The shady side of sun protection
Sitting on the beach in the shade of your umbrella this summer might not be giving you the protection you think. Most of us are well aware of the need to use sunscreen but often we sit in shaded areas without sunscreen for an hour or longer reading a book or just relaxing.
In summer, UV intensity in New Zealand is 50% higher than at the same latitude in Europe and has increased by 12% in the last ten years because of environmental changes. Shade provides immediate relief from heat and the intensity of direct sunlight but its ability to provide protection from UV radiation is more limited than most people realise.
UV radiation bounces of atmospheric particles and is scattered in various directions. In other words it doesn’t come down in a straight line and stop at your beach umbrella. As a result small shaded areas are a high-risk for people without sunscreen.
So what about trees? The Queensland Institute of Medical Research in Brisbane deduced a fair skinned person sheltering under a tree could suffer sunburn in less than an hour. An average pine tree provides a SPF factor of around 3.7, in other words 37 minutes until burn time. Only trees with thick foliage that completely cut out the sun give better protection.
Does this mean seeking shade is not worthwhile? Not at all. If you wear sunscreen on your face with an SPF 15 and you sit under a tree with an SPF 3, the full effect is an SPF factor of 45. In short, sit in the shade but don’t forget the sunscreen.