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Julian D. Marshall,¹ Michael Brauer,² and Lawrence D. Frank³

¹Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota, USA; ²School of Environmental Health, and ³School of Community and Regional Planning, University of British Columbia, Vancouver, British Columbia, Canada

Abstract
Background: The built environment may influence health in part through the promotion of physical activity and exposure to pollution. To date, no studies have explored interactions between neighborhood walkability and air pollution exposure.

Methods: We estimated concentrations of nitric oxide (NO) , a marker for direct vehicle emissions) , and ozone (O₃) and a neighborhood walkability score, for 49,702 (89% of total) postal codes in Vancouver, British Columbia, Canada. NO concentrations were estimated from a land-use regression model, O₃ was estimated from ambient monitoring data ; walkability was calculated based on geographic attributes such as land-use mix, street connectivity, and residential density.

Results: All three attributes exhibit an urban–rural gradient, with high walkability and NO concentrations, and low O₃ concentrations, near the city center. Lower-income areas tend to have higher NO concentrations and walkability and lower O₃ concentrations. Higher-income areas tend to have lower pollution (NO and O₃) . “Sweet-spot” neighborhoods (low pollution, high walkability) are generally located near but not at the city center and are almost exclusively higher income.

Policy implications: Increased concentration of activities in urban settings yields both health costs and benefits. Our research identifies neighborhoods that do especially well (and especially poorly) for walkability and air pollution exposure. Work is needed to ensure that the poor do not bear an undue burden of urban air pollution and that neighborhoods designed for walking, bicycling, or mass transit do not adversely affect resident’s exposure to air pollution. Analyses presented here could be replicated in other cities and tracked over time to better understand interactions among neighborhood walkability, air pollution exposure, and income level.

Key words: air quality, built environment, exercise, infill, pedestrian friendliness, physical activity, sprawl, traffic, urban design, urban environmental health, vehicle emissions. Environ Health Perspect 117:1752–1759 (2009) . doi:10.1289/ehp.0900595 available via http://dx.doi.org/ [Online 20 July 2009]

Address correspondence to J. Marshall, Department of Civil Engineering, University of Minnesota, 162 Civil Engineering, Minneapolis, MN 55455 USA. Telephone: (612) 625-2397. Fax: (612) 626-7750. E-mail: julian@umn.edu

Supplemental Material is available online (doi:10.1289/ehp.0900595.S1 via http://dx.doi.org/) .

We thank M. Bechle and S. Henderson for assistance in generating figures.

The authors declare they have no competing financial interests.

Received 20 January 2009 ; accepted 20 July 2009.