Ultra Violet Radiation

Ultraviolet radiation is found naturally in sunlight. Exposure to ultraviolet radiation can cause our skin to tan. It can also cause:

• Sunburn

• Skin cancer

• Eye cataracts

• Premature ageing of the skin.

There is a public health issue about ultraviolet radiation from the Sun and sun beds. Health education programs aim to inform people about the dangers of ultraviolet radiation. We cannot see or feel ultraviolet radiation, but our skin responds to it by turning darker. This happens in an attempt to reduce the amount of ultraviolet radiation that reaches deeper skin tissues. Darker skins absorb more ultraviolet light, so less ultraviolet radiation reaches the deeper tissues. This is important because ultraviolet radiation can cause normal cells to become cancerous.

Sunscreens can reduce the damage caused by ultraviolet radiation. They contain chemicals that absorb a lot of the radiation and prevent it from reaching our skin. They may also contain chemicals that reflect some of the radiation away from the skin. Manufacturers of sunscreens make products with different sun protection factors, SPFs: the higher the factor, the longer you can stay out in the sun without burning; high factor sunscreens reduce the risks from ultraviolet radiation more than low factor sunscreens.

If, for example, you would get sunburnt after ten minutes in the sun, with Factor 5 applied you could stay in the sun for 50 minutes - or for 500 minutes with Factor 50 applied. But the real time is usually lower, because some of the sun block gets absorbed by the skin, and some gets rubbed off.

The ozone layer is the part of the upper atmosphere where ozone is found in the highest concentrations. The ozone there absorbs ultraviolet radiation, preventing most of it from reaching the ground. This is important because ultraviolet radiation can lead to skin cancer.

Near the end of the last century, scientists discovered that ozone levels over the Antarctic were reduced. This discovery was unexpected. Chemists knew that reactive chlorine atoms could destroy ozone. They also knew that chemicals called chlorofluorocarbons - CFCs - break down in ultraviolet light to release reactive chlorine atoms. Scientists used these ideas to explain the low ozone levels.

CFCs were once used widely in insulating foam and aerosol spray-cans. Once released, they gradually spread through the atmosphere, eventually reaching the ozone layer. Once there, they destroy ozone. CFCs have now been almost completely replaced by chemicals that do not cause this damage.