Dave and Gerry's Alonissos Island Information Site
 

Summer Sun

The sun is what we crave when we go away on holiday to Greece and islands like Alonissos and the sun provides a feeling of well-being and the ultra violet (UV) rays trigger Vitamin D synthesis which promotes calcium absorption and protects the body from thin, brittle or misshapen bones.  However, UV rays can also trigger skin cancer, cause ageing of the skin and promote the formation of cataracts in the eyes.  A representation of the UV spectrum can be seen below.
 
 
The high energy vacuum UV, Far UV and UVC radiation is thankfully totally absorbed by the ozone layer in the stratosphere and oxygen molecules in the air.  The UVB rays are affected by atmospheric conditions and on a clear day almost all the radiation reaches the Earth's surface whereas on a cloudy day only about a third of the rays reach the surface.  All the UVA rays reach the Earth's surface.  The two forms of UV impinging on human skin have differing effects.
 
UVAThese rays penetrate deepest into the skin and can cause skin cancer.  Associated with suntans but accelerates the ageing (A=Ageing) process and in extreme cases can result in dry, scaly, wrinkled and leathery skin.
UVBThese rays have higher energy and therefore do more damage to the skin which is seen as sunburn (B=Burning).  UVB rays promote the formation of cataracts and lead to the development of skin cancers, some of which can prove fatal.
 
Peoples skin react differently in the sun depending on their skin type.  Dave has a fair complexion and burns more than tans whereas Gerry has a darker complexion and tans more than burns.  Skin types and subtypes are defined by the Reykdal-Smith System as shown in the table below:
 
Skin Type SubType Reaction to Sun
1   Always burns, never tans
2 2A  /  2B  /  2C Usually burns, tans with difficulty
3 3A /  3B Sometimes burns, sometimes tans
4   Burn minimally, always tans
5   Rarely burns, tans profusely
6   Never burns, deeply tans
 
When you buy a sun lotion it has a Sun Protection Factor (SPF) number between 0 and 50 on the package.  The larger the number the greater the protection from the harmful effects of UVB.  With no protection you will burn in the minimum time associated with your skin type.  Multiply this time by the SPF and this is the minimum burn time with the sun protection.  Note that most sun lotions DO NOT protect againgst UVA because they are formulated to allow you to tan without burning.  Also, people only put a thin layer onto their skin and so only get about one quarter of the real protection at that SPF.  The table below shows how much UVB is absorbed and how much gets through to your skin.
 
Sun Protection Factor (SPF) 50 35 20 14 12 10 8 6 4 2
UVB Blocked (%) 98 97 95 93 91.5 90 88-88 82-84 72-77 34-59
UVB Falling on Skin (%) 2 3 5 7 8.5 10 12-13 16-18 23-28 41-66
 
The most accurate way to determine the SPF you need is to know the UV Index (UVI) figure which relates to the intensity of the sun.  This can be obtained from weather programmes and in newspapers during the summer time.  The index scales from 0 - 15 but the upper reading is normally shown as 10+.  From the table below you can determine the minimum time in the sun before burning if you know your skin type and the UVI for any day.  
 
 Time To Sunburn for Skin Types 1 - 6 and Subtypes  (Minutes)
1
2
3
4
5
6
UVI Value  
A
B
C
A
B
     
1 - Minimal Exposure Level
90
126
168
210
252
306
366
432
504
3 - Low Exposure Level
30
42
56
70
84
102
122
144
168
6 - Moderate Exposure Level
15
21
28
35
42
51
61
72
84
9 - High Exposure Level
12
16
21
27
32
39
46
54
63
12 - Very High Exposure Level
8
10
14
18
21
26
31
36
42
 
When on holiday on Alonissos our advice to you is as follows:
  • Use at least a factor 15 suncream and apply liberally 20-30 minutes before exposure
  • Avoid being in the direct sun between midday and 4pm in the afternoon
  • Always wear a wide-brimmed hat in the sun to avoid sunstroke
  • Drink plenty of water and put salt on food to stop dehydration and sodium depletion
  • Sit in the shade because the sun will always find you
  • Wear sunglasses to protect from the harmful UV rays on your eyes
  • Cover up where possible because fabrics have more sun protection than sun creams
Hopefully this information will keep you happy and healthy during your stay on the island of Alonissos.
 
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