NORMs (naturally-occurring radioactive materials) can be found in granite as well as most other naturally occurring stone materials. According to Radon.com, NORMs emit measurable amounts of radiation.
The EPA claims that only when radon levels exceed 4 pCi/L (picoCuries per liter) in a given area is there cause for concern. Exposure to more concentrated radon levels poses risks to a person's health.
Granite countertops are found in countless homes across the globe. The average radon emissions from a granite countertop are around 1.9 pCi/ ft^2 (picoCuries per square foot per hour) according to GreenBuildingElements.com.
Radon is easily detectable. Curious consumers can purchase at-home radon detection kits to test the radon levels produced by a given granite item or countertop in their home. According to GreenBuildingElements.com, California residents can purchase these kits for $5 to $25.
The soil under a home produces more radon levels than the typical granite countertop, according to Radon.com. People are more likely to be affected by radon emissions from the soil under the foundation of their home than the radon emissions from their granite counter.