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Radon is a colourless, odourless, tasteless radioactive gas found naturally in the environment. It is released into the air during the natural breakdown of uranium in rocks and soil. Once released, radon breaks down into radioactive elements that can attach to dust and other substances in the air we breathe. It’s also a common type of radiation exposure.

  • How you’re exposed to radon

    We are exposed to radon when we breathe in contaminated air. You may be exposed to radon-contaminated air for a variety of reasons:

    • Indoor air can have high levels of radon when radon from the soil and rocks around the home seeps in and builds up in enclosed spaces that are poorly ventilated. 
    • Workplace exposure can occur from air in uranium and other underground mines that naturally have high levels of radon if proper ventilation systems are not in place. The Canadian Nuclear Safety Commission and provincial mining authorities regulate the levels of radon in these mines. Other underground workers, such as subway or tunnel workers, may also be at high risk of radon exposure.
    • Outdoor air also contains some radon. Radon levels outdoors or in the open air are usually very low (between 5 and 15 Bq/m3) since the radon gas is continuously diluted by fresh air. Because of this, radon gas is unable to build up to levels high enough to pose a health risk.
    • It’s rare, but radon can also be found in water. Radon in water can be a problem when the water is from the ground, such as from private or community wells. Radon is released from the water into the air during normal use such as showering or cooking. However, most communities get water from reservoirs or other open bodies of water where radon concentrations are very low.
  • Radon and cancer

    The International Agency for Research on Cancer (IARC) classifies radon as a known cause of cancer. Find out more about how cancer-causing substances are classified.

    Exposure to radon gas increases your risk of lung cancer. This risk depends on the level and length of exposure, as well as if you are a smoker. Lung cancer can develop after years of radon exposure. Health Canada estimates that about 16% of lung cancer deaths are related to being exposed to radon in the home. Radon exposure is the leading cause of lung cancer in non-smokers and it’s estimated that in Canada there are more than 3300 lung cancer deaths related to radon each year. If you smoke, you are at an even higher risk of developing lung cancer if you are exposed to radon.

  • Our recommendation

    Radon levels in most homes should be reduced to as low as reasonably achievable. The age of your home is not a good indicator of how high indoor radon levels could be – the only way to know how much radon is in your home is to test. 

    The Canadian Cancer Society recommends that Canadians test their homes for radon and take action to reduce high levels.

    To test your home for radon, you can purchase a test kit at some hardware stores, or online from several organizations working to reduce radon. You can also hire a certified professional to perform a test for you. Find out more about how to test for radon in your home.

    Health Canada’s radon action guideline is 200 Bcq/m3, but other jurisdictions have set different limits. The World Health Organization (WHO) recommends a limit of 100-300 Bcq/m3, and the United States has a limit of 148 Bcq/m3.

    If the level of radon is above 200 Bcq/m3, you should work with a C-NRPP certified professional to lower the levels in your home. However, even if the radon levels are below 200 Bcq/m3, you may still want to take action to lower the levels in your home.

  • Purchase a radon test kit

    The Canadian Cancer Society recommends testing your home when the weather is cold and your windows are closed using a long-term test kit.

    Your kit should be placed in the lowest lived-in level of your home and left there for at least 3 months before sending it away for analysis. Kits are small, discreet devices that collect data about the air inside your home.

    Purchase a discounted test kit here. $12 from each kit purchased will support the Canadian Cancer Society. Offer good until July 30th, 2017 - while quantities last.

    *The Canadian Cancer Society does not endorse any one specific brand of test kit.

  • Take Action

    The Canadian Cancer Society believes all Ontarians have the right to know if they are being exposed to cancer-causing substances so they can make informed decisions affecting about their health. We recommend that the Government of Ontario adopts the National Building Code guidelines regarding radon mitigation into Ontario’s Building Code and conduct a public education program on radon.



David Rex I was staying in St. John’s all by my lonesome because my wife was too sick to travel with me. Daffodil Place was my lifeline.

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