A new first ever national study has revealed that trees help save human lives on a greater extent by reducing respiratory problems.
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While trees' pollution removal equated to an average air quality improvement of less than 1 percent, the impacts of that improvement are substantial. Researchers valued the human health effects of the reduced air pollution at nearly 7 billion dollars every year and they and save more than 850 human lives a year as they prevent 670,000 incidences of acute respiratory symptoms.
The scientists found that pollution removal was substantially higher in rural areas than urban areas; however the effects on human health were substantially greater in urban areas than rural areas.
The study considered four pollutants for which the U.S. 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 included 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.
Trees' benefits vary with tree cover across the nation. 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.
Dave Nowak, of the U.S. Forest Service's Northern Research Station, said that in terms of impacts on human health, trees in urban areas were substantially more important than rural trees due to their proximity to people and 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 study 'Tree and Forest Effects on Air Quality and Human Health in the United States' is published in the journal Environmental Pollution.
