Radiation is a general term that refers to any sort of energy that can travel through space either as a wave or a particle. Examples of radiation include light, radio waves and microwaves.
There are two types of radiation, which are described in more detail below:
- non-ionising radiation (low energy)
- ionising radiation (high energy)
When people talk about the dangers of radiation, they are referring to ionising radiation (see risks of radiation for more information). However, ionising radiation is only a threat to health when a person is exposed to a significantly high dose, such as after the nuclear plant disaster at Chernobyl in the former Soviet Union in 1986.
Ionising radiation actually has important medical uses - for example, X-rays are used to diagnose certain conditions, and radiotherapy is used to treat cancer. For more information, see when radiation is used in medicine.
Non-ionising radiation
Non-ionising radiation is a less powerful type of radiation. It does not usually pose a threat to human health (with the exception of very high doses that can generate heat and burn the skin).
Examples of non-ionising radiation include:
- visible light
- microwaves
- radio and radar waves
- mobile phone signals
- 'wi-fi' - wireless internet connections
Ionising radiation
Ionising radiation is a more powerful form of radiation than non-ionising radiation. It is capable of damaging living cells and, in high enough doses, poses a threat to human health.
Examples of ionising radiation include X-rays and gamma rays, which are widely used in medicine for diagnostic and treatment purposes. Gamma rays are usually more powerful than X-rays and are sometimes used to sterilise certain materials.
To date, there have been more than 200 documented cases of accidents involving lost and mishandled sources of ionising radiation, particularly for industrial purposes.
These types of incidents appear to be becoming more common as the use of ionising radiation increases around the world, including places where controls are less stringent than in the UK.
For more information, read the World Health Organization's leaflet What is ionising radiation?
Last updated: 04 October 2011
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