Dirty density: Air quality and the density of American cities
利用美国城市数据，研究发现城市密度增加会显著提高居民空气污染暴露水平，并带来可观的健康成本，提示密度政策在减排与健康之间存在权衡。
We study the effect of urban density on the exposure of city dwellers to air pollution using data from the United States urban system. Exploiting geological features to instrument for density, we find an economically and statistically significant pollution-density elasticity of 0.14. We assess the health implications of these estimates and find that increased density in an average city leads to sizeable mortality costs. Our findings highlight the possible trade-off between reducing global greenhouse gas emissions, which is associated with denser cities according to prior empirical research, and preserving local air quality and human health within cities.