In 2012, a Canada-wide radon survey indicated that 6.9% of Canadian houses had radon levels which exceeded Health Canada's 200Bq/m3 limit. The 2024 Cross Canada radon survey however indicated that 17.8% of residential properties exceeded the 200 Bq/m3 guideline, nearly a 2.5 fold increase over 2012. In 2012 14000 houses were surveyed compared to 70000 in 2024. In my testing of houses In London and surrounding area, I found that 20% of houses tested were in fact over the Health Canada limit.  The simplest explanation is that radon levels in Canadian residences have increased over the past decade due in part to changing building practices, i.e. newer houses have higher levels than older houses, increased air tightness, coupled with limited or imbalanced air flow and fresh air exchange, changes in concrete used in foundations, and other factors such as soil type, and detector location.

In 2012  31% of detectors were placed below ground level and 58% were placed on a floor level above ground. In 2024, 68% were placed below ground where the highest radon levels are expected. Increased radon levels may also be due to increased energy efficiency through retrofit of older houses through federal and provincial retrofit incentive programs.

In 2024, in the Central Region (ON, QC), 16.4% of houses had an average radon level above the 200 Bq/m3 guideline and 22.9% had an average between 100 and 200 Bq/m3. The WHO (World Health Organization) maintains that levels which are at 100 Bq/m3 should be of concern because this is the level they maintain is where cancer may be initiated. In the US, the level is 148 Bq/m3

(4 PiC/L).

What about the type of residential dwelling? Does that play any role in radon exposure? Single detached houses had the highest levels with 19% above the HC (Health Canada) limits and an average of 84 Bq/m3. This was followed by semi-detached houses with an average of 60.2 Bq/m3 and with 10% above the HC limits. Row-style housing and row condos had an average of 48.9 Bq/m3 and 6.6% (1:15) exceeded the limit.  Again, in my professional testing in London and surrounding areas, I found 20% of residential houses above the 200 Bq/m3 limits. This only represents data from those who were concerned about their radon levels and wanted a test. On on small crescent  in North London, I had 4 separate houses over the 200 Bq/m3 level. All required mitigation; fortunately these houses were fairly new and fell under mitigation covered by Tarion Warranty.

                             You will never know whether you are "living with a killer in your basement" until you test!