Why We Cannot Rely on Radon Maps

What are Radon Maps?

Radon maps, like the EPA's Map of Radon Zones, are designed to estimate where radon levels are most likely to be high across the United States. These maps divide areas into three zones:

• Zone 1: Predicted average indoor radon levels > 4.0 pCi/L (high risk)
• Zone 2: Predicted average levels between 2.0 and 4.0 pCi/L (moderate risk)
• Zone 3: Predicted average levels < 2.0 pCi/L (low risk)

Health Canada divides their zones by the percentage of homes that are higher than 200 Bq/m³:

• 10% or higher
• 1-10%
• <1%

At first glance, these maps seem like a helpful tool—but they don't tell the full story. According to the 2024 Cross-Canada Radon Report, “There are no areas of Canada that are radon free.”

The Limitations of Radon Maps

1. Radon maps can become outdated

EPA's radon map was developed in 1993, using data from the early 1990's. In the decades since, building codes, construction methods, and populations patters have changed significantly—but the map hasn't.

Radon levels can shift over time due to:

• New residential developments
• Soil disturbances from construction
• Changing weather patterns
• Renovations and HVAC changes in home
• Updates to energy efficient construction techniques

Yet, the U.S. maps haven't evolved to reflect these dynamic factors, making them an outdated reference for modern homes.

Since their last report in 2012, the 2024 Cross-Canada Radon Report found that 17.8% of Canadian homes have radon at or above the 200 Bq/m³ limit compared to 6.9% of homes in 2012. This 250% increase can be attributed to airtight and energy efficient building construction and building retrofits over the last 12 years that causes radon to become trapped within homes.

2. Maps only reflect tested homes and not all homes

Radon maps only reflect the homes that have actually been tested for radon. Most homes in the U.S. and Canada have never been tested.

That means the maps are biased on limited, incomplete data, often skewed by:

• Homeowners who were already concerned about radon
• Homes in areas with higher radon awareness
• Regions with state, province, or local radon testing initiatives

As a result, radon maps may show a "low risk" for an area simply because very few homes have been tested there, not because the radon levels are actually low.

3. Radon varies dramatically

Even if you live in a "low-risk zone", your home could still have dangerously high radon levels. Why? Because radon has no correlation to zip/postal codes or zones.

Factors that influence radon levels in a specific home include:

• Cracks or gaps in your basement or crawlspace
• Type of foundation (slab, crawlspace, basement)
• Ventilation patterns

Studies show that two homes on the same street can have vastly different radon levels. Relying on a generalized map offers a false sense of security.

4. The need for individual home testing

Given the limitations of radon maps and the potential for significant radon exposure in any home, it is crucial for homeowners to conduct individual radon testing. The EPA, CDC, Health Canada, and other health organizations recommend that all homes, regardless of location, be tested to ensure accurate assessment and mitigation of radon risks. Testing your home for radon is simple is simple, affordable, and the only reliable solution.

Recommended Radon Detectors:

• Radtrak - ideal for accurate, long-term exposure analysis.
• Rapidos Short-Term Radon Detector - great for flexible testing periods.
• Quickscreen - used when fast turnaround is critical.

Pro Tip: Even if your neighbor tested low, your home could test high. Every home is different — and every home should be tested.

While radon maps provide a general overview of potential radon risks, their limitations necessitate a more individual approach to radon testing. Homeowners should not rely solely on these maps but should proactively test their homes to ensure safety and peace of mind.

Don’t Rely on the Map — Trust the Test