Radon in Quebec: The Silent Cause of Lung Cancer (and How to Test Your Home)

If you own a home in Quebec, there's a number you should probably know — and it has nothing to do with what your house is worth. It's the level of radon in the air you breathe inside it.

Radon is a colourless, odourless, radioactive gas that comes from the natural decay of uranium in soil and bedrock. It seeps up through foundation cracks and basement floors and builds up indoors. You can't see it, smell it, or taste it. The only way to know if your home has a problem is to test for it.

And it's worth knowing: in Canada, radon exposure is the leading cause of lung cancer after smoking, responsible for an estimated 16% of lung cancer deaths and over 3,000 deaths every year, according to Health Canada.

Why Quebec homes need to pay attention

Radon levels vary house by house — even neighbours can have very different readings — but Quebec's geology contains pockets of uranium-bearing bedrock, particularly in:

• The Outaouais region, where some of the highest radon readings in Canada have been recorded
• Parts of Montérégie and the Eastern Townships, with elevated readings in many sampled homes
• Greater Montreal, where readings vary but action-level results are not uncommon, especially in older basements

Health Canada's guideline is to take action when long-term indoor levels exceed 200 Bq/m³ (becquerels per cubic metre). The World Health Organization uses a stricter threshold of 100 Bq/m³.

How to test your home

The good news: testing is cheap and easy. You have two practical options.

Do-it-yourself long-term kit

A long-term alpha-track test kit costs around $30 to $50 CAD. You place it in the lowest lived-in level of the home (usually the basement) for at least 90 days — ideally during the heating season, when windows stay closed — then mail it back to a lab for analysis. The result is a single number representing your average indoor radon level.

Avoid relying on short-term tests (a few days) as your only data — radon levels swing dramatically with weather, season, and ventilation. A 90-day average is what regulators trust.

Hire a certified professional

For a faster or more detailed assessment, hire a measurement professional certified by the Canadian National Radon Proficiency Program (C-NRPP). Expect to pay a few hundred dollars and receive a written report with recommendations.

What if your home tests high?

Don't panic — radon problems are always fixable, and the fix is typically a one-time investment.

The standard solution is called sub-slab depressurization (SSD). A small electric fan is installed to draw radon-laden air from beneath your foundation and vent it outside through a sealed pipe, before it ever enters your living space.

• Typical cost: $2,500 to $4,000 CAD for a single-family home
• Effectiveness: most properly installed systems reduce indoor radon by 80–95%
• Operating cost: the fan runs continuously but uses minimal electricity (roughly $5–$10 per month)

Other lower-cost interventions — sealing visible cracks, improving basement ventilation — can help marginally, but SSD is what consistently brings levels safely below the guideline.

Should you test before buying a home?

It's becoming a common request, especially for older homes with finished basements. A buyer-paid 90-day test doesn't fit a normal closing timeline, but a short-term screening test (1–7 days) can be included as a contingency, with a long-term test conducted after possession. If a problem turns up, the mitigation cost can sometimes be negotiated into the purchase.

Radon is one of the only health risks in your home that you can solve permanently for a few thousand dollars. Step one is finding out where you stand.

If you've never tested, this is the cheapest piece of due diligence you can do for your home — and yourself.