Although urban air pollution poses a serious threat to public health worldwide, the role of urban form in mitigating or aggravating air pollution is unresolved, especially in expanding cities within the developing world. We measured “circularity,” “fragmentation,” and “compactness” of the urban form of 350 cities in the rapidly urbanizing Yangtze River Delta (YRD) of eastern China over two decades from 1998 to 2015. The cities were further stratified by population into small (<500,000), medium-sized (500,000–1,000,000), and large cities (>1,000,000). We then employed ridge regression to investigate relationships between satellite-derived estimates of PM2.5 concentrations and urban form among all of the cities.
Results/Conclusions
Urban form had a relatively stronger impact on PM2.5 concentrations in small and medium-sized cities than in large cities. Although in general, urban circularity was not a statistically significant predictor of PM2.5 concentrations, fragmentation and compactness were important. After controlling for population, land area, and climate, more sprawled cities had lower PM2.5 concentrations than their more spatially compact counterparts. This was probably due to the beneficial effect of increased intermixing of urban and forest land on removal of PM2.5 within fragmented as opposed to contiguous cities. Our findings indicate that spatial policies in YRD should avoid building single- or circular-shaped cities with a monocentric form. Conversely, moderately scattered and polycentric urban development should be encouraged to mitigate PM2.5 pollution.