Air Quality and Urban Form in U.S. Urban Areas: Evidence from Regulatory Monitors

Abstract

The layout of an urban area can impact air pollution via changes in emissions and their spatial distribution. Here, we explore relationships between air quality and urban form based on cross-sectional observations for 111 U.S. urban areas. We employ stepwise linear regression to quantify how long-term population-weighted outdoor concentrations of ozone, fine particulate matter (PM(2.5)), and other criteria pollutants measured by the U.S. Environmental Protection Agency depend on urban form, climate, transportation, city size, income, and region. Aspects of urban form evaluated here include city shape, road density, jobs-housing imbalance, population density, and population centrality. We find that population density is associated with higher population-weighted PM(2.5) concentrations (p < 0.01); population centrality is associated with lower population-weighted ozone and PM(2.5) concentrations (p < 0.01); and transit supply is associated with lower population-weighted PM(2.5) concentrations (p < 0.1). Among pollutants, interquartile range changes in urban form variables are associated with 4%-12% changes in population-weighted concentrations-amounts comparable, for example, to changes in climatic factors. Our empirical findings are consistent with prior modeling research and suggest that urban form could potentially play a modest but important role in achieving (or not achieving) long-term air quality goals.

Evaluating the dynamic impacts of urban form on transportation and environmental outcomes in US cities

“…On the other hand, cities with higher land use mix (mix_f) were found to be experiencing higher ozone concentrations, although the influence is much smaller than that of the density factor. While prior cross-sectional studies give mixed results on environmental impacts of different sprawl measures (Stone 2008;Clark et al 2011;Bereitschaft and Debbage 2013), our longitudinal analysis shows another dimension of this pattern and suggests that cities with higher density are having better air quality over time.…”

“…Schweitzer and Zhou (2010) and Clark et al (2011) suggest that increasing density may raise the air pollutant exposure to some urban residents. While increased population density can reduce automobile dependency, it can also concentrate people in urban neighborhoods with poor air Estimation based on hybrid models (robust standard error in parenthesis) * 0.05 probability level, ** 0.01 probability level, *** 0.001 probability level quality (Schweitzer and Zhou 2010).…”

“…Schweitzer and Zhou (2010) took a finer scale approach and found that neighborhoods in less sprawling US metropolitan areas, generally exhibited lower concentrations of O 3 , but higher O 3 and PM 2.5 exposures due to a greater concentration of people living in areas with higher air pollutant concentrations. Through an analysis of 111 U.S. Census defined urban areas, Clark et al (2011) found that those with more centralized populations were associated with lower population-weighted PM 2.5 and O 3 concentrations, whereas those with higher population densities were associated with significantly higher populationweighted PM 2.5 concentrations. So, in the case of environmental outcomes also we see conflicting results on the impacts of urban sprawl.…”

“…A limited number of studies have empirically evaluated the direct associations between urban form and the emission or concentration of air pollution (Stone 2008;Schweitzer and Zhou 2010;Bechle et al 2011;Clark et al 2011). Although it is generally assumed that the relationship between land use and vehicle travel holds implications for tailpipe emissions and air quality, only a handful of studies has sought to statistically link urban form to vehicle emissions directly (Stone 2008).…”

Effect of Land Use and Cover Change on Air Quality in Urban Sprawl

“…As a direct result of urban sprawl, land use/cover changes (LUCC), as well as their spatial distribution (i.e., landscape pattern) variations may affect pollutants emission indirectly through industrial layout, travel behavior, and other human activities [3,8,9]. In view of the widespread health impacts of air pollution [10,11], studies have increasingly focused on the association between LUCC and air pollution variation caused by urban sprawl, including research on numerical simulations and empirical statistical modeling.…”