Some granite countertops do emit elevated levels of radon, a radioactive gas that can cause lung cancer. The Environmental Protection Agency says homeowners should take action if radon gas levels in their home exceeds 4 picocuries per liter of air, and some granite countertops have been found to let off far more than that. However, it is not true that all granite countertops emit alarming amounts of radon. Most countertops tested for this emission either registered no release of the gas or such a small quantity that it was statistically insignificant when compared to ordinary background radiation all of us live with. Just how much of a health risk this phenomenon truly poses to homeowners is still a matter of debate, with some researchers pegging the cancer risk from granite countertops at "one in a million." Regarding the question of radon in granite countertops, the EPA said, "Some granite used for countertops may contribute variably to indoor radon levels. At this time, however, EPA does not believe sufficient data exist to conclude that the types of granite commonly used in countertops are significantly increasing indoor radon levels." Inexpensive kits that test for radon (running about $20 to $30 each) can be purchased at hardware stores or bought online through the National Safety Council.
(This report is courtesy of Snopes.com.)