Exploring the pathways of urban green space exposure on respiratory health: An empirical study in Nanjing, China

Pathways of association between green space (GS) exposure and respiratory health continue stimulating scholars' research interest. However, the mechanisms underlying the multidimensional association between GS exposure and respiratory health remain to be clarified. Therefore, this study aimed to construct a research framework for exploring the mechanisms affecting the hypothesized pathways (physical activity, air pollution) based on the dynamic quantification of multidimensional exposure indicators (spatial and visual exposure). This study used urban green spaces in Nanjing, China, as sample sites for a pilot experiment. The parallel mediating effect of GS exposure on respiratory health through physical activity and air pollution was explored by partial least squares (PLS) modeling, and the effect of differences in GS exposure levels on this parallel mediating model was explored. The results showed that a dynamic monitoring system of multiple indicators is more conducive to characterizing the actual GS exposure of the population. Promoting physical activity and reducing air quality were both mediating pathways affecting GS exposure and respiratory health, with physical activity being the most critical mediating variable, accounting for 43.06 % and 51.02 % of the total indirect effects, respectively. And variables such as age, BMI, and gender do not affect the mechanism. The respiratory health-promoting benefits of performing short-term exposure in urban green spaces had a lagged effect of at least 4 hours. The results of this study will help environmental epidemiologists to elucidate the pathways and mechanisms by which the green space system affects respiratory health and provide evidence for local governments to implement efficient and respiratory-healthy green space planning and design.