Radon is a naturally occurring radioactive gas that forms from the breakdown of uranium and thorium in soil, rock, and water. This invisible, odorless, and tasteless gas can seep into homes through cracks in foundations, walls, or floors. Its presence often goes unnoticed, making it a silent concern for indoor air quality. Radon gas itself does not pose the primary threat; rather, its radioactive decay products, known as progeny, are the source of health concerns when inhaled.
Understanding Long-Term Exposure
Long-term exposure to radon is defined as continuous presence over months or even years. This extended duration is concerning because radon’s health risks are cumulative. The effects of radon build up over time, meaning even lower levels can become significant if exposure is sustained for prolonged periods.
Radon levels inside a home can fluctuate considerably, influenced by factors such as weather, season, and household ventilation patterns. Therefore, a brief measurement might not accurately reflect the average radon concentration a household experiences throughout the year. Assessing long-term average exposure is crucial for determining the true risk profile of a home and making informed decisions about potential mitigation.
Health Implications of Sustained Radon Presence
Sustained exposure to radon primarily affects the lungs, leading to an increased risk of lung cancer. When radon gas decays, it produces tiny, solid radioactive particles called progeny. These progeny can attach to dust particles in the air and, when inhaled, become lodged in the lining of the lungs.
Once in the lungs, these trapped radioactive particles emit alpha radiation. This radiation damages the DNA within lung cells, potentially leading to genetic mutations and uncontrolled cell growth, which are hallmarks of cancer. Lung cancer is the only cancer definitively linked to radon exposure through extensive research. Radon exposure is recognized as the second leading cause of lung cancer overall, and it is the primary cause among non-smokers. The risk of developing lung cancer from radon increases with both the concentration of radon and the duration of exposure.
Measuring Radon Over Time
Accurately assessing long-term radon levels in a home is achieved through specific testing methods designed to capture variations over an extended period. While short-term tests provide a quick snapshot, they may not represent the average exposure due to daily and seasonal fluctuations. For this reason, long-term radon tests, typically conducted for 90 days to one year, are recommended to determine a more reliable average radon concentration.
Two common types of long-term radon detectors are alpha track detectors and electret ion chambers. Alpha track detectors contain a special plastic material that records microscopic “tracks” when struck by alpha particles during radon decay. After the testing period, the detector is sent to a laboratory where these tracks are counted and analyzed to calculate the average radon level. Electret ion chambers (EICs) utilize a pre-charged disk, known as an electret, housed within a chamber. As radon gas enters the chamber and decays, the resulting ionization reduces the charge. The change in charge, measured with a specialized reader, corresponds to the average radon concentration over the test duration.
Strategies for Reducing Radon Exposure
Reducing long-term radon exposure involves specific mitigation techniques designed to prevent radon entry and remove it from indoor air. The most effective and widely used method for homes with a basement or slab-on-grade foundation is sub-slab depressurization (SSD). This system involves installing a pipe through the foundation slab and connecting it to a fan, which continuously draws radon gas from beneath the house and vents it safely outdoors, above the roofline.
For homes with crawl spaces, a sub-membrane depressurization system is often employed, which involves placing a high-density plastic sheet over the crawl space floor and then using a fan to draw radon from beneath the sheet. Sealing major cracks and openings in the foundation, such as those around pipes or utility penetrations, can also help reduce radon entry. Improving general household ventilation, potentially through systems like heat recovery ventilators (HRVs), can dilute indoor radon concentrations. It is recommended to engage qualified professionals for radon mitigation to ensure proper design and installation. After mitigation, retesting the home is important to confirm that radon levels have been successfully reduced to acceptable concentrations.