From Pollution to Action: How Soil Extraction Methods for Potentially Harmful Elements Influence Human Health Risk Estimates

Assessing human health risks from potentially harmful elements (PHEs) in soils is crucial, since surpassing legally defined risk levels may mandate soil remediation in accordance with national regulations. This study evaluates the human health risks associated with PHEs in soils using various in vitro bioaccessibility extraction methods and Monte Carlo simulations. Concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Sn, Tl, Zn were investigated in soil samples using total element content (TC; aqua regia digestion) and six in vitro bioaccessibility extraction methods: BCR three-step sequential extraction (BCR), USEPA SW-846 Method 1340 (USEPA), ISO 17924:2018 (ISO), the BARGE Unified Bioaccessibility Method (UBM), the Simple Bioavailability Extraction Test (SBET), and the Physiologically Based Extraction Test (PBET). Research identified Fe, Mn, and Zn as the most abundant elements across all methods, while Sb, Tl, and Sn frequently fell below the limit of quantification in less intensive extractions. Non-carcinogenic (HQ) and carcinogenic (CR) health risk was evaluated for children and adults across residential, agricultural, and recreational exposure scenarios. Most assessed risk values remained below regulatory thresholds. For children in the residential scenario, the 95th percentile non-carcinogenic risk calculated from total concentrations exceeded the acceptable value of 1, indicating potential health concern. Carcinogenic risk was dominated by As and was highest in the agricultural exposure scenario when total concentrations were used. Incorporating bioaccessibility data substantially reduced estimated risks across all exposure settings, often demonstrating their value in achieving more accurate and realistic assessments of human exposure. These findings highlight that extraction method choice critically influences whether soils are classified as requiring remediation and therefore plays a crucial role in evidence-based risk evaluation, soil management, and regulatory decision-making. • Bioaccessibility tests markedly lowered human health risk estimates in soils • Total concentration overestimated both non-carcinogenic and carcinogenic risk • Monte Carlo simulations captured realistic variability in all exposure scenarios • As was the primary driver of carcinogenic risk, especially in agricultural areas • Risk-based assessments enable targeted and efficient soil remediation strategies