Radiation is energy in the form of particles or waves. Radiation is emitted naturally in sunlight and is also made by man for use in X-rays, cancer treatment, and for nuclear facilities and weapons.

Long-term exposure to small amounts of radiation can lead to gene mutations and increase the risk of cancer, while exposure to a large amount over a brief period can lead to radiation sickness. Some examples of the symptoms seen in radiation sickness include nausea, skin burns, hair loss and reduced organ function. In severe cases, exposure to a large amount of radiation can even cause death.

In terms of radiation in relation to health, two forms of radiation can be considered: non-ionising radiation (low energy radiation) and ionising radiation (high energy radiation).

As the more powerful form of radiation, ionising radiation is more likely to damage tissue than non-ionising radiation. The main source of exposure to ionising radiation is the radiation used during medical exams such as X-ray or computed tomography scans. However, the amounts of radiation used are so small that the risk of any damaging effects is minimal. Even when radiotherapy is used to treat cancer, the amount of ionising radiation used is so carefully controlled that the risk of problems associated with exposure is tiny.

Examples of non-ionising radiation include visible light, microwaves, ultraviolet (UV) radiation, infrared radiation, radio waves, radar waves, mobile phone signals and wireless internet connections.

The main source of non-ionising radiation that has been proven damaging to health is UV-radiation. High levels of UV-radiation can cause sunburn and increase the risk of skin cancer developing.

Some researchers have suggested that the use of telecommunications devices such as mobile phones may be damaging, but no risk associated with the use of these devices has yet been identified in any scientific studies.