Exploring Links Between Trees and Air Quality

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According to the American Lung Association, the Cleveland area has some of the worst air quality from what’s called year-round “particle” pollution – things that come from industry and automobiles. An emerging area of research focuses on the role urban forests play in “cleaning the air” and how disappearing tree canopy impacts human health. In the continuing series “Tracking the Trees,” Kay Colby takes a look at trees and asthma.



On a hot summer day, 49-year old Vernice Lester points to a little black pack by her side, describing its role in her life.  

 “This is my old faithful,” Lester says. “Everywhere I go I take it with me.”

What could be a purse, is actually a portable oxygen machine helping Lester breathe.  She has severe asthma and COPD. She says both are aggravated by heat and humidity. “It’s like suffocating, like somebody’s choking me”, Lester says. “I’m not getting any air in my lungs.”

Cleveland Clinic pulmonologist Sumita Khatri, says another issue for her patients like Lester is air quality.  In a 2016 report from the American Lung Association, Cleveland-Akron-Canton ranked as the 11th worst out of the top 25 metro areas for people at risk for year-round particle pollution.

Dr. Khatri says, “Particle matter is the small dust and aerosols comprised of various components that are just floating in the air. It comes from cars and trucks, as well as industry.”

Using computer mapping and mathematical modeling, U.S. Forest Service scientist David Nowak, PhD, helped develop a tool that quantified the role “trees” played in cleaning the air in 2010. Nowak says, Overall forests in the U.S. removed 17 million tons of pollution. Pollutants go to the interior of the leaf and are dissolved.  In terms of particulate matter, the surface of the plants capture particles so they’re directly removed. That’s one of the dominant ways trees improve air quality.”

Using Nowak’s tool, a Northeast Ohio Tree Consortium calculates that Cleveland trees remove just under 830,000 pounds of air pollution per year. But the worry is that the City continues to lose almost 100 acres of tree canopy per year due to things like development, disease, and shrinking budgets for tree maintenance.  Colby Sattler, an arborist with the Western Reserve Land Conservancy, says fewer trees may also play a role in higher asthma rates. According to Sattler, “Both locally and nationally we see this trend with many indicators in health and wellness. And specifically with the rates of asthma and upper respiratory disease, those neighborhoods with the lowest tree canopy have the higher rates.”

While the causes of diseases like asthma are multi-factorial, Cleveland Clinic’s Dr. Khatri sees maintaining and planting trees as an easy rallying point to help underserved communities. She says, “I think what communities will see is that trees mean prosperity, and greenness, and attention. It’s a common language – right? Like who doesn’t really love a tree?”

In 2016, Cleveland’s City Planning Commission approved a “tree plan.” One part highlights neighborhoods with low tree canopy in relationship to needs such as the percent of the population with asthma. Authors of the plan say large-growing trees with big leaves like the White Oak or the London planetree are known to be good “air cleaners.” A future goal would be to plant those types of trees in neighborhoods with the highest rates of asthma. But the challenge remains coming up with funding and resources to support that kind of “targeted planting.”


To view a report by the Cuyahoga County Planning Commission that shows how different cities throughout Cuyahoga County stack up when it comes to tree canopy, click here.

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