Trees are saving more than 850 human lives a year and preventing almost 670,000 incidences of acute respiratory symptoms, says an estimate of air pollution removal by trees in the US by the US Forest Service scientists and collaborators.
While the pollution removal by trees equated to an average air quality improvement of less than 1 percent, the impacts of that improvement were substantial.
Researchers valued the human health effects of the reduced air pollution at nearly $7 billion (Rs.42,000 crore) every year.
"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," said Michael Rains, director Northern Research Station, US Forest Service.
The study considered four pollutants for which the US Environmental Protection Agency (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 the United States, approximately 130,000 PM2.5-related deaths and 4,700 ozone-related deaths in 2005 were attributed to air pollution.
Tree cover in the United States is estimated at 34.2 percent but varies from 2.6 percent in North Dakota to 88.9 percent in New Hampshire.
"In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people," Dave Nowak from US Forest Service noted.
The study appeared in the journal Environmental Pollution.
