Heads up, yuppies: Must-have granite countertops may emit worrisome levels of radon and radiation. While granite is known to contain radioactive uranium, which emits radon gas as it decays, the vast majority of countertops emit far less radiation than what we’re constantly exposed to from outer space and the earth’s crust. But as demand for granite countertops soars and vendors expand their selection — some now stock hundreds of types of the rock from dozens of countries — a small number of countertops have been found to emit radiation at a level that could conceivably pose a health risk. “It’s not that all granite is dangerous,” says one radon measurement and mitigation technician. “But I’ve seen a few that might heat up your Cheerios a little.” You’re more likely to be struck by lightning than to get cancer from your countertop, says radiation expert David J. Brenner; but, he adds, “If you can choose another counter that doesn’t elevate your risk, however slightly, why wouldn’t you?”