Radon Testing
Testing indoor air for radon, a radioactive gas from soil and rock that you cannot see, smell or taste.
Last revised
Key takeaways
- EPA action level: 4 pCi/L or higher: fix the home
- Between 2 and 4 pCi/L: EPA recommends considering a fix
- Most useful single change: Test every home, whatever its age or location; neighbors' results do not predict yours.
- Commonest mistake: Assuming new homes or homes without basements are radon-free.
- See a doctor if any of the signs under "When to get help" below apply to you.
Why it matters
Radon is the second leading cause of lung cancer in the US and the leading cause among people who have never smoked, and testing is the only way to know your level.
The numbers, in one place
| Measure | Figure |
|---|---|
| EPA action level | 4 pCi/L or higher: fix the home |
| Between 2 and 4 pCi/L | EPA recommends considering a fix |
| Homes with elevated radon | about 1 in 15 US homes, per EPA |
| Lung cancer deaths linked to radon | about 21,000 a year, per EPA |
| Where to test | the lowest lived-in level of the home |
What helps
- Test every home, whatever its age or location; neighbors' results do not predict yours
- Use a short-term test kit, then a follow-up test if the result is 4 pCi/L or higher
- Hire a qualified radon mitigation contractor if levels are high; a common fix is a vent pipe and fan system
- Retest after mitigation and every 2 years afterward, and after major renovations
- Ask your state radon program about low-cost test kits
What to avoid
- Assuming new homes or homes without basements are radon-free
- Testing with windows open or during a strong storm, which can skew results
- Smoking, which greatly increases the lung cancer risk from radon
In depth
Radon forms naturally when uranium in soil and rock breaks down. As a gas, it moves up through the ground and slips into buildings through cracks in foundations, gaps around pipes, sump pits and crawl spaces. Outdoors it disperses quickly, but indoors it can build up. The way a house is built, the soil beneath it and even the weather affect how much enters, which is why two neighboring homes can have very different readings.
The danger comes from what radon turns into. When you breathe it in, radon and its short-lived breakdown products can lodge in the lining of your lungs and release small bursts of radiation. Over years, that radiation can damage the DNA in lung cells, raising the chance that a cancer will develop. Radon causes no symptoms while you breathe it, and it does not cause headaches, rashes or other short-term illness, so a home can feel perfectly comfortable while still carrying a high level.
The risk depends on both the level and how many years you are exposed, which is why the focus is on long-term averages rather than a single day's reading. Smoking multiplies the effect: people who smoke and live with high radon have a much higher lung cancer risk than people exposed to either alone. The encouraging part is that radon problems are well understood, testing is inexpensive, and proven mitigation systems can bring levels down substantially in most homes.
Causes and risk factors
- Uranium-bearing soil and rock beneath the home, which varies widely by area
- Cracks in slabs and foundation walls, and gaps around pipes and wiring
- Basements, crawl spaces and sump pits open to the soil
- Lower air pressure inside the home, which draws soil gas in, especially in winter
- Radon released from private well water during showering and washing
- Tightly sealed homes with little ventilation, which can let levels build
How it is checked
There is no medical test that measures how much radon you have breathed. The home is what gets tested. Short-term tests, which stay in place for a few days up to about three months, give a quick snapshot and are a good first step. Long-term tests, left for more than 90 days, give a better picture of your year-round average because radon rises and falls with seasons and weather. A qualified radon measurement professional can also test, and is commonly used during home sales.
For your health, the question your doctor will focus on is your overall lung cancer risk. Radon history is worth mentioning, but current US screening guidance from the USPSTF is based on age and smoking history: yearly low-dose CT scans are recommended for adults 50 to 80 who have a 20 pack-year smoking history and smoke now or quit within the past 15 years. Your doctor can explain whether you qualify and what screening involves.
Related topics
- Air Quality: What the Evidence Actually Says (Respiratory Health)
- Carbon Monoxide During Power Outages: What the Evidence Actually Says (Heat, Cold and Weather Safety)
- Sun Protection: What the Evidence Actually Says (Skin Health)
- Reducing Cancer Risk: Sorting the Evidence From the Noise (Cancer Awareness)
Where to go next
- Radon Testing: Just the Figures
- Radon Testing: What Published Guidance Supports
- Environmental Health: The Complete Guide
- What the Guidance Really Says About Mold at Home
- What the Guidance Really Says About Drinking Water and Private Wells
When to get help
See your doctor about lung cancer screening and any symptoms if you have lived with high radon, especially if you smoke or used to. See your doctor for a cough that will not go away, coughing up blood, chest pain or unexplained weight loss, and call 911 for severe trouble breathing or coughing up large amounts of blood.
Where this comes from
- EPA — A Citizen's Guide to Radon
- National Cancer Institute — Radon and Cancer
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.