Radon Gas and Indoor Health: What Every Homeowner Should Know

By Your Health Magazine Contributor

Your Health Magazine Contributor

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Radon Gas and Indoor Health: What Every Homeowner Should Know

Radon is a naturally occurring radioactive gas that forms when uranium and radium break down in soil, rock, and groundwater. It is colorless, odorless, and tasteless, making it completely undetectable by human senses. Because it accumulates silently inside homes and other buildings, radon has become one of the most widely discussed environmental health concerns in the United States.

WHAT IS RADON AND HOW DOES IT ENTER HOMES?

Radon originates from the natural decay of uranium found in nearly all soils. As the gas forms beneath the ground, it migrates upward and can seep into buildings through foundation cracks, gaps around service pipes, and construction joints. Basements and lower floors tend to accumulate the highest concentrations because they are closest to the source.

No type of home is immune. The gas has been found in properties of all ages, from older homes with porous foundations to newly built energy-efficient structures. In tightly sealed modern homes, radon can sometimes reach higher concentrations than in older, draftier buildings because there is less natural air exchange to dilute the gas.

WHY RADON IS CONSIDERED A SERIOUS HEALTH CONCERN

The International Agency for Research on Cancer classifies radon as a Group 1 carcinogen. In the United States, the Environmental Protection Agency identifies radon as the second leading cause of lung cancer, responsible for approximately 21,000 deaths each year. Only tobacco smoking causes more lung cancer fatalities in the country.

When radon is inhaled, it decays inside the lungs and releases alpha particles that can damage DNA in lung cells. This damage, accumulated over years of exposure, may eventually lead to cancerous mutations. The risk increases with higher concentrations and longer periods of exposure, which is why homes where people spend significant time indoors are the primary focus of testing and mitigation efforts.

The EPA has established an action level of 4.0 picocuries per liter (pCi/L). At or above that threshold, the agency recommends taking steps to reduce indoor levels. The EPA also notes that there is no known completely safe level of radon exposure.

THE ROLE OF A RADON DETECTOR

Because radon cannot be identified by sight, smell, or taste, the only way to know whether it is present at hazardous levels is through testing. A radon detector is a specialized device that measures the concentration of the gas in indoor air and provides readings in pCi/L.

Testing options include short-term charcoal test kits that run for two to seven days, and long-term alpha track detectors that monitor levels for 90 days or more. Long-term tests are generally considered more representative because radon concentrations fluctuate based on seasonal changes, weather patterns, and how a home is ventilated. A single short-term snapshot may not capture the full picture.

Digital continuous monitors offer the added benefit of real-time tracking, allowing homeowners to observe how levels change throughout the day or during different seasons. These devices have become more affordable and accessible in recent years, making routine monitoring practical for a wider range of households.

WHO SHOULD CONSIDER RADON TESTING

The EPA recommends that all homes be tested for radon, regardless of geographic location, age, or construction type. Certain circumstances make testing particularly important. Homes with basements or ground-contact living spaces, properties located in regions with high radon potential, and buildings undergoing major renovation all represent situations where testing is widely considered a priority.

Home buyers are routinely advised to request radon test results or to arrange testing as part of the property inspection process. Schools, daycare facilities, and workplaces are also settings where radon monitoring is considered good practice, given that children and employees spend extended hours indoors and may face greater cumulative exposure over time.

WHEN ELEVATED LEVELS ARE FOUND

When testing reveals levels at or above the EPA action level, mitigation is the standard course of action. The most widely used approach is sub-slab depressurization, which involves routing a pipe through the foundation to draw radon from beneath the structure and vent it safely outside before it can enter the living space. When properly installed, these systems typically reduce indoor radon concentrations by up to 99 percent.

Installation costs for mitigation systems generally range from $800 to $2,500, depending on home design and the complexity of the problem. After installation, annual retesting is recommended to confirm that the system continues to function correctly. Radon levels can shift over time as the structure ages or as ventilation patterns change.

SEASONAL VARIATION AND TESTING TIMING

Radon concentrations inside homes are not static. They tend to peak during winter months when buildings are tightly sealed, and heating systems create pressure differences that pull more gas upward from the soil. Testing during the heating season provides a picture of the highest likely exposure conditions.

Summer readings, while generally lower due to open windows and greater ventilation, may not represent the conditions during which residents face the greatest risk. Long-term monitoring that spans multiple seasons is the most reliable way to understand a home’s overall radon profile.

THE LIMITS OF VENTILATION AS A SOLUTION

Increasing indoor ventilation by opening windows can temporarily dilute radon concentrations. Studies suggest this approach may reduce levels by 25 to 75 percent while windows remain open. However, concentrations return to previous levels once the home is closed again, making ventilation alone an impractical long-term strategy, particularly in regions with extreme temperatures.

Ventilation does not address the entry point of the gas. Without a system that prevents radon from entering the structure in the first place, the source of the problem remains unchanged. Mitigation systems that block entry at the foundation level are widely regarded as the only effective permanent solution.

RADON IN WATER SUPPLIES

Radon can also dissolve in groundwater and enter homes through well water. When water containing radon is used for showering, dishwashing, or laundry, some of the gas is released into the indoor air. Municipal water systems typically treat for radon before distribution, but homes served by private wells should be tested separately.

Water-based radon generally contributes a smaller share of total indoor exposure compared to soil gas infiltration, but in homes with very high water radon concentrations, the contribution can become more significant.

TAKEAWAYS

●       Radon is the second leading cause of lung cancer in the United States, according to the EPA.

●       The gas is entirely undetectable by human senses and requires specialized equipment to measure.

●       The EPA recommends testing all homes regardless of age, location, or construction type.

●       Long-term testing produces more representative results than a single short-term measurement.

●       Sub-slab depressurization systems can reduce indoor radon levels by up to 99 percent when properly installed.

●       The EPA action level is 4.0 pCi/L, but the agency notes that no completely safe level of exposure has been established.

●       Private well water should be tested for radon separately from indoor air.

COMMON QUESTIONS

What does the EPA action level for radon actually mean?

The EPA has set 4.0 picocuries per liter (pCi/L) as the threshold at which homeowners are advised to take action to reduce indoor radon levels. This does not mean that levels below 4.0 pCi/L are considered completely safe. The EPA also recommends considering mitigation for levels between 2.0 and 4.0 pCi/L, and the World Health Organization recommends a lower reference level of 2.7 pCi/L. The action level is a practical guideline rather than a guarantee of safety below that point.

How long does a radon test take?

Short-term radon tests using activated charcoal canisters typically run for two to seven days. Long-term tests, which use alpha track detectors, are left in place for 90 days or more. Long-term testing is generally preferred because it accounts for natural fluctuations in radon levels across different weather conditions and seasons. For real estate transactions, short-term tests are commonly used because of time constraints, but results should be interpreted with that limitation in mind.

Is radon a concern in newer homes?

Yes. While newer homes may be built with radon-resistant construction features such as polyethylene sheeting beneath the slab and rough-in piping for mitigation systems, these measures reduce rather than eliminate radon entry. In some cases, the energy-efficient sealing common in modern construction traps radon at higher concentrations than older, less airtight structures. All homes, regardless of age, benefit from testing.

Can radon levels vary within the same neighborhood?

Yes, significantly. Radon concentrations depend on the local geology, the soil type directly beneath a specific property, the construction of the foundation, and the building’s ventilation characteristics. Two homes side by side can have very different indoor radon levels. Regional maps published by the EPA indicate potential radon zones but do not predict the level in any individual home. Testing is the only reliable way to assess the actual situation in a specific property.

What happens to radon levels after a mitigation system is installed?

A properly installed sub-slab depressurization system typically reduces indoor radon concentrations to well below the EPA action level, often below 2.0 pCi/L. Annual retesting after installation is recommended to confirm that the system continues to perform as intended. Mechanical fans used in these systems can wear out over time, and changes to the structure, such as renovations or foundation work, may affect performance.

Should radon testing be repeated after major home renovations?

Yes. Major renovations that affect the foundation, basement, or overall ventilation of a home can alter how radon enters and accumulates. Finishing a basement, adding new HVAC systems, or sealing air gaps can all change the indoor radon profile. Retesting after significant construction work is considered standard practice to ensure that previously acceptable levels have not changed as a result of the renovation.