What is the UV Index?

You may not realise that ultraviolet (UV) radiation from the sun can still get through to your skin, whether the day is hot or cold, sunny or overcast.

There is a common misconception that UV radiation is higher when temperatures are warmer. The Ultraviolet Index (UVI) measure, launched in October 2003, makes it easier to understand when UV levels are a risk to your skin.

The UV Index is an international, scientific measure of cancer-causing radiation from the sun, developed by the World Health Organization and modified to reflect New Zealand's unique conditions.

Find the UV Index for your region today.

The dial, similar to that used by the New Zealand Rural Fire Service, has replaced the formerly used "Burn Time", which measured the risk of burning in units of minutes. It has been developed by the Cancer Society and the Health Sponsorship Council, with the help of NIWA and the New Zealand MetService.

The index not only shows whether UV levels are high or low, but, in a world first, New Zealand has linked these levels with appropriate sun behaviour. For example, where levels are extremely high at 11+, people are advised to reschedule outdoor activities for the early morning and evening, seek shade between 11am and 4pm, and reapply sunscreen regularly (see below).

UV levels and recommended behaviour

• Levels 1 & 2: The UV level is low.
  LOW - Low protection required. You can safely stay outside.
   
• Levels 3 to 5: This indicates moderate UV levels.
  MODERATE - Protection required when spending long periods in the sun.
  
  
• Levels 6 & 7: Protection is essential.
  HIGH - Protection essential. 'Slip, slop, slap and wrap.'
  
  
• Levels 8 to 10: People should take great precaution.
  VERY HIGH - Seek shade between 11am and 4pm. 'Slip, slop, slap and wrap.' Reapply sunscreen regularly.
  
  
• Level 11+: This is regarded as extreme and full protection is essential.
  EXTREME - Reschedule outdoor activities for early morning/evening. Shade is essential between 11am and 4pm. Reapply sunscreen regularly. 

By knowing when they are at risk, people can protect themselves, says Dr Judith Galtry of the Cancer Society. Up until now, many have wrongly assumed they are not at risk of UV radiation when temperatures are not so high. "But the fact is temperature and UV levels are not related," she says.

People should remember that temperature (or the heating effect) is caused by the sun's infrared radiation, while sunburn is caused by UV radiation that cannot be felt.

As MetService market manager media, Chris Stephenson, puts it, "People think because it's overcast, they can't be damaged and that's even more dangerous because they spend long periods outdoors unprotected.

"But if they check the UV Index, they will know when they are at risk."

Each year in New Zealand, more than 300 people die from skin cancer and more than 50,000 cases are diagnosed. Despite this, at the first sign of sun, most Kiwis head straight for the beach.

To do your best to protect yourself:

• Avoid the sun between 11am and 4pm
• Wear protective clothing
• Use a broad-spectrum sunscreen, SPF 30
• Apply sunscreen 15-20 minutes before going outside
• Reapply sunscreen at least every two hours, or more on perspiring, exercising or swimming
• Apply sunscreen even if it is overcast, as UV rays can pass through cloud
• Remember that reflection off water, snow and sand can cause sunburn.

You should also remember about after-sun care. In the case of sunburn, a moisturiser will not prevent peeling but will help relieve the irritation of dry, flaky skin. Pinetarsol will also reduce the itching.

Most importantly, people should monitor their freckles and moles, and immediately consult a doctor if they notice a change in size, colour, shape, height, surrounding skin, surface texture or sensation. Also see: Skin self examination

Related topics

Also see Melanoma and Sunscreens, Sun - clothing and hats

Original material adapted from Pharmacy Today, with permission. Updated February 2008 by everybody.