The idea that radio frequency waves emitted by cell phones might penetrate users’ skulls, damage brain cells, and cause brain tumors has worried some people for decades. But there’s very little evidence that this occurs. “There’s a greater risk of physical harm from not paying attention to where you’re walking or driving while using a cell phone,” argues Linda Nebeling, PhD, deputy associate director of the National Cancer Institute (NCI)’s Behavior Research Program in Rockville, Maryland. That said, other experts suggest playing it safe until more is known. “I frequently tell patients to use a wired earpiece if they’re worried,” says Otis Brawley, MD, chief medical officer of the American Cancer Society (ACS). (Children may be more vulnerable to cell phone radiation than adults, who have thicker skull bones.) And if you store your phone in a T-shirt pocket or bra, break the habit, advises Marisa Weiss, MD, founder and chief medical officer of Breastcancer.org. “Even if you’re not using it, the antenna is still active, and breast tissue is highly sensitive,” she explains.