Radon is a naturally occurring radioactive gas that is produced by the breakdown of uranium in soil and rock. It is colourless, odourless, and tasteless, which means it cannot be detected without testing. Health Canada identifies radon as the second leading cause of lung cancer in the country after tobacco smoke, responsible for an estimated 3,000 deaths per year in Canada. Despite this, radon remains poorly understood by most homebuyers and is inadequately addressed in a significant proportion of real estate transactions.
Realtors who understand radon and can speak to it knowledgeably are providing a genuine service that protects their clients health and demonstrates a depth of professional knowledge that most agents lack.
Where Radon Is Most Prevalent in Canada
Radon levels vary significantly across Canada depending on local geology. Health Canada has mapped radon risk zones across the country, and certain areas have consistently elevated levels. Manitoba, Saskatchewan, and parts of the Northwest Territories and Nunavut have among the highest average radon concentrations in the country. Significant portions of New Brunswick, Ontario, and British Columbia also have elevated radon risks depending on local geology.
The important point for realtors is that radon cannot be predicted by location alone. Two houses on the same street can have dramatically different radon levels depending on how each is constructed, how air circulates through the foundation, and local soil conditions. The only way to know the radon level in a specific home is to test it.
Health Canada Guidelines and What They Mean for Real Estate
Health Canada recommends that Canadians take action to reduce radon levels in their homes when radon exceeds 200 becquerels per cubic metre, which is the national guideline level. Many health professionals and testing organizations advocate for action at lower levels, and the World Health Organization recommends action above 100 Bq per cubic metre. New construction in Canada is now subject to building code requirements in many provinces that mandate radon-resistant construction techniques.
For existing homes, the question is whether the property has been tested and what the results showed. Properties where radon testing has been conducted and results are available give buyers real information. Properties that have never been tested present an unknown that buyers should be aware of and may want to address as part of their purchase decision.
Radon Testing in the Context of a Real Estate Transaction
Radon testing can be conducted as part of the home inspection process. Short-term tests using charcoal canisters placed in the lowest livable area of the home for 48 to 96 hours can provide an indication, though longer-term testing of three months or more produces more accurate results because radon levels fluctuate with weather and seasons. For buyers who want more definitive information, Health Canada recommends long-term testing with an electret ion chamber or alpha track detector.
As a realtor, your role is not to conduct or interpret radon tests. Your role is to ensure your buyer clients are aware that radon testing is an option and that in areas with known elevated risk, it is worth considering. You should also be prepared to discuss radon mitigation: the installation of a sub-slab depressurization system that vents radon from beneath the foundation to the exterior. These systems typically cost between $1,500 and $3,500 to install and are highly effective at reducing indoor radon levels when properly installed.
Disclosure Obligations and Professional Responsibility
Canadian real estate regulations generally require sellers to disclose known material defects that affect the health and safety of the occupants. Whether a known elevated radon level constitutes a material defect that must be disclosed varies by province and by the specific facts, and you should consult your brokerage legal counsel or real estate board for specific guidance in your market.
What is clear is that a realtor who is aware of an elevated radon level in a property and does not ensure that buyers have access to that information has created a professional liability exposure that could be significant if the buyer suffers health consequences from radon exposure in the property they purchased. When in doubt, the safer professional position is to ensure the information is disclosed and documented rather than to assume it does not need to be.
