Exposure to radiation

All exposures to ionizing radiation carry a risk of biological damage, although this risk decreases as the exposure decreases. For example, the risk associated with natural background radiation is very small, although elevated levels of naturally occurring radon increase the risk of lung cancer. For workers in certain industries, such as miners and medical radiographers, the risk is slightly higher. Exposure levels as a result of a nuclear or radiological emergency can vary widely, depending on the nature of the incident, the type of radiation involved, and even weather patterns.

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Dose assessment

There are a number of factors that must be taken into consideration in calculating the quantity, or dose, of radiation a person has received, including:

Radiation dose terminology

The terminology used for specifying radiation dose and its effects on the human body has been developed to account for all the factors that are important in determining its biological impact. The most frequently used dose measurements are absorbed dose, equivalent dose, effective dose, and collective dose, which are all briefly described below.

Radiation exposure limits

The Canadian Nuclear Safety Commission (CNSC) is the federal regulator of nuclear facilities and materials in Canada. It is responsible for setting radiation dose limits in order to protect workers, such as nuclear power workers and medical personnel who work with sources of ionizing radiation, from overexposure to those sources. The CNSC also sets dose limits to protect the general public from overexposure to radiation from licensed nuclear facilities or substances in Canada.

Radiation dose limits

Current Canadian dose limits for exposure to licensed sources of radiation
Population Group Dose Limits: Over Five Years Dose Limits: Annual
Worker 100 mSv 50 mSv
Public n/a 1 mSv

Health Canada's role

Health Canada supports and maintains the National Dosimetry Services and the National Dose Registry, which monitor, track, and record doses received by those who work with sources of ionizing radiation. Health Canada is also responsible for setting dose limits for emergency responders in the event of an uncontrolled release of radioactive materials.

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