Are Granite Countertops Radioactive? Radon Facts for NJ

Yes, in a trace way, and for most homes the stone is not the part to worry about. Granite contains small amounts of uranium and thorium, which are naturally radioactive, and the amount varies from slab to slab. The EPA says it is extremely unlikely that radiation from a granite countertop would raise your annual dose above normal background levels. The open question is radon gas, and the EPA says the data is not good enough to settle it.

Two things are easy to mix up. Radiation is energy the stone gives off directly, mostly small amounts of beta and gamma rays that fade quickly as you move away. Radon is a gas that forms when uranium in rock breaks down, and it is the one that can build up indoors.

Some older pages call granite completely safe. The EPA does not say that, and no agency below promises every slab is the same.

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Usually not. The EPA says radiation from granite decreases quickly with distance and that it is extremely unlikely to raise annual doses above normal background. The same EPA radon page also says some types of granite may emit gamma radiation above typical background levels. That is why numbers differ by slab.

Connecticut measured more than 400 granite slabs, samples and countertops and found most showed insignificant increases over background levels. For the highest slab it measured, leaning on it two hours a day for a year would add about 10 to 13 millirem. The average American gets about 360 millirem a year from all sources, and background in Connecticut commonly varies by 40 to 50 millirem a year. Connecticut's page was last updated in December 2008 and measured dose, not radon in homes.

An older EPA page, updated April 2020 and now only an archived snapshot, called countertops not a key contributor to radiation in the average home and noted that granite is not porous and its exposed surfaces are treated with sealant. Treat that as dated background, not the EPA's current word.

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Granite can release radon, because the uranium in the rock decays into it. What nobody has settled is how much that adds to a real home. In its April 2026 update the EPA says the existing data is insufficient to conclude that commonly used countertop granite significantly raises indoor radon, and that a generally accepted testing protocol for countertops does not exist.

The EPA also says the principal source of radon in homes is the soil in contact with basement floors and walls, and that no regulations cover radon or radiation from granite countertops. A University of Georgia radon educator put soil at nearly 70 percent of radon sources and building materials at about 2.5 percent, the second figure footnoted to a testing company, so treat it as an estimate.

The Natural Stone Institute, a stone industry group, points to a 2008 review of more than 500 radon measurements and a 2010 Health Canada test of 33 granite types, and it reports radon from granite far below outdoor air. We read the group's page, not the studies, so take this as industry evidence, not proof that every slab is fine.

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Because radon from any source is a real health problem, and only a house test tells you what you breathe. The EPA says radon is responsible for about 21,000 lung cancer deaths every year, about 2,900 of them among people who never smoked, and the CDC says there is no known safe level.

The unit on a result is picocuries per liter of air, a measure of how much radioactivity is in each liter. The EPA action level is 4 picocuries per liter. At 4 or more, the EPA health page says to remedy the problem as soon as possible. New Jersey's DEP says radon enters homes through openings that touch the ground, such as foundation cracks, gaps around pipes and sump pits, and it recommends that all homes be tested.

A test cannot tell you whether the countertop caused a reading. It tells you whether your family's air needs action, and the fix is the same either way.

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Buy a New Jersey certified test kit or hire a certified radon measurement company, and put the device in the lowest livable level of the home, not in the kitchen. The rules below come from New Jersey DEP granite guidance dated August 22, 2008, the only state text we could open. Its current radon pages would not load for us, so confirm details with the NJDEP Radon Program.

Certification matters here. That 2008 text says it is against the law to do radon testing or mitigation without certification, and that a retail kit should carry its producer's New Jersey certification number, which begins with MEB9 followed by four digits. It also pointed homeowners to a state list of certified companies, including ones that mail a kit, at njradon.org. That pointer dates from 2008, so ask the NJDEP Radon Program for its current list.

A mailed kit is simple: follow the instructions, fill in the form, and send the device to the lab in the pre-addressed envelope. The result comes back in picocuries per liter.

• Lowest livable level: the lowest level used or usable as living space, such as a finished or unfinished basement, or a first floor with no basement. A crawl space does not count.
• Not in kitchens, bathrooms, laundry rooms or closets, and not in direct sunlight, drafts, high heat or high humidity. DEP says moisture, heat and exhaust systems disturb the test.
• At least 20 inches off the floor, 4 inches from other objects and 36 inches from doors and windows to the outside.
• Never under a bowl or covered. DEP says confining the device inflates the reading.
• For short tests, keep exterior windows and doors closed, starting at least 12 hours before any test shorter than four days, and do not run attic or window fans. DEP says ventilation can raise or lower radon in unpredictable ways.
• If you still want a check near the granite, DEP says to test a room next to the kitchen in addition to the lowest livable level.

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Test the house first. It is the only option in the table with an accepted method behind it, and it is what the EPA and New Jersey's DEP both ask for.

If your result is 4 or higher, fix the home. The EPA's January 2026 page says the most effective action may be to install a device that removes radon from the air in the home, rather than removing the countertops. Its April page says commonly used mitigation techniques can bring radon from the soil under a home down to 2 or less. The 2008 DEP text says about half of mitigated New Jersey homes reached under 1, and that the contractor must be certified too. The CDC says to retest after the work, and that opening windows or improving airflow alone is only a temporary measure.

Under 4, the 2008 DEP text says you may ask a mitigation company whether it can come down further.

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Ask for the stone's name and country or quarry of origin, and whether it has been sealed. Then ask what the shop can and cannot say about radon. A countertop shop is not a radon lab. Penn State's 2008 piece said most granite suppliers do not have the means or facilities to test for radioactivity, so our guess is that nobody will hand you a certificate for a slab.

If the answer matters to your family, run the house test first and choose the slab with the result in hand. A home result will not isolate the countertop, because ventilation moves radon readings around, but it shows whether the air needs action.

At New Granite & Marble the usual path starts with a written estimate from your measurements, and you choose the slab at the stone yard. Bring your measurements, a rough layout showing the sink, the cooking surface and the backsplash, and your radon result if you have one.

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More on this site: granite countertops, quartz countertops, how our process works and ask the shop.