Green Cities Reduce Pollution

Trees and bushes growing in the world’s metropolises reduce air pollutants by 8 times more than previously realized.

Aug 30, 2012
Jef Akst

City projects aiming at making neighborhoods more green are doing the world good, according to a new report published in Environmental Science & Technology this week (August 29). Such greenery can reduce levels of nitrogen dioxide (NO2) and microscopic particulate matter (PM), two potentially harmful pollutants, by 8 times more than previously estimated.

NO2 and PM levels often exceed safe levels in cities, explained Thomas Pugh Lancaster University in a press release, but previous work has suggested that trees and other plants remove some of those pollutants, improving air quality for city residents—but the reduction was only by about 5 percent. The new study found that if enough plants are used, in what the researchers term “urban street canyons,” they can lower street level NO2 and PM by as much as 40 and 60 percent, respectively. In addition to just planting trees and shrubs around the city, people could build plant-covered billboards, they suggest.

“Judicious use of vegetation can create an efficient urban pollutant filter, yielding rapid and sustained improvements in street-level air quality in dense urban areas,” the authors wrote.