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What Types of Soil Contain the Highest Levels of Radon


Radon is everywhere. Not to scare you, but this cancer-causing, radioactive gas could be lurking in your neighborhood. You can’t see it or smell it, but there’s a really good chance that it’s there. That’s because radon gas occurs naturally from the breakdown of uranium deep beneath the earth’s surface. Obviously, certain areas of the country are more prone to radon than others depending upon the topography and soil structure. Radon testing can help you determine if your home is harboring this dangerous gas.

Before you freak out that you are living in a toxic house built on soil, containing high levels of radon, it’s important to understand:

  • What is radon?
  • Where does radon come from?
  • Which soils contain the most radon?
  • Where are radon levels the highest?
  • How can you find out if there is radon in your home?

Keep reading to learn more about this common, yet highly dangerous gas that is lurking in almost every neighborhood, possibly including yours.

What is Radon?

To put it in simple, layman’s terms, radon gas comes from the natural breakdown of uranium in rocks. According to a report in the International Journal of Environmental Research and Public Health, radioactive radon is released from the soil into the air and groundwater.

Radon gas puts people at risk when it accumulates in high levels in indoor air and drinking water. It is also known to cause lung cancer.

Where Does Radon Come From?

Radon gas can be found throughout the United States – literally from coast to coast. In fact, there is radon in every single state, although at different levels and not all amounts are considered dangerous.

Not to get too complicated, but radon gas is a byproduct of the element radium which ultimately comes from uranium. According to a report by the U.S. Geological Survey, uranium is the parent element and is found deep within the earth’s crust. It’s billions of years old. As time passes, it breaks down forming radium, the daughter element. When solid radium decays, it releases radon gas. All three are radioactive substances.

The reason radon gas is found everywhere is because uranium is everywhere – all rocks are composed of at least a trace amount of it. Over time, the rocks beneath the earth’s surface break down and turn into soil. So, if the deep rocks in the area contain uranium, it stands to reason that the soil at the surface will too.

Because radon is a gas, it’s easy for it to permeate the soil, escaping into the air and even groundwater. If your house is built on land that contains high amounts of radon, then the gas can get inside your home. That typically happens through cracks in the foundation or basement, as well as gaps in construction materials. Radon gas can also enter your home through the plumbing including pipes, the sump pump system, or even drains.

It’s also important to note that radon is often found in the groundwater in areas with high levels of uranium. This becomes a concern if the water supply comes from a home well or from a “small public water” department. Without a water treatment program to remove radon, it can be ingested while drinking or inhaled from steam in the shower.

Which Soil Has the Most Radon?

So, now that you know where radon gas comes from, you can better understand why it is more prevalent in some areas of the country than others. Since radon gas forms from the breakdown of uranium in the bedrock deep within the earth, it must pass through the various layers before it can escape. The more dense the soil is, the harder it is for the radon gas to permeate it.

The U.S. Geological Survey explains that radon moves easily and quickly through porous soils, like sand and gravel, and slower through more solid soils, clay being one such example. Moisture has a lot to do with this. In wet soil, like clay, it’s harder for the radon to permeate it, so the radon often becomes trapped and deteriorates before it reaches the surface. In dry, porous soils, radon gas is able to quickly escape into the air.

Where Are Radon Levels the Highest?

Areas with dry or highly permeable soil often see an increased level of “indoor radon.” This includes hills, canyons, and places where glaciers once were. So, it’s not surprising that the states with the highest levels of radon gas tend to be in the northern and most mountainous parts of the country. Montana, home to Glacier National Park, is almost entirely in what the Environmental Protection Agency (EPA) considers a “red zone” (places with a high level of indoor radon). The Rocky Mountain states, from Idaho down to New Mexico, are also in the red zone.

As previously stated, radon gas is found everywhere – even in coastal states. Connecticut has exceptionally high radon levels, affecting one in three homes. Nationwide, the average is “one out of every 15 homes,” according to the EPA. The cities in Connecticut with the highest levels of radon tend to be located in the southern part of the state. It’s believed the gravel and sandy soil in that area allows the radon gas to easily escape, allowing it to enter homes and water supplies.

On the contrary, Florida has low levels of radon gas because much of the state is composed of a thin layer of soil over limestone, a dense rock with very few pores. It’s so strong that limestone is often used in making cement. This consistency makes it extremely hard for radon gas to permeate from the uranium buried deep beneath the earth’s surface.

How Can You Find Out if There is Radon in Your Home?

Not only is radon everywhere, but it is also highly carcinogenic. The Surgeon General declared radon to be “the second leading cause of lung cancer in the United States,” behind smoking. For this reason, you definitely want to find out if you and your family are in danger. Fortunately, a simple radon test can determine if your home is contaminated.

The test will measure the air quality and water quality to make sure you are living in a safe environment. If dangerously high levels of radon are detected, a mitigation service can remove radon from the soil and the air you breathe, as well as the groundwater. This is done by using specially designed equipment that basically works as a super-powered fan.


No matter where you live, there is the danger of radon gas lurking beneath your home. It’s more of a concern if you live in areas with porous soil, such as sand and gravel, where the radioactive gas can easily permeate into the air and water supply. Even if that is the case in your community, you need not panic. Radon remediation can protect you and your family from this cancer-causing gas, making your home a perfectly safe place in which to live.