Over 850,000 lives saved and 670,000 less cute respiratory symptoms due to trees
The American Lung Association in April released the State of the Air report that showed America’s air quality had improved from the previous year but ozone readings had increased since the 2013 report. The association said 147.6 million people live in areas where air quality remains unhealthy, almost 16 million more than the 2013 report.
Trees remove air pollution by the interception of particulate matter on plant surfaces and the absorption of gaseous pollutants through the leaf stomata. While trees pollution removal is associated to air quality improvement of less than 1% the impacts of that improvement are substantial.the magnitude and value of the effects of trees and forests on air quality and human health across the United States remains unknown.
Researchers from the U.S. Forest Service’s Northern Research Station and the Davey Institute estimated the amount of air pollution (nitrogen dioxide, ozone, sulfur dioxide, and particulate matter less than 2.5 microns (PM2.5) in aerodynamic diameter) 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. The four pollutants have established air quality standards established by the U.S. EPA.
Health effects related to air pollution include impacts on pulmonary, cardiac, vascular, and neurological systems. In the United States, approximately 130,000 PM2.5-related deaths and 4,700 ozone-related deaths in 2005 were attributed to air pollution.
The results showed the total amount of pollution removal in 2010 by trees and forests in the conterminous United States was 17.4 million with a human health value of $6.8 billion.
Removal was substantially greater in rural areas (16.7 million trees) compared to urban areas (651,000 trees, but the pollution removal monetary value in 2010 was substantially greater in urban areas ($4.7 billion) compared to rural areas ($2.2 billion).
The greatest amount for pollution removal was for ozone and nitrogen dioxide, while the greatest value associated with removal was for particle matter ess than2.5 microns and ozone.
States with the greatest pollution removal amounts were California, Texas and Georgia, while states with greatest pollution removal values were Florida, Pennsylvania and California. Most of these benefits were influenced by the effects of reducing human mortality, with a national reduction of more than 850 incidences of human mortality.
Other substantial health benefits included the reduction of more than 670,000 incidences of acute respiratory symptoms, 430,000 incidences of asthma exacerbation and 200,000 school days lost.
In their discussion the researchers write” Modeling broad-scale effects of pollution removal by trees on air pollution concentrations and human health reveals that while the percent reduction in pollution concentration averages less than one percent, trees remove substantial amounts of pollution and can produce substantial health benefits and monetary values across the nation, with most of the health values derived from urban trees.”
Michael T. Rains, Director of the Forest Service’s Northern Research Station and the Forest Products Laboratory commented “With more than 80 percent of Americans living in urban area, this research underscores how truly essential urban forests are to people across the nation.” “Information and tools developed by Forest Service research are contributing to communities valuing and managing the 138 million acres of trees and forests that grace the nation’s cities, towns and communities.”
According to David Nowak, U.S. Forest Service's Northern Research Station, Project Leader / Research Forester and one of the researchers of this study "In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people.” 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."
This study is published in the journal Environmental Pollution.