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We all know that exposure to the sun for extended periods can be harmful, yet we all enjoy sunbathing when we can. The World Health Organisation[1] (WHO) has produced a lot of literature for our benefit about the dangers of too much sun. Their ultraviolet (UV) forecast helps us to reduce the impact of UV on our health. It begins by telling us that whilst sunlight is essential for health it also carries risks.

The strength of UV varies depending on where you are in the world, the time of year and on a number of different weather factors such as the amount of cloud cover. Small amounts of UV exposure can be beneficial as it is essential in the production of vitamin D, however over exposure to UV can lead to serious health issues.

UV INDEX THROUGHOUT THE YEAR

The UV index forecast provided by the UK Met Office identifies the strength of the UV radiation from the sun at a particular place on a particular day, allowing you to take the necessary precautions to help reduce the impact of UV on your health.

The forecast is expressed as a 'Solar UV Index', a system developed by the World Health Organisation. The Met Office UV forecasts include the effects of:

  • The position of the sun in the sky
  • Forecast cloud cover
  • Ozone amounts in the stratosphere

Generally, you can interpret the UV Index as shown below, but more information about how this can affect you is given later on.

UV Index

Index

Exposure

1-2

Low

3-5

Moderate

6-7 

High

8-10 

Very High

11 

Extreme

IN THE UK

The UV index does not exceed 8 in the UK (8 is rare; 7 may occur on exceptional days, mostly in the two weeks towards the end of June), however indices of 9 and 10 are common in the Mediterranean area.

IN THE USA

The UV index values vary widely depending on where you are The example map for May 2016 (below) gives an idea of this variation.

UV Index USA May 2016

In general terms, the ratings can be interpreted as shown below.

A UV INDEX READING OF 0 TO 2 (MORE THAN AN HOUR EXPOSURE BEFORE SKIN IS DAMAGED)

Means low danger from the sun's UV rays for the average person.

  • Wear sunglasses on bright days
  • If you burn easily, cover up and use broad spectrum SPF 30+ sunscreen
  • Watch out for bright surfaces, like sand, water and snow, which reflect UV and increase exposure

A UV INDEX READING OF 3 TO 5 (SKIN DAMAGE TO BE EXPECTED AFTER 45 MINUTES EXPOSURE)

Means moderate risk of harm from unprotected sun exposure.

  • Stay in shade near midday when the sun is strongest
  • If outdoors, wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses
  • Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days, and after swimming or sweating
  • Watch out for bright surfaces, like sand, water and snow, which reflect UV and increase exposure

A UV INDEX READING OF 6 TO 7 (SKIN DAMAGE TO BE EXPECTED AFTER 30 MINUTES EXPOSURE)

Means high risk of harm from unprotected sun exposure. Protection against skin and eye damage is needed.

  • Reduce time in the sun between 10 a.m. and 4 p.m.
  • If outdoors, seek shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses
  • Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days, and after swimming or sweating
  • Watch out for bright surfaces, like sand, water and snow, which reflect UV and increase exposure

A UV INDEX READING OF 8 TO 10 (SKIN DAMAGE TO BE EXPECTED AFTER 15 MINUTES EXPOSURE)

Means very high risk of harm from unprotected sun exposure. Take extra precautions because unprotected skin and eyes will be damaged and can burn quickly.

  • Minimise sun exposure between 10 a.m. and 4 p.m.
  • If outdoors, seek shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses
  • Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days, and after swimming or sweating
  • Watch out for bright surfaces, like sand, water and snow, which reflect UV and increase exposure

A UV INDEX READING OF 11 OR MORE (SKIN DAMAGE TO BE EXPECTED IN LESS THAN 10 MINUTES)

Means extreme risk of harm from unprotected sun exposure. Take all precautions because unprotected skin and eyes can burn in minutes.

  • Try to avoid sun exposure between 10 a.m. and 4 p.m.
  • If outdoors, seek shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses
  • Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days, and after swimming or sweating
  • Watch out for bright surfaces, like sand, water and snow, which reflect UV and increase exposure

THE SHADOW RULE

An easy way to tell how much UV exposure you are getting is to look for your shadow:

  • If your shadow is taller than you are (in the early morning and late afternoon), your UV exposure is likely to be lower
  • If your shadow is shorter than you are (around midday), you are being exposed to higher levels of UV radiation. Seek shade and protect your skin and eyes

UV PROTECTION FACTOR (UPF) – FOR CLOTHING

In recent years it has been recognised that there is a need for consumers to know what protection their clothes provide against excessive UV exposure. This began in Australia where the incidence of skin cancer has reached alarming levels:

Every year, in Australia[2]:

  • Skin cancers account for around 80% of all newly diagnosed cancers
  • Between 95 and 99% of skin cancers are caused by exposure to the sun
  • GPs have over 1 million patient consultations per year for skin cancer
  • The incidence of skin cancer is one of the highest in the world, two to three times the rates in Canada, the US and the UK

In Australia, almost 14% of adults, 24% of teenagers and 8% of children are sunburnt on an average summer weekend. Many people get sunburnt when they are taking part in water sports and activities at the beach or a pool, as well gardening or having a barbeque.

Sunburn is also common on cooler or overcast days, as many people mistakenly believe UV radiation is not as strong. This is untrue – you can still be sunburnt when the temperature is cool.

Sun exposure that doesn't result in burning can still cause damage to skin cells and increase your risk of developing skin cancer. Evidence suggests that regular exposure to UV radiation year after year can also lead to skin cancer.

Generally speaking, when a garment makes a claim in respect of UPF, the values can be interpreted as shown in the table below.

UPF Range[3]

Radiation Protection Category

15-24

Good Protection

25-39

Very Good Protection

  40-50+

Excellent Protection

The above results come from testing the textile materials for the UPF which is a complex process and whilst every effort is made to give meaningful results, the materials under test can vary in colour and/or density and the conditions under which they are worn can mean a reduction in the protection they provide. For example when the fabric is stretched, the opacity can increase allowing through more radiation than the results indicate. When fabrics are wet as with swimwear, the UPF value can be affected too.

The UPF value given is normally that when the fabric is dry and unstretched so care needs to be taken when interpreting the results.

In Europe, the decision was made that a testing standard[4] was needed which closely followed the Australian standard but which allowed only those materials with a UPF value of 40 or higher to be labelled as sun protective. The proscribed labelling is shown here and together with this label, the warning that “The protection offered by this item may be reduced with use or if stretched or wet.”

Proscribed EU UPF Label

PROTECTING YOURSELF WHEN SUNBATHING

It goes without saying that the use of a suitable sunscreen on exposed skin is essential when sunbathing. However, people do forget, or perhaps are not aware, that some clothing is not giving the protection against UV radiation that might be expected, so it is necessary to put the sunscreen on even those areas covered by clothing. This is especially important with stretchy materials such as swimwear. When unstretched a swimsuit fabric may be quite opaque, but when stretched it can become a more open mesh as seen in the photomicrograph of a lady’s swimsuit fabric below and let through those harmful rays directly to skin which is unprotected.

Stretched Fabric Weave

[1] World Heath Organisation Intersun program

[2] www.cancer.org.au/about-cancer/types-of-cancer/skin-cancer.html

[3] From AS/NZS 4399

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