As demand for granite has increased, exotic stones are being imported from remote corners of the world and greater scrutiny is needed, said William Llope, a nuclear physicist at Rice University in Houston. Llope started testing granites as a hobby after he was asked to test a countertop and was surprised at the level of radiation.
"It's an uncontrolled situation," he said. "The majority of granites are quiet," with radiation levels that are negligible when compared to background radiation. But there are now about 2,000 granites being exported from about 70 countries, he noted. Some quarries within miles of uranium mines.
"Some stones from Namibia and Brazil are wicked hot." Still, the health risk is ambiguous and probably long-term.
"You're not going to spend six months in your kitchen and die of cancer," Llope said. But extended exposure to the hottest granites he's tested has the potential to increase lifetime cancer risk, especially for young children.
Many in the industry believe that any risk is being wildly overblown by those with commercial motives. Guido Gliori, president of the Marble Institute, says that some of the research linking granite and radiation has been funded by manufacturers of competing countertop materials, including Cambria, the company that produces quartz countertops.