Summary of Key Points:

  • Any home in Canada has the potential to contain dangerously high radioactive radon levels, just as long as it is built on the ground.
  • The following residential building types may face even higher radon levels: newer homes, single-storey homes, and homes with larger floor plans or higher ceilings. However, high radon levels can and do exist in homes that do not meet this criteria as well.
  • Working from home, making renovations that could cause radon to build up more easily, and smoking tobacco products are all examples of behaviour that increase your radon risk as well.
  • Even if none of the above apply to you, you should still test your home for radon with a long-term testing kit recommended by Health Canada. Radon maps and looking at a neighbour’s radon test results cannot indicate how much radon is in your home, since radon levels differ from one home to the next. The only way to know your personal radon level is to test. You can order the correct kind of testing kit at cost from The Evict Radon National Study.

Any home built on the ground can contain high radon levels, since radon is a gas produced when uranium and radium-containing minerals break down in the ground, and can easily enter buildings through their foundations. But there are some more individual factors that may increase the likelihood of your home containing dangerous amounts of radon, so it’s vital to understand the risk factors if you want to keep your home as free as possible from this hazardous gas.

The Evict Radon National Study is dedicated to collecting information and sharing resources that can help Canadians take steps to test their homes for radon and mitigate its presence when necessary. Below, we’ll cover some of the factors associated with particularly high radon, and explain why testing is so important—for all home types.

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Radon in the Home: High-Risk Built Environments

Specific built environments hit three risk factors for high radon levels—colloquially referred to as the “3 Cs”. These stand for:

  • Capture: some homes are built in such a way that radon is able to enter more easily.
  • Contain: certain homes have features that help prevent radon from escaping.
  • Concentrate: typically, a combination of the first two Cs results in radon levels increasing.

Here are a few factors that are associated with radon collecting more readily in homes. Remember, this is not an exhaustive list—any home in Canada can have radon accumulate to dangerous levels.

Newer Homes

More recently constructed homes in Canada have been built to be more airtight and energy efficient, which is a positive feature as this helps reduce both energy use and heating or cooling bills during the very cold or very warm months. Energy-efficient homes do not necessarily have high radon as, for example, these types of homes in many other nations (such as Sweden) typically have lower radon relative to other building types. The essential thing to bear in mind (as far as radon is concerned) is that the balance between incoming fresh air and outgoing stale air within an otherwise well-sealed and air-tight property needs to be just that—balanced.

Radon problems arise in energy efficient houses when there are imbalances between the amount of air leaving the home (too much) compared to the amount of fresh air being brought in (not enough), as this situation can create suction effects where the home essentially makes up the difference by “sucking on the ground”, increasing the likelihood of a high radon problem. The Evict Radon National Study has found, unfortunately, that Canadian homes built in the late 20th century and 21st century (so far) contain much higher average radon levels compared to those built in earlier times.

Current theories suggest that the airtight construction, together with frequently unbalanced intake and exhalation of air from the building, may contribute to the higher radon levels seen today. We stress that this is fixable, and is not a reason to avoid the many benefits of increased energy efficiency for a building.

Via Adobe Stock.

Single-Storey Homes (Bunglaows)

New homes aren’t the only property type that captures radon more easily compared to others—bungalows (or single storey homes) are also shown to have some of the highest average radon levels of any residential property type. This is for two main reasons: First, typical bungalows are designed with larger floor plans, meaning the surface area of the home that sits on top of the soil is generally larger and so has that much more area upon which to draw radon into the home.

The second reason is that, with only one storey, bungalows by their very design will have fewer overall windows, balconies, or doors compared to a typical multi-storey homes where each added floor has more points of dilution. A point of dilution is any point through which potentially high radon air within the home can be exchanged with low radon air from outside.

Larger Homes

No matter what the home type, however, the more square footage a given home has, the more of it is in contact with the ground. This can increase radon for a few reasons as well. First, bigger homes have more space where radon can rise up through the soil below and enter.

Second, larger homes require larger foundations—and for a typical concrete foundation, that likely means a larger “gap” that forms around the edges where the foundation meets the walls of the lowest level of the home. This effect is due to how concrete shrinks as it dries (the larger the concrete slab, the more it contracts), and means bigger channels through which radon from under the foundation can enter the property.

Third, bigger Canadian homes, on average, also come with higher ceilings. This creates “chimney effects” (where hot air that rises higher up creates a more powerful draw upon lower levels), which have the potential to increase average radon concentrations.

As we’ve mentioned previously, these factors can mean even higher radon in Canadian homes that are already amongst the most ‘at-risk’ globally. Even homes that do not meet these criteria have been shown to be at risk of containing harmful levels of radon. Regardless of how large your home is, what style, or how old it is, the only way you can be absolutely sure of your individual exposure is to test it for radon.

Lifestyle Factors: Behaviours, Jobs, and Activities that Can Raise Your Radon Exposure Risk

The many features of the built environment you spend your time in are important radon risk factors, but equally important to your health are your regular routines and activities within those environments, including your time spent at play and at work. Here are some lifestyle factors and behaviours that can modify the amount of radiation your lungs will absorb from the radon you experience throughout your life, thereby altering your lifetime risk of lung cancer.

Via Adobe Stock.

Working from Home

The more time you spend in an environment with high radon levels, the more radiation from radon you will absorb, and so radon will pose a greater threat to your long term health. Allowing for a typical 8 hour work day for 5 days a week, the 40 hours each week that Canadians spend breathing the air in our offices (or schools) really adds up quickly, and so matters a lot for long term health.
Many workplaces are in office buildings or places (such as outside, or in vehicles) with lower (or no) radon, either due to occupational health and safety regulation or simply how those buildings are built. However, if your workplace is also a residential property such as your own home, then the risks of radon exposure are likely to be much higher versus a more traditional indoor workplace.

As the pandemic has reshaped the traditional work space balance, and as employers are now developing work-from-home agreements, few employers in Canada consider radon exposure a significant occupational hazard. That being the case, to understand and reduce your risk, it’s important to test your home office for radon levels, and take steps to reduce radon gas if levels are found to be high. For more information, read about what to do if you find out you have high indoor radon levels.

Modernizing or Renovating Your Home

Energy efficiency is important for keeping your heating and/or cooling bills manageable and reducing your carbon footprint. However, you should also test your home’s radon levels after making many other different renovations that have the potential to affect the way air flows through your home. Examples of home renovations that may lead to a change in your indoor radon levels include:

  • Installing a new furnace or air conditioning unit
  • Developing a basement
  • Replacing, removing, or adding windows, or improving window glazing
  • Replacing, removing, or adding doors or interior walls
  • Adding, removing, or decommissioning (blocking up but not removing) a chimney
  • Adding, replacing or otherwise altering the insulation material in your roof
  • Replacing your roof with new and/or different materials
  • Adding a Heat Recovery Ventilator (HRV) to the home’s ventilation system

Via Adobe Stock.

Smoking Tobacco Products

While smoking tobacco products won’t directly alter your home’s radon level, it will combine with radon exposure to alter your overall lifetime risk of lung cancer. Smoking tobacco accounts for approximately 85% of all lung cancer deaths, and nearly 30% of cancer deaths in total—making it Canada’s leading cause of lung cancer (radon is the 2nd leading cause).

Although radon exposure and smoking tobacco are each risk factors for lung cancer on their own, smoking tobacco multiplies the risk of getting lung cancer from radon exposure considerably. You can think of it this way: it is not “1+1=2” in terms of the combined risk of lung cancer from radon and tobacco; rather it is closer to “1+1=17”—meaning that those who are experiencing both exposures are at far higher risk compared to those with single exposure.

Testing Is the Only Way to Know Your Radon Risk

Hopefully, the list above allows you to better understand the many individual-level radon risk factors that exist for Canadians, above and beyond the already considerable risk we as a nation face compared to the rest of the world.

We emphasize that radon-testing your own home and places of work, study, or play is strongly recommended, even if some of these added risk factors are not a part of your daily life. As previously mentioned, radon can exist in any Canadian household, regardless of whether or not the risk factors above are present.

Understanding how personalized radon exposure (and health risks) can be also helps explain why it is very common for radon levels to differ significantly between homes in close proximity to one another—and why making important health decisions from an over-generalized radon map (or using your neighbour’s radon test result) is not a reliable way to estimate your own risk. The only way to understand the risk radon poses to your health is by ordering a long-term test kit recommended as being reliable by Health Canada and other public health agencies.

See also:

The Evict Radon National Study provides Health Canada recommended long-term radon test kits at cost to help people across the country participate anonymously as civilian scientists in our research and help keep Canadian households safer from radon’s effects. Order your test kit here or contact us for more information. All work performed as part of The Evict Radon National Study is non-profit and for the benefit of Canadians everywhere.