A new study puts a hard number on the value of trees to human health. U.S. Forest Service scientists and collaborators calculate that trees, by removing air pollution as they respirate, save more than 850 lives a year in the U.S. and prevent 670,000 incidences of acute respiratory symptoms. The study assessed the impact of trees on four pollutants for which the U.S. Environmental Protection Agency has established air quality standards: nitrogen dioxide, ozone, sulfur dioxide and fine particles (less than 2.5 microns in diameter). The researchers calculated that trees remove less than 1 percent of air pollution — but say that even that seemingly small amount has substantial health impacts. The study, “Tree and Forest Effects on Air Quality and Human Health in the United States,” was published recently in the journal Environmental Pollution and is available online.
Not everything comes up roses when it comes to trees. A study published last year found that trees can add to air pollution by giving off a compound that helps produce lung-damaging particulate matter.
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— James Eng, NBC News