Radon is a naturally occurring radioactive gas that forms deep within the earth. This gas is odorless, colorless, and tasteless, meaning its presence cannot be detected without specialized testing equipment. The term “radon poisoning” is misleading because exposure does not cause immediate, acute symptoms like those from carbon monoxide or other toxins. Instead, the danger lies in chronic exposure over many years, which can lead to serious long-term health consequences. Understanding this long-term risk is the only way to safeguard indoor environments effectively.
Understanding Radon Gas and Exposure
Radon gas originates from the natural radioactive decay of uranium and radium, elements commonly found in the soil, rock, and water beneath our homes. As uranium breaks down, radon gas is continuously produced and moves freely through porous soil and rock formations. The gas enters a building through various pathways where the structure meets the ground, including cracks in the foundation slab or walls.
Gaps around utility pipes, floor drains, and sump pumps also serve as common entry points. A pressure difference, often created by the natural stack effect, draws the radon-laden soil gas upward into the lower levels of the home. Once indoors, the gas can accumulate and become concentrated, especially in basements and crawl spaces.
The threat emerges when radon decays into solid, radioactive particles known as radon progeny. These particles attach to dust and other airborne materials. When inhaled, they lodge in the lining of the lungs, releasing radiation that damages the DNA of the lung tissue. This ongoing cellular damage is the mechanism leading to the health consequence associated with chronic radon exposure.
Health Effects of Chronic Radon Exposure
The most significant health outcome linked to prolonged inhalation of radon decay products is lung cancer. The Environmental Protection Agency estimates that radon exposure is the second leading cause of lung cancer in the United States, after cigarette smoking. There are no acute physical warning signs, such as dizziness or nausea, that indicate a person is currently being exposed to high levels of radon.
The disease develops over a long latency period, with symptoms appearing 5 to 25 years after chronic exposure began. The signs people incorrectly associate with “radon poisoning” are indicators of advanced lung cancer triggered by years of radiation damage. These symptoms often do not manifest until the disease has progressed significantly.
Indicators of advanced lung cancer include a persistent cough that worsens over time or the coughing up of blood. Individuals may also experience shortness of breath, hoarseness, or recurring respiratory infections like bronchitis or pneumonia. Smokers exposed to elevated radon levels face a significantly higher risk of developing lung cancer, as the combined damage to lung tissue is compounded.
Testing and Measuring Radon Levels
Since radon exposure produces no immediate symptoms, the only reliable way to determine the level of risk within a home is through testing. Devices are placed in the lowest lived-in level of the home, typically the basement or first floor, to capture representative exposure data.
Testing falls into two categories: short-term and long-term. Short-term tests (e.g., charcoal canisters) measure levels over two to seven days, often used for initial screening or real estate transactions. Long-term tests run for 90 days or more, providing a more accurate annual average by accounting for seasonal fluctuations.
Radon concentration is measured in picocuries per liter of air (pCi/L). The action level recommended for intervention is 4.0 pCi/L. Any home testing at or above this concentration should be fixed to reduce the long-term health risk.
Practical Steps for Radon Reduction
Once testing confirms elevated radon levels, the most effective method for reduction is the installation of a mitigation system. The technique commonly used for homes with a basement or slab-on-grade foundation is called sub-slab depressurization. This system actively prevents radon from entering the home by changing the pressure dynamics beneath the foundation.
The process involves drilling a hole through the foundation slab and inserting a pipe into the soil beneath. An in-line fan is attached to this pipe, running continuously to create a negative pressure that draws the radon gas out of the soil. The extracted gas is then safely vented through the pipe to the outdoor air, typically above the roofline, where it quickly dissipates.
While sub-slab depressurization can reduce indoor radon levels by up to 99%, sealing cracks and other foundation openings is a complementary step. Sealing alone is not sufficient to lower high radon concentrations consistently, but it helps the depressurization system work more efficiently. Other methods, such as sub-membrane depressurization for crawlspaces, also use a fan and venting system to divert the gas away from the living space.