Do granite countertops give off radon? What EPA says and what actually matters

Every few years, news stories raise alarms about granite countertops giving off radon or radiation. It's true that some natural stone contains small amounts of uranium, thorium, and radium, and that radium can decay into radon. But how much does a countertop actually contribute to the radon in your home? This guide summarizes what EPA says, and what to focus on instead.

What EPA says

EPA's position is clear: it believes the principal source of radon in homes is the soil in contact with basement floors and walls. Its guidance on countertops says:

• Natural rocks such as granite may emit radiation and radon gas, but the levels attributable to such sources are not typically high.
• To reduce radon risk, you should first test the air in your home to find the radon level. EPA notes that do-it-yourself test kits are available through retail outlets and online, starting at about $25.
• If your home has a radon level of 4 pCi/L or more, you should take steps to fix it and reduce the radon level.
• No generally accepted radiation testing protocol for countertops exists, and neither imported nor domestic granite products are required to undergo radiation testing.
• A specially trained radiation professional may be able to test for other radon sources, such as granite or drinking water, when diagnosing a home's radon problem.

EPA's Consumer's Guide to Radon Reduction adds that building materials, including some concrete products, can give off radon, but rarely cause radon problems by themselves. Radon gas in soils is the principal source of elevated radon levels in U.S. homes.

Why soil matters more than stone

Think about the scale. Soil gas enters through the entire footprint of your foundation, and it's constantly replenished from a huge volume of earth beneath the house. Your house's slight vacuum pulls it in continuously, especially in winter. A countertop is a few square feet of stone with a limited amount of radium, sitting in a ventilated room. Even when a particular slab emits measurable radon, it's usually a small contribution compared with soil gas.

That's why EPA's advice starts with an air test, not a countertop test. If your home's air is below the action level, the countertop isn't creating a radon problem. If it's above, soil gas is overwhelmingly the most likely cause, and a mitigation system is the fix.

What about radiation, not just radon?

Some stones also emit small amounts of gamma radiation directly. Concerns about this are separate from radon. As EPA notes, there's no generally accepted protocol for testing countertops, and radiation concentrations can vary within a single slab. Consumer Geiger counters can detect radiation, but interpreting the readings meaningfully is difficult without professional training. If you have specific concerns, a qualified radiation professional can assess your situation.

If you're worried about your countertop

1. Test the air in your home first. Use a short-term test in the lowest lived-in level, following closed-house conditions. You can also place a second test in the kitchen for comparison.
2. Compare to EPA's levels. The average indoor level in U.S. homes is about 1.3 pCi/L. EPA recommends fixing at 4 pCi/L or higher and considering it between 2 and 4.
3. If the kitchen reads much higher than the rest of the house and above the action level, talk with a radon professional about diagnosing sources. Soil gas entry near the kitchen, through plumbing penetrations for example, is still more likely than the stone itself.
4. If the whole house is elevated, plan for standard mitigation. Replacing countertops won't fix a soil gas problem.

Choosing countertops

If you're remodeling and want to minimize any concern, you can ask suppliers for information about the stone's origin. Some suppliers have had samples tested. Remember, though, that EPA says levels from such sources aren't typically high. Choosing a countertop based on radon fears alone is rarely necessary. Testing your home's air is a far better use of time and money.

Frequently asked questions

Should I remove my granite countertops? EPA's guidance doesn't call for removing countertops. It says the radon levels attributable to natural rock like granite aren't typically high, and that the key step is testing your home's air and fixing it if it's 4 pCi/L or higher.

Can I test my countertop with a radon kit placed on it? A kit placed on a countertop measures the air in that spot, not radiation from the stone. EPA notes there's no generally accepted protocol for testing countertops. Follow the kit's placement instructions, which usually say to put it in a living area about 20 inches or more above the floor, away from drafts.

What about other stone, like quartzite, marble or engineered quartz? All natural stone contains some trace radioactive elements, in amounts that vary by type and quarry. The same principle applies: soil gas is the dominant radon source in homes, and an air test tells you whether there's a problem.

What about concrete or other building materials? EPA's Consumer's Guide notes that building materials, including some concrete products, can give off radon, but rarely cause radon problems by themselves.

Does a radon mitigation system help if a countertop is a source? A sub-slab system targets soil gas, not the stone. That's another reason to measure first: if your levels drop below the action level after soil suction is installed, the countertop wasn't a meaningful source.

Where can I get a test kit? Hardware stores, online labs, and many state radon programs sell or give away kits. EPA notes DIY kits start at about $25.

The bottom line

Granite countertops make headlines, but soil is the real radon source in almost every home. Test your air, fix it if it's high, and enjoy your kitchen. See how to test your home for radon and radon myths and facts.

Key takeaways

• EPA says soil is the principal source of radon in homes.
• Radon levels from natural stone like granite aren't typically high, according to EPA.
• No generally accepted protocol exists for testing countertops.
• Test your home's air first, and fix it if it's 4 pCi/L or higher.