Trees help keep our world clean and healthy by filtering particles out of the air we breathe, decreasing the risk of respiratory illnesses.
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Donovan, Geoffrey H., David T. Butry, Yvonne L. Michael, Jeffrey P. Prestemon, Andrew M. Liebhold, Demetrios Gatziolis, and Megan Y. Mao. 2013."The Relationship Between Trees and Human Health: Evidence from the Spread of the Emerald Ash Borer." American Journal of Preventive Medicine 44.2 (2013): 139-45. Elsevier. Web. 13 January 2016.