Radon is a naturally occurring, radioactive gas that forms when uranium in soil and rock breaks down. It is colorless, odorless, and tasteless, so it cannot be detected without testing equipment. Radon is dangerous because prolonged exposure to elevated levels is the leading cause of lung cancer among non-smokers and the second-leading cause overall, according to the EPA.
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What is Radon Gas?
Radon gas is produced by the natural decay of uranium found in nearly all soil. As uranium breaks down, it releases radon, which rises through the ground and seeps into buildings through foudation cracks, sump pits, and gaps around pipes.
Radon exists outdoors too, but it disperses harmlessly in open air. The danger comes from radon accumulating indoors, where concentrations can build up in basements and lower levels that have less air exchange with the outside.
Because Wisconsin sits on soil and bedrock known for higher uranium content, homes in Whitefish Bay, Wauwatosa, West Allis, and South Milwaukee are frequently found with elevated radon levels during testing.
How is Radon Measured?
Radon is measured in picocuries per liter of air, abbreviated pCi/L. This unit reflects the rate of radioactive decay occurring in a given volume of air.
The EPA has set 4.0 pCi/L as the action level, the point at which homeowners should take steps to reduce radon exposure. The World Health Organization recommends an even lower reference level of 2.7 pCi/L, reflecting a more conservative international health standard.
No level of radon exposure is completely risk-free. Radon risk increases proportionally with concentration and duration of exposure, which is why testing matters even in homes below 4.0 pCi/L.
Why is Radon Dangerous?
Radon is classified as a Group A human carcinogen by the EPA, placing it in the same risk category as asbestos and secondhand smoke. When inhaled, radon decays into radioactive particles that lodge in lung tissue and emit alpha radiation, which damages cells and DNA over time.
This cellular damage accumulates with prolonged exposure and can eventually lead to lung cancer. The EPA estimates radon exposure causes approximately 21,000 lung cancer deaths in the United States each year.
Key risk factors include:
- Duration of exposure — years of exposure in a home with elevated radon compounds the risk.
- Concentration level — higher pCi/L readings mean faster cellular damage.
- Smoking status — smokers exposed to radon face a dramatically higher combined risk than either factor alone.
For a deeper look at the biological mechanisms, see our explanation of how radon affects your health.
How Does Radon Get Into a Home?
Radon enters buildings primarily through the foundation, following the path of least resistance from soil gas pressure differences between the ground and the home’s interior.
Common entry points include:
- Cracks in concrete slabs and foundation walls
- Gaps around pipes, sump pumps, and utility penetrations
- Exposed dirt floors in crawl spaces
- Block wall cavities and construction joints
Homes with well water can also introduce radon through faucets and showerheads, though soil gas infiltration is the dominant pathway.
What Are the Symptoms of Radon Exposure?
Radon exposure produces no immediate symptoms. There is no headache, cough, or physical sensation that signals elevated radon in real time, which is why testing is the only reliable detection method.
Long-term exposure symptoms typically only appear as radon-induced lung cancer develops, often decades after initial exposure. This latency period is precisely why the EPA and state radon programs urge every home to be tested regardless of how occupants feel. For a full breakdown, read our article on symptoms of radon exposure.
How Do You Test for Radon?
Radon testing uses either short-term or long-term devices placed in the lowest livable level of a home.
- Short-term tests run 2–7 days and give a quick snapshot, useful for real estate transactions.
- Long-term tests run 90 days to a year and provide a more accurate average, since radon levels fluctuate with weather and season.
Testing should follow ANSI/AARST protocols to ensure accurate, defensible results. Homeowners in Whitefish Bay, Wauwatosa, West Allis, and South Milwaukee can review our full process in what radon testing involves and why it matters.
How Do You Fix a Radon Problem?
The most effective and widely used solution is sub-slab depressurization. This system uses a pipe inserted through the foundation slab connected to a radon fan that draws radon gas from beneath the home and vents it safely above the roofline.
Sub-slab depressurization typically reduces indoor radon levels by 80–99%. Other mitigation methods include sealing foundation cracks, sump pit covers, and crawl space encapsulation, though these are usually supplements to, not replacements for, active depressurization.
Mitigation should always be performed by a contractor certified through the National Radon Proficiency Program (NRPP) or National Radon Safety Board (NRSB). Improperly installed systems can fail to lower radon levels or create new pressure imbalances in the home.
Frequently Asked Questions
Is radon dangerous at any level?
Radon risk exists at any concentration, though it increases with higher pCi/L readings and longer exposure. The EPA action level of 4.0 pCi/L is the threshold for recommended mitigation, not a safety cutoff.
Can radon be in any home, new or old?
Yes. Radon comes from soil, not building materials or age. New construction, older homes, homes with basements, and homes with crawl spaces can all have elevated radon.
How often should I test my home for radon?
The EPA recommends testing every two years, and immediately after any major foundation work, renovation, or HVAC changes that could alter airflow.
Does opening windows reduce radon?
Temporarily, yes, but this is not a permanent fix. Radon returns to prior levels once windows close. Only a certified mitigation system provides lasting reduction.
Is radon only a basement problem?
Basements typically show the highest concentrations since they sit closest to the soil, but radon can migrate to upper floors, especially in homes with poor air sealing between levels.
Conclusion
Radon is not a dramatic threat that announces itself. It is quiet, persistent, and dangerous precisely because it goes unnoticed. Understanding what radon is and why it matters empowers homeowners to take control of their indoor air quality.
Testing is simple. Mitigation is effective. The risk is real, but it is also manageable with the right knowledge and professional support. By addressing radon proactively, you protect your health, your home, and your peace of mind.
If you live in Whitefish Bay, Wauwatosa, West Allis, or South Milwaukee, Milwaukee Radon Mitigation provides certified radon testing and mitigation system installation. Call 414-455-7279 to schedule a test or consultation.
