Walking through Problems of Urban Air Quality

December 8, 2009 · 0 comments

Doctors tell us to get more exercise—walking is as good for the body as for the environment. But is it healthy to take a walk in neighborhoods where walking is actually practical? If Vancouver, British Columbia, is representative of most urban areas, then the answer is “no.”

A recent study in Environmental Health Perspectives found that areas that rate highly for both walkability and air quality house only about 2% of the city’s population (they tend to be high-income regions a few miles from downtown).

The nitric oxide and the resulting ozone from auto emissions tend to concentrate in different parts of the city: nitric acid is more pervasive downtown, because ozone takes longer to form and has often drifted from its city sources before reaching its greatest concentrations in the suburbs.

The authors suggest that living in high-rises have an unintended health benefit: they are usually in a walkable environment and also allow most residents to spend much of their time farther away from street-level emissions.

These roadway air quality problems can be quite serious. A new study of the Los Angeles area connects asthma in children with proximity to heavy-traffic areas, with 9% of all childhood asthma cases in Long Beach and 6% in Riverside attributable to living within 75 meters of a major road.

“The impact of roadway proximity on the overall burden of asthma-related illness is remarkable,” said principal investigator Rob McConnell of the University of Southern California. “Air pollution is a more important contributor to the burden of childhood asthma than is generally recognized, especially to more severe episodes requiring visits to a clinic or emergency room.”

The study in the American Journal of Public Health also highlighted the impact of shipping in the region—the Los Angeles-Long Beach port is the largest in the United States—by estimating that 21% of asthma-related bronchitis episodes in Long Beach (about 1,400 cases total) and 8% in Riverside (3,400 cases) were caused by nitrogen dioxide emitted by ships.

If the air is the problem, then meteorology may offer some of the solutions. In a poster to be presented Monday (2:30 pm; Environment and Health Symposium) at the AMS Annual Meeting, David Quesada will report on correlations between weather—including humidity, rain, and winds—and asthma in Miami, Florida, where residents suffer above-average asthma incidence.

With pollen and particulate data in hand, the project may identify ways to help residents live well in an urban environment—without necessarily building more high-rises.