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Tree and forest effects on air quality and human health

Key Message

The effect of trees in removing pollution can produce substantial health benefits, such as on pulmonary, cardiac, vascular, and neurological systems, and monetary values across the United States, with most of the health values derived from urban trees.


Nowak, David J. et al. (2014). Tree and forest effects on air quality and human health in the United States. Environmental Pollution. 193 (2014): 119–129.


Trees remove various types of air pollution, such as nitrogen dioxide (NO2), ozone (O3), particulate matter less than2.5 microns (PM2.5), and sulfur dioxide (SO2) but the magnitude and value of the effects of trees and forests on air quality and human health across the United States remains unknown. Health effects related to air pollution include impacts on pulmonary, cardiac, vascular, and neurological systems. In the United States, approximately 130,000 PM 2.5-related deaths and 4700 O3-related deaths in 2005 were attributed to air pollution. While various studies have estimated pollution removal by trees, most studies on pollution removal do not directly link the removal with improved human health effects and associated health values.

This study uses computer simulation to estimate the amount of air pollution (NO2, O3, PM2.5, SO2) that is permanently removed by trees and forests within urban and rural areas of the conterminous United States in 2010, and its associated monetary value and impact on human health.


Computer simulations with local environmental data reveal that trees and forests in the conterminous United States removed 17.4 million tonnes (t) of air pollution in 2010 (range: 9.0-23.2 million t), with human health effects valued at 6.8 billion U.S. dollars (range: $1.5-13.0 billion). While this pollution removal equated to an average air quality improvement of less than one percent, the effects were substantial. Most of the pollution removal occurred in rural areas, while most of the health impacts and values were within urban areas. Health impacts included the avoidance of more than 850 incidences of human mortality and 670,000 incidences of acute respiratory symptoms.


Benefit Statements / Outcomes

Leadership Provided By:

  • Leisure Information Network (LIN)
  • Alberta Recreation and Parks Association

On Behalf Of:

  • Canadian Parks and Recreation Association (CPRAA)

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