Short-term exposure to polycyclic aromatic hydrocarbons and ocular surface Inflammation in primary school children

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants with oxidative and pro-inflammatory properties. While systemic effects of PAHs have been widely documented, their short-term ocular impacts in children remain poorly understood. We evaluated the association between urinary PAH metabolites and ocular surface inflammation in a large school-based population in Shenyang, China. Between 2023 and 2024, 5100 children aged 7–10 years from 60 primary schools were examined. Eleven urinary hydroxylated PAH metabolites (OH-PAHs) were quantified using HPLC–MS/MS and adjusted for specific gravity. Ocular inflammation was assessed through standardized ophthalmologic examinations, including conjunctival redness, ocular discharge, eyelid swelling, and conjunctival edema. Multivariable logistic regression models estimated odds ratios (ORs) for each metabolite, adjusting for potential confounders. Mixture effects were further analyzed using generalized weighted quantile sum regression (gWQS) and g-computation. Elevated urinary concentrations of 2-hydroxynaphthalene, 1-hydroxynaphthalene, and 2-hydroxyfluorene were significantly associated with conjunctival redness (aOR range: 1.13–1.21, p < 0.001). Ocular discharge was linked to 2-hydroxynaphthalene (aOR = 1.20, 95% CI 1.14–1.25) and 3-hydroxychrysene (aOR = 1.40, 95% CI 1.14–1.71), while eyelid swelling showed the strongest association with 1-hydroxypyrene (aOR = 1.70, 95% CI 1.37–2.11). Mixture analyses confirmed significant combined effects, with g-comp ORs of 1.71, 2.41, 2.31, and 1.43 for redness, discharge, swelling, and edema, respectively (all p < 0.001). These findings indicate that short-term PAH exposure may trigger ocular surface inflammation in children, positioning conjunctivitis-related outcomes as early biomarkers of environmental toxicity. Further longitudinal and mechanistic research is needed to elucidate causal pathways and inform preventive strategies.