WEST LAFAYETTE, Ind. A Purdue University method to estimate the amount of protection trees provide against ultraviolet-B radiation may influence how communities are built and the incidence of skin cancer.
"We now have a model to predict how much UV-B radiation people receive under different amounts of tree cover," said meteorologist Richard Grant, Purdue agronomy professor. "If you're in what most people consider shade, you're still getting 40 percent to 60 percent of the UV-B exposure that would hit you in direct sunlight."
Experts consider UV-B to be the most damaging of earth atmosphere-penetrating solar radiation, which also includes UV-A. More than 1 million cases of skin cancer, either basal, squamous or melanoma, are expected to occur in the United States this year, according to the Centers for Disease Control and Prevention (CDC).
Grant and his research team report their findings in the April issue of Photochemistry and Photobiology. The paper describes development and verification of a three-dimensional model that can predict how much UV-B radiation exposure exists under trees affording varying amounts of shade. The scientists then used the model to estimate how much exposure people received in residential suburban areas under cloud-free skies.
"Our model takes into consideration the fraction of sky you can see through the tree canopy," Grant said. They assessed a scenario to determine the effect of tree cover on children's daily UV-B exposure.
Several factors influence the amount of UV-B exposure. These include altitude, latitude (distance from the equator), time of day and tree cover. The researchers used all of these elements in their calculations.
At latitudes from 15 degrees to 60 degrees or approximately from Hawaii to Juneau, Alaska when 50 percent of the sky is visible through the trees, protection from the rays approximately doubles the time one can be in direct sunlight and get the same amoun
Contact: Susan A. Steeves