Ecological risk-based soil thresholds for polycyclic aromatic hydrocarbons (PAHs) addressing direct contact and food chain exposure in China.

Polycyclic aromatic hydrocarbons (PAHs) are pervasive soil pollutants that pose significant environmental risks. However, research on soil threshold standards for PAHs in China remains limited. This study aims to establish soil threshold methods for PAHs by analyzing direct contact and food chain exposures using Chinese native species. Six PAHs were selected based on their molecular structures, and toxicity data for both pathways were utilized to estimate the thresholds. The estimated thresholds for direct contact are as follows: naphthalene (23 mg/kg), phenanthrene (10 mg/kg), fluorene (2 mg/kg), pyrene (6 mg/kg), fluoranthene (4 mg/kg), and benzo[a]pyrene (1 mg/kg). For food chain exposure, the thresholds are: naphthalene (171 mg/kg), phenanthrene (205 mg/kg), fluorene (44 mg/kg), pyrene (202 mg/kg), fluoranthene (58 mg/kg), and benzo[a]pyrene (6 mg/kg). Comparisons with international soil PAH thresholds reveal significant variations among countries, highlighting the importance of developing localized, science-based guidelines for China. The study also demonstrates that PAH thresholds are strongly influenced by the number and type of aromatic rings in their structures. To refine soil quality standards in China, the study recommends incorporating more comprehensive toxicity data and key soil properties (e.g., pH, clay content) and integrating these standards into regional regulations while promoting collaborative environmental management. These findings provide valuable guidance for managing PAHs and enhancing soil pollution control in China.