Electromagnetic radiation carries energy. The higher the frequency of the radiation, the more enrgy it carries. The highest frequency, most energetic radiation are in order of decreasing energy, Gamma, X – Rays and ultraviolet rays.
Gamma and X – Rays are energetic enough to ionise atoms in your body. Ionised atoms are very reactive and can react in ways that cause mutations in your DNA. These mutations can lead eventually to cancer.
Better known to many people though, is the danger from ultraviolet radiation. Unlike Gamma and X – rays, some ultraviolet radiation from the Sun penetrates all the way to the Earth's surface. UV rays can also cause mutations, by ionising atoms and breaking the weak bonds that holds the strands of your DNA together. If the bonds reform, they can reform in ways that can lead to mutations and eventually cancer.
The human race has lived with the danger from UV for a long time, and has evolved to reduce the danger. People with dark skin are more resistant to the danger. Melanin – the chemical that gives skin a dark pigment in some people – absorbs most UV radiation before it can penetrate deep into the skin. The surface of the skin is made up of dead cells, so the radiation is prevented from reaching living cells that it could damage. People with lighter skin are more in danger because the ultraviolet radiation can penetrate to the living skin cells and cause damage there.
In the late twentieth and early twenty first century, the danger from ultraviolet radiation increased because production and release of chemical – especially CFCs – into the atmosphere resulted in the ozone layer, which absorbed virtually all ultraviolet radiation, becoming thinner and developing holes over parts of the Earth. People living in these parts experienced enhanced exposure to ultraviolet radiation and suffered an increase in the rate of skin cancer.
In fact, whenever anybody sunbathes, they are exposed to ultraviolet radiation. Sunbathers can reduce the danger by using sunscreen. Sunscreen acts in the same way as melanin, to absorb ultraviolet radiation and prevent it reaching the underlying living cells.