Air pollution is a serious concern. The burning of fossil fuels has introduced a steady flow of unhealthy pollutants into our atmosphere. Very few urban areas can meet national clean air standards. We are surrounded by efficient air cleaning machines - trees. Trees remove many pollutants from the atmosphere, including nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), and particulate matter of ten microns or less (PM10).

To determine the air pollution removal capacity of the urban with respect to the pollutants listed above, economists measure the cost that a society would have to pay in areas such as healthcare, if the trees removed no air pollutants. The state public service commission develops these costs in each state.

Trees and Air Quality around the Country

City, Pounds of pollutants removed annually by trees, Annual value of trees

Washington, DC    878,000    $2.1 million

Atlanta, GA Metro Area    19,000,000    $47 million

Portland, OR Metro Area    2,000,000    $4.8 million

Denver, CO Metro Area    1,100,000    $2.6 million

To learn how CITYgreen calculates carbon storage and sequestration, click here.

Trees and Energy Conservation

Anyone who has ever sat under a tree on a hot summer day knows
the cooling ability of trees, but trees can do more than just provide
shade from the hot sun. Trees cool our neighborhoods in the summer and
save us money on energy costs and related air pollution. Trees are most
effective when located to shade air conditioners, windows, or walls and
when located on the side of the home receiving the most solar exposure.
Urban forests reduce the phenomena of urban heat islands through tree’s
cooling capacities. It is estimated that 1,000 people die each year from

An additional benefit of conserving energy with strategically
planted trees, local power plants are not required to produce as much
electricity, and thus emit less pollution, including carbon. In urban
and suburban areas, the amount of this avoided carbon output outweighs
even the amount of carbon sequestered by the natural forest as it grows.