UV Rays

Everything you need to know about UV Rays

The Sun

Ultraviolet radiation emitted by the sun is composed of three wavelengths: UVA, UVB and UVC.

UVC is absorbed by the ozone layer and doesn’t reach the Earth’s surface. UVA and UVB cause tanning, burning, ageing, wrinkling and skin cancer.

UVA rays are present all year round and can penetrate glass and clouds. Thus we are exposed to large doses of UVA throughout our lifetime.

UVB intensity varies by season, location and time of day. As a general rule, the highest levels of UVB reach the UK between the hours of 10am and 4pm between April and October.


Factors affecting the intensity of UV radiation from the sun

  • Position of the sun – the higher in the sky the higher the UV level - Midday is usually when max levels occur.
  • The time of year – summer is when UV levels peak in Northern Ireland.
  • Latitude – the closer to the equator the higher the UV levels.
  • Cloud cover – heavy clouds significantly reduce UV, but thin cloud offers little or no protection.
  • Altitude – at higher altitudes the thinner atmosphere filters less UV radiation.
  • Ozone level – certain pollutants are gradually eroding the earth’s protective shield, known as the ozone layer therefore higher levels of UV radiation are now reaching the earth. Ozone levels vary throughout the year.

Remember UV Levels are not Related to Temperature

Cool bright days even with light cloud can have damaging levels of UV radiation.

Solar UV Index

The solar index tells us how much UV radiation is reaching us from the sun on any one day. During the summer months the UK weather forecasters use it to indicate how quickly we can burn  when we are outside and how careful we need to be to prevent burning. The index is represented by coloured triangles with a number in the centre. The colours range from blue through to red depending on how high a risk is posed on that day.

 

Solar Index

  Solar Index

Skin Type

1/2

3/4

5

6

7

8

9

10

11-12

white & burns

low

med

high

v.high

v.high

v.high

v.high

v.high

v.high

white & tans

low

low

med

med

high

high

high

high

v.high

brown

low

low

low

med

med

med

med

high

v.high

black

low

low

low

low

med

med

med

med

v.high


The Solar index was developed by the World Health Organisation and has a scale of 0 – 20, but in the UK and Europe it rarely rises above 10. It is a much more accurate way of determining your risk of burning than knowing the time of day or the time of year. The Solar index forecasts include the effects of:

  • The position of the sun in the sky.
  • Cloud cover.
  • The amount of ozone in the stratosphere.

The measurements are taken by the National Radiological Protection Board at six different sites in the UK and are updated each hour.

So What do the Numbers Mean?

The risk of damage to your skin can be assessed based on your skin type from the information below:


 

1- 2 Low Risk. The sun is unlikely to burn you whatever your skin type.

 


 

3- 4 Low – Medium Risk. If you have fair or sensitive skin you are at medium risk and should use adequate sun protection. Children fall into this category.

 


5- 6 High Risk. Everyone needs to use sun protection if they are outside, the recommended SPF being 15+.

  • People with black skin however are at low risk.

7+ High to Very High Risk. Everyone should cover up as well as using sunscreen regardless of his or her skin colour.


10 Very High Risk.

  • People with white skin are at a very high risk.
  • People with brown skin are at medium to high risk.
  • People with black skin are at medium risk.