Radon is a naturally occurring, invisible, and odorless radioactive gas that forms from the breakdown of uranium found in soil and rock. Radon can seep from the ground into homes and other buildings, where it may accumulate to unhealthy concentrations. The gas is recognized as a serious environmental health hazard due to its radioactive nature. While the established risk is heavily focused on the respiratory system, the potential for systemic effects like leukemia requires careful examination.
Understanding Radon’s Primary Health Mechanism
The health risk from radon comes not from the gas itself, but from its subsequent decay products, known as radon progeny. As the gas decays, it transforms into a series of short-lived, solid radioactive isotopes, including polonium-218 and polonium-214. These progeny are electrically charged and readily attach themselves to airborne dust particles inside a home.
When these particles are inhaled, they lodge deep within the cellular structures of the lungs and airways. Once deposited, the radon progeny emit alpha radiation, a highly energetic but short-range form of ionizing radiation. This alpha radiation directly damages the DNA within the basal and secretory cells of the bronchial epithelium, the target cells for carcinogenesis.
Repeated DNA damage from these alpha particles can overwhelm the body’s natural repair mechanisms, leading to genetic mutations. This localized tissue damage within the respiratory tract is the established pathway for cancer development. Radon exposure is recognized worldwide as the second leading cause of lung cancer, and the leading cause among non-smokers.
Scientific Consensus on Radon and Leukemia
The question of whether radon can cause leukemia centers on whether the alpha particles can reach the blood-forming cells in the bone marrow, the site of leukemia development. The primary biological mechanism for lung cancer involves localized damage to the lung tissue from inhaled progeny. Alpha particles travel only a very short distance—the thickness of a piece of paper—meaning they generally cannot penetrate from the lung into the bloodstream or other distant tissues.
Despite this biological limitation, the potential link between residential radon and leukemia, particularly childhood leukemia, has been the subject of numerous epidemiological studies. The evidence gathered so far has been mixed and inconsistent. The National Cancer Institute (NCI) and the Environmental Protection Agency (EPA) currently state that the evidence is inconclusive or insufficient to establish a definitive causal link between residential radon exposure and leukemia.
Some recent studies have suggested a statistical association between higher average residential radon concentrations and an increased risk of childhood leukemia. For instance, one meta-analysis reported a pooled odds ratio suggesting a significant increase in the incidence of childhood leukemia with residential radon exposure. Scientists hypothesize that if a link exists, it might be due to the systemic circulation of radon dissolved in the blood or the migration of damaged cells. Lung cancer remains the only proven cancer associated with inhaled radon exposure.
Testing Your Home and Reducing Radon Exposure
Regardless of the ongoing debate about leukemia, the established risk of lung cancer makes testing for radon a highly recommended public health action. Testing is the only way to determine if a home has elevated levels, as the gas is undetectable by human senses. The EPA recommends that all homes below the third floor be tested, as most indoor radon originates from the soil directly beneath the foundation.
Radon testing is done using either short-term (two to 90 days) or long-term kits (more than 90 days). Long-term tests provide a more accurate year-round average. The EPA recommends taking action to reduce radon levels if the result is confirmed to be 4 picocuries per liter (pCi/L) or higher.
Radon reduction systems, often called mitigation systems, are effective and can reduce indoor levels by up to 99 percent. The most common technique is Sub-Slab Depressurization (SSD). This method uses a vent pipe and a fan to draw radon gas from beneath the foundation and safely release it outside above the roofline. Sealing major entry points like cracks in the foundation is also an important part of any mitigation strategy.