When reading real estate listings, most of us would associate granite countertops with luxury homes, and consider them a coveted feature. That is, unless you knew they could be emitting elevated levels of radon, a radioactive gas that can cause lung cancer. A recent New York Times article, "What's Lurking in Your Countertop?" chronicled the trials of one homeowner and doctor who found that his radon gas levels were reading 100 picocuries per liter, a far cry from 4 picocuries per liter, which the Environmental Protection Agency (E.P.A.) considers a health risk. Apparently, as the popularity of granite countertops has increased in the last decade, so have reports of potentially hazardous countertops. While most "health physicists and radiation experts agree that most granite countertops emit radiation and radon at extremely low levels," the risk of exposure from "exotic and striated varieties from Brazil and Namibia," has yet to be evaluated. When it comes down to it, "There is no known safe level of radon or radiation," says an E.P.A. program analyst. So, if you can choose a risk-free alternative, why wouldn't you? At the very least, it's a smart idea to have your countertops tested.