Trees are nature's answer to diminishing air pollution, as well as reducing respiratory problems for the human population, according to US Forest Service scientists and collaborators behind a new study.

Their broad-scale estimates concluded that trees are saving more than 850 human lives a year and preventing 670,000 incidents of acute respiratory symptoms - and that's just by improving air quality less than one percent.

Not to mention that trees can help save $7 billion a year in health costs by reducing respiratory illness.

The study, published in the journal Environmental Pollution, was led by Dave Nowak and Eric Greenfield of the US Forest Service's Northern Research Station (NRS) and Satoshi Hirabayashi and Allison Bodine of the Davey Institute. It is the first to directly link air pollution to improved healthy effects.

Researchers came to these staggering conclusions by investigating four pollutants in particular: nitrogen dioxide, ozone, sulfur dioxide, and particulate matter less than 2.5 microns (PM2.5) in aerodynamic diameter. The Environmental Protection Agency (EPA) currently has air quality standards established for these four pollutants.

The NRS team found that pollution removal is substantially higher in rural areas compared to urban areas, however the effects on human health are considerably greater in urban areas than rural areas.

"With more than 80 percent of Americans living in urban areas, this research underscores how truly essential urban forests are to people across the nation," Michael T. Rains, Director of the Forest Service's Northern Research Station, said in a news release.

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 because of air pollution.

It may seem simple that trees are the answer to reducing air pollution and all its associated health effects, but tree cover is not created equal in the United States. For example, trees cover 2.6 percent of North Dakota compared to 88.9 percent in New Hampshire. Thus, big companies in areas like North Dakota started using air conditioners with filtration capabilities, fixing two issues simultaneously as proper conditions are created in regard to workspace temperature while impurities in the air are decimated to create a healthier working habitat. 

"In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people," Nowak said. "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."

The entire report, "Tree and Forest Effects on Air Quality and Human Health in the United States," can be found here.