Study Shows How Trees Help CREATE Smog

Apr 26, 2013

Leaves produce a substance that exacerbates smog, a new study finds.
Credit Laura Candler

A new study from researchers at the University of North Carolina at Chapel Hill has revealed exactly how trees play a role in smog production. The question has been a source of scientific uncertainty for years, and the findings are a milestone in air pollution research, with potentially significant implications for public health.

For a long time, researchers have known that trees’ leaves emit a substance called isoprene, which provides a protective layer against temperature fluctuations and oxygen damage. In 2004, researchers discovered that this substance could play a role in creating particulate matter –air pollutants that lead to lung cancer, asthma, and have a damaging effect on the environment. But how exactly that happened was unclear.

The new study from UNC at Chapel Hill’s Gillings School of Global Public Health was published in the Proceedings of the National Academy of Sciences, and it pinpoints exactly how isoprene creates particulate matter. When trees release the substance, it is chemically altered by sunlight and reacts with man-made nitrogen oxides to create particulate  matter, or smog.

“The work presents a dramatic new wrinkle in the arguments for reducing man-made pollutants worldwide,” Jason Surratt said in a statement released by UNC at Chapel Hill. Surratt is an assistant professor of environmental sciences and engineering at the Gillings School of Global Public Health and one of the paper’s 18 authors.  “Isoprene evolved to protect trees and plants, but because of the presence of nitrogen oxides, it is involved in producing this negative effect on health and the environment.”

Surratt also said that cutting down all the trees is not a solution, “but we can work on reducing these man-made emissions to cut down the production of fine particulate matter.”