children. Pearson correlation showed strong positive associations between pH and cadmium (r = 0.999), electrical conductivity and zinc (r = 0.999), and dissolved oxygen and cadmium (r = 0.990). Cluster analysis grouped the Borehole and Well 2 together, while Well 1 stood apart due to its elevated contamination profile. p-values for metal concentration differences across sources were statistically significant (p < 0.05). The study confirms significant groundwater contamination around the Karu dumpsite, with multiple heavy metals exceeding safe limits. Children are at higher risk due to cumulative exposure. Urgent interventions including regular monitoring, improved waste management, and public health education are recommended.