Comprehensive assessment of heavy metal(loid) contamination and health risks in agricultural soils near the Menzel Bourguiba steel smelter, Tunisia

Abstract This study assessed heavy metal(loid) pollution (As, Pb, Zn, Fe, Cd, Cu, Cr, Ni) and the associated health risks in agricultural soils near the Menzel Bourguiba steel smelter in northeastern Tunisia. The extent of contamination was quantified using multiple pollution indices, including the geo-accumulation index (Igeo) and enrichment factor. Health risks were evaluated using both deterministic and probabilistic approaches, incorporating Monte Carlo simulation to characterize uncertainty and Sobol sensitivity analysis to identify key influencing parameters. Mean heavy metal(loid) concentrations (mg kg −1 ) decreased in the order of Fe (28,136) > Zn (480.73) > Cr (184.85) > Pb (147.12) > Ni (73.5) > Cu (55.50) > As (15.97) > Cd (5.27). Pollution indices consistently identified Cadmium (Cd) and Lead (Pb) as the primary contributors to soil contamination. Enrichment factor analysis revealed extreme enrichment for Cd, with concentrations exceeding background levels by up to 58 times. Probabilistic risk assessment indicated a high potential for adverse health effects. For children, the non-carcinogenic Hazard Index for lead exceeded the safe limit of 1 in over 50% of simulations. The Total Carcinogenic Risk (TCR) for children surpassed the acceptable threshold (1 × 10 −4 ) in over 80% of simulations for As, Cr, and Cd. For adults, the TCR for Cd exceeded this threshold in over 70% of cases. The 95th percentile of the simulated TCR for children reached 5.7 × 10 −3 , a value 57 times higher than the acceptable limit. Sobol analysis identified the soil ingestion rate as the primary source of uncertainty in the risk models (contributing 68–74%). These findings indicate that the soil contamination poses a significant health risk to the local population, warranting targeted intervention strategies.