Urban green space, respiratory health and rising temperatures: An examination of the complex relationship between green space and adult asthma across racialized neighborhoods in Los Angeles County

Using spatial regressions in Piecewise Structural Equation Modeling, this study aims to investigate the relationship between urban green space (UGS) and adult asthma-related emergency department (ED) visits in urbanized Los Angeles County. Controlling for socioeconomic and built-environment factors at the neighborhood scale, we examine both direct associations between various UGS types—trees, grass, and water bodies—and asthma ED visit rates, as well as indirect pathways through air pollution (PM2.5) and land surface temperature (LST). Our findings reveal distinct pathways through which UGS types are associated with asthma ED visit rates. Proportions of trees and water bodies are negatively associated with asthma ED visit rates through different indirect pathways: trees through both LST and PM2.5 pathways, and water bodies through the LST pathway. Grass proportions, conversely, are positively associated with asthma ED visit rates both directly and indirectly through LST. We also highlight variations in these associations across different racialized communities. Specifically, in predominantly White communities, tree proportions demonstrate an additional direct negative association with asthma ED visit rates, whereas the positive associations between grass proportions and both asthma ED visit rates and LST, observed in minoritized communities of color, are not present. Moreover, the overall positive association between grass proportions and asthma ED visit rates is significantly stronger in minoritized communities of color. This research suggests prioritizing trees and water bodies over grass in green infrastructure planning and advocates for a context-specific approach in urban planning and public health management to optimize the benefits of UGS.