Association of atmospheric oxidants and fine particulates with polycystic ovary syndrome and the reproductive trajectory: Protective role of residential greenness.

Polycystic ovary syndrome (PCOS) affects 11%-13% of reproductive-aged women globally. However, the impacts of ambient oxidants [characterized by ozone (O3) and nitrogen dioxide (NO2)], fine particulate matter (PM2.5) and its components, and residential greenness, on the risk of PCOS and its clinical reproductive trajectory have not been studied. We conducted a retrospective cohort study from 2014 to 2025 (976 PCOS cases and 5271 controls), logistic regression estimated associations between PCOS risk and environmental exposures. Among PCOS patients, modified Poisson and Andersen-Gill models evaluated exposure impacts on a sequence of adverse pregnancy outcomes (APOs). Exposure to all assessed pollutants was associated with increased PCOS risk. Each 1 μg/m3 increase in oxidants was linked to higher odds of PCOS [odds ratio (OR): 1.07, 95% confidence interval (95% CI): 1.05-1.08], exceeding any individual component. Among PM2.5 components, black carbon demonstrated the strongest association with PCOS risk (OR: 1.66, 95% CI: 1.53-1.80). In contrast, higher residential greenness (per 0.005 unit increase in 100-m buffer normalized differential vegetation index) was protective against PCOS risk (OR: 0.96, 95% CI: 0.95-0.96). Among PCOS patient subcohort, both long- and short-term pollutant exposures were associated with increased APOs risks along the clinical reproductive trajectory. PM2.5 components' effects [hazard ratios (HRs): 1.01-3.63] exceeded those of total PM2.5 mass (HRs: 1.01-1.05). Briefly speaking, ambient oxidants and PM2.5 are key environmental risk factors for the development of PCOS and the adverse clinical trajectory. Residential greenness represents a modifiable, nature-based strategy to help mitigate the PCOS burden and improve reproductive health.