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Background radiation released by soil, rocks and cosmic rays is always in the environment.

Most of it comes from natural sources but some also comes from artificial sources.

Radioactive sources are found all around us and in our bodies.

Most radioactive background activity comes from natural sources such as:

• An isotope of carbon, Carbon-14, found in carbon dioxide in the air and in the cells of all living organisms.
• Soils and rocks containing uranium which is radioactive. These may be used for building materials. When uranium decays radon, a radioactive gas, is released.
• Cosmic rays - radiation reaching the Earth from outer space.

Human behaviour adds slightly to the background activity that we are exposed to through medical X-rays, radioactive waste from nuclear power plants and the radioactive fallout from nuclear weapons testing.

As a result, gas, living things and plants absorb radioactive materials from the soil, which are then passed along the food chain.

For example, by eating a banana which contains radioactive potassium.

As it passes along the food chain the concentration of radioactivity will increase.

The actual amount of radiation that a person is exposed to depends on where they live, what job they do and many other things.

There is little we can do about natural background radiation, although people who live in areas with a high background due to radon gas require homes to be well ventilated to remove the gas.