Radiation is energy that moves in the form of waves or particles. This energy is emitted both inside the body and externally, through both natural and man-made processes.
All life forms emit a certain amount of radiation, with all humans, plants and animals accumulating radioisotopes as they ingest food, air and water. Some forms of radiation such as potassium-40 emit high-energy rays that can be detected using measurement systems. Together with background radiation, these sources of internal radiation add to a person’s total radiation dose.
Background radiation is emitted from both naturally occurring and man-made sources. Natural sources include cosmic radiation, radon, radiation in the body, solar radiation and external terrestrial radiation. Man-made forms of radiation are used in X-rays, cancer treatment, nuclear facilities and nuclear weapons.
In terms of the effects of radiation on health, two main forms of radiation should be considered and these include 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-rays 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.
Globally, the average exposure to ionising radiation per year is around 3 mSv, with the main sources being natural (around 80%). The remainder of exposure is to man-made forms such as those used in medical imaging techniques. Exposure to man-made forms is generally much higher in developed countries where the use of nuclear imaging techniques is much more common than in developing countries.
Examples of non-ionising radiation include visible light, microwaves, ultraviolet (UV) radiation, infrared radiation, radio and radar waves, mobile phone signals and wireless internet connections.
The main sources 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 a 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.
Occupational exposure to radiation is also a consideration in terms of protecting people’s health. Individuals exposed to radiation at work are protected by regulatory frameworks to ensure their exposure does not exceed 50 mSV per year. Instruments called dosimeters are used to check the levels of radiation employees are exposed to. Examples of occupational fields where such testing may be required include the following:
- The airline industry
- Nuclear medicine and radiology
- Industrial radiography
- Nuclear power plants and processing plants
Reviewed by Sally Robertson, BSc