Staying safe in the sun

Tuesday 17th May 2011 by Dr Liz Bentley

It is easy to think of sunburn as something that doesn't really happen in the UK, but it can and it often does. You don't have to be sunbathing to get sunburnt; it may happen while you are playing sport, walking or even working outdoors. To ensure you have fun in the sun either in the UK or abroad, we have put together a sun factfile to encourage you to enjoy the sun safely through the UK summer.

UV and the UV index

There are two types of ultraviolet (UV) radiation which can damage your skin - UVA and UVB. UVB is the cause of most sunburn, whereas UVA ages the skin but contributes significantly less towards sunburn. UV rays are invisible and cannot be felt - the sun's heat comes from infrared radiation.

The UV index is a standard measure of the strength of ultraviolet radiation from the sun at a particular place and time. The index is a linear scale, with higher numbers indicating higher UV exposure levels. The main purpose of the scale is to provide an easy to understand forecast of UV intensity to the general public. Canada was the first country to produce a UV index forecast in 1992, with other countries soon following their lead and the index is now standardised by the World Health Organisation (WHO).

The UV level is highest in the UK between the hours of 11-3pm, but the strength of the UV is dependent upon a range of factors:

-Month of the year: high risk months are May-September
-Cloud cover: even through overcast skies 30-40% of UV still reaches the ground. When the sky is half covered (50%) 80% of the UV reaches the ground
-Altitude: the higher up you go, the stronger the UV
-Reflection: water reflects 5-10% of UV, 15% reflects from sand and a whopping 75% reflects from the snow- meaning skiers should always take extra precautions.

The UV index given in weather forecasts is a prediction of the UV levels at solar noon (typically the four hour period around midday). The calculations are weighted in favor of the UV wavelengths to which human skin is most sensitive according to the McKinlay-Diffey Erythema action spectrum. Both the USA and Australia now issue UV alerts for days with intense UV radiation.

You can check the UV index on the Met Office website for the UK and the whole of Europe, with specific information for cities across the UK and Europe.

Cancer Research UK produces a handy table for working out UV burn risks depending on your skin type and the UV levels

What you should do

Cancer Research UK and their SunSmart campaign recommend buying sunscreens with:

-a Sun Protection Factor (SPF) of at least 15 - The higher the SPF the better
-'broad-spectrum' sunscreens with a star rating of four stars or more (this protects against UVA and UVB rays). The higher the number of stars the greater the protection
-apply plenty of sunscreen and reapply regularly, including when you have been in the pool or the sea
-check the expiry date on your sunscreen - many have a shelf life of 2-3 years
-people tend to use less sunscreen than they should- use around two teaspoonfuls of sunscreen for your head, arms and neck and two tablespoonfuls if you're covering your entire body
-try and find shade, under a tree or canopy, or indoors between 11-3pm, the times in the UK when the sun is at its strongest.

Useful links

Cancer Research UK SunSmart Campaign
NHS sun safety Q&A
Met Office UV forecast
BBC Health

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