Association between eye-level greenness and lung function in urban Chinese children

Background: Health effects of greenness perceived by residents at eye level has received increasing attention. However, the associations between eye-level greenness and respiratory health are unknown. The aim of the study was to investigate the associations between exposure to eye-level greenness and lung function in children. Methods: From 2012 to 2013, a total of 6740 school children in seven cities in northeast China were recruited into this cross-sectional study. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), peak expiratory flow rate (PEF), and maximum mid expiratory flow rate (MMEF) were measured to evaluate lung function and to define lung impairment. Eye-level greenness was extracted from segmented Tencent Map street view images, and a corresponding green view index (GVI) was calculated. Higher GVIs mean more greenness coverage. Mixed-effects logistic regressions were used to estimate the health effects on lung impairment per interquartile range (IQR) increase in GVI. Linear regressions were used to estimate the associations between GVI and lung function. The health effects of ambient air pollutants were also assessed, including particulate matter with an aerodynamic diameter <1.0 mu m (PM1), <2.5 mu m (PM2.5), <10 mu m (PM10) as well as nitrogen dioxide (NO2). Results: An increase of GVI(800m) was associated with lung impairment in FEV1, FVC, PEF and MMEF, with ORs ranging from 0.68 (95% CI: 0.59, 0.79) to 0.83 (95% CI: 0.74, 0.93). The associations between an IQR increase of GVI(800m) and FEV1 (48.15 ml, 95% CI: 30.33-65.97 ml), FVC (50.57 ml, 95% CI: 30.65-70.48 ml), PEF (149.59 ml/s, 95% CI: 109.79-189.38 ml/s), and MMEF (61.18 ml/s, 95% CI: 31.07-91.29 ml/s) were significant, and PM1, PM2.5, and PM10 were found to be mediators of this relationship. Conclusion: More eye-level greenness was associated with better lung function and reduced impairment. However, eye-level greenness associations with lung function became non-significant once lower particulate matter air pollution exposures were considered.