A note before you read. This is general information for Canadian homeowners — not medical, legal, financial, or warranty advice. Radon results are reported against Health Canada's guideline of 200 Bq/m³. RadonTest.ca coordinates test-kit logistics and sample submission only; we do not interpret your results or assess your health. All analysis is performed independently by a Canadian C-NRPP-certified laboratory, and health questions belong with Health Canada and your physician.
Quick answer
For the overwhelming majority of Canadian homes, the dominant source of indoor radon is soil gas drawn in through the foundation — not granite countertops or other building materials. Granite, tile, concrete, brick and stone can emit trace amounts of radon, but their contribution to the air you breathe is typically negligible next to what seeps up from the ground. You cannot tell your radon level from the material in your kitchen — the only way to know is to test the home with a long-term detector, then compare the result with Health Canada's 200 Bq/m³ guideline.
Where household radon actually comes from
Radon is a colourless, odourless, radioactive gas that forms naturally as uranium in soil and rock decays. It is present in trace amounts almost everywhere. The problem is not radon outdoors, where it disperses harmlessly, but radon that accumulates inside a building.
Health Canada is clear about the main pathway: the ground under and around your foundation. Because the air pressure inside a heated home is usually slightly lower than the pressure in the soil, your house gently pulls soil gas — radon included — in through any opening it can find. Common entry points include cracks in foundation walls and floor slabs, construction joints, gaps around service pipes and support posts, floor drains, sump pits, and unfinished dirt floors in crawl spaces.
That pressure-driven flow is why radon tends to be highest in basements and lower levels, closest to the soil, and why two nearly identical houses on the same street can have very different readings. Soil chemistry, foundation design, and how many entry points a home has all matter far more than what your counters are made of.
The granite countertop myth — and why it persists
The idea that a granite countertop is "giving off radon" into your kitchen is one of the most stubborn radon misconceptions out there. It persists for a few understandable reasons:
- A grain of truth. Granite is an igneous rock, and some granite does contain small amounts of uranium, thorium and radium. In principle, any material containing these elements can release a little radon. "Can emit some" gets rounded up, in headlines and sales pitches, to "is dangerous."
- Scary-sounding demos. A sensitive radiation meter held against certain slabs may tick up slightly. That measures the stone at its surface — not the radon concentration in your room's air, which is what actually affects exposure.
- Marketing and confusion. Radon is invisible and unfamiliar, so a visible, tangible object like a countertop feels like a satisfying culprit. It is easier to point at a slab than at the soil you can't see.
None of this makes granite a meaningful radon source in a typical home. The trace radon a countertop might release is diluted into the whole volume of household air and is usually swamped by ordinary ventilation — and by the far larger flow coming from the ground.
What Health Canada's testing actually found
You don't have to take the reassurance on faith. Health Canada has looked at this directly. The department studied radon emanation from a range of the most popular tiles and granite countertops sold in Canada and found they added very little radon to indoor levels. In a February 2010 study of 33 types of granite commonly purchased in Canada, none were found to release significant levels of radon.
Health Canada's plain-language summary is blunt: materials used to build a house — stone, brick, cement or granite, for example — are not a significant source of radon in Canada. The primary source is, and remains, the soil the building sits on.
Do concrete, brick, stone or drywall matter?
The same logic applies to other building materials. Concrete, cinder block, brick, natural stone and gypsum drywall can all contain trace naturally occurring radioactive elements, and each can release a tiny amount of radon. In real homes, though, that contribution is generally very small compared with soil-gas infiltration. Here is a rough way to picture the relative contributions:
| Source | Can it emit radon? | Typical contribution to indoor air |
|---|---|---|
| Soil gas under/around the foundation | Yes — the main pathway | Dominant source in the vast majority of homes |
| Granite countertops / ceramic tile | Trace, varies by stone | Very small; Health Canada study found little added |
| Concrete, cinder block, brick | Trace | Usually negligible |
| Natural stone, gypsum drywall | Trace | Usually negligible |
| Private well water (some regions) | Can release radon when agitated | Minor for most homes; region-dependent |
The one caveat worth naming is well water in certain areas: water from a private drilled well can carry dissolved radon that is released into the air when you shower or run taps. Even then, for most households the airborne contribution is modest, and it is region-dependent. If you rely on a private well and have concerns, water-specific testing exists separately from the air test discussed here.
The real takeaway: test the home, not the countertop
Here is the practical point that cuts through the whole debate: you cannot predict your radon level from the materials in your home, its age, its price, or how it looks. Radon is invisible and odourless, and levels vary enormously from house to house. A brand-new home with quartz counters can test high; a century-old home with a granite vanity can test low. The material is not the variable that decides it — the soil, the foundation and the airflow are.
So the answer to "should I test my countertop?" is essentially no. The meaningful measurement is the radon concentration in the air of your living space, over time. For that, Health Canada recommends a long-term test using an alpha-track detector for at least 91 days. A long-term test is ideal during the heating season, when homes are closed up, but updated Health Canada guidance allows testing at any time of year. Place the detector in the lowest lived-in level of the home and leave it undisturbed for the full period. Where to set it down matters, so it's worth planning placement before you start.
If radon is worth understanding at all — and it is, given it's the leading cause of lung cancer in Canadians who have never smoked — see is radon dangerous? for the health context. Results are measured against Health Canada's guideline of 200 Bq/m³: at or above that level, remediation is recommended; below it, no action is recommended — though there is no threshold below which radon carries zero risk, so lower is always better.
FAQ
Do granite countertops cause radon in a home? Not to any meaningful degree in typical Canadian homes. Some granite contains trace uranium and can release a little radon, but Health Canada's testing found popular granites and tiles add very little to indoor levels. The dominant source is soil gas entering through the foundation.
Should I test my granite countertop for radon? No. Testing a slab tells you little about the air you breathe. The measurement that matters is the radon concentration in your home's air over at least 91 days.
Can concrete, brick or stone raise my radon level? They can emit trace radon, but the contribution is usually negligible compared with soil-gas infiltration. They are not considered a significant radon source in Canada.
Why do people worry about granite and radon? Because granite genuinely contains small amounts of radioactive elements, and a surface radiation reading can look alarming. That surface reading is not the same as the radon concentration in your room's air.
If my countertop isn't the problem, what is? Almost always the ground. Radon-rich soil gas is pulled into the home through cracks, joints, sumps and gaps in the foundation, and it concentrates in basements and lower levels.
Does well water add radon? In some regions, a private drilled well can carry dissolved radon released into the air during showering or tap use. For most homes the airborne contribution is small and region-dependent; water testing is separate from the air test.
How do I find out my home's actual radon level? Run a long-term alpha-track test for at least 91 days in the lowest lived-in level, then compare the result with Health Canada's 200 Bq/m³ guideline.
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Sources
- Health Canada — Radon: What you need to know: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radon-what-you-need-to-know.html
- Health Canada — Radon gas: it's in your home: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/radon-your-home-health-canada-2009.html
- Health Canada — Radon: Reduction Guide for Canadians: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/radon-reduction-guide-canadians-health-canada.html
- Health Canada — Guide for Radon Measurements in Residential Dwellings (Homes): https://www.canada.ca/en/health-canada/services/publications/health-risks-safety/guide-radon-measurements-residential-dwellings.html
- Canadian Cancer Society — Radon: https://cancer.ca/en/cancer-information/reduce-your-risk/know-your-environment/radon
- Canadian National Radon Proficiency Program (C-NRPP): https://c-nrpp.ca/
Ready to get a real answer for your home?
Stop guessing about your counters and measure what matters. The RadonTest.ca radon test kit is all-inclusive: a C-NRPP-listed detector, tracked shipping both ways, analysis by a Canadian C-NRPP-certified laboratory, and an official Certificate of Analysis reported against Health Canada's 200 Bq/m³ guideline. Test the home, not the countertop.
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