Beach umbrellas do not block all harmful sunlightNearly 40% of UV radiation can still get through
If you're planning your summer holiday, you probably know that you need to keep out of the sun's harmful radiation. But if your plan is to sit under the shade of a beach umbrella you may need to think again.
A new study has found that while beach umbrellas are effective in blocking out direct sun rays, you can still be exposed to harmful Ultra Violet radiation that reflects back under the umbrella.
"The umbrella intercepts the direct radiation that comes from the Sun, but part of the diffused radiation, which makes up approximately 60% of the total, comes from the sky not covered by the umbrella," said study leader José Antonio Martínez-Lozano from the University of Valencia.
The good news is that a canvas umbrella can absorb most of the direct radiation, with as little as 5% managing to penetrate the material - but this does not prevent diffused ultraviolet radiation from penetrating through the sides.
The results were obtained by putting a sensor beneath an umbrella and measuring the actual UV radiation received. Additional calculations were carried out by simulating the typical behaviour of people on the beach - for instance, people tend to move around and stand from time to time, rather than just lying still within the shade of the covering.
"We have proven that irradiance (radiation incidence per unit of surface area) that reaches the ground covered by an umbrella is 34% of the total," Dr Martínez-Lozano said.
The study is published in the journal Photochemistry and Photobiology.
Excess exposure to UV radiation has been linked to a range of medical conditions, from eye disorders such as cataracts, to weakness of the immune system and DNA damage as well as increased risk of skin cancer.
If you are planning to spend time on the beach this summer, you should follow our guide to staying safe in the sun even if you are taking an umbrella with you!
This article was published on Wed 21 July 2010
Image © Dmitry Ersler - Fotolia.com
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