Global Challenges/Chemistry Solutions

Promoting Public Health: Green plants reduce pollution on city streets up to eight times more than previously believed

September 10, 2012


Green plants reduce pollution on city streets up
to eight times more than previously believed.

Credit: iStock.

Summary

Trees, bushes and other greenery growing in
the concrete-and-glass canyons of cities can
reduce levels of two of the most worrisome
air pollutants by eight times more than
previously believed, a new study has found.
A report on the research appears in the ACS
journal Environmental Science & Technology.

Today’s report concludes that trees, bushes and other greenery growing in the concrete-and-glass canyons of cities can reduce levels of two of the most worrisome air pollutants by eight times more than previously believed. A report on the research appears in the ACS journal Environmental Science & Technology.

Thomas Pugh, Ph.D., who is now with Karlsruhe Institute of Technology and is lead author of the paper, explains that concentrations of nitrogen dioxide and microscopic particulate matter — both of which can be harmful to human health — exceed safe levels on the streets of many cities. Here’s Pugh…

“Past research suggested that trees and other green plants can improve urban air quality by removing those pollutants from the air. However, the improvement seemed to be small, typically a reduction of less than 5 percent.”

The new study sought a better understanding of the effects of green plants in the sometimes stagnant air of enclosed city streets, which the authors term "urban street canyons."

“We concluded that judicious placement of grass, climbing ivy and other plants in urban canyons can reduce the concentration at street level of nitrogen dioxide by as much as 40 percent and particulate matter by 60 percent, much more than previous studies indicate. In some cases, increasing the depth of these canyons by building plant-covered ‘green billboards’ to increase the amount of pollutant removal could help.”

The study also concluded that while covering existing canyon surfaces in green plants was always beneficial for air quality, street trees might worsen street-level air quality in the most polluted canyons, where increased trapping of pollutants in the canyon can outweigh their ability to remove pollution from the air. The authors suggest that city planners carefully consider the benefits of planting trees in these areas.

Smart Chemists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Please check out more of our full-length podcasts on wide-ranging issues facing chemistry and science, such as promoting public health, developing new fuels and confronting climate change, at www.acs.org/GlobalChallengesToday’s podcast was written by Katie Cottingham. I’m Adam Dylewski at the American Chemical Society in Washington.

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Thomas Pugh, Ph.D.,
Karlsruhe Institute of Technology
Karlsruhe, Baden-WÜrttemberg, Germany