Radon is an element on the periodic table and a naturally occurring trace gas in the atmosphere. Radon is also radioactive, and when it accumulates indoors or in underground caves above its normal atmospheric concentrations, it poses a serious health risk to humans. Radon is estimated to be the second leading cause of lung cancer in the United States. Indoor radon concentrations can be reduced through mitigation strategies and equipment.
Radon Origins
Radon is a member of the family of "noble gases" and is the 86th element on the periodic table. On Earth, radon is produced as a product of the normal radioactive decay of uranium-238, which occurs naturally in the soil all over the planet. Although the concentration of uranium is low, it can vary sufficiently to lead to very different radon risks in different regions.
How Radon Enters Buildings
As uranium's "decay chain" progresses, the atoms change, or transmute, into an isotope of thorium and then several other elements before becoming radon. At Earth temperatures radon exists as a gas, and when formed in the soil it immediately begins moving upwards towards the atmosphere. If there's a building in the way, the radon will seep inside through small cracks, holes and imperfections in the foundation. Once inside, the radon will tend to accumulate in the air.
Radon Radioactivity
Once in the air, radon continues to decay into new elements like polonium, but both radon and its progeny do so much faster than most of the preceding elements in the chain. This means that they give off more high-energy particles in a given period of time.
How Radon Causes Damage
The high-energy alpha particles emitted by radon and its progeny don't penetrate skin. If the radon is already inside the body, however, when the decay process takes place, such as in air in the lungs, the particles can cause serious cellular damage.
When an alpha particle crosses the nucleus of a cell, it can affect the DNA and cause the cell's genetic code to change, or mutate, in a random fashion. Even if the alpha particle misses a cell nucleus, it can impact other molecules, initiating chain reactions that cause cellular damage that eventually may reach the DNA.
If the cell continues to reproduce, mutations can be passed on to progeny cells. If the DNA's code is sufficiently damaged, the cell or its progeny can begin growing out of control, leading to cancer.
Exposure Thresholds and Testing
The U.S. Environmental Protection Agency has determined indoor radiation thresholds beyond which mitigation is necessary to reduce safety hazards. Either of the two "action levels", 4 picocuries (pCi) per liter, or 150 becquerels (Bq) per cubic meter, indicates unsafe radiation exposure for building inhabitants.
The level of airborne radiation in a home or building can be determined by direct testing. Simple-to-use, lab-certified radon test kits are available in many stores and online. More involved testing can be done by a professional.
Reducing Radon Hazards
Although the National Cancer Institute estimates that radon is the second leading cause of lung cancer in the U.S., the mitigation of indoor radon risk is a common and well-understood practice.
Because radon enters homes from underground, most mitigation systems use sump fans to blow radon-laden air from below the basement to the outdoors via a dedicated vent. This method may be assisted by improvements in indoor ventilation and the sealing of some foundation cracks.
References
- University of Minnesota: Radon: Molecular Action and Genetic Effects
- Air Chek: Radon in your home -- what should you do?
- U.S. Environmental Proteciton Agency: A Citizen's Guide to Radon
- U.S. National Cancer Institute: Radon and Cancer: Questions and Answers
- U.S. Geological Survey: The Geology of Radon
Member Comments