Backscatter X-ray scanners use X-ray photons. Millimeter-wave scanners use far-infrared/microwave photons. To the best of my knowledge, nobody's every shown tha

Backscatter X-ray scanners use X-ray photons. Millimeter-wave scanners use far-infrared/microwave photons. To the best of my knowledge, nobody's every shown that microwaves or infrared light cause cancer: the photons just don't have enough energy to cause that kind of cell damage. (Yes, this is quibbling about what was probably just an error in definition; I think your comments are right as applied to backscatter X-ray scanners. But if we keep our language straight, our arguments against these blasted things will be that much harder to dismiss.)