Radon is a naturally occurring radioactive gas, a significant public health challenge within indoor environments. Formed deep within the earth, this gas is colorless, odorless, and tasteless, making it undetectable by human senses. It is produced during the natural decay of uranium and radium, which are present in nearly all types of soil and rock formations. Radon moves freely through the ground and accumulates inside homes, schools, and workplaces, creating an indoor air quality concern.
What Radon Is and How Exposure Occurs
The source of radon gas is the radioactive breakdown of uranium, a heavy metal found worldwide. As uranium decays, it produces radium, which then breaks down into the gaseous element radon-222. This gas seeps up from the soil and rock beneath a structure, entering buildings through openings like cracks in the foundation, gaps around utility pipes, and floor drains. Once inside, the gas can become trapped and build up to elevated concentrations, especially in basements and lower levels.
The danger begins when inhaled radon gas further decays, producing short-lived radioactive particles known as radon progeny or decay products. These solid, charged particles attach themselves to dust and other airborne particulates. When a person breathes, these contaminated particles are drawn deep into the lungs and deposited onto the cells lining the airways. While the radon gas itself is mostly exhaled, the inhalation and deposition of these decay products cause internal exposure.
Why Immediate Symptoms Are Misleading
Many individuals search for immediate symptoms of radon exposure, such as a headache, fatigue, or a sudden cough, but this is based on a misunderstanding. No distinct, acute, or short-term health effects appear immediately following exposure to elevated radon levels. Because the gas has no smell, color, or taste, a person can be exposed to high concentrations for years without any warning.
The signs sometimes associated with “radon poisoning,” such as a persistent cough, wheezing, or shortness of breath, are symptoms of the eventual disease, not the exposure itself. These respiratory symptoms often indicate that the exposure has already resulted in long-term damage. The lack of warning signs makes testing the only reliable way to determine if a health risk is present.
The Primary Health Risk of Chronic Exposure
Chronic radon exposure leads to the development of lung cancer. When inhaled decay products lodge in the lungs, they emit small bursts of alpha radiation. This radiation directly damages the DNA within the lung cells, which can lead to malignant transformation. This process is latent, meaning the cancer usually takes many years (often 5 to 25 years) to manifest after the initial exposure.
Radon exposure is the second leading cause of lung cancer in the United States, following only cigarette smoking. It is also the leading cause of lung cancer among people who have never smoked. The Environmental Protection Agency (EPA) estimates that radon exposure contributes to approximately 21,000 lung cancer deaths annually in the U.S.
The risk is substantially amplified for smokers. For these individuals, the risk of developing lung cancer from radon exposure can be 10 to 20 times greater compared to non-smokers exposed to the same levels. This synergistic effect means the combined exposure is far more harmful than the separate effects added together. The radioactive particles compound the damage inflicted by tobacco smoke chemicals, increasing the likelihood of cell mutation.
Testing and Reducing Radon Levels
Since there are no physical symptoms, testing is the necessary first step to determine the concentration of radon in a home. Testing is simple, involving placing a small detection device in the lowest lived-in area for a specific period. Both short-term tests (lasting two to 90 days) and long-term tests (lasting more than 90 days) are available to measure the average radon level.
The EPA has established an action level of 4 picocuries per liter (pCi/L), recommending that homes with levels at or above this concentration should be fixed. Experts advise considering mitigation for levels between 2 pCi/L and 4 pCi/L, as no level of radon exposure is considered entirely safe.
The most common and effective technique for reducing high levels is Sub-Slab Depressurization (SSD). This process uses a vent pipe and a fan to draw radon from beneath the foundation and safely vent it outside above the roofline. Sealing cracks in the foundation is a component of mitigation, but it is typically used in conjunction with a ventilation system, not as a standalone solution.