Health risk assessment of heavy metal(loid)s in a soil-rice system in the selenium-enriched area based on Monte Carlo simulation and bioaccessibility.

Abstract

Although selenium (Se)-enriched soils represent a scarce resource, heavy metal contamination has restricted their utilization. The Huigu Town region, recognized as one of China's naturally Se-enriched areas, was selected for this study. We collected 30 paired rice grain and paddy soil samples to investigate the concentrations of heavy metal(loid)s (Se, As, Cd, Cr, Cu, Ni, Pb, and Zn), pollution levels, and health risks within the soil-rice system. Results indicated that the mean concentrations of Se, As, Cd, and Cu in soils exceeded regional background values. While rice grains exhibited Se enrichment, none of the heavy metal(loid)s exceeded the Chinese national standard for food safety. Health risk assessment adjusted by Physiologically Based Extraction Test (PBET) and Simplified Bioaccessibility Extraction Test (SBET), revealed lower carcinogenic and non-carcinogenic risks compared to total concentration-based assessment. Non-carcinogenic risk was within safe thresholds, and carcinogenic risk remained within tolerable limits. Monte Carlo simulations indicated that the cumulative probability of intolerable carcinogenic risk for both children and adults in the study area was less than 1%. Sensitivity analysis identified exposure frequency and dermal adsorption coefficient as the dominant contributors to carcinogenic risk across populations. Despite residing in a Se-enriched region, residents face potential risks of inadequate dietary Se intake, which could be mitigated through implementing dietary adjustments and soil matrix amelioration strategies.