Radon Levels by Province: Canada's Highest-Risk Areas (and How to Test)

Radon is a naturally occurring radioactive gas. It forms as uranium in soil and rock breaks down, and outdoors it disperses harmlessly into the open air. The trouble begins when it seeps into an enclosed space — through foundation cracks, sump openings, gaps around pipes — and accumulates in the lowest levels of a home, where you can't see, smell, or taste it.

Over years of exposure, that buildup matters. Radon is the second leading cause of lung cancer in Canada after smoking, and it is the number-one cause among people who have never smoked. Health Canada attributes about 16 per cent of lung cancer deaths in the country to radon, which works out to more than 3,200 deaths every year. Those are sobering figures, and they are exactly why the gas is worth a few minutes of your attention.

The reassuring flip side is that radon is both measurable and reducible. Unlike many household health concerns, this one has a clear guideline, a straightforward test, and a proven fix. If you want the full picture of how radon behaves and what it does inside a home, our complete homeowner's guide to radon in Canadian homes covers the science in depth. For this article, the goal is narrower and more practical: figure out where your region lands, and what to do about your own four walls.

The most detailed province-by-province picture we have comes from Health Canada's Cross-Canada Survey of Radon Concentrations in Homes, which collected long-term measurements from nearly 14,000 homes across the country. The table below ranks each province and territory by the share of tested homes that came back above Canada's 200 becquerels-per-cubic-metre guideline — the level at which Health Canada recommends taking action. (A becquerel per cubic metre, or Bq/m³, is simply the unit used to measure how much radon is in the air.)

Source: Health Canada, Cross-Canada Survey of Radon Concentrations in Homes. Figures are the share of tested homes above the guideline, not population-weighted estimates. *Nunavut's 0% reflects a very small survey sample — read it as "lowest measured," not "no risk."

Two things are worth understanding before you read your own row. The first is what "per cent above 200" actually means: it's the proportion of homes in that survey whose long-term reading landed over the guideline, not a prediction for any single house. The second is timing. The provincial breakdown above comes from a survey conducted between 2007 and 2012, and it remains the most granular government dataset we have by province. More recent work suggests the problem is, if anything, more widespread than those older numbers implied. The 2024 Cross-Canada Survey, led by the Evict Radon National Study together with Health Canada and other partners, found that roughly 1 in 5 Canadian homes — about 17.8 per cent — now test at or above the guideline. Newer, more tightly sealed homes are part of that story, because the same construction that saves energy can also trap soil gas indoors.

Numbers in a table tell you where you rank. The geology underneath tells you why. Grouping the country by region makes the pattern easier to hold in your head — and easier to relate to your own backyard.

The Prairies

The Prairies carry some of the highest radon levels in the country, and the culprit is the ground itself: flat, uranium-bearing soils that release radon readily. Manitoba sits near the top of the national ranking, with 23.7 per cent of tested homes above the guideline, and in some parts of the province more than 40 per cent of homes tested high. Saskatchewan follows at 16.3 per cent, with the city of Regina standing out sharply — over half of surveyed homes there have come back above the guideline. Alberta is the gentler outlier of the three at 6.6 per cent, though "gentler" is relative; elevated homes turn up across the province, and far fewer Alberta homes have been tested than the risk warrants.

Atlantic Canada

Atlantic Canada is a study in contrasts shaped by bedrock. New Brunswick tops the entire national list at 24.8 per cent of tested homes above the guideline, and it also records the highest share of very-high results — 6.1 per cent of homes over 600 Bq/m³ — a reflection of the granite and uranium-rich rock beneath much of the province. Nova Scotia, with its own granite pockets, comes in at 8.8 per cent. Newfoundland and Labrador sits lower at 5.9 per cent, and Prince Edward Island posts the lowest provincial share in the country at 3.5 per cent. Even on gentle, sandy P.E.I., though, "lowest" is not "none" — about one tested home in 28 still came back high.

Central Canada

Ontario and Quebec are where the population-versus-percentage distinction matters most. Quebec's survey figure is 10.1 per cent of tested homes above the guideline, with levels varying by region as the underlying bedrock changes. Ontario's provincial number looks modest at 8.2 per cent, but that single figure hides a lot of local variation: 13 of the province's 36 health regions had more than 10 per cent of homes testing high. Because Ontario and Quebec are home to so many Canadians, even a "moderate" percentage translates into a very large number of houses — and the 2024 data places Central Canada at 20.2 per cent of homes above the guideline, higher than the older provincial averages suggested.

The West Coast and the Interior

British Columbia is the clearest example of why a provincial average can mislead. Province-wide, 7.9 per cent of tested homes exceeded the guideline — a comfortable-sounding number driven down by the low-radon coast. Travel inland, though, and the picture changes completely. In interior communities such as Castlegar, over half of tested homes have come back above the guideline, among the highest readings observed anywhere in Canada. If you live in the B.C. interior, your provincial average is close to meaningless; your valley is what counts.

The North

The territories round out the high-risk end of the spectrum. The Yukon ranks among the most elevated jurisdictions in the country, with 19.6 per cent of tested homes above the guideline and a notable 5.8 per cent above 600 Bq/m³. The Northwest Territories is far lower at 5.4 per cent, and Nunavut recorded no homes above the guideline in the survey — though that result rests on a very small sample and should be read as encouraging rather than conclusive.

If there is one idea to carry away from the ranking, it's this: a provincial percentage describes a crowd, not your home. Radon enters through the ground directly beneath your foundation, and the amount of uranium in that specific soil — plus how your house breathes, where it cracks, and how it's heated — determines your number. That's why neighbours can test years apart and land in completely different places.

The survey itself makes the point vividly. Of the 121 health regions Health Canada measured, 112 had homes above the guideline. High radon is not confined to the "bad" provinces; it has shown up in nearly every corner of the country, including regions whose overall averages look low.

It also helps to retire a common assumption: that a newer home is a safe home. Modern, well-sealed houses can actually concentrate radon more effectively than drafty older ones, because the same airtightness that lowers your heating bill also gives soil gas fewer ways to escape. Age, price, and tidiness tell you nothing reliable about radon.

Testing is where worry turns into a number you can act on, and it's far less involved than most people expect. The single most important thing to get right is the duration. Radon levels swing day to day and season to season, so a quick snapshot can badly mislead you. Health Canada recommends a long-term test of more than 91 days, ideally run through the heating season when windows stay shut and indoor levels peak. A test measured over months reflects how you actually live in your home far better than one measured over days.

You have two credible device options, and both should carry certification from the Canadian National Radon Proficiency Program — C-NRPP — which is the mark that a device has passed Canadian performance testing. The first is a long-term alpha-track kit, usually $30 to $60, which you leave in place for the testing period and then mail to a lab for analysis. The second is a consumer-grade continuous electronic radon monitor, which Health Canada now recognizes when it meets C-NRPP standards and which gives you an ongoing on-screen reading. If you're weighing the trade-offs and cost of each route, our breakdown of DIY radon test kits versus professional radon testing walks through what you're really paying for.

Placement matters as much as duration. Put the device on the lowest level of your home that you actually use for more than a few hours a day — a finished basement, a ground-floor bedroom — and keep it away from drafts, exterior doors and windows, and sump pits, all of which can skew the reading. Then leave it alone and let it do its work.

Because the heating season is when indoor radon tends to peak, the calendar quietly shapes your testing plan. A long-term test needs at least 91 days inside that window, which means starting in the fall gives you the cleanest run before spring arrives and windows start opening again. Leave it too late and you can run out of cold-weather days before the test has gathered enough data to trust. We get into the practical timing — including the point each spring when the season effectively closes — in our look at why the radon testing season has a hard deadline. The simple rule: if you've been meaning to test, the best time to start is the next cool stretch, not "someday."

When your result comes back, comparing it to the guideline tells you what to do next. Canada's action level is 200 Bq/m³. The World Health Organization uses a more conservative reference level of 100 Bq/m³, and if you've seen American guidance, the U.S. figure of 4 picocuries per litre works out to roughly 148 Bq/m³ — useful context, but in Canada the 200 mark is the one that drives decisions.

Health Canada pairs the guideline with clear remediation timeframes. A reading under 200 means no action is needed, though it's wise to re-test every few years or after major renovations that change how your home is sealed or ventilated. A reading between 200 and 600 calls for a fix within two years. A reading above 600 — the highest-risk tier — should be addressed within one year. Worth remembering, too, is that there is no known perfectly safe level of radon; the aim is to get as low as reasonably possible, and any reduction is a genuine gain for your household.

If your number lands in the murky middle and you're not sure how seriously to take it, our guide to making sense of low, borderline, and high radon readings helps you interpret it.

A high result is unwelcome news, but it lands in the category of solvable problems — and the fix is well-established. The standard approach is active sub-slab depressurization, which is less intimidating than it sounds: a contractor runs a sealed pipe through the foundation slab and connects it to a quiet, continuously running fan that draws soil gas out from under the house and vents it safely above the roofline, before it can enter your living space.

It works, and it works dramatically. A properly installed system routinely cuts indoor radon by 80 to 90 per cent, often bringing a high reading well below the guideline. According to Take Action on Radon, a national public-education program, a typical system in an existing Canadian home costs in the range of $2,000 to $3,000 — call it about $2,500 for a straightforward installation, with larger or more complex homes running higher. For a permanent reduction in a known health risk, many homeowners find that's money well spent.

If you want to understand what drives the price up or down, our detailed look at what a radon mitigation system costs in Canada breaks it down. One firm rule applies once the system is in: always re-test afterward to confirm it brought your number down.

Cost shouldn't be the reason a high reading goes unaddressed, and for some households there's direct help. The Canadian Lung Association runs a radon mitigation grant — known as the Lungs Matter program — that provides up to $1,500 toward the cost of installing a system. It's aimed at two groups: homeowners who have been diagnosed with lung cancer, regardless of income, and low-to-moderate-income households, with thresholds that vary by province. To qualify, you'll need proof of a long-term test showing levels above the guideline, which is one more reason to test properly the first time. Our overview of who qualifies for the Canadian Lung Association radon grant and how to apply covers the details. Whether or not you're eligible for assistance, Health Canada recommends hiring a C-NRPP-certified professional for the mitigation work itself, so you know the system meets Canadian standards.