Stoplights are hot spots for airborne pollution

Intersections expose drivers to 29 times as many harmful particles as the open road

car at an intersection

RED LIGHT, GREEN LIGHT  Drivers may spend only a tiny fraction of their time at stoplights, but that’s when they inhale a higher concentration of pollutants than when in motion.

Sara B./flickr (CC BY-NC 2.0)

Being stuck at a red light isn’t just frustrating — it’s bad for your health. Drivers are exposed to more harmful pollutants when idling at intersections than when zooming along an open road, scientists report February 12 in Atmospheric Environment.

When cars and trucks burn fuel, they emit tiny pollutants that have been linked to heart and respiratory illness. To see whether intersections are hot spots for these nanoparticles, researchers drove in a six-kilometer loop through Guildford, England, and measured how the concentration of pollution changed along the route.

Though the drivers only spent roughly 2 percent of their time at stoplights, that time accounted for about 25 percent of their total exposure to pollutants. At intersections, the concentration of nanoparticles was up to 29 times as high as it was on uncongested stretches of road.

“You emit a lot more particles when you are at a traffic light,” says study coauthor Prashant Kumar, a civil and environmental engineer at the University of Surrey in England. So do all the cars idling right next to you. And accelerating — that moment you rev the engine when the light turns green — releases more emissions than driving at a steady pace.

The good news is that drivers have at least a little control over how much pollution they inhale. “If you are at a traffic light, it is best to keep the windows up and the fan off,” says Kumar. Drivers should also try to keep their distance from the car in front of them.

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