Hiding out under an umbrella at the beach this summer might not completely protect you from the sun, a new study suggests.
The results show 34 percent of the sun's ultraviolent radiation can reach the ground shaded by a beach umbrella. Ultraviolent, or UV, rays emitted by the sun can cause sunburns as well as damage the DNA within cells and lead to skin cancer, such as melanoma.
Umbrellas can absorb most of the sunlight that shines down from directly above, but radiation can still get through from the sides, the researchers found.
To carry out the project, the team positioned an ultraviolet ray sensor on the base of a canvas umbrella painted blue and white, with a radius of 31.5 inches (80 cm) and height of 4.9 feet (1.5 meters).
"The umbrella intercepts the direct radiation that comes from the sun, but part of the diffused radiation, which makes up approximately 60 percent of the total, reaches the sensor from the sky not covered by the umbrella," said study researcher José Antonio Martínez-Lozano, of the University of Valencia in Spain.
The results are published in the journal Photochemistry and Photobiology.
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