Assessment of potentially toxic elements concentration and distribution in soils at automobile mechanic workshops across different geological environments: a review

This study reviewed previous works on potentially toxic elements (PTEs) in soils at automobile mechanic workshops (AMWs) across different geological environments in Nigeria, with the aim to investigate the extent of PTEs pollution, ecological risks and potential human health hazards. The results from previous studies (thirty-six published articles) revealed significant variation in PTEs distribution in the soils around the workshops, with higher levels compared to control soils. The mean concentration of PTEs (mg/kg) including Pb (0.28 to 1689.56), Cr (0.11 to 137.08), Cd (0.008 to 51.47), and Zn (0.56 to 424.4) was used to calculate the pollution indices, human health risk and statistical relationship between PTEs and geological environments. The mean geo-accumulation index (mIgeo: 0.00–4.44), pollution load index (PLI: 0.01–32.57) and potentially ecological risk factor (RI: 0.59–1200.8) revealed that the pollution levels in AMW soils range from unpolluted to extremely polluted across the three geological environments. Human health risk assessment indicated that children and adults are not at risk of developing non-cancer and cancer diseases. Pairwise relationships among PTEs particularly for Cu-Mn and Fe-Mn showed strong correlation across the three environments. Based on the research findings, regular monitoring and strategic urban planning are essential to mitigate pollution and health hazards.