RADON: Invisible, Odourless, Tasteless and Undetectable

how radon gas enters your home through the ground

Aside from a laundry room and storage, basements are used predominantly as living spaces – an apartment, a family room, a playroom for the children, an office or an exercise room. 

When radon gas is released from the ground into the outdoor air it is not a concern, however, when it is released in an enclosed space like the basement of a house, it can accumulate to high levels of toxicity posing a health risk for you and your family.

how radon gas enters your home through the ground

If your home does not have a basement and the ground floor is in contact with the earth, has a crawl space or built slab-on grade - this article concerns you too.

What are the Health Risks?

When radon is inhaled, it breaks down into radioactive elements and emits alpha particles that are absorbed by lung tissue, which can result in cell death or damage. The risk of developing lung cancer from radon depends on the concentration of radon in the air and the length of exposure. 

For smokers, the combination of smoking and exposure to radon can significantly increase the risk of lung cancer. 

The World Health Organization (WHO) estimates that radon causes up to 15% of lung cancers worldwide.  Radon is responsible for approximately 2,900 lung cancer deaths annually in Canada and about 21,000 deaths in the US.

Recent studies by the WHO confirmed that lung cancer risk extends to radon levels well below the current standards in North America and Europe.  Health Canada recommends that all homeowners test their homes for radon gas in the interest of their family's safety. 

Radon exposure is linked to roughly 16% of lung cancer deaths in Canada, and is the second leading cause of lung cancer after smoking.

Aside from lung cancer, there is no evidence that radon exposure causes other harmful effects, i.e. forms of cancer, respiratory diseases such as asthma, or symptoms of persistent coughing or headaches.


What are the Health Risks for Children?

“Using data from a number of radon surveys, it was assessed that on average, radon progeny concentrations in Canadian homes are about three times higher than in school buildings, 4.7 times higher than in public buildings and indoor workplaces, and 12 times higher than in outdoor air.  Canadian statistics show that most Canadians spend about 70% of their time indoors at home, 20% indoors away from home and 10% in outdoors.  Due to relatively higher radon concentration in residential homes and longer time spent indoors at home, the exposure at home contributes to 90% of the radon-induced lung-cancer risk,” states Jing Chen in the article, “Risk Assessment for Radon Exposure in Various Indoor Environments” published by Oxford Academic in January 2019.

children in basement playroom

Jing Chen states that if a child lived in a home with a very high radon concentration of 2,000 Bq/m3 for four years, the Lifetime Relative Risk (LRR) is equivalent to a lifetime radon exposure of 100 Bq/m3 and the risk is about 50% higher than the baseline, lung cancer risk of people that have never smoked.

The equivalency of lifetime risk between short periods with high exposure in childhood and lifetime constant exposure clearly supports the Canadian Radon Guideline recommendation that the higher the radon concentration, the sooner remedial measures should be taken. 

Jing Chen, Head of Radiological Impact Section of the Radiation Protection Bureau for Health Canada authored several technical notes, one of which is entitled, "Canadian Relative Risk from Radon Exposure for Short Periods in Childhood Compared to a Lifetime" published in the International Journal of Environmental Research and Public Health.

Dr. Jing Chen is a member of Canadian Radiation Protection Association, Radiation Protection Dosimetry, Radiation Environmental Biophysics, advisor to the United Nations Scientific Committee on the Effects of Atomic Radiation, the Radioactivity Expert Group, Arctic Monitoring and Assessment Programme (AMAP), and Expert Group on Radiological Protection Science, OECD Nuclear Energy Agency's Committee on Radiation Protection and Public Health (CRPPH).

bedroom in basement

How does radon enter a house?

Radon enters a house when there is direct contact with the ground, regardless if you have a basement, a crawl space or if your home is built slab-on grade.

Radon is a radioactive gas that occurs naturally when uranium in soil and rock breaks down.  Air pressure inside your home is usually lower than in the soil surrounding the foundation of your home.  Things like the use of air exchangers, exhaust fans and clothes dryers cause the difference in pressure.  When air is pushed out of the house, outside air is pulled back in to replace it and much of the replacement air comes from the ground surrounding the house bringing gases such as radon with it.  Radon enters your home in any opening where your home contacts the soil, such as: 

how radon gas enters the house
  • cracks in the foundation walls and in floor slabs
  • dirt floors
  • construction joints
  • gaps around service pipes
  • support posts
  • window casements
  • floor drains
  • sumps, and
  • cavities inside walls


Drinking water that contains radon is far less harmful than breathing radon. 

When the ground produces radon, it can dissolve and accumulate in water from underground sources, such as wells.  When radon in water is agitated by daily household use, it escapes from the water and goes into the air.  Health risks are not from ingestion but from radon inhalation.

crack in the foundation

Radon concentrations fluctuate seasonally, but are usually higher in winter than in summer, and are usually higher at night than during the day because the sealing of buildings (to conserve energy) and the closing of doors and windows (at bedtime), reduces the intake of outdoor air which allows the build-up of radon.

Radon Levels in Canada

Concentrations of radon are usually higher in areas where there is a greater amount of uranium in underlying rock and soil.  Almost every home in Canada has some amount of radon and levels will vary from one home to another even if they are next to each other.  A small percentage of homes will have radon levels above the guideline and the ONLY way to be sure is to perform a test.

The current Canadian guideline for radon in indoor air for homes is 200 Becquerels per cubic metre (200 Bq/m3) which was reduced from 800 Bq/m3 based on new information about potential health risks.  The Becquerel is the unit scientists use to measure the number of radioactive decays of radon atoms.  One Becquerel corresponds to one disintegration per second.

While the international community uses the Becquerel per cubic meter of air (Bq/³) measurement, the USA uses the picocurie per litre to measure radon.  One pCi/L is equivalent to 37 Bq/m³.

In 2012, Health Canada performed approximately 14,000 radon tests in homes across the country and found that over 1,500 homes (about 7%) had radon levels above the guideline.  

The five highest radon values were found in:

Armstrong Station, Ontario (5,657 Bq/m3)

Bas-Paquetville, New Brunswick (5,590 Bq/m3)

Sparwood, British Columbia (2941 Bq/m3)

Gaspé, Quebec (2,923 Bq/m3)

Gooderham, Ontario (2,741 Bq/m3).

inhaling radon gas

World Health Organization (WHO) Launches International Radon Project

In an effort to reduce the rate of lung cancer around the world, WHO launched an international radon project to increase awareness, collect data and encourage action to reduce radon-related risks.  The U.S. Environmental Protection Agency is one of several government agencies and countries supporting this initiative and is encouraged by WHO's attention to this important public health issue.

WHO recommends the guideline of 100 Bq/m3 for all countries.

"Radon poses an easily reducible health risk to populations all over the world, but has not up to now received widespread attention," said Dr. Michael Repacholi, coordinator of WHO’s Radiation and Environmental Health Unit. 

"Radon in our homes is the main source of exposure to ionizing radiation, and accounts for 50% of the public’s exposure to naturally-occurring sources of radiation in many countries."

How Can You Reduce the Level of Radon in Your Home?

You can reduce the level of radon by using methods that are affordable, practical and with regular maintenance, may in fact protect the value of your home.  If radon in your home is above the allowable 200 Bq/m3, take the following steps to reduce the level:

home safety
  • Ventilate the basement sub-flooring by installing a small pump that will draw the radon from below the concrete slab to the outside before it can enter your home (commonly known as Sub Slab Depressurisation and typically performed by a Contractor).
  • Increase the mechanical ventilation via a Heat Recovery Ventilator (HRV) to allow an exchange of air.
  • Seal all cracks and openings in foundation walls and floors, and around pipes and drains.

The cost for radon reduction are typically from $500.00 to $3,000.00 depending on the size and design of a home and the work that his required.

The standard method for reducing radon in a home is called 'active soil depressurization', which is usually completed by a contractor.  A pipe is installed through the foundation floor and is connected to the outside.  A fan attached to the pipe draws radon from under the home, before it gets inside, and releases it outside, where it is diluted.

In 2010, new National Building Codes were introduced to protect people against radon.  These new codes require new homes to have a vapour barrier to reduce the entry of radon.  They also require a 'rough-in' for a radon reduction system, which will significantly lower costs if action has to be taken later to reduce radon levels in the home.

How Do You Test Your Home for Radon?

test your home for radon gas

You can test your home for radon by purchasing a do-it-yourself kit or by hiring a certified radon mitigation professional from an accredited organization that will conduct a long-term test for a minimum of three months.

All measurements should be made in the lowest level of the house (usually the basement), that is used or occupied for more than four hours per day.

For some people the lowest level of the house is the ground level of the house.  Potential measurement locations include family rooms, living rooms, dens, playrooms and bedrooms.  A lower level bedroom is preferred because people generally spend more time in their bedrooms than in any other room in the house.  Similarly, if there are children in the house, the lowest level bedrooms or other areas such as a playroom are preferred.

The two most common types of radon detectors used for testing houses are short term and long-term detectors. The short-term detectors are used for a period of 2-7 days and the long-term detectors can be used for a period of 1 to 12 months. Since the radon concentration inside a house varies over time, measurements gathered over a longer period of time will give a more accurate indication of the radon level in a house.  Health Canada recommends that houses be tested for a minimum of 3 months, ideally between September and April when windows and doors are typically kept closed. 

If you intend on conducting the radon test yourself read the manufacturer's instructions and follow the guidelines listed below when placing a radon detector in your home:

  1. Make the measurement in the lowest lived-in area of your home where you or family members spend four or more hours per day.
  2. Avoid taking measurements in the kitchen. The exhaust fan as well as humidity and airborne particles from cooking may affect the accuracy of some types of radon detectors. Do not take measurements in the washroom because little time is spent there.
  3. Place the detector where it will not be disturbed during the measurement period and avoid small-enclosed areas, such as a cupboard or closet.
  4. Do not place the detector close to an outside wall or near a sump or floor drain.
  5. Avoid placing the detector in drafts from heating or air conditioning vents, near windows or doors, or sources of heat, such as stoves, fireplaces or strong sunlight.
  6. Place the detector a minimum of 50cm from any floor, wall or ceiling and more than 20cm from all other objects.

Where Can You Purchase a Radon Test Kit?

Radon test kits are relatively simple to use and can be purchased on the internet or at home improvement retailers across Canada.  The radon test kit includes instructions on how to set up the test and how to send it back to a lab for analysis once the testing period is over.  The kits range from $25.00 to $75.00. 

For more information on do-it-yourself radon test kits, contact Health Canada's Radiation Protection Bureau at radon@hc-sc.gc.ca or 613-946-6384.

Health Canada recognizes the certified Canadian National Radon Proficiency Program (C-NRPP), offered through the American Association of Radon Scientists and Technologists (AARST).




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