What are the most common radon levels in New Brunswick basements and which regions have the highest natural radon risk?

New Brunswick has some of the highest residential radon levels in Canada, with certain regions showing average indoor concentrations well above the Health Canada action level of 200 Bq/m3. Radon is a naturally occurring radioactive gas produced by the decay of uranium in rock and soil. It seeps into basements through cracks in foundation walls and floors, gaps around pipes, floor drains, and sump pits. Because radon is colourless and odourless, testing is the only way to know your exposure level.

Health Canada's Cross-Canada Survey of Radon Concentrations found that approximately 18-20% of homes tested in New Brunswick exceeded the 200 Bq/m3 guideline, which is significantly higher than the national average of roughly 7%. Some areas of the province have concentrations measured in the thousands of Bq/m3, making radon testing before any basement finishing work an absolute necessity.

The regions with the highest natural radon risk in New Brunswick include the Fredericton area and the upper Saint John River valley, where the underlying geology contains granitic bedrock with elevated uranium content. The Sussex-Hampton corridor in the Kennebecasis River valley is another well-documented high-radon area. Parts of Charlotte County near the Bay of Fundy coast have also shown elevated readings. In these areas, it is common to find homes testing at 500-2,000+ Bq/m3 without mitigation.

The Moncton area generally has lower radon levels than the Fredericton region due to different underlying geology — the sedimentary rock and sandy/silty soils in the Moncton basin tend to produce less radon. However, pockets of elevated radon exist throughout the Greater Moncton area, and individual home results can vary dramatically even on the same street. Saint John is mixed, with some neighbourhoods showing elevated levels, particularly in areas built on rock rather than the heavy clay that characterizes much of the city.

Northern New Brunswick (Bathurst, Campbellton, Edmundston, Miramichi) has variable radon levels depending on local geology. The Bathurst mining district has mineral-rich bedrock that can produce elevated radon in some areas.

Testing is straightforward and inexpensive. A long-term test kit (placed in the lowest lived-in level for 91+ days during the heating season, October through April) costs $30-$50 and gives the most accurate annual average reading. Professional short-term testing (48 hours to 7 days using continuous radon monitors) costs $150-$300 and is useful for real estate transactions or when you need results quickly before starting renovation work.

If your test shows levels above 200 Bq/m3, a sub-slab depressurization system is the standard mitigation approach. A contractor installs a pipe through the basement slab connected to a fan that draws radon gas from beneath the foundation and vents it above the roofline. This system typically costs $2,000-$4,000 in New Brunswick and can reduce radon levels by 80-95%. The critical point for anyone planning a basement renovation is that this system is dramatically easier and cheaper to install before the basement is finished — routing the pipe and sealing the slab after walls, flooring, and a finished ceiling are in place adds cost and disruption.

Every homeowner in New Brunswick should test for radon before finishing a basement, regardless of which region they live in. The geology can vary at a hyperlocal level, and your neighbour's low reading does not guarantee yours will be low.

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