Carcinogenic and non-carcinogenic risk assessment of selected heavy metals in soil and groundwater at mechanic workshops in Ilesa, Nigeria

This study examines heavy metal pollution and associated health risks in soil and groundwater at mechanic workshops in Ilesa, south western Nigeria. Heavy metals analyzed (Pb, Fe, Cu, Cr, Co, Ni, Zn, As) were quantified using atomic absorption spectrophotometry. Soil concentrations exceeded target values for most metals, while groundwater levels surpassed permissible limits, except for Cu and Fe. Health risk assessments showed total hazard index (HI) values of 1.81 × 10³ for children, indicating high non-carcinogenic risks, while adult HI was 2.1 × 10⁻¹, below the threshold. Carcinogenic risks for Cr, Ni, and Pb exceeded the acceptable range for both age groups, with ingestion being the primary exposure pathway. Groundwater posed significant non-carcinogenic and carcinogenic risks, particularly from Pb and Cr, while as remained within safe limits. Children were found to be at greater risk than adults.