Exposure to Ionizing Radiation Fact Sheet
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
Health Risks from Radiation Exposure
Radiation can cause immediate health effects when there is exposure to relatively high doses (greater than 1000 millisieverts) of radiation over a very short period of time. This is known as "acute" exposure. Health effects from acute exposure can include skin redness, hair loss, radiation burns and acute radiation syndrome.
Chronic exposure to radiation at lower doses over a long period of time (years as opposed to seconds) can have long-term health effects. The most common long-term effect of chronic radiation exposure is an increased risk of cancer. The amount of radiation that the average Canadian is exposed to from naturally occurring and artificial sources is not a health concern.
Radiation Exposure from Nuclear Incident in Japan
Based on the information available, the amount of radiation reaching Canada is miniscule and does not pose a health risk to Canadians.
Current information also shows that even though there are areas of Japan outside of the evacuation zone that have elevated radiation levels, they are still well below the level at which health risks would occur.
More information on radiation levels in Japan is available on the Foreign Affairs and International Trade Canada website.
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