What is Radon and Where Does It Come From?

If you’re a homeowner or business owner in the Greater Toronto Area, you’ve likely heard the term “radon” mentioned in discussions about home safety and indoor air quality. But what exactly is this invisible threat, and why should Toronto residents be particularly concerned about it? As a restoration company with over 15 years of experience serving the GTA, Restoration Mate has seen firsthand the importance of radon awareness and testing in protecting your property and the health of everyone inside it.

Radon is a naturally occurring radioactive gas that you cannot see, smell, or taste, yet it poses significant health risks when it accumulates in enclosed spaces. In Ontario, radon exposure is the leading cause of lung cancer among non-smokers and is responsible for approximately 16% of all lung cancer deaths in Canada. For Toronto homeowners and businesses, understanding radon—where it comes from, how it enters your property, and what you can do about it—is an essential part of maintaining a safe and healthy indoor environment.

Understanding Radon: The Invisible Threat in Your Home

What Exactly Is Radon?

Radon is a colorless, odorless, and tasteless radioactive gas that forms naturally through the breakdown of uranium in soil, rock, and water. It’s part of the natural decay chain of uranium-238, which is present in varying concentrations throughout the earth’s crust. As uranium decays, it transforms into radium, which then decays into radon gas. This radon gas can move freely through the soil and eventually find its way into the air we breathe.

The scientific designation for this gas is radon-222, and it has a half-life of approximately 3.8 days. This means that radon atoms continuously decay into other radioactive particles called radon progeny or radon daughters. These decay products can attach to dust particles in the air, and when inhaled, they can lodge in the lungs and emit radiation that damages lung tissue over time.

Why Is Radon Dangerous?

The danger of radon lies not in the gas itself, but in its radioactive decay products. When radon decays, it produces alpha particles—a form of ionizing radiation that is highly damaging to living tissue. While radon gas can be exhaled before it decays, the solid radon decay products can stick to the lining of the lungs, where they continue to emit radiation and cause cellular damage.

Long-term exposure to elevated radon levels significantly increases your risk of developing lung cancer. According to Health Canada, radon is responsible for more than 3,000 lung cancer deaths in Canada each year. The risk is particularly elevated for smokers, as the combination of radon exposure and tobacco smoke creates a synergistic effect that dramatically increases lung cancer risk. However, non-smokers are also at considerable risk, making radon the number one cause of lung cancer among people who have never smoked.

The health effects of radon exposure are cumulative, meaning the risk increases with both the concentration of radon and the length of time you’re exposed to it. This is why radon testing is so important—you could be living or working in a high-radon environment for years without any symptoms or warning signs, all while your risk of lung cancer steadily increases.

Radon Levels in Toronto and the GTA

Toronto and the Greater Toronto Area have varying levels of radon risk depending on the underlying geology and soil composition. While some areas of Ontario have been identified as higher-risk zones, radon can be found in problematic concentrations anywhere in the GTA. The geology of Southern Ontario includes various rock formations that contain uranium, and the breakdown of this uranium contributes to radon gas production.

Health Canada has established a guideline of 200 Becquerels per cubic meter (Bq/m³) as the acceptable radon level in Canadian homes. Any reading above this level warrants remedial action to reduce radon concentrations. However, it’s important to note that there is no completely safe level of radon exposure—even levels below 200 Bq/m³ carry some risk, though the health impact is significantly reduced at lower concentrations.

Recent studies have shown that a significant percentage of homes in Ontario exceed Health Canada’s guideline, and Toronto is no exception. The only way to know your property’s radon level is through proper testing, as radon concentrations can vary dramatically even between neighboring properties.

Where Does Radon Come From and How Does It Enter Your Property?

Natural Sources of Radon in the Environment

Radon originates from the natural decay of uranium, which is present in nearly all soils, rocks, and water to some degree. The concentration of uranium varies based on geological factors, with certain rock types—such as granite, shale, phosphate, and uranium-bearing minerals—containing higher levels. In the Toronto area, the bedrock composition and soil characteristics can contribute to radon production.

The GTA sits on various geological formations, including sedimentary rocks from different geological periods. These formations can contain varying amounts of uranium, which means radon potential can differ significantly across different neighborhoods and municipalities within the greater Toronto region. Factors such as soil permeability, moisture content, and the presence of cracks or fissures in the bedrock all influence how easily radon gas can migrate through the ground and potentially enter buildings.

Water sources can also contain dissolved radon, particularly groundwater from wells that passes through uranium-containing rock. While this is less of a concern for Toronto residents who receive treated municipal water, properties in the outer GTA that rely on well water should be aware that radon can be released into indoor air when water is used for showering, washing, and other household activities.

Common Entry Points for Radon in Buildings

Radon enters buildings through openings that connect the structure to the ground. The soil beneath and around your property contains air that is typically under slightly different pressure than the air inside your building. This pressure difference, combined with the stack effect (the tendency of warm air to rise and exit through upper floors), creates a slight vacuum that draws radon-laden air from the soil into your property.

The most common entry points for radon include:

• Cracks in foundation walls and floors: Even hairline cracks can provide pathways for radon gas to enter your basement or lowest level
• Gaps around service pipes: Openings where plumbing, electrical, or utility lines enter the building create direct pathways from the soil
• Floor drains and sump pump openings: These features often connect directly to the soil or drainage systems beneath your foundation
• Construction joints: The joint where the floor meets the walls is a common weak point in foundation sealing
• Porous concrete blocks and mortar: Older foundations with block construction and deteriorating mortar can allow radon to permeate through the walls
• Crawl spaces: Homes with crawl spaces are particularly vulnerable if these spaces aren’t properly sealed and ventilated
• Well water: As mentioned earlier, properties using groundwater from wells may introduce radon through water use

In Toronto’s older neighborhoods, many homes were built before radon was recognized as a health concern, and construction methods didn’t include radon-resistant features. Even newer constructions can have elevated radon levels if they were built on uranium-rich soil or if the foundation work wasn’t specifically designed with radon mitigation in mind.

Factors That Influence Radon Levels in Toronto Properties

Several factors specific to the Toronto area can influence radon concentrations in your property:

Seasonal variations: Radon levels typically fluctuate throughout the year, often reaching higher concentrations during winter months. This occurs because Toronto’s cold winters mean homes are sealed tightly to conserve heat, reducing natural ventilation and allowing radon to accumulate. Additionally, the heating system creates stronger stack effects that can draw more radon from the soil.

Building characteristics: The age, construction type, and condition of your property all affect radon levels. Older Toronto homes with stone or brick foundations may have more cracks and gaps than newer constructions. However, newer homes aren’t immune—poor construction practices or settling can create entry points in any building regardless of age.

Lifestyle factors: How you use your property affects radon concentrations. Properties that are frequently ventilated through open windows will generally have lower radon levels than those that remain sealed. Finished basements that are used as living spaces expose occupants to potentially higher radon concentrations since basements typically have the highest levels in any building.

Surrounding development: Changes to the area around your property, such as nearby excavation or construction, can alter soil pressure and potentially affect radon entry into your building.

The Importance of Radon Testing for Toronto Homeowners and Businesses

Why Every Property Should Be Tested

Since radon is completely undetectable without specialized equipment, testing is the only way to know if your Toronto property has elevated radon levels. You cannot predict radon concentrations based on your neighbors’ test results, the age of your building, or the neighborhood you’re in—the only reliable method is to conduct your own radon testing.

Health Canada recommends that all Canadian homes be tested for radon, regardless of location or building type. This recommendation extends to commercial properties, schools, daycare centers, and any building where people spend significant amounts of time. For businesses in Toronto and the GTA, radon testing isn’t just about protecting your employees and customers—it’s also about due diligence and liability protection.

The good news is that radon testing is straightforward, affordable, and non-invasive. Long-term testing, which measures radon levels over a minimum of three months, provides the most accurate assessment of your property’s radon risk. This extended testing period accounts for seasonal variations and daily fluctuations in radon concentrations.

Understanding Radon Testing Methods

There are two primary categories of radon testing: short-term and long-term testing.

Short-term tests last from two days to 90 days and can provide a quick snapshot of radon levels. These tests are useful for initial screening or when you need results quickly, such as during a real estate transaction. However, because radon levels vary over time, short-term tests may not accurately represent your property’s average annual radon concentration.

Long-term tests run for a minimum of three months and up to one year. These tests are the gold standard for radon measurement because they account for seasonal variations and provide a more accurate picture of average radon exposure. Health Canada recommends long-term testing to make informed decisions about whether mitigation is necessary.

Both digital electronic radon monitors and passive devices (such as alpha track detectors) are available for radon testing. Professional radon testing companies in the Toronto area can provide testing equipment and analysis, or you can purchase do-it-yourself test kits from hardware stores or online retailers. If you choose to test yourself, follow the instructions carefully and ensure the test device is placed in the lowest lived-in level of your property, away from windows, doors, and high-humidity areas.

When to Test for Radon in Your Toronto Property

Health Canada recommends testing your property during the fall or winter months when radon levels are typically highest due to reduced ventilation and increased pressure differences between indoor and outdoor air. However, you can test at any time of year—the key is to conduct a long-term test that captures seasonal variations.

You should consider radon testing when:

• Moving into a new home or commercial property in the GTA
• Finishing a basement or making significant renovations that affect the lowest level
• Before listing your property for sale, to address any issues proactively
• After any construction or excavation near your property
• Periodically every few years, as radon levels can change over time
• If you’re spending more time in basement areas or converting them to living spaces

For Toronto businesses, regular radon testing should be part of your building maintenance and safety protocols, particularly if employees work in below-grade spaces.

Radon Mitigation: Protecting Your Toronto Property and Health

What to Do If Your Radon Test Results Are Elevated

If your radon test reveals levels above Health Canada’s guideline of 200 Bq/m³, don’t panic—radon mitigation systems are highly effective at reducing concentrations, often by up to 99%. The first step is to contact a certified radon mitigation professional who can assess your property and recommend the most appropriate reduction strategies.

Even if your levels are between 100 and 200 Bq/m³, Health Canada recommends taking action to reduce radon exposure, particularly if you have children or spend significant time in lower levels of your property. Remember, there is no completely safe level of radon exposure, and the risk increases with both concentration and duration of exposure.

Common Radon Mitigation Techniques

Professional radon mitigation typically involves one or more of the following approaches:

Active Soil Depressurization (ASD): This is the most effective and commonly used mitigation method. A qualified contractor installs a pipe system that draws radon from beneath the foundation and vents it safely above the roofline where it quickly dilutes in the outdoor air. A fan is used to create negative pressure beneath the foundation, preventing radon from entering the building.

Sealing cracks and openings: While sealing alone is rarely sufficient as a complete mitigation strategy, it’s an important component of any radon reduction plan. Sealing foundation cracks, gaps around pipes, and other entry points helps reduce radon infiltration and improves the effectiveness of other mitigation methods.

Improving ventilation: Increasing natural or mechanical ventilation can help reduce radon concentrations, though this is typically a supplementary approach rather than a complete solution. For Toronto’s climate, this method alone is often impractical during winter months when maintaining comfortable temperatures requires keeping the building sealed.

Sub-membrane depressurization: For properties with crawl spaces, installing a vapor barrier over the exposed earth and using a fan system to remove radon from beneath the membrane can be highly effective.

The specific mitigation approach for your Toronto property will depend on factors such as your foundation type, the current radon levels, the layout of your building, and your budget. A certified radon mitigation professional can provide a detailed assessment and recommendation.

Building Code Considerations in Toronto

While Ontario’s building code has incorporated some provisions related to radon-resistant construction in recent years, many properties in Toronto were built before these requirements existed. The current code includes requirements for rough-ins that facilitate future radon mitigation if testing reveals elevated levels, but it doesn’t mandate active radon prevention systems in all new constructions.

For property owners in Toronto and the GTA, this means that even newer homes may not have adequate radon protection, and testing remains essential regardless of when your property was built. If you’re planning construction or major renovations, consider incorporating radon-resistant features proactively—it’s far more cost-effective to install these systems during construction than to retrofit them later.

Partnering with Restoration Mate for Comprehensive Property Protection

Why Choose Restoration Mate for Your Radon Testing Needs

At Restoration Mate, we understand that protecting your Toronto property goes beyond addressing visible damage from water, fire, or mold. Indoor air quality and environmental hazards like radon are equally important to the long-term health and safety of your property and its occupants. With over 15 years of experience serving homeowners and businesses throughout the Greater Toronto Area, we’ve built our reputation on providing comprehensive restoration solutions that address both immediate concerns and long-term property health.

While radon testing and mitigation require specialized expertise, our extensive experience in property assessment and restoration positions us to help you understand how radon concerns fit into your overall property maintenance and safety strategy. We work with certified radon professionals and can guide you through the testing process, help you interpret your results, and connect you with qualified mitigation specialists when needed.

Our Comprehensive Approach to Property Health

Radon concerns often intersect with other property issues we regularly address at Restoration Mate. For example, water damage in basements can create cracks in foundations that serve as radon entry points. Mold remediation projects may reveal foundation issues that need attention to prevent both moisture and radon infiltration. When we perform restoration work on your property, we take a holistic view that considers all aspects of your building’s health and safety.

Our team is trained to identify potential pathways for radon entry during our restoration assessments. Whether we’re addressing water damage, mold growth, or fire restoration in your Toronto property, we can alert you to foundation conditions that might warrant radon testing and help you develop a comprehensive plan to protect your investment and the health of everyone who uses the space.

Taking Action: Your Next Steps for Radon Protection

Don’t wait to address radon concerns in your Toronto or GTA property. The longer you’re exposed to elevated radon levels, the greater your health risk becomes. Here’s what we recommend:

For homeowners: Schedule a long-term radon test during the fall or winter months to get the most accurate reading of your property’s radon levels. If you’ve recently completed water damage restoration, foundation repairs, or any work that affected your basement or crawl space, radon testing should be part of your post-restoration checklist.

For business owners: Incorporate radon testing into your regular property maintenance schedule, particularly if employees work in below-grade spaces. Document your testing and any mitigation efforts to demonstrate your commitment to providing a safe workplace.

For anyone with property concerns: If you’re dealing with water damage, mold issues, or fire restoration needs anywhere in the Greater Toronto Area, contact Restoration Mate. We’ll not only address your immediate restoration needs but also help you identify any related concerns—including potential radon risks—that should be on your radar.

With over 15 years of experience providing water, mold, and fire damage restoration services throughout Toronto and the GTA, Restoration Mate is your trusted partner in maintaining a safe, healthy property. We’re here to answer your questions, provide expert guidance, and connect you with the specialized services you need—including radon testing and mitigation—to protect what matters most.

Contact Restoration Mate today to discuss your property’s restoration needs and learn more about creating a comprehensive safety plan that addresses all potential hazards, from visible damage to invisible threats like radon. Your property’s health and your family’s safety are too important to leave to chance.