Radon, referring to radionuclide (222Rn), is a gas that cannot be detected by human senses, as it is tasteless, colorless, and odorless. This radioactive gas occurs naturally through the decay of uranium, which is present in varying degrees in all soil and bedrock [1]. Since radon is a gas, it can easily move through soil and bedrock, where it can escape into outdoor air or infiltrate homes or buildings. Once radon is released from the ground, it quickly dilutes and is no longer a significant health hazard in the outdoor air.
The air pressure inside a building is usually lower than the pressure outside and in the soil, particularly in the lower foundation levels, which can cause the building to act like a vacuum and draw in soil gases, including radon, through any openings. Common entry points for radon gas include gaps around service pipes, construction joints, cracks in foundation walls, and floor slabs, among others. High concentrations of radon gas can accumulate in indoor air and pose a health risk to the occupants [1]. In addition, water supply can be another source of radon infiltration in buildings or homes. Radon may dissolve and accumulate in groundwater affecting regions that rely on private or community wells.
Research has indicated that inhaling radon gas increases the risk of lung cancer, which is significantly higher than the risk of stomach cancer from ingesting water with high radon levels. However, when water containing high levels of radon is agitated during activities such as showering, washing clothes, or cooking, the gas can be released into the indoor air, which can pose a health risk to occupants. Therefore, the health risks associated with radon dissolved in water are from the inhalation of air that contains radon gas that has been released, not from ingestion.
Regardless of the age, type of construction or location of the home/building, the only way to accurately quantify indoor radon levels is to conduct testing after occupancy.
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