Impact of industrial activities on soil quality in urban settings: a study of heavy metal concentrations in Lamashegu, Ghana

Abstract Soil contamination from industrial activity poses serious ecological and public health concerns, particularly in urban areas with limited environmental oversight. This study assessed heavy metal concentrations in topsoil samples from the Lamashegu industrial area in Tamale, Ghana, where auto-mechanic workshops are densely concentrated. Composite soil samples were collected from three zones and analysed for Fe, Zn, Pb, Cr, Ni, Cd, and As using Atomic Absorption Spectrometry (AAS). The mean concentrations of these metals followed the order: Fe (11,497.78 mg/kg) > Zn (166.63 mg/kg) > Pb (115.32 mg/kg) > Cr (71.73 mg/kg) > Ni (17.46 mg/kg) > Cd (2.38 mg/kg) > As (3.12 mg/kg). Pollution levels were evaluated using indices such as the Enrichment Factor (EF), Contamination Factor (CF), Pollution Load Index (PLI), Integrated Pollution Index (IPI), and Geo-accumulation Index (I_geo). Zones B and C recorded higher PLI values (2.86 and 2.53, respectively), indicating moderate to high pollution levels. The highest IPI value (3.37) was observed in Zone C. Among the metals, Fe, Cd, and As showed the highest levels of contamination, while Zn and Pb were moderately enriched. A human health risk assessment (HRA) was conducted for both children and adults, considering ingestion, inhalation, and dermal contact exposure pathways. The hazard index (HI) for all metals across all zones remained below the safety threshold of 1, suggesting minimal non-carcinogenic risk. However, children exhibited higher average HI and HQ values than adults, indicating greater susceptibility. Carcinogenic risk estimates for Cr, As, Ni, and Cd fell within the acceptable range of 1 × 10⁻⁶ to 1 × 10⁻⁴, with a total cancer risk (TCR) averaging 3.28 × 10⁻⁵. These findings highlight the need for continuous environmental monitoring and targeted pollution control efforts to mitigate long-term health risks, particularly among vulnerable populations such as children.