US trees remove tons of pollution, save hundreds of lives, study says
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* Natalie McGill

More Americans are living longer and breathing easier thanks to trees — especially in urban areas, according to a recent study.

In 2010, tree air pollution removal saved more than 850 lives, prevented 670,000 incidents of respiratory health issues and resulted in $6.8 billion in pollution-related health care costs, according to a study published online July 10 in *Environment Pollution*.

Most prior research on air pollution does not make the link of tree pollution removal to human health, said David Nowak, PhD, a study author and project leader for the United States Department of Agriculture’s Forest Service.

“The human health numbers are all new to us,” Nowak told *The Nation’s Health*. “The magnitude of the health effects — 850 lives and 670,000 respiratory symptoms — I didn’t know what to expect, so it was interesting if not surprising.”

Trees remove air pollution gases such as ozone through their leaves and remove pollution such as particulate matter by capturing particles and sending some of the particles back out into the atmosphere due to wind, the study said. Ozone, for example, can make breathing difficult and worsen existing respiratory issues such as asthma, according to the Environmental Protection Agency.

The study, which covered urban and rural areas in the contiguous 48 states, analyzed pollution removal by trees in 2010 using data such as total tree cover, daily leaf area and hourly weather and pollution concentration.

The study looked at pollutants of nitrogen dioxide, ozone, sulfur dioxide and particulate matter less than 2.5 microns.

Researchers used EPA’s Environmental Benefits Mapping and Analysis Program, in addition to air pollution output and census data, to determine the effects on public health and costs associated with air pollution-related health issues.

While the trees contributed to a less than 1 percent air quality improvement, they overall helped remove 19 million tons of air pollution in 2010, the study said. Though trees removed more pollution in rural areas compared to urban, there was a greater savings in health care costs in urban areas. Tree air pollution removal was linked to $4.7 billion in savings in urban areas compared to $2.2 billion in rural ones, the study said.

Nowak said he hopes this study will influence public health professionals and people who manage vegetation to help them understand how trees have an impact on air quality and human health.

“In terms of public health, I hope this research advances the dialogue on how we design cities to improve air quality and therefore human health using vegetation,” Nowak said. “Trees are common elements in cities. Urban tree cover in the U.S. averages 35 percent, but is often higher in forested regions of our nation, where many people live.”

To view the study, visit [www.nrs.fs.fed.us/pubs/46102](http://www.nrs.fs.fed.us/pubs/46102).

*   Copyright The Nation’s Health, American Public Health Association