The distinction you are trying to make is not between emitting and not emitting radiation - most of these scanners emit some form of electromagnetic radiation.

The distinction you are trying to make is not between emitting and not emitting radiation - most of these scanners emit some form of electromagnetic radiation. The distinction you're trying to make is between ionizing radiation (x-rays; causes cancer) and non-ionizing radiation (all other sorts of electromagnetic radiation including visible light, infrared, microwaves, and so on; doesn't cause cancer). The TSA currently has some scanners that scan using x-rays and some that scan with non-ionizing radiation. A regular boring old security camera is also a scanner that emits non-ionizing radiation - most of them use infrared LEDs to illuminate at night. If you could see into the infrared it would look like every security camera has a big flashlight mounted next to it, shining on you. So the target, you, gets irradiated with non-ionizing infrared rays, which bounce back to the camera and are recorded. Using different wavelengths of illumination, you find that some of them penetrate clothes easily to see what's underneath. That's what the NYPD/security apparatus are interested in.