What is radon?

The Basics

Radon is a naturally-occuring, gaseous element which is radioactive. It can infiltrate buildings through foundations and collect inside, creating a cancer risk for occupants. 

The Technical

Uranium238, the uranium isotope most commonly found in Earth's crust, has an unstable nucleus and emits alpha particles, which are essentially helium but without its two electrons; this process is known as alpha-type radioactive decay.

When an atom of Uranium238 loses an alpha particle, it becomes Thorium234, which then loses a beta particle to become Protactinium234, which then loses another beta particle to become Uranium234. After two more alpha particles are lost, you have Radium226 which loses another alpha to finally become Radon222. This form of Radon is the most stable, and therefore the most likely to be present, but there are four other isotopes which occur in trace quantities in nature as the direct decay products of either Radium or Astatine.

What are the health risks?

The Basics

Radon can cause cancer. Because it’s a gas, the greatest risk is of lung cancers, followed by blood, bone, and lymphnode cancers. Humans cannot detect the gas on their own due to its odorless, tasteless, and colorless properties. 

The Technical

When a particle is emitted from an atom, the particle can physically hit and damage DNA. If one strand in the DNA double helix is damaged, there are mechanisms to repair it using the other strand as a template, but, if both strands are damaged, it can lead to genome rearrangements which lead to cell mutations. Cell mutations that lead to abnormal growth or function are the cause of cancer.

Since the Radon found in homes primarily emits alpha particles, which are larger and more easily blocked by clothing and air, the largest risk is of the gas being breathed in and then emitting particles which damage lung tissue, but there's also a risk of the gas entering the bloodstream and emitting particles where they can affect blood and bone cells.

If Radon is not ventilated from a space, it continues to decay through the chain, with each link being another radioactive atom that poses health risks, until it becomes lead.

Where is radon found?

The Basics

Radon risks vary by local geology, construction materials and methods, and occupant habits such as regular opening of doors and windows or use of ventilation. Maps are available to help determine the likelihood of an area having radon issues, but only a thorough inspection by a qualified professional can tell you about the risks in a particular building. Even neighbors can have very different levels of radon in their home.

The Technical

Most soils in the United States have at least some level of radioactive minerals present, several of which are parents of a Radon isotope. When these elements decay to their Radon state, the gas collects in pockets within the rock and soil. The collection is similar to that of Natural Gas, except that it is heavier than normal air instead of lighter. Its density helps it say in the Earth's crust, but natural and human-caused disturbances can cause this gas to rise, such as earthquakes, nearby underground drilling and pumping, construction of the building, and negative pressure inside the building. For example, high winds blowing over an attic vent can create negative pressures that "suck" the radon gas up through cracks in the foundation. Once in a building, Radon's weight concentrates the gas in lower areas of the home, such as basements or the lowest floor.

What can be done to prevent it?

New construction developers can perform risk assessments and use certain design techniques, construction methods, or construction materials to prevent occupants from inhaling the radon gas.

The Technical

Developers can first reference maps of radon prone areas and soil maps to determine if radon-producing minerals are commonly present in the area. Next, soil inspectors can analyze each plot to determine the hyper-local geology and soil composition to provide a more-detailed risk assessment. If any risk is found to be present, the building can be constructed with some form of false or raised foundation that allows the radon to collect in a cavity that is ventilated by pulling fresh air into the space from near ground-level and venting it out near the roof.

The image below shows the wood form used as the foundation perimeter, a few inches of concrete poured in the bottom of the form, and then a bunch of plastic risers that look like 'step stools' and form cavities under them. Those pictured are Radon Iglus and, once all are in place, concrete will be poured on top to create a hollow foundation that can be ventilated.

What can be done to fix it?

If a building is found to have high levels of radon, mitigation methods used will depend on the construction materials and methods used, as well as site makeup and conditions.

If the building has a crawl space or basement, it can often be fitted with piping and fans to vent the gas from the space beneath the first floor.

If the building has a slab foundation, there are polymer sealants that can be applied to prevent the gas from entering through pores and cracks in the foundation if levels are light. For higher concentrations, it may be necessary to build piers under the foundation to hold up the home while the soil around the slab is excavated to allow for porous pipes and fans to be installed and surrounded by a porous aggregate (gravel), allowing the area under the foundation to be ventilated.

If the conditions do not allow for the above, it may be necessary to install high-volume ventilation throughout the building to remove the gas once it enters the home.