A unique study by the U.S. Forest Service and the Davey Institute directly links the removal of air pollution with improved human health.  Most interesting for us who live in Nairobi is that while the scientists found that pollution removal is substantially higher in rural areas than urban areas, the effects on human health are substantially greater in urban areas than rural areas.

While trees improve only an average air quality improvement of less than 1 percent, the impacts of that improvement are substantial.  It was calculated that trees are saving more than 850 human lives a year and preventing 670,000 incidences of acute respiratory symptoms in the US.

“… this research underscores how truly essential urban forests are to people across the nation,” said Michael T. Rains, Director of the Forest Service’s Northern Research Station and the Forest Products Laboratory.

Trees at City Park forest. Photo by cngarachu.

The study considered four pollutants for which the U.S. EPA has established air quality standards: nitrogen dioxide, ozone, sulfur dioxide, and particulate matter less than 2.5 microns (PM2.5) in aerodynamic diameter. Health effects related to air pollution include impacts on pulmonary, cardiac, vascular, and neurological systems.

“In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people,” Nowak said. “We found that in general, the greater the tree cover, the greater the pollution removal, and the greater the removal and population density, the greater the value of human health benefits.”

Let us plant more trees in Nairobi—they not only add beauty to our city, but help us enormously in staying healthy!

The news release with this report can be found here.