Assessing soil pollution potential through spatial heavy metal bioaccessibility for health risk evaluation

Incorporating bioaccessibility into health risk assessments enhances the accuracy of exposure estimates for heavy metal (HM) pollution, supports targeted remediation, and informs public health and policy decisions, particularly for vulnerable populations. Because HM bioaccessibility depends on local soil and geographic characteristics, identifying its relationship with soil properties is crucial for assessing soil pollution potential. Although HM concentrations can be measured relatively easily, bioaccessibility requires complex laboratory procedures, limiting routine applications in regulatory contexts. Integrating spatial information with bioaccessibility-based risk assessments can help identify pollution hotspots and better protect at-risk groups. This study developed a novel approach that spatially integrates HM bioaccessibility into health risk assessment. Using the simple bioaccessibility extraction test (SBET), farmland soils from 98 sites across Taiwan were analyzed to establish predictive equations for six common HMs: cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn). These equations were combined with previous soil survey data to generate spatial SBET maps across all agricultural regions in Taiwan. Results showed clear geographic variations: high Cd SBET (50%-100%) occurred in northern Taiwan with acidic soils, while elevated Cu and Zn SBET (45%-60%) were found in southern Taiwan with lower clay contents. We further applied the spatial SBET maps to Changhua County, a representative agricultural region. Infants and children exhibited higher non-carcinogenic risks (hazard index >0.01), especially in western villages, while adults had lower risks (<0.005). Seniors showed concerns of carcinogenic risks (total cancer risk index >1.0E-6). This study presents a practical and scalable framework for integrating soil bioaccessibility into spatial risk assessments, helping policymakers identify high-risk areas, prioritize remediation, and optimize healthare resource allocation, supporting Sustainable Development Goals (SDGs) of good health and well-being (SDG 3) and life on land (SDG 15).