The backscatter machines, meanwhile, are low-level X-ray machines that expose bodies to as much radiation as about two minutes of flying in an airplane does. In other words, if you already use a cell phone and you already fly, you are already exposing your body to more radiation than these scanners will.
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http://news.cnet.com/8301-27083_3-10...#ixzz1JRAgu5m8