The New York Times has an interesting article about the possibility of granite countertops containing uranium and emitting cancer-causing radon. According to the article, "health physicists and radiation experts agree that most granite countertops emit radiation and radon at extremely low levels. They say these emissions are insignificant compared with so-called background radiation that is constantly raining down from outer space or seeping up from the Earth’s crust, not to mention emanating from man-made sources like X-rays, luminous watches and smoke detectors." At the same time, the EPA "has been receiving calls from radon inspectors as well as from concerned homeowners about granite countertops with radiation measurements several times above background levels."
With the growing popularity of granite countertops in recent years, this is sure to be a hot topic, one in which everyone agrees more research is necessary. In the meantime, here's what to do now. From the article: "To find a certified technician to determine whether radiation or radon is emanating from a granite countertop, homeowners can contact the American Association of Radon Scientists and Technologists (aarst.org). Testing costs between $100 and $300. Information on certified technicians and do-it-yourself radon testing kits is available from the Environmental Protection Agency's Web site at epa.gov/radon, as well as from state or regional indoor air environment offices, which can be found at epa.gov/iaq/whereyoulive.html. Kits test for radon, not radiation, and cost $20 to $30. They are sold at hardware stores and online."