Trees produce oxygen, which is vital for most living beings. But their importance has multiplied in the age of rising air pollution. According to a study by the U.S. Forest Service and collaborators, trees save more than 850 human lives in the United States every year. What’s more, they prevent more than 670,000 incidences of acute respiratory symptoms.

Palm trees

Trees removed 19 million tons of air pollutants in 2010

It underlines the role trees play in air pollution removal. The study was conducted by Dave Nowak and Eric Greenfield of the United States Forest Service and Satoshi Hirabayashi and Allison Bodine of the Davey Institute. Scientists found that trees removed more than 19 million tons of air pollutants from the U.S. skies in 2010 alone. Though air pollutant removal by trees leads to less than 1% improvement in the average air quality, the impacts were substantial. The Forest Service estimates that the removal of these pollutants saved Americans about $7 billion in health care costs in 2010.

Michael Rains, director of the U.S. Forest Service’s Northern Research Station, said that about 80% of Americans live in urban areas. This research shows how important urban forests are to the U.S. population. Scientists considered four pollutants for this study: ozone, nitrogen oxide, sulfur oxide and particulate matter less than 2.5 microns (PM2.5) in diameter. These were taken into consideration because the U.S. Environmental Protection Agency (EPA) has laid down air quality standards for each of them.

About 34.2% of the U.S. land covered with trees

Air pollutants affect human health directly as well as indirectly. Direct inhalation of polluted air could affect pulmonary, vascular, cardiac and neurological systems. Indirectly, they affect human health by harming crops and the health of ecosystems. This study directly links the removal of air pollutants with improved human health.

Statistics shows that, in 2005, about 4,700 ozone-related deaths and 130,000 PM2.5-related deaths were attributed to air pollution. About 34.2% of the total U.S. land is covered with trees, but the ratio varies widely from just 2.6% in North Dakota to about 89% in New Hampshire. The study appeared in the journal Environmental Pollution.