In 2010, trees removed more than 17 million metric tons of pollution from the air. In doing so, they saved more than $6.8 billion dollars in health care costs associated with pollution-related diseases, like bronchitis and asthma.
In a recent paper in the journal Environmental Pollution, US Forest Service researcher David J. Nowak explains:
Most of the pollution removal occurred in rural areas, while most of the health impacts and values were within urban areas. Health impacts included the avoidance of more than 850 incidences of human mortality and 670,000 incidences of acute respiratory symptoms.
In addition, he estimates that the trees helped avoid 430,000 incidences of asthma exacerbation and kept kids in school 200,000 times that year.
All that from scrubbing just 1% of the air pollution we generate each year.