The leading cause of lung cancer among non-smokers in Canada, radon comes from the natural breakdown of uranium in soil, rock and water that seeps into homes through any opening, breaking down in the lungs with radioactive particles that can damage lung cells and tissue.

“This can potentially lead to cancer. However, it’s not an immediate risk as it takes many years for lung cancer to potentially develop after exposure,” explains Connie Choy, air quality coordinator at the Ontario Lung Association. “There are no warning signs or symptoms that may indicate a high radon level, but people who smoke and are exposed to high radon levels have a higher chance of developing lung cancer.”

How radon enters a home

The challenge is that radon can enter a home through open contact with the ground, such as cracks in the foundation and floor or around pipes and floor drains. Levels can fluctuate based on a number of factors that include soil type, foundation condition, home design and ventilation level. It’s also more prevalent in winter than in summer. 

Locating threats

Houses tend to be more susceptible because of closer contact to the ground, whereas condominiums and apartment buildings usually only have higher concentrations up to the third floor. 

“One occupant of the home might use the furnace and air conditioning in a different way than another, so trying to estimate the radon concentration inside of a home based on location or geography is difficult, if not impossible,” says Jason Sadowski, manager of national laboratories at the Radiation Institute of Canada (RSIC).

“It’s important to get your home tested, and the only way to get rid of a radon problem is through remediation, not maintenance,”

Health Canada’s guideline for indoor radon levels is 200 Becquerels/cubic metre, and levels exceeding that require action to bring it down. There is no provincial law regulating mandatory testing in Ontario, and homeowners and real estate agents aren’t required to provide results to buyers. It’s also not possible to predict what the indoor radon concentration might be when building a home. 

“Once the house is built you have disturbed the soil conditions beneath it,” he says. “The soil beneath the slab will dry out, since rain water will no longer collect and saturate in that region. Basically, building the house has changed the dynamics of air flow throughout the soil.”

Testing and remediation

Home improvement contractor and TV personality, Mike Holmes, points out that a “stack effect” can draw higher levels of radon into different parts of the home at certain times of the year by creating a natural air vacuum where the pressure inside is less than the pressure outside. When heat rises, this effect draws radon out of the ground and into the home, making it hard to determine where it’s coming from and where it’s settled most. 

Fortunately, testing for radon is easy, though even short-term tests are between three-to-seven days with all windows and doors kept shut. Experts from the Canadian National Radon Proficiency Program (C-NRPP) can perform the test affordably, typically recommending a long-term minimum of three months. 

“It’s important to get your home tested, and the only way to get rid of a radon problem is through remediation, not maintenance,” Holmes says.