Radiation can be classified as ionizing or non-ionizing. Ionizing radiation has sufficient energy to remove electrons from atoms or molecules. Radiation that has enough energy to move or vibrate atoms, but not enough to remove electrons, is called non-ionizing radiation.
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Sources of radiation
Sources of naturally occurring radiation include:
- radioactive material found in rocks and soils
- cosmic radiation
- ultraviolet radiation from the sun
Radiation can also be generated by artificial sources, including:
- medical or clinical devices such as X-ray machines and ultrasound devices
- household or personal products such as microwave ovens and cell phones
- industrial or commercial equipment such as telecommunication towers and nuclear power generating stations
- nuclear fallout resulting from past military experimentation and weapons development
As unstable atoms decay, they release radiation in the form of electromagnetic waves and subatomic particles. Some forms of this radiation can detach electrons from, or ionize, other atoms as they pass through matter. This is referred to as ionizing radiation.
Sources of ionizing radiation exposure
Every day, Canadians come in contact with ionizing radiation in their living and work environments.
Canadians are exposed to naturally-occurring radiation in the environment from rocks and soil, as well as cosmic radiation from space. These sources of radiation are referred to as "background" radiation.
Ionizing radiation can also be generated from artificial sources including medical or clinical devices, such as X-ray machines and CT scanners.
Exposure levels in Canada
The average Canadian is exposed to between 2 and 3 millisieverts (mSv) of radiation annually from background radiation.
Here are a few examples of radiation levels from various sources:
- A long, cross-country air flight could expose a person to about 0.03 millisieverts of radiation
- A CT scan can expose a person to between 5 and 30 millisieverts of radiation depending on the area being scanned
- A chest X-ray could expose a patient to an estimated 0.1 millisieverts of radiation
- A dental X-ray could expose a patient to an estimated 0.01 millisieverts of radiation
- A mammogram could expose a patient to an estimated 3 millisieverts of radiation
On a daily basis, Canadians are exposed to non-ionizing radiation generated by household wiring, lighting, and electrical appliances such as microwave ovens, hair dryers, and toasters. In the workplace, common sources include computer monitors, photocopiers, fax machines, and fluorescent lights. Power lines and electric tools also a form of non-ionizing radiation. Some medical applications of non-ionizing radiation include short-wave diathermy and magnetic resonance imaging (MRI).
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