Radon is a Leading Cause of Lung Cancer: Learn How to Reduce the Risk

October 31, 2017

November is Radon Action Month, a good time to refresh your knowledge and consider how you can help your patients reduce their risks of exposure and related illnesses.

In this article, family physician Dr. Farhan Asrar explains why it’s important for patients to know about radon and its risks, and answers some common questions for patients and family doctors alike.

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What is radon and why should we care about possible exposure?

Radon is a colourless and odourless radioactive gas that is formed naturally from the breakdown of uranium in the soil. In homes, radon can build up to levels that can pose a health concern.Radon is the second leading cause of lung cancer and, even at levels commonly found in homes, exposure poses a risk of cancer. In Canada, 16 per cent of deaths from lung cancer are attributable to radon, accounting for approximately 3,200 deaths each year.

How does radon end up in the home?

All homes have some level of radon. Radon can enter homes through any opening which contacts the soil, including cracks or foundation gaps, and floor drains.

What are the risks of developing lung cancer related to radon exposure?

The risk of lung cancer due to radon depends on three factors: the level of radon, duration of exposure, and whether you smoke.

The current Canadian guideline for indoor radon is 200 Bq/m3. (Radon concentration is expressed in Becquerels per cubic metre (Bq/m3). An estimated 8.2 per cent of homes in Ontario have radon above these guideline levels.

The risk of developing lung cancer from exposure to radon at the Canadian guideline level (200 Bq/m3) is 2 per cent. At higher levels of exposure, the risk increases to 5 per cent. However, the combination of smoking and radon exposure increases the risk even further – to 17% at 200 Bq/m3, and to 30 per cent at 800 Bq/m3

How can we reduce the risk of illness from radon exposure?

The first thing to do is to educate yourself and your patients about radon and how to reduce the risk of exposure. Various resources, online education courses and videos are available through Health Canada.

Then, take steps to reduce the risk. For example, if you needed to give your patient another reason to quit smoking, now you have it.

Anyone concerned about their risk can test their home for radon. Radon test kits can be purchased from hardware stores or online with instructions on how to test and obtain results. (Information about detectors and testing can be found on the Take Action on Radon website.) Health Canada recommends testing continuously for a minimum of three months using a radon detector, preferably during winter when doors and windows are likely to be sealed. 

What should I do if home radon levels are higher than the guideline?

Health Canada suggests taking steps to reduce radon levels as soon as possible if test levels are above the guideline level, and recommends hiring professionals who are Canadian National Radon Proficiency Program (C-NRPP) certified to do the work.

Radon reduction methods may include sealing cracks or openings around pipes and in the foundation, and/or installing a pipe from the sub-flooring to the outside (most likely through a wall or the roof). These steps alone can reduce radon levels by 90 per cent.

Where can I and my patients find more information?

  • Health Canada maintains a dedicated radon information page on its website, including resources, pamphlets and tear-out information sheets for your patients.
  • The Take Action on Radon network, led by The Lung Association and Scout Environmental, conducts radon outreach and education during Radon Action Month.


  • Bush, K (Health Canada). Radon, is it in your patient’s homes. Presentation by Kelley Bush (Health Canada) for the CFPC AQHI Train the Trainer Project (2017)

©All Rights Reserved.  Radon.  Health Canada, 2017.    Adapted and reproduced with permission from the Ministry of Health, 2017.

Dr. Farhan M. Asrar

About the author: Dr. Farhan Asrar is Assistant Professor with the Department of Family and Community Medicine, University of Toronto, and cross-appointed with the Dalla Lana School of Public Health. He is also a trainer in the College of Family Physicians of Canada’s Train-the-Trainer Project, which is funded by Health Canada to help educate health professionals on safe environments, including climate change and health, the Air Quality Health Index, and radon.