Human health risk and remedial goal assessment using Monte Carlo simulation: a case study of arsenic contaminated allotment gardens in southern Poland.

This study quantified total arsenic (As), gastric-phase in vitro bioaccessible As (IVBA), and associated direct-soil-exposure risks for children and adults in mining-affected allotment gardens in Złoty Stok, Poland. Deterministic calculations and Monte Carlo simulations were applied to incidental soil ingestion, dermal contact, and inhalation of resuspended particles. Total As ranged from 433 to 1148 mgkg⁻1, while IVBA ranged from 4.5 to 23.5%. Under the total-As multi-pathway scenario, median hazard indices were 5.50 for children and 0.62 for adults. The 5th (P05) and 95th (P95) percentiles are 2.26 and 15.18 for children and 0.29 and 1.89 for adults. Median total cancer risk (CRtotal) was 1.78 × 10⁻4 for children and 1.06 × 10⁻4 for adults. Also, 80.0% of simulated child profiles and 54.0% of adult profiles produced CRtotal estimates at or above 10⁻4. Deterministic dose and risk estimate generally fell between the probabilistic medians and P95 values. Applying IVBA only to the ingestion pathway reduced the median ingestion-related hazard quotient and cancer risk by 89.3%. Ingestion and dermal contact accounted for nearly all modeled risk, whereas inhalation contributed negligibly. Partial rank correlation analysis identified total soil As and soil ingestion rate as the principal positive risk drivers, while body weight was inversely associated with risk. At a target cancer risk of 10⁻5, the conservative child P05 remedial goal increased from 13.0 mgkg⁻1 under the total-As model to 34.8 mgkg⁻1 after IVBA adjustment of ingestion. The Polish soil-quality value of 20 mgkg⁻1 therefore lies between these two estimates, but both remedial goals remain far below the measured soil As concentrations, indicating that substantial reduction of direct soil exposure would be required across the study area.