Exposure to ambient air pollution and visual impairment in children: A nationwide cross-sectional study in China.

Evidence concerning exposure to air pollution and visual impairment is scarce. We evaluated the associations of ambient air pollution with visual impairment and visual acuity levels in Chinese schoolchildren. We recruited 61,995 children from 7 provinces/municipalities across China. Concentrations of air pollutants (i.e., particulate matter with an aerodynamic diameter of ≤ 1.0 µm [PM1], ≤ 2.5 µm [PM2.5], and 10 µm [PM10] as well as nitrogen dioxides [NO2]) were measured using machine learning methods. Visual acuity levels were measured using standard protocols. We used SAS PROC SURVEYLOGISTIC to assess the association between air pollution and visual impairment. An interquartile range increase in PM1, PM2.5, PM10, and NO2 was associated with a 1.133- (95% CI, 1.035-1.240), 1.267- (95% CI, 1.082-1.484), 1.142- (95% CI, 1.019-1.281), and 1.276-fold (95% CI, 1.173-1.388) increased odds of visual impairment, and the associations were stronger in children being boys, older, living in rural areas, and born to parents who had a lower educational level or smoked, compared to their counterparts. These results suggest that exposure to air pollution were positively associated with the odds of visual impairment, and the association may be modified by children's age, sex, and residential area as well as parental education level and cigarette smoking.