Radon is a naturally occurring radioactive gas that has no color, odor, or taste. It is produced by the decay of uranium, which is commonly found in water, rock, and soil. The removal of radon that has infiltrated and become trapped in residential or other structures is known as radon mitigation. As radon inhalation and ingestion pose serious health risks, radon mitigation can help protect the health of the occupants of a building at risk for radon contamination.
Ingress of radon into a building primarily happens by two modes. As radon gas filters up through the soil, it may enter a building through cracks in the foundation, gaps in construction joints, spaces in walls, and other voids and become trapped inside the building. Occupants are then at risk of inhalation of this hazardous substance.
Another way radon may enter a building is through the water supply. Radon gas can be naturally dissolved in water, especially groundwater, which may then be transported into a building through use of a well for the building’s water supply. Ingestion of dissolved radon in contaminated water is one risk, but use of contaminated water may drive radon gas out of solution into the air, posing an inhalation risk as well.
Inhalation is the primary health risk related to radon. As a radioactive substance, radon breaks down over time and releases energy as it does so. Such energy may damage fragile tissue — such as lung cells — when inhaled, thereby increasing the risk of developing lung cancer. A secondary risk is related to ingestion of radon, such as in contaminated water, which is linked to increased risk of stomach cancer.
Radon mitigation may involve removal of radon from both a building’s air and water. Prevention of radon infiltration into the air of a building typically involves a process known as active soil depressurization. This process uses a fan to proactively vent radon gas from the soil and route it outside of the building through a vent pipe. This gets rid of the radon before it is trapped inside a building.
Removal of radon from water is most commonly done by one of two techniques. Aeration treatment may be used to agitate radon gas out of solution with the water and into the air where it can be dealt with by the normal radon mitigation procedures for removing it from air. Alternatively, radon may be removed by filtering contaminated or suspect water through granular activated carbon which bonds with radon. This bonding then sequesters radon from the water supply, making the filtered water available for use.
Where filtration is used for radon mitigation, a filtration device at the point of entry of the water supply to the building is typically recommended over devices at the points of use. This helps to ensure that the entire water supply is subjected to radon mitigation and that such mitigation takes place before the water enters the building, keeping radon gas from transferring to the building’s breathable air.