Without the sun there would be no life on earth. Its light, warmth and energy are fundamental to plants and animals alike. However the sun produces such an intensive light that it would be fatal without a layer of gas called ozone. Situated high in the earth’s stratosphere, the ozone acts as a sunscreen to allow safer levels of sunlight to filter through.
However, continued industrialisation, mainly in the western world, has sent clouds of toxic pollution into the atmosphere. This has eroded the ozone gases and greatly reduced its protective capacities. As a result of this we have been forced to reconsider our relationship with the sun, and protect ourselves from it.
UVA and UVB
Energy emitted by the sun is a consolidation of many layers of light, all travelling at different frequencies, like radio waves. In terms of sun protection, ultra violet light (UV) concerns us the most. When it reaches earth, UV light is divided into two frequencies: A and B.
UVA rays penetrate the skin in to the dermis. They are responsible for accelerated ageing in exposed skin, activating free radical cells that damage and degrade the collagen and elastic fibres that give skin its suppleness and elasticity.
UVA rays are also implicated in certain sun allergies – although conversely, some dry skin conditions such as psoriasis can register an improvement following controlled low level exposure to UVA. These rays can penetrate dense cloud cover, light clothing and untinted glass, and they reach the earth at a constant rate all year round and all around the earth.
UVB rays are responsible for sunburn and ultimately skin cancer, although it is exposure to low levels of UVB that aids the internal synthesis of vitamin D in the human body. These rays reach the earth at a greater rate and intensity nearer to the equator, and during the summer months.
UVB rays can be restricted by cloud cover, clothing and UV protective glass. On reaching the skin, UVB rays penetrate the epidermis. Here, melanocytes react by secreting melanin and placing it over the DNA nucleus of every skin cell in this layer. The effect of this is a visible darkening of the skin, which we think of as a sun ‘tan’.
The natural phenomenon signals that the skin is under attack and is fighting to protect itself. Western culture has come to value the sun ‘tan’ as a sign of health and vitality. What a ‘tan’ actually indicates is deep skin damage.
UVB rays are so aggressive they can cause healthy cells to mutate into ‘free radicals’. These ‘wild’ cells are incomplete at a molecular level and steal electrons from other, healthy cells. This has an accumulative, degenerative effect on the body in all sorts of ways. At its mildest level, free radicals cause the skin to age, and at their worst they trigger the kind of mutant cell behaviour that leads to skin cancers, the worst kind being malignant melanoma.
Not only does the sun promote the formation of free radicals, or abnormal cells, it suppresses the body’s defence mechanism against them. The Langerhans cells usually expel such potentially damaging cells, but they are sensitive to sunlight and desert the epidermis when they feel it under attack from UV rays. Meanwhile the P53 gene, which binds to damaged DNA and extracts it from the cells, is decommissioned by sunlight, and this further exposes your skin to extensive structural damage.