Bioaccessibility-integrated probabilistic risk assessment for poly-aromatic hydrocarbons in Chinese soils

This study establishes a probabilistic risk assessment framework for polycyclic aromatic hydrocarbons (PAHs) in Chinese soils by integrating bioaccessibility data and regional concentration variability. This approach provides more realistic and scientifically robust health risk evaluations compared to traditional total concentration-based methods. Through systematic literature review of 697 general land use sites and 245 industrially contaminated sites, PAHs contamination patterns were characterized across different land use types and regions. General land use soils showed pronounced north-south gradient with northern regions exhibiting 2-4 times higher contamination than southern regions. Industrially contaminated sites demonstrated severe contamination primarily in northern and southeastern coastal regions, with typical coking, steel smelting, and petrochemical plants showing one order of magnitude higher risk levels than general land use soils. Persistent PAHs accumulation in soils under general land uses was identified despite the emission reduction efforts, whereas a gradual decline was shown for industrially contaminated sites following remediation over the past decade. In addition, significantly lower bioaccessibility with a median value less than 35% for carcinogenic PAHs than low-ring PAHs were identified, reducing estimated health risks by approximately 50%. Spatial risk distribution was visualized through ArcGIS-based kriging interpolation using 1000 Monte Carlo simulated samples per region. Probabilistic assessment demonstrated that carcinogenic risks in soils under general land uses remained below the regulatory risk threshold of 1 × 10^-6, whereas soils under industrially contaminated sites posed substantially higher risks, nearly two orders of magnitude higher than those under general land uses particularly in North China with a mean risk level of 1.73 × 10^-5 magnitude. BaP and DahA were identified as primary risk drivers, contributing 71-86% to the total carcinogenic risks. Global sensitivity analysis further identified soil PAH concentration and bioaccessibility as the primary drivers of risk uncertainty, with child exposure duration playing an additional critical role in general land use settings. These findings underscore the necessities for bioaccessibility-integrated, region-specific, and land use-differentiated management strategies.