Radioactivity - what is radioactivity?
Radiation is a general term used to describe the emission or transfer of energy, as waves or particles, through the air or other substances. Familiar kinds of radiation are the sun's rays, microwaves used for cooking in microwave ovens, radar used to track or guide planes, and radiowaves for mobile phones.
Ionising radiation from radioactivity is caused by the disintegration of an extremely small piece of matter known as a nucleus. The nucleus is itself a constituent part of another minute particle known as an atom. All matter is made up of atoms.
There are various forms of ionising radiation depending on the nucleus and form of decay involved:
There are a number of sources of ionising radiation and all can interact with the human body to cause damage.
Possible damage to the human body by ionising radiation depends on a number of factors:
- the amount of radiation involved
- the kind of ionising radiation which the body is exposed to (alpha, beta, gamma, x-rays)
- whether the radiation source is inside or outside the body
- assuming the radiation source is inside the body, in what part of the body the source is located, how long it stays there and the type of organ which absorbs the radiation.
Properties of radiation
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ALPHA radiation has very little penetrating power. Materials that emit alpha radiation outside the body are harmless, since they are already stopped by the skin. But when these materials enter the body through inhalation or swallowing, they may be harmful.
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BETA radiation is able to penetrate further through up to 1 or 2cm of tissue. Outside the body materials that emit beta radiation may be harmful to the surface tissue of the body; when such materials enter the body, they may harm the organs in which they are present.
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GAMMA radiation penetrates even further and is able to go straight through the body. This may harm the organs in the body. X-rays are the same nature as gamma rays and can also affect the organs in the body.
Sources of radiation
Natural sources
The world in which we live is a naturally radioactive environment. All matter is made up of 92 elements some of which are naturally radioactive.
This natural radioactivity may be found in rocks, in soil, in materials used for buildings construction, in foods and liquids that we eat and drink, and in the human body itself.
Cosmic radiation, arising from the sun or other galactic bodies, also contributes to natural radiation exposure.
Man-made sources
A number of man's activities involve the use of radioactive materials. The most important of these is the use of radioactive materials for medical applications such as the diagnosis and treatment of cancer patients.
Some manufactured goods also contain small radioactive sources, e.g. smoke detectors. Energy generation - for example nuclear energy production, extraction of oil and natural gas, and burning coal - also involves the release of small amounts of radioactivity to the environment.
There is also a low level of residual radioactivity in the environment from the nuclear bomb tests of the 1950s and 1960s.
A severe nuclear accident, like Chernobyl, can add to this man-made radioactivity in the environment.
Page last modified: 10 February 2006