© Scott Olson/Getty ImagesA sign at a Transportation Security Administration (TSA) checkpoint instructs passengers about the use of the full-body scanner at O'Hare International Airport on March 15, 2010 in Chicago, Ill.
But some scientists with expertise in imaging and cancer say the evidence made public to support those claims is unreliable. And in a new letter sent to White House science adviser John Holdren, they question why the TSA won't make the scanners available for independent testing by outside scientists.
The machines, which are designed to reveal objects hidden under clothing, have the potential to close a significant security gap for the TSA because metal detectors can't find explosives or ceramic knives, which can be just as sharp as the box cutters that hijackers used on 9/11.
They are also important for TSA's public relations battle over the alternative, the "enhanced pat-down," which has bred an epidemic of viral videos: A 6-year-old girl is touched from head to toe. A former Miss USA says she was violated. A software programmer warns a screener, "If you touch my junk, I'm going to have you arrested."
After the underwear bomber tried to blow up a Northwest Airlines plane on Christmas Day 2009, the TSA ramped up deployment of full-body scanners and plans to have them at nearly every security line by 2014.
