Longitudinal study of temporal trends in urinary polycyclic aromatic hydrocarbon metabolites and their repeated cross-sectional association with oxidative stress

Continuous human biomonitoring of urinary monohydroxy polycyclic aromatic hydrocarbon metabolites (OH-PAHs) enables the characterization of temporal trends and exposure patterns. In this study, we investigated the temporal trends in urinary concentrations of OH-PAHs among residents in Guangzhou from 2018 to 2023 through serial cross-sectional human biomonitoring programs. We further assessed the annual associations between urinary OH-PAHs and oxidative stress biomarkers to examine the temporal stability of these relationships over the study period. We observed a significant decreasing trend in urinary concentrations of OH-PAHs from 2018 to 2020, a notable rebound in 2021 (P < 0.001), followed by a subsequent decrease during 2022-2023 (P < 0.001). Similar temporal patterns were also observed for individual metabolites. Males consistently showed significantly higher urinary concentrations of OH-PAHs compared to females, with concentrations showing an increasing trend with age in the population. Year-specific multivariate linear regression analyses demonstrated different patterns across different metabolites. However, 1-hydroxyphenanthrene showed consistent positive associations with oxidative stress and could be used as a reliable biomarker for polycyclicaromatichydrocarbon-induced oxidative stress. Furthermore, quantile g-computation analyses further demonstrated consistently joint effects of urinary concentrations of OH-PAHs on oxidative stress thought the study periods, demonstrating the cumulative contribution of polycyclicaromatichydrocarbon exposure on oxidative stress burden. The random forest analysis of OH-PAHs, demographics, and lifestyle factors, identified that phenanthrene metabolites were the most significant contributors to elevated oxidative stress levels. The results characterized temporal fluctuations in urinary OH-PAH concentrations. The study represents one of the longest assessments of year-to-year changes in urinary OH-PAH concentrations within a single major metropolitan population and allowed us to investigate whether the association between urinary OH-PAHs and oxidative stress persisted or varied year-by-year under real-world environmental conditions.