Radon Gas

What is radon gas?

Radon is a radioactive gas that is produced naturally from the gradual breakdown of uranium in rock and soil. Radon gas can move into homes and other buildings through cracks in the walls or floor of foundations, or through gaps around service pipes, window casements, floor drains, sumps and other openings. Soil gas infiltration is the most important source of radon in indoor environments. Other lesser sources can include well water and certain building materials.

You can’t see, taste or smell radon. The only way to know the level of radon in a home or other building is to test for it. Do-it-yourself test kits are available at most hardware and home improvement stores and online. Testing can also be done by a radon measurement professional.

Health Canada has established a guideline of 200 Becquerels per cubic metre (200 Bq/m3) for radon in indoor air in dwellings. A Becquerel is a measurement of radioactive decay. The World Health Organization guideline is a range from 100- 300 Bq/m3, with higher levels in the range considered acceptable if the ideal of 100 Bq/m3 cannot be met due to country-specific conditions.

Home safety for your kids' sake

What are the health risks of radon exposure?

Being exposed to high levels of radon in indoor air increases the risk of developing lung cancer.

Long-term exposure to elevated radon is the second leading cause of lung cancer after smoking, and it is the leading cause of lung cancer in non-smokers.

According to Health Canada, radon causes 16 percent of lung cancer deaths in Canada.

The risk of cancer depends on the level of radon and how long a person is exposed to those levels.

Exposure to cigarette smoke combined with high radon levels significantly increases the risk of developing lung cancer. A person who has had long-term exposure to high radon levels has a 1 in 20 chance of developing lung cancer. When long-term exposure to elevated radon occurs together with exposure to cigarette smoke, the risk of developing lung cancer increases to 1 in 3.

Lung cancer is a deadly disease. It is the leading cause of cancer death for both men and women, and accounts for more than a quarter of all cancer mortality.1 Approximately 8 out of 10 people with lung cancer will die from it. On average, 70 Canadians are diagnosed with lung cancer every day, and each day, on average, 55 die from it.2 Lung cancer is rare in children. However, the effects of exposure to carcinogenic substances, such as tobacco smoke and radon, are cumulative  - the longer a person is exposed, the greater their risk. Thus, preventing radon exposures during in childhood will reduce lifetime risk.

Research from Health Canada3 points to the importance of preventing childhood exposures to radon. A child exposed for just two years to radon concentrations of 8,000 Bq/m3 has the same risk of developing lung cancer as a person who has lived a lifetime in a home with radon concentrations of slightly above 200 Bq/m3.

Where is radon found in Canada?

Radon is found across Canada. Concentrations differ, but are usually higher in areas with more uranium in the underlying rock and soil. Health Canada conducted a Cross-Canada Survey of Radon Concentrations in Homes in 2009-2011, testing radon levels in a sample of nearly 14,000 homes. The results from this two-year study indicate that 6.9% of Canadians are living in homes with radon levels above the current radon guideline of 200 Bq/m3.

While the cross-Canada survey cannot be used to predict radon levels in an individual home or neighborhood, the results show that some jurisdictions have higher prevalence of homes likely to fall above the Health Canada guideline. In New Brunswick and Manitoba, for example, more than one in 5 homes is estimated to have radon levels above 200 Bq/m3. (The full report of the Cross-Canada Survey is available at: http://www.hc-sc.gc.ca/ewh-semt/radiation/radon/survey-sondage-eng.php).

Radon concentrations will vary from one house to another, even if they are similar and next door to each other. The amount of radon in a home will depend on many factors including:

  • Soil characteristics: Radon concentrations can vary enormously depending on the uranium content of the soil. As well, radon flows more easily through some soils than others, for example sand versus clay.
  • Construction type: The type of home and its design affect the amount of contact with the soil and the number and size of entry points for radon.
  • Foundation condition: Foundations with numerous cracks and openings have more potential entry points for radon.
  • Occupant lifestyle: The use of exhaust fans, windows and fireplaces, for example, influences the pressure difference between the house and the soil. This pressure difference can draw radon indoors and influences the rate of exchange of outdoor and indoor air.
  • Weather: Variations in weather (e.g., temperature, wind, barometric pressure, precipitation, etc.) can affect the amount of radon that enters a home.

Because there are so many factors, it is not possible to predict the radon level in a home; the only way to know for sure is to test.

How to determine the radon level in a building, and what should be done if elevated levels are found?

Residents can test their homes for radon using a do-it-yourself test kits, available from many hardware and home building supply retailers, or online. A long-term test (minimum of 3 months) conducted during the winter season when windows and doors mostly closed is recommended. The test involves placing a small passive sampler on the lowest occupied level of the home or building and leaving it undisturbed for a minimum of three months. The unit should be placed on a secure surface (e.g., bookshelf or table) located away from heating or A/C vents, windows or doors. At end of the test period, the test unit should be sealed into the envelope provided and mailed to the laboratory for processing. Results are typically returned by mail or email within a few weeks.

If the radon level is above the Health Canada guideline of 200 Bq/m3, action should be taken to lower the radon concentration. If the levels are between 200 – 600 Bq/m3, Health Canada recommends taking action within two years to reduce the radon levels. If the levels are 600 Bq/m3 or higher, mitigation should be done within a year.

There are several ways to reduce radon levels in a home or building: installing a radon mitigation system, sealing up cracks and gaps in the foundation and/or increasing ventilation.

In most cases, installing a radon mitigation system will be the most effective means of bringing radon levels down to an acceptable level. Sub-slab depressurization (also called active soil depressurization) is the most effective and reliable radon reduction technique. This method involves installing a pipe through the foundation floor slab to the exterior of the building (either the roof or an outside wall) and attaching a fan that runs continuously to draw the radon gas from below the home and into the outdoors where it is quickly diluted.

A certified radon mitigation contractor should be used to conduct a radon mitigation. To find a certified mitigator, contact the  Canadian National Radon Proficiency Program (C-NRPP) at 1-855-722-6777, the Canadian Association of Radon Scientists and Technologists (CARST) at info@carst.ca or Health Canada at radon@hc-sc.gc.ca.

It is important to retest the radon levels after the mitigation to be sure the levels have dropped below the guideline.

Comprehensive guidance on radon testing and remediation can be found in the new Health Canada publication Radon – Reduction Guide for Canadians available at http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/radon_canadians-canadiens/index-eng.php

At present, homeowners and landlords in Canada are not legally required to test for radon or to remediate if high levels of radon are found.


1 Canadian Cancer Society. http://www.cancer.ca/en/cancer-information/cancer-type/lung/statistics/?region=pe

2 The Lung Association. http://www.lung.ca/lung101-renseignez/statistics-statistiques/lungdiseases-maladiespoumon/index_e.php#lungcancer

3 Chen, J. Canadian Lung Cancer Relative Risk from Radon Exposure for Short Periods in Childhood Compared to a Lifetime. Int. J. Environ. Res. Public Health. 2013. 10, 1916-1926