Radon: What It Is, Where It Comes From, and Why It Matters
Radon is one of those things most people have heard of, but few really understand. It doesn’t have a smell, color, or taste, and it doesn’t cause immediate symptoms. Yet over time, it can have serious health effects.
At its core, radon is a naturally occurring radioactive gas. It forms when uranium in soil, rock, and groundwater breaks down. Because it’s a gas, it can move through the ground and eventually enter buildings.
Where Radon Comes From
Radon is present in the soil almost everywhere. The amount varies depending on local geology, but no area is completely free of it.
As uranium breaks down underground, it releases radon gas. That gas travels upward through the soil and can enter homes and buildings through openings such as:
Cracks in concrete foundations
Gaps around pipes and utility lines
Crawlspaces with exposed soil
Sump pits or floor drains
Once inside, radon can accumulate, especially in lower levels like basements.
Why Radon Matters
The concern with radon comes from long-term exposure. When radon gas is inhaled, radioactive particles can become trapped in the lungs. Over time, this exposure increases the risk of lung cancer.
According to the Environmental Protection Agency, radon is the second leading cause of lung cancer in the United States.
What makes radon unique compared to other indoor air concerns is that it does not cause immediate irritation or warning signs. People can live in a home for years without realizing elevated levels are present.
How Radon Levels Are Measured
Radon is measured in picocuries per liter (pCi/L), which reflects the concentration of radioactive decay occurring in the air.
Typical guidance levels are:
Below 2.0 pCi/L – generally considered low
Between 2.0 and 4.0 pCi/L – moderate range
4.0 pCi/L and above – level where action is recommended
The EPA has established 4.0 pCi/L as the point at which mitigation should be considered, though lower levels can still carry some risk over long periods.
Why Some Homes Have Higher Levels Than Others
Radon levels can vary significantly from one home to another, even if they are next door to each other. Several factors influence this:
Soil composition and uranium content
Foundation type (basement, slab, crawlspace)
Construction quality and sealing
Ventilation and air pressure differences inside the home
Weather conditions can also play a role. For example, colder temperatures can increase the “stack effect,” which pulls radon from the soil into the home.
Testing for Radon
Because radon cannot be detected by human senses, testing is the only way to determine if it is present at elevated levels.
There are two general approaches:
Short-term testing, typically lasting 2 to 3 days, which provides a quick snapshot
Long-term testing, which runs for several months and gives a more accurate average over time
Testing is often performed during real estate transactions, but it can be done at any time to better understand indoor air conditions.
What Happens If Radon Levels Are High
If elevated radon levels are found, mitigation systems can be installed to reduce concentrations inside the building.
The most common method is called sub-slab depressurization. This involves installing a vent pipe and fan system that pulls radon gas from beneath the foundation and releases it safely above the roofline.
These systems are widely used and can significantly lower radon levels when properly installed.
A Quiet but Important Indoor Air Issue
Radon doesn’t get as much attention as mold or air quality issues you can see or smell, but it is one of the more important environmental factors in a home.
Because it is invisible and long-term in nature, it tends to go unnoticed. Understanding what radon is and how it behaves is the first step in managing it.