Household solid fuel combustion-related PAH exposure in rural northern China: Associations of phenanthrene metabolites with DNA damage and systemic inflammation

The relevance of urinary hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) to oxidative-stress and inflammatory biomarkers remains unclear, particularly in rural populations exposed to household solid-fuel combustion. In this cross-sectional study, we investigated urinary OH-PAH profiles and their associations with biomarkers of oxidative DNA damage, systemic inflammation, and vascular repair among 77 rural residents in northern China during winter. The summed concentration of ten urinary OH-PAHs (ΣOH-PAHs) ranged from 0.0499 to 7.0414 μg g⁻¹ UCr. Hydroxylated phenanthrene metabolites (OH-PHEs) accounted for the largest fraction (44%), indicating phenanthrene as a major contributor to the internal PAH metabolite burden. Among metabolite groups, ΣOH-PHEs showed the strongest positive associations with 8-hydroxy-2′-deoxyguanosine (8-OHdG) and C-reactive protein (CRP). These results suggest that OH-PHEs may serve as priority internal-exposure biomarkers associated with oxidative DNA damage and systemic inflammation. Exploratory Bayesian kernel machine regression further suggested isomer-specific association patterns: 1-hydroxyphenanthrene (1-OHPhe) showed the most prominent signal for 8-OHdG, whereas 2-OHPhe and 3-OHPhe were more closely associated with CRP. In a small subset with paired airborne PAH measurements, exploratory mediation analysis yielded positive indirect-effect estimates for OH-PHEs in the association between airborne phenanthrene and 8-OHdG. These findings highlight phenanthrene metabolites as important PAH internal-exposure indicators in rural solid-fuel settings and support source-targeted exposure reduction and health-risk prevention.