Association of long-term exposure to ambient air pollution and myopia in Chinese children

Ambient air pollution is recognized as a major global health concern, but evidence on its association with childhood myopia remains limited, particularly under multi-pollutant exposure conditions. A school-based study was conducted in Tianjin, China, including 212,566 students in grades 4-6. The 3-yr mean concentrations of particulate matter with aerodynamic diameter ≤ 2.5 μm (PM_2.5), its major components (sulfate (SO₄^2-), nitrate (NO₃^-), ammonium (NH₄⁺), organic matter (OM), and black carbon (BC)), and ozone (O₃) were estimated using machine-learning exposure models and linked to school locations. Restricted cubic splines and quartile-based modified Poisson models were used to assess single-pollutant exposure-response relationships, and quantile-based g-computation was applied to estimate joint pollutant associations. In single-pollutant models, the highest quartile of SO₄^2- was associated with higher myopia prevalence compared with the lowest quartile (PR = 1.10; 95% CI, 1.07-1.13). O₃ showed weaker and non-monotonic positive patterns (Q4 vs Q1: PR = 1.03; 95% CI, 1.00-1.05). In mixture analyses, a one-quartile increase in joint exposure was associated with higher myopia prevalence (PR = 1.017; 95% CI, 1.007-1.027). Sensitivity analyses generally supported the direction of the main findings. These findings suggest that long-term exposure to specific ambient air pollutants may be associated with myopia in school-aged children.