A new report reveals that nearly 18% of Canadian homes — or one in five — contain radon levels at or above 200 becquerels per cubic metre (Bq/m³), the threshold at which Health Canada advises action to reduce indoor radon levels.
Evidence continues to emerge showing that the number of high-radon homes across Canada has been increasing in the 12 years since the first Cross Canada Radon Report. Now, there are an estimated 10.3 million Canadians living in houses with high radon, increasing their risk of developing lung cancer in the future, says a coalition of researchers led by Aaron Goodarzi, a professor of biochemistry and molecular biology at the University of Calgary’s Cumming School of Medicine.
“Alarmingly, this report concludes that Canadians are among the most highly radon-exposed people on Earth, and that means we urgently need to address this to avoid a future of prevalent, but otherwise avoidable lung cancers,” suggests Goodarzi, who is also the Canada Research Chair for Radiation Exposure Disease.
Radon is a colourless, odourless and radioactive gas produced deep underground that forms when uranium and thorium in rocks and soil begins to break down, the report states. “Radioactive decay” changes these elements into radium, a solid radioactive metal, which breaks down further into radon gas and migrates to the surface.
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According to Health Canada, radon gas can enter buildings and homes through cracks and gaps in foundations, drains, sump pumps, etc. Levels of radon in houses can vary depending on local geology, according to the report. Other factors include when a building was constructed and how it’s ventilated. In the report, no areas of Canada were found to be free of high radon exposure risk, and all Canadians are encouraged to test where they live, the researchers said.
The report is informed by data from the 2021 Canadian census and more than 75,000 long-term radon readings from across Canada. It is funded by the Canadian Institutes of Health Research Healthy Cities Research Initiative, Health Canada, the Alberta Real Estate Foundation, and the Canadian Cancer Society.
The report notes that radon has become the second leading cause of cancer in Canada. Lifetime lung cancer risk increases by 16% for exposure to every 100 Bq/m³ of radon, the report warns. It states that the average radon level of a Canadian residential building (including single-detached, semi-detached, and row-style residential houses) is 84.7 Bq/m³.
“Canada has among one of the highest rates of lung cancer globally, despite one of the lowest rates of tobacco smoking,” says Goodarzi. “Two in five cases of lung cancer diagnosed in Canada today are of a non-tobacco origin, and one of the reasons for this is our record-high exposure to other potent causes of lung cancer such as radon within the indoor air where we live, work and play.”
There are areas of Canada where high indoor radon levels are more prevalent, including Atlantic Canada, Prairie Canada, the North, and the British Columbia Interior, the report states.
