Some airport scanners may pose a cancer threat for people over age 65 and women genetically predisposed to breast cancer, a Fort Lauderdale, Fla., doctor said. Dr. Edward Dauer, head of radiology at Florida Medical Center, said the scanners\' low dose of radiation penetrates just below skin level, possibly endangering the eye lens, the thyroid and a woman\'s breasts, the South Florida Sun Sentinel reported Sunday. \"I think it\'s potentially a real danger to the public,\" he said, explaining that even a small dose could be a risk for people predisposed to cancer. \"This is an additional exposure.\" The Transportation Security Administration said the scanners are safe and cites independent studies that said radiation levels are well below acceptable limits. The scanners in question use \"backscatter technology\" to create an image of a passenger that allows security personnel to see whether suspect items are hidden underneath clothing. The TSA has installed about 250 of the backscatter scanners at 40 U.S. airports, including the Fort Lauderdale-Hollywood International Airport, and airports in Los Angeles, Chicago, Boston and New York\'s John F. Kennedy International Airport. The problem, Dauer said, is the machines emit ionizing radiation. \"Ionizing means it knocks the electrons out of your body, which breaks your DNA chain, which can cause death or cancer,\" he said. The agency also uses more than 540 millimeter-wave scanners, considered a safer option because they don\'t rely on radiation, the Sun Sentinel reported.