Radon and Lung Cancer: The Numbers Every Canadian Should Know
Radon causes about 3,000 lung cancer deaths in Canada every year.
Yet almost no one talks about it. There’s no ad campaign. No alarm. No one feels sick from it today.
That’s the strange part. Radon is the second-leading cause of lung cancer in Canada, right behind smoking.
This post gives you the real numbers. How many deaths. How the risk builds.
We’ll also cover why smokers carry the most, and what your own radon level means for your odds.
The short version:
- Radon causes about 3,000 lung cancer deaths a year in Canada, roughly 16% of all lung cancer deaths.
- It’s the number one cause of lung cancer in people who’ve never smoked.
- Smokers face the biggest risk. Tobacco and radon multiply each other, not just add.
- The risk builds over years, based on your level and how long you breathe it.
- The only way to know your risk is a test. A kit costs about $35. A pro test is $99.
How many people does radon actually kill?
Radon causes roughly 3,000 lung cancer deaths in Canada each year. That’s about 16% of all lung cancer deaths in the country.
Some Health Canada estimates put the number closer to 3,300. Either way, it’s a big number for a gas most people never think about.
Let’s put it in context. Radon kills more Canadians a year than house fires.
CAREX Canada, the country’s main carcinogen tracker, lists radon as a Group 1 known human carcinogen.
So the danger is real and it’s proven. It just doesn’t look like the dangers we’re used to.
Why radon causes cancer, in plain English
Radon is a gas that seeps up from the soil. You can’t see it, smell it, or taste it.
You breathe it in. Most of it leaves on your next breath. That part is harmless.
The harm comes from what radon breaks down into. As it decays, it makes tiny solid bits called radon daughters. These stick to dust in the air.
You breathe that dust, and some of it lands deep in your lungs. Once it’s stuck there, each bit keeps decaying. Each decay fires a small burst of radiation straight at the lung tissue next to it.
Over years, those bursts damage the DNA in your lung cells. Your body repairs most of it. But some damage slips through. Over time, that can turn into cancer.
That’s the whole mechanism. No cough. No fever.
No warning. Just slow damage that adds up.
The dose matters: level times time
Radon risk isn’t yes or no. It’s a sliding scale.
Two things drive it. How high your level is. And how long you breathe it.
Health Canada and CAREX have put real numbers on this. A lifetime non-smoker living in a home at the 200 Bq/m³ action level has about a 1 in 20 chance of radon-related lung cancer.
Double the level, and the risk roughly doubles. Cut your years of exposure, and it drops. That’s why fixing a high home early matters. Every year at a lower level is a year of less damage.
Here’s the rough picture for a lifetime non-smoker.
| Your radon level | Lifetime lung cancer risk (non-smoker) |
|---|---|
| Around 100 Bq/m³ | About 1 in 40 |
| Around 200 Bq/m³ (the guideline) | About 1 in 20 |
| Around 800 Bq/m³ | About 1 in 5 |
These are estimates, not promises. But they show the pattern. The higher the number and the longer you live with it, the higher your odds.
That’s why Health Canada says to test your home and fix anything above 200 Bq/m³.
The smoker multiplier: worse than the sum
Here’s the part that surprises people most.
If you smoke, radon doesn’t just add to your risk. It multiplies it.
For a lifetime non-smoker in a home at 200 Bq/m³, the risk is about 1 in 20. For a smoker in the very same home, it jumps to about 1 in 3.
Read that again. One in three.
The two risks don’t stack politely. Tobacco damage and radon damage hit the same cells and the same repair systems. Your body can patch one. It struggles to keep up with both.
This works both ways, and that’s the hopeful part. Quitting smoking is the single biggest lever you have. Fixing your radon is the second. Do both, and you cut your risk more than either one alone.
If someone in your home smokes, radon testing isn’t optional. The smoker in a high-radon house carries the heaviest lung cancer risk of anyone, by a wide margin.
If this is your home, our post on radon and smoking’s combined risk has more.
What the Ontario research found
This isn’t just national data. Researchers have studied Ontario specifically.
A peer-reviewed study in the journal Cancer Causes & Control looked at how many lung cancers in Ontario trace back to radon.
The study’s real point was hopeful, though. Many of those cancers are preventable. Lower the radon in Ontario homes, and you prevent hundreds of lung cancers over time.
That’s the whole reason testing matters. Radon is one of the few lung cancer causes you can actually remove from your home. You can’t undo years of city air. You can fix your basement.
Ontario has real geology behind this too. Much of the province sits on uranium-bearing bedrock and glacial soil that gives off radon. For the regional picture, see our radon map of Ontario.
Radon vs other lung cancer causes
People often ask how radon stacks up. Here’s the honest ranking for causes of lung cancer in Canada.
| Cause | Rank in Canada | Can you remove it from your home? |
|---|---|---|
| Smoking | #1 | Yes, by quitting |
| Radon | #2 | Yes, by testing and mitigating |
| Second-hand smoke | Major contributor | Yes, by going smoke-free indoors |
| Asbestos | Smaller, occupational | Rarely, needs abatement |
| Outdoor air pollution | Smaller | Not really |
A few things stand out.
Smoking is number one by a mile. Nothing else comes close.
But radon is number two. And unlike outdoor air or past exposures, it’s sitting in your house right now, waiting to be measured and fixed.
That makes radon one of the most fixable lung cancer risks you have.
But a high test isn’t an emergency
This is where a lot of scary articles get it wrong.
Say you test and get 450 Bq/m³ back. That’s over double the guideline.
Don’t panic. You don’t need to move out. You don’t need to keep your kids out of the house tonight.
The harm builds over years, not hours. One more month at a high level barely changes the lifetime math.
Health Canada even publishes timelines to fix it:
- 2 years for readings between 200 and 600 Bq/m³
- 1 year for readings between 600 and 1,000 Bq/m³
- 6 months for readings above 1,000 Bq/m³
So take it seriously. Get a quote. Plan the work. But sleep tonight.
DIY vs hire a pro
You can handle a lot of this yourself. Some parts need help. Here’s the honest split.
| Task | DIY is fine | Hire a pro |
|---|---|---|
| Long-term test for peace of mind | Yes, $35 to $60 kit | Only if you want a faster answer |
| Short-term test for a real estate deal | No, the other side won’t accept it | Yes, $99 to $399 |
| Tarion warranty claim test | No, needs a certified report | Yes, from the C-NRPP directory |
| Sealing small visible cracks | Yes, with the right caulk | Only if cracks are wide or deep |
| Full mitigation system | No | Yes, fan sizing and pipe routing matter |
The honest read: a $35 long-term kit from a hardware store or Take Action on Radon works fine for most homes.
If your number comes back high, or you’re on a real estate or warranty deadline, that’s when a pro test earns its cost. Ours is $99 flat.
A working mitigation system drops radon levels by 80 to 99 percent.
Who should test first
Not every home is equal. If any of these fit you, move testing up your list.
- Someone in the house smokes or used to smoke
- A child or teen sleeps in a basement bedroom
- Your home was built after 1980 and sealed tight
- You’ve never tested, and you’ve lived there for years
- You’re buying or selling, or you have a new build under Tarion
The World Health Organization backs this up. It recommends every home be tested and calls radon a leading cause of lung cancer worldwide.
For why kids carry more of this risk than adults, read our post on radon and children.
What to do this week
You don’t need a big plan. You need three steps.
Order a test. A long-term kit costs about $35 and takes five minutes to set up. Health Canada recommends every Canadian home test at least once.
Place it right. Put it on the lowest level you spend time on. Keep it away from drafts and outside walls. Leave it for 91 days.
Act on the number. Under 100, you’re set for five years. Between 100 and 200, retest. Over 200, plan a mitigation within Health Canada’s timeline.
Want to skip the wait? A pro short-term test takes 3 to 7 days for $99. Less precise than a long-term kit, but good enough to act on.
For the full risk picture, read is radon dangerous. Every source we use is public at /sources.
Frequently asked questions
Does radon really cause lung cancer?
Yes. Radon is the second-leading cause of lung cancer in Canada, after smoking, and the number one cause in people who’ve never smoked. Health Canada and the Canadian Cancer Society both confirm it, and CAREX Canada lists it as a Group 1 known carcinogen. It’s linked to about 16% of lung cancer deaths in the country.
How many people die from radon-related lung cancer in Canada?
About 3,000 a year, by Canadian Cancer Society and Health Canada estimates. Some Health Canada figures run closer to 3,300. That’s more deaths than house fires and carbon monoxide combined, but they’re spread across decades, so radon rarely gets attention.
How long does it take radon to cause cancer?
Years, not days. There’s no acute sickness from home-level radon. The risk builds slowly as decay particles damage lung DNA over time. That’s why a high test result isn’t an emergency, and why fixing a high home early still lowers your lifetime risk.
Is radon lung cancer worse for smokers?
Much worse, because the risks multiply rather than add. A lifetime non-smoker at 200 Bq/m³ has about a 1 in 20 chance of radon-related lung cancer. A smoker in the same home faces about 1 in 3. Quitting smoking and fixing radon together cut the risk far more than either alone.
What radon level raises my cancer risk?
Any level carries some risk, and it climbs with the number. Health Canada’s action level is 200 Bq/m³. At that level, a lifetime non-smoker has roughly a 1 in 20 chance of radon-related lung cancer. The higher your reading and the longer you breathe it, the higher the odds, which is why testing and mitigating matter.
Got more questions? Our FAQ page covers the most common ones in plain English.
Authored by the Breathe Radon Free Team. Every claim is backed by a primary source. Full bibliography at /sources.
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