Can Granite Countertops Release Radon? (And Other Surprising Sources No One Talks About)
Published July 29, 2025 | Updated November 17, 2025
Photo by Clay Banks
If you picture basements and foundation cracks when you think about radon, you’re right—the bedrock and soil beneath your home is the primary source of indoor radon. But(!) I regularly get questions about other potential sources: "Can my granite countertops release radon?" "Is there radon in my well water?" "Will an air purifier fix my radon problem?"
These are very smart questions, and the answers aren't always what you'd expect. As a physician who evaluates home materials with a skeptical stance, here is the evidence-based truth about uncommon radon sources and why air purifiers don't actually work.
The Granite Countertop Question: Should You Worry?
No, you should not worry. Yes, granite can contain trace amounts of uranium and thorium, which decay into radon gas, but most granite contributes such a small amount that it's undetectable compared to radon entering through your foundation, or even compared to regular, background outdoor levels. (FYI, a high indoor level is ≥4.0 pCi/L, and regular background outdoor radon air levels hover around 0.4 pCi/L.)
What you can actually do:
If you're still concerned about existing granite countertops, here's a practical approach: Get two 90-day radon test kits. Place one in your basement or lowest floor (the standard testing location) and one on or very near your granite countertop. If the countertop reading is significantly higher than your basement reading, your granite may be contributing.
Important caveat: This isn't a scientifically validated testing method, but it can give you directional information. For ongoing peace of mind, a continuous radon monitor placed in your kitchen can track whether your countertops are actually affecting your air quality over time.
In short, unsealed granite is still one of the healthiest countertop materials you can choose—it's non-toxic, durable, and doesn't off-gas VOCs like some synthetic surfaces. The radon risk from most residential granite is minimal.
Radon in Well Water: An Overlooked Route of Exposure
One source of exposure that is often overlooked and is worth your time worrying about is radon dissolved into well water. Radon can dissolve into groundwater, and when you use that water in your home—especially for hot showers, dishwashing, or laundry—the radon gas is released into your indoor air.
According to the EPA, water typically contributes only 1-2% of indoor airborne radon. But if your well water contains very high radon levels (and many private wells do), that percentage can be enough to push you over safe exposure limits.
The health risk you actually need to worry about:
The primary concern isn't drinking radon-contaminated water (though there may be a slight increased risk of stomach cancer). The real problem is inhalation. Every time you run hot water, radon gas is released as steam and you breathe it in. Over years of daily showers, that adds up.
Unlike city water supplies—which are required to meet federal safety standards—private wells aren't federally regulated for radon. Many states don't test for it either. If you're on well water, you're responsible for testing it yourself.
What you should do:
Start by testing your indoor air with a radon monitor or 90-day test kit
If your air levels are high (≥4.0 pCi/L) and you use well water, test your water too
If your well water exceeds safe radon levels, contact your county for water filtration and mitigation assistance.
For most homes, soil is still the dominant radon source. But if you're on a private well in an area with radon-rich bedrock (granite, shale, limestone), waterborne radon shouldn't be dismissed.
Photo by Clay Banks
Natural Gas: Another Radon Source No One Mentions
If you burn natural gas in your home—whether through a gas stove, furnace, or water heater—you're introducing small amounts of radon into your indoor air. Natural gas can contain radon because it's extracted from underground deposits where uranium naturally occurs.
The contribution is generally low compared to soil sources, but it's cumulative. If you already have elevated radon from your foundation and you're also burning gas indoors without proper ventilation, you're compounding your exposure.
This is yet another reason to ensure adequate ventilation around gas appliances and to test your home's air regularly—especially if you've recently switched from electric to gas heating or cooking.
Why Air Purifiers Don't Remove Radon (Even Though Everyone Thinks They Should)
When people discover high radon levels, one of the first questions I get is: "Can I just run an air purifier?"
The short answer: No!
Here's why: Radon is a radioactive gas, not a particle. Most air purifiers—even high-end HEPA models—are designed to capture particulate matter like dust, pollen, mold spores, and smoke.
Some people assume activated carbon filters will help, since activated carbon and other minerals can absorb gases. And technically, yes—thick carbon filters can absorb small amounts of radon. But you would need an industrial-scale filtration system running continuously to make any meaningful dent in radon levels. The amount of activated carbon in a residential air purifier is nowhere near sufficient.
What about radon decay products?
Radon gas decays into radioactive particles that attach to dust, get inhaled, and then lodge in your lungs. Some advanced air purifiers with thick carbon beds may capture a small percentage of these decay products, but they won't stop radon gas from entering your home and continuously generating new decay products.
Even manufacturers of high-end air purifiers acknowledge this. Air purifiers are useful for particle pollution, VOCs, and allergens—but they are not a radon solution.
The only effective fix is a properly installed radon mitigation system (typically active soil depressurization), which uses a vent pipe and fan to draw radon from beneath your foundation and exhaust it above your roofline before it ever enters your living space.
How to Know If These Sources Are Affecting Your Home
The only way to know whether granite, well water, or natural gas is contributing to your radon levels is to test your air—and ideally, test continuously over time.
Short-term radon tests (2-4 days) won't capture fluctuations caused by seasonal water table changes, varying natural gas usage, or temperature shifts that affect granite off-gassing. You need long-term data.
A continuous radon monitor lets you:
Track whether levels spike when you're using hot water (indicating a well water contribution)
Compare readings in different rooms (like basement vs. kitchen near granite counters)
Monitor trends after installing mitigation or switching from gas to electric appliances
For my recommendations on the most accurate continuous radon monitors—and which ones actually have third-party verification (since the U.S. has no federal accuracy standards for consumer radon detectors)—see my complete guide to radon detector kits here.
The Bottom Line: Test First, Panic Second
Granite countertops, well water, and natural gas can all contribute small amounts of radon to your indoor air. But in the vast majority of homes, soil beneath your foundation is still the primary source.
Don't avoid granite counters or rip them out based on fear. Don't assume your well water is the problem without testing. And definitely don't waste money on an air purifier hoping it will fix radon—it won't.
Instead: Test your air first. If levels are high, work with a certified radon mitigation professional to identify where radon is actually entering your home and install the appropriate system. Then re-test to confirm it worked.
Radon is a real health risk—it's the second-leading cause of lung cancer in the U.S., responsible for 21,000 deaths annually—but it's also fixable. With accurate testing and proper mitigation, you can reduce your exposure to near-outdoor background levels (typically below 0.4 pCi/L).
Start with continuous monitoring so you understand your true exposure, not just a snapshot. For detailed guidance on choosing the right radon detector, visit my radon detector guide here.
Sources:
U.S. Environmental Protection Agency – Radon Information, epa.gov
U.S. Environmental Protection Agency – Granite Countertops and Radon, epa.gov
Centers for Disease Control and Prevention – Radon and Health, cdc.gov
Cleveland Clinic – Radon Gas: Causes, Exposure, Symptoms, my.clevelandclinic.org
