Radon is a naturally occurring, invisible, and odorless radioactive gas. It is a known human carcinogen, but its role in the development or exacerbation of non-cancerous respiratory conditions, such as asthma, is a growing public health concern. Asthma is a chronic respiratory disease characterized by airway inflammation and constriction. This article examines the current scientific understanding of the potential link between residential radon exposure and asthma, reviewing the evidence and detailing steps homeowners can take to reduce their risk.
Understanding Radon Gas and Exposure
Radon is a byproduct of the natural radioactive decay of uranium, which is present in nearly all soil and rock formations. As uranium breaks down, it produces radium, which then decays into the gaseous element radon-222. This gas rises through the ground and seeps into buildings through cracks in foundations, floor slabs, and openings around utility pipes.
Because radon is heavier than air, it often accumulates in the lowest levels of a structure, making exposure predominantly an indoor air quality issue. Once trapped inside a home, especially one with poor ventilation, the gas concentration can build up to harmful levels. The primary concern is not the gas itself, but the short-lived radioactive particles it creates as it continues to decay.
How Radon Damages Respiratory Cells
The process of harm begins when radon gas breaks down into solid radioactive particles known as radon progeny or decay products. These decay products, such as polonium-218 and polonium-214, are tiny and readily attach themselves to airborne dust and aerosols. When inhaled, these particles become lodged in the lining of the airways and the epithelial cells of the lung.
Once deposited, the radioactive progeny emit bursts of alpha radiation, a highly energetic form of ionizing radiation. Although alpha particles have limited tissue penetration, they cause significant biological damage to the cells they strike, including the respiratory epithelium. This direct radiation exposure can lead to DNA breakage, genetic mutations, and cellular damage.
The tissue damage initiates a chronic inflammatory response as the body attempts repair. This persistent inflammation and irritation of the respiratory tract lining is a plausible biological mechanism for increasing airway sensitivity. The resulting cellular changes and sustained irritation can contribute to the development of various respiratory illnesses.
The Scientific Evidence Linking Radon to Asthma
Radon’s link to lung cancer is undisputed, confirming it as the second leading cause of the disease after smoking. However, the evidence specifically linking residential radon exposure to the causation of asthma—the initial development of the condition—is less definitive. Many studies have found the connection to be inconsistent when compared to well-known environmental triggers like mold and dust mites.
More recent epidemiological evidence focuses on the effect of radon on individuals who already have asthma, especially children. Research indicates that residential radon exposure may be associated with increased asthma morbidity, suggesting it acts as an environmental risk factor that worsens the condition. Studies on school-aged children with asthma have demonstrated that those exposed to higher levels of radon experienced more frequent symptom flare-ups and increased airway inflammation.
The mechanism for this exacerbation is the chronic irritation and inflammation of the airways caused by the inhaled radioactive particles. This damage increases the sensitivity of the bronchial tubes, making them more reactive to common asthma triggers. Therefore, while radon may not be the primary cause of asthma, it appears to be a factor that can significantly worsen the respiratory health of those already diagnosed.
Testing and Reducing Radon Levels
Testing the air in your home is the only reliable way to determine if you are being exposed to elevated radon levels, as the gas is colorless and odorless. Two main types of tests are available: short-term tests (two to ninety days) and long-term tests (more than ninety days). The long-term test provides a more accurate representation of the home’s average annual radon concentration due to seasonal fluctuations.
EPA Guidelines and Mitigation
The Environmental Protection Agency (EPA) recommends taking action to reduce radon levels if the result is 4 picocuries per liter (pCi/L) or higher. While 4 pCi/L is the action level, the EPA suggests considering mitigation if levels fall between 2 and 4 pCi/L. Radon reduction systems, when properly installed, can lower indoor concentrations by up to 99 percent.
The most common and effective technique for mitigation is called sub-slab depressurization. This system uses a vent pipe and a fan to pull radon from beneath the house and safely vent it outside. Sealing large cracks and other foundation openings is a complementary step that makes the depressurization system more efficient. Homeowners should hire a qualified radon mitigation contractor to ensure the system is designed correctly.