Links between city walkability and air pollution exposure has revealed that some neighborhoods might be good for walking, but they could have poor air quality, analyzes a new study.
University of Minnesota faculty member Julian Marshall and University of British Columbia faculty Michael Brauer and Lawrence Frank did the study for the city of Vancouver to check the potential environmental health effects caused by neighborhood location, layout and city design.
The team observed that on average, neighborhoods downtown are more walkable even though they have high levels of some pollutants, while suburban locations are less walkable and have high levels of different pollutants.
Meanwhile, the neighborhoods that fare well for pollution and walkability tend to be a few miles away from the downtown area, however, these "win-win" urban residential neighborhoods are rare and contain only about two percent of the population studied.
These neighborhoods are characterized by relatively high-income, while neighborhoods that fare poorly for both pollution and walkability tend to be in the suburbs and are generally middle-income.
Marshall, a civil engineering faculty member in the University of Minnesota's Institute of Technology, said: "Research has shown that exposure to air pollution adversely affects human health by triggering or exacerbating a number of health issues such as asthma and heart disease.
"Likewise, physical inactivity is linked to an array of negative health effects including heart disease and diabetes. Neighborhood design can influence air pollution and walkability; more walkable neighborhoods may encourage higher daily activity levels."
The researchers evaluated concentrations of nitric oxide, a marker of motor vehicle exhaust, and ozone, a pollutant formed when vehicle exhaust and other pollutants react, for 49,702 postal codes (89 percent of all postal codes) in Vancouver.
They then assigned a walkability score by analyzing four common attributes of neighborhood design: land-use mixing, intersection density, population density and for retail areas, the relative amount of land area for shopping versus for parking.
Marshall added: "The finding that nitric oxide concentrations are highest downtown, while ozone concentrations are highest in the suburbs, is not surprising. Motor vehicle exhaust is most concentrated downtown, leading to the high nitric oxide concentrations downtown.
" In contrast, ozone takes time to form. Air masses have moved away from downtown-often, to suburban areas-by the time ozone concentrations reach their highest levels. Thus, reductions in vehicle emissions can benefit people who live near high-traffic areas and also people living in less dense areas."
The research study was published in the November 2009 issue of Environmental Health Perspectives.