air pollution

How walkable is your neighborhood?

111009_walkability

Researchers studying the metropolitan area of Vancouver found a complex interplay between neighborhoods’ walkability and air pollution. Downtown neighborhoods are generally more walkable but have high levels of nitric oxide. Suburban areas tend to be less walkable but have their own issues with pollution; namely, higher concentrations of ozone.

U. MINNESOTA (US)—Life in the suburbs may not be all its cracked up to be. A new study finds that the suburbs fare poorly in both walkability—the degree of ease for walking—and in pollution levels.

Researchers at the University of Minnesota conducted the study for the metropolitan area of Vancouver, British Columbia, the site of the 2010 Winter Olympics, and found that only 2 percent of the areas they studies were both walkable and had lower levels of air pollution.

Census data shows that the people who live in those neighborhoods have relatively high incomes, suggesting that they are desirable places to live and perhaps unaffordable to many.

The study, published in the November issue of Environmental Health Perspectives, is the first to explore interactions between neighborhood walkability and air pollution exposure. The researchers include Julian Marshall, assistant professor in civil engineering at the University of Minnesota’s Institute of Technology, and University of British Columbia faculty Michael Brauer and Lawrence Frank.

Researchers assigned a walkability score by analyzing four attributes of neighborhood design: population density, intersection density, land-use mixing (e.g., residential and retail), and ratio of land area devoted to shopping versus parking.

More walkable neighborhoods tend to have mixed land uses, with stores and shops within walking distance of houses. Areas with low intersection density contain more circuitous road networks, making them less walkable.

Marshall and colleagues found a complex interplay between neighborhoods’ walkability and air pollution. Downtown neighborhoods are generally more walkable but have high levels of nitric oxide—a marker of motor vehicle exhaust.

Suburban areas, on the other hand, tend to be less walkable but have their own issues with pollution; namely, higher concentrations of ozone, which can occur from air masses that have migrated away from downtown.

“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,” says Marshall.

“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 study’s findings suggest the need for urban planners to consider both walkability and air pollution, while realizing that certain neighborhoods are prone to high levels of pollution-either nitric oxide or ozone.

“There is urban planning now that focuses on walkability and exercise-friendliness,” Marshall says. But while that idea is on planners’ minds, “the connection to air pollution isn’t as much.”

Fortunately, addressing walkability might naturally lessen air pollution. Creating neighborhoods that allow for alternative transportation modes such as biking, walking, and public transit is one way to reduce motor vehicle emissions, the study suggests.

It’s about “allowing people to live in a less car-dependent neighborhood, if they wish to,” Marshall says. “The built environment—how we choose to structure our infrastructure—influences how we act, and [consequently] our health,” Marshall says. “If there’s no sidewalk, you’re less likely to walk.”

In the future, the researchers hope to investigate changes over time in walkability and pollution, and also study other urban areas to see how spatial patterns may differ.

University of Minnesota news: www1.umn.edu/news/

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