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A new study from researchers at the University of Leeds says that pedestrians can easily reduce their exposure to air pollution simply by crossing the street. Now, knowing just which side of the street is the correct one takes a little more know-how, reports Science Daily. Maybe there should be an app created for this sort of thing, or even just a crosswalk alerting pedestrians to the better side of the street.University of Leeds Professor of Environmental Modeling Alison Tomlin says that air pollution, especially in small, tight spaces is dramatically affected by wind patterns and the location of tall buildings. In particular, her research, "showed that pollution tended to accumulate on the leeward side of the street, (the sheltered side) in relation to the wind's direction at rooftop level." Or more specifically, air pollution tends to accumulate in pockets created by closely set buildings.
One finding that might not be so obvious is that carbon monoxide is up to four times higher on parallel side streets, rather than on main streets. For anyone who has ever ridden a bike on city streets and just been engulfed in vehicle exhaust, it seems counterintuitive that side streets are actually worse. According to this study, the parallel side streets don't have enough air flow and thus allow the air pollution to collect up.
The study itself just monitored one very busy intersection in West London over an 8 week period, so clearly not every intersection will be exactly the same. Though they say their findings are pretty much what you would expect. Pollution concentrations are higher at intersections, especially where cars tend to sit idle for awhile, but the wind then blows the air pollution into certain pockets a little further down the street. If the pollution is able to pass up and over surrounding buildings, then it tends not to come back and mix into side streets.
Ultimately the study recommends that bikers and pedestrians consider moving a street or two away from main intersections in order to avoid air pollution concentrations, just don't migrate to those parallel side streets. :Science Daily
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