Health risks from persistent heavy metal contamination in crops and water at an abandoned naturally revegetated galamsey site in Ghana

Abstract

Despite increasing interest in the environmental legacies of artisanal and small-scale gold mining (ASGM), the health implications associated with the consumption of crops cultivated on abandoned, naturally revegetated mine sites (ANRGS) in Ghana remain critically under-researched. In response to this gap, the present study comprehensively assesses heavy metal contamination in cucumber, soil, and pit water sampled from a six-year-old abandoned, naturally revegetated illegal mining site (ANRGS). Human health risk assessments were conducted rigorously using standard models for Chronic Daily Intake (CDI), Hazard Quotient (HQ), Hazard Index (HI), and Incremental Lifetime Cancer Risk (ILCR). Heavy metal concentrations in soil, pit water, and cucumber were measured using standard acid digestion and analysed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS, Nexion 2000, PerkinElmer), along with a Palintest multi-meter for water quality parameters, following validated protocols. The results revealed that cucumber fruits produced from the ANRGS were contaminated with high levels of Hg, Cd, Cu, As, and Pb, which exceeded the USEPA reference doses. Soil samples recorded concentrations of Hg (28.61 mg/kg), Cd (44.19 mg/kg), Pb (25.91 mg/kg), Fe (2073.1 mg/kg), As (30.08 mg/kg), and Cu (286.55 mg/kg), all above recommended soil guidelines. Although pit water met WHO physical standards, it was significantly contaminated with Cu, Cd, and As, surpassing WHO limits for drinking and irrigation. The health risk analysis indicated both noncarcinogenic and carcinogenic risks for children and adults through cucumber and pit water consumption. The Hazard Index (HI) ranged from 0.447 to 380 for children and 0.13-173 for adults, associated with cancer risks due to elevated As, Cd, and Pb levels. Children were more vulnerable to both health risks than adults. The study concludes that cucumbers grown on ANRGS at Ajamesu pose significant health risks and are unfit for consumption.