Updated November 2026 · Data: Health Canada Cross-Canada Survey of Radon Concentrations in Homes (2012), 2024 Cross-Canada Survey · Sources
In Health Canada’s national radon survey, 8.2% of homes tested in Ontario were above the Canadian guideline of 200 Bq/m³, and 0.9% were above 600 Bq/m³. Weighted by population, Health Canada estimated that 4.6% of people in Ontario lived in homes above 200 Bq/m³ (national figure: 6.9%). The 2024 Cross-Canada survey, which found radon levels rising across the country, estimates high radon in Central Canada: about one in six homes.
Regional results are not your home’s level. Neighbouring homes can have very different radon levels. The only way to know yours is a long-term test.
Radon by health region in Ontario
| Health region | Homes tested | Above 200 Bq/m³ | Above 600 Bq/m³ |
|---|---|---|---|
| District of Algoma Health Unit | 93 | 8.6% | 1.1% |
| Brant County Health Unit | 96 | 10.4% | 1.0% |
| Durham Regional Health Unit | 95 | 0.0% | 0.0% |
| Elgin-St. Thomas Health Unit | 92 | 7.6% | 1.1% |
| Grey Bruce Health Unit | 99 | 11.1% | 1.0% |
| Haldimand-Norfolk Health Unit | 116 | 2.6% | 0.0% |
| Haliburton, Kawartha, Pine Ridge District Health Unit | 98 | 6.1% | 1.0% |
| Halton Regional Health Unit | 102 | 4.9% | 0.0% |
| City of Hamilton Health Unit | 100 | 5.0% | 0.0% |
| Hastings and Prince Edward Counties Health Unit | 99 | 12.1% | 2.0% |
| Huron County Health Unit | 109 | 11.0% | 0.9% |
| Chatham-Kent Health Unit | 201 | 18.4% | 3.0% |
| Kingston, Frontenac and Lennox and Addington Health Unit | 99 | 11.1% | 1.0% |
| Lambton Health Unit | 176 | 8.5% | 0.6% |
| Leeds, Grenville and Lanark District Health Unit | 108 | 19.4% | 1.8% |
| Middlesex-London Health Unit | 109 | 1.8% | 0.0% |
| Niagara Regional Area Health Unit | 100 | 2.0% | 2.0% |
| North Bay Parry Sound District Health Unit | 104 | 1.9% | 0.0% |
| Northwestern Health Unit | 209 | 13.9% | 1.9% |
| City of Ottawa Health Unit | 64 | 6.2% | 0.0% |
| Oxford County Health Unit | 104 | 11.5% | 0.9% |
| Peel Regional Health Unit | 89 | 0.0% | 0.0% |
| Perth District Health Unit | 108 | 12.0% | 0.9% |
| Peterborough County-City Health Unit | 112 | 9.8% | 0.9% |
| Porcupine Health Unit | 96 | 1.0% | 0.0% |
| Renfrew County and District Health Unit | 100 | 9.0% | 1.0% |
| Eastern Ontario Health Unit | 99 | 6.1% | 1.0% |
| Simcoe Muskoka District Health Unit | 110 | 0.9% | 0.0% |
| Sudbury and District Health Unit | 97 | 5.1% | 1.0% |
| Thunder Bay District Health Unit | 108 | 12.0% | 0.9% |
| Timiskaming Health Unit | 102 | 7.8% | 1.0% |
| Waterloo Health Unit | 101 | 4.0% | 0.0% |
| Wellington-Dufferin-Guelph Health Unit | 92 | 10.9% | 2.2% |
| Windsor-Essex County Health Unit | 195 | 13.8% | 1.0% |
| York Regional Health Unit | 95 | 0.0% | 0.0% |
| City of Toronto Health Unit | 73 | 2.7% | 0.0% |
Highest shares above 200 Bq/m³: Leeds, Grenville and Lanark District Health Unit (19.4%), Chatham-Kent Health Unit (18.4%), Northwestern Health Unit (13.9%).
Radon test results by community in Ontario
The 100 Radon Test Kit Challenge, run by Take Action on Radon (a Health Canada-funded initiative), gives communities long-term 91-day alpha track tests and publishes a report for each one. These are recent results, mostly from 2019 to 2026, and are a useful local snapshot, but each is based on a limited number of volunteer homes.
| Community | Homes tested | Above 200 Bq/m³ | Report |
|---|---|---|---|
| Augusta | 50 | 22% | |
| Baden & Wilmot | 78 | 4% | |
| Cavan Monaghan | 53 | 8% | |
| Chatham-Kent | 125 | 25% | |
| Clarence-Rockland | 160 | 21% | |
| Greater Madawaska/Calabogie | 83 | 41% | |
| Kenora | 69 | 6% | |
| Leeds and 1000 Island | 75 | 24% | |
| Mallorytown/ Front of Yonge | 96 | 31% | |
| North Grenville | 90 | 24% | |
| North Kawartha | 51 | 47% | |
| Ottawa | 335 | 18% | |
| Port Colborne | 93 | 8% | |
| Renfrew County/ Pembroke | 69 | 13% | |
| St. Thomas and Woodstock | 115 | 15% | |
| Wellington County | 117 | 9% |
Highest shares above the guideline (40+ homes tested): North Kawartha (47%), Greater Madawaska/Calabogie (41%), Mallorytown/ Front of Yonge (31%).
How to test your home
- Health Canada recommends a long-term test of at least 91 days, with at least 91 days during the heating season (fall and winter), when radon levels are usually highest.
- Test the lowest level of the home where someone spends at least four hours a day.
- Long-term test kits are sold by hardware stores, online and by some health units and lung associations.
If your level is above 200 Bq/m³
The Canadian guideline is 200 Bq/m³ (about 5.4 pCi/L; the U.S. EPA action level of 4 pCi/L is about 148 Bq/m³). If your result is above 200 Bq/m³, Health Canada recommends taking corrective action to lower the level within one year, and hiring a professional certified by the Canadian National Radon Proficiency Program (C-NRPP). The most common fix is sub-slab depressurization: a pipe and fan draw radon from under the foundation and vent it outside.
Frequently asked questions
Is radon a problem in Ontario?
Yes. In Health Canada’s survey, 8.2% of homes tested in Ontario were above 200 Bq/m³, and the 2024 Cross-Canada survey found radon levels rising nationally. Any home can have high radon, so testing is the only way to know.
What is the radon guideline in Canada?
200 Bq/m³ in the normal occupancy area of a home. If a long-term test is above that, Health Canada recommends fixing the home within one year.
How do I test for radon in Ontario?
Use a long-term test kit for at least 91 days during the heating season, placed in the lowest lived-in level. If the result is above 200 Bq/m³, hire a C-NRPP certified professional.
Compare all provinces and territories: Radon in Canada.
Sources
- Take Action on Radon: 100 Radon Test Kit Challenge community reports (retrieved November 2026)
- Health Canada: Cross-Canada Survey of Radon Concentrations in Homes, Final Report (2012), Tables 1, 2, 3 and 5
- University of Calgary: 2024 Cross-Canada radon survey news release (October 23, 2024)
- Health Canada: Government of Canada Radon Guideline
- Health Canada: Guide for Radon Measurements in Residential Dwellings
- C-NRPP