Managing exposure to ionizing radiation

On this page:

• Exposure to ionizing radiation
• Managing radiation exposure
• Examples of exposure management and responsible authorities

Exposure to ionizing radiation

Everyone is exposed to ionizing radiation all of the time. Sources include naturally occurring radioactivity from rocks and soil, cosmic rays and, to a very small extent, human activities. This is called background radiation and it varies across Canada, depending on factors such as local geology and altitude. Other factors that can contribute to an individual’s exposure level, or “dose,” include their job, medical diagnostics and treatments, and air travel. For most Canadians, the biggest single source of exposure is radon.

Managing radiation exposure

Radiation protection is about managing exposure so that people, animals, and the environment are protected from the harmful effects of radiation.

Authorities set levels, expressed in terms of radiation dose over a period of time (e.g. millisieverts per year (mSv/y) or activity concentration (e.g., becquerels per cubic meter (Bq/m³)). In Canada, authorities establish these levels by considering international recommendations from organizations such as the International Commission on Radiological Protection and the International Atomic Energy Agency.

Examples of exposure management and responsible authorities

The following settings are subject to exposure management in Canada, either by regulation or voluntary guidelines:

• Licensed nuclear facilities and activities: Criteria for occupational and public exposure, including dose limits, are established by the Canadian Nuclear Safety Commission (CNSC) in the Radiation Protection Regulations and supporting documents. The Radiation Protection Regulations also require that occupational doses for Nuclear Energy Workers be reported to the National Dose Registry.
• Occupational exposure to sources not licensed by the CNSC: Provinces and territories may set limits on occupational doses from sources such as X-ray imaging devices used in a medical setting, or from industrial practices that increase occupational exposure from naturally occurring radioactive materials (NORM). The Federal-Provincial-Territorial Radiation Protection Committee provides recommendations for dose limitation for NORM industries in the Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM).
• Radon: Exposure to radon at home is the largest contributor to radiation dose for most Canadians. Health Canada recommends that all Canadians test their homes, workplaces, and public buildings for radon and take action when the average annual concentration exceeds 200 Bq/m³. More information on radon and how to protect yourself is available through Take Action on Radon.  
• Radioactivity in drinking water: Health Canada publishes Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Radiological Parameters, which is prepared in collaboration with the Federal-Provincial-Territorial Committee on Drinking Water.
• Nuclear emergencies: Provincial and territorial response organizations establish dose-based action levels to support decision-making in an emergency situation. These align closely with the recommendations in the Generic Criteria and Operational Intervention Levels for Nuclear Emergency Planning and Response, which was developed by Health Canada in collaboration with federal and provincial/territorial response organizations and stakeholders.