News Brief

Kids Breathe Easier When Trees Eat Smog

Study shows how urban trees save millions in medical bills, using a new method to model smog concentrations.

Tree Canopy and Smog Reductions in Portland

Source: Environmental Pollution 194 (2014) 96–104
Portland citizens could save $7 million annually by planting more trees, according to researchers at Portland State University. The team of biologists, environmental scientists, and urban planners developed a new methodology that could help municipalities maximize the health effects of urban greenery.

The researchers first developed a novel way to model highly localized pollution levels, noting that people living within 200 m (0.12 miles) of major roadways are at much higher risk for asthma and other respiratory problems. (Current methods of modeling air-pollution levels capture a much larger radius, typically greater than 10 km, or 6.2 miles.) By accurately predicting where pollutants concentrate, they argue, urban planners will be able to strategize about where mitigation is needed.

In the course of this work, the scientists discovered dramatic reductions in expected pollution levels in areas with high concentrations of trees. The team drew on epidemiological research to arrive at the $7 million projected savings for Portland but added that their work should be applicable everywhere.

“Due to the geographic variation in the distribution of air pollutants in a city, the health impacts are not uniform and tend to be increasingly borne by susceptible and socially disadvantaged urban populations,” they note. “Our study demonstrates the need to monitor or model air pollutants at a highly local scale in order to correctly assess the health impacts of urban air pollutants and to address social equity issues.”

Published September 16, 2014

Melton, P. (2014, September 16). Kids Breathe Easier When Trees Eat Smog. Retrieved from

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September 17, 2014 - 10:45 am

As you might imagine, in our modern, de-industrialized cities, air pollution is not as much from industry as it once was, but is much more from cars. This is especially true near highways and heavily used arteries.

Air pollution from cars, seemingly combustion products and grit, comes in many forms. The sort described in this article is probably 2.5 micron or larger in size and  mostly affect respiratory health. 

Another key type of pollutant is defined as Ultra Fine Particulate. These are also combustion products, but they have less effect on respiratory health but much greater effect on cardiovascular health. The other key quality of ultra fine particulates is that the concentrations are much higher the closer you get to a highway. Because of this quality, changing air management in buildings near to highways, and generally avoiding building near highways, are important for avoiding serious adverse health effects. You always figured it was true.... now the evidence is pretty strong.

For more information, take a look at the Community Assessment of Freeway Exposure and Health study, linked here: