I totally concur with RadioGirl, and am an RF engineer as well. I posted this rather lengthy explanation to my Facebook group last July, and will repost here:
A little primer about radio and x-rays.

Radio consists of radiated waves of different frequencies. These frequencies run from DC up to the far infrared frequencies. More than 100 years of research and experimentation has pretty much proven that "radio" waves have no mutinogenic effects on tissue. At lower frequencies, these waves pass harmlessly through tissue and apparently do no damage, even at very high power levels. At very high frequencies (microwave), these waves seem to be absorbed and there is a heating effect on tissue. Tissue destruction can occur if the power level is high enough, but even at these high levels damage is due to burning and destroying tissue, not mutinogenic effects, like cancer.

High power microwaves are used to cook stuff, like TV dinners, because the waves are absorbed by water-bearing items and converted to heat. The same frequency waves at much lower levels appear to be harmless, causing only slight heating without destruction of tissue. At even lower levels, history has proven them completely harmless.

We are constantly bombarded by radio waves, and can't escape them. Just think how many radio and television stations you can receive at your house, how many cell phone towers, microwave links, satellite dishes, etc there are in your locale. Even the automatic door openers at the market and bank are beaming microwaves at you to "see" you and open the door. Your computer emits low to medium frequency radio waves, in addition to the wireless adapter which transmits microwaves. Your TV emits spurious radio waves. Every CPU in your phone, car, digital appliance, etc emits radio waves of some frequency or multiple frequencies. Your microwave oven even leaks a small amount of microwaves. Your cell phone is a microwave radio as well.

It is accepted in the scientific community that ordinary radio waves are harmless below a certain amount of power (expressed in W/CM2). Because of the heating effects of higher frequencies (microwaves), the safe power levels are much lower than at lower frequencies. Even above the "safe" limit, cancer is not induced. There are no known MUTINOGENIC effects.

While I completely disagree with naked body scanners, and will never subject myself to one, the frequency and power levels employed are clearly a non -issue. Your cell phone and the wireless adapter in your laptop are thousands of times more powerful, and they are generally considered safe. There is no proof that cell phones are dangerous, although millions have been spent researching the matter, but there is no repeatable, scientific evidence.

X-Rays, however, are a completely different animal. Their frequency is so high, that they are considered "energetic particles", not waves. They interact with tissue knocking atoms out of their orbits, and have known, certain mutinogenic effects. They absolutely induce cancer, although there is some argument whether or not there is a "safe" threshold. X-ray body scanners operate below what some scientists consider this safe threshold, but there is no universal agreement about this. Therefore it is prudent to avoid unnecessary x-rays from any source, unless there is clear benefit to be derived, like medical and dental x-rays.

Remember that the US and other countries outlawed Freon, with the rationale that depleting the ozone in the atmosphere would increase the UV radiation on the ground, causing more cancers in people. These are the same bozos beaming x-rays at us, certainly causing some cancers, but nobody knows how many. For this reason, x-ray scanners need to be immediately abandoned, and the EU has outlawed them for Europe. Only the US and UK have been duped into using these machines, as they do produce higher image quality than the MM wave type, and they clearly had better lobbying. Remember that Michael Chertoff was the former head of TSA before promoting these things - he has the right "connections".

All that being said, the MM wave scanners with auto detect software appear to be safe for your privacy and safe for your body, providing there is no raw image storage or review. However, they are expensive and slow as well as ineffective, causing lots of false positives due to medical devices, folds of fabric, lint in pockets, etc. This is the WRONG METHODOLOGY for finding explosive materials! The X-ray type scanners need to be pushed into the ocean immediately. Better yet, push them all in the ocean and bring on the dogs and save a BIG PILE of money!