No, I am not trolling. Please try to read comments more charitably instead of assuming malice. Yes, I was comparing skin dose to the annual limit for the whole body. Depending on what you count as skin, skin is 2-5% of an adult's mass. So it would take thousands of scans per year to exceed the dose limit. In other words, safe.

I know what a sievert is (your definition is incorrect) and I know different types of ionizing radiation affect different tissues differently. But the safety margin is so great (89,000!) that it would take a new mechanism of action for such a tiny dose of X-rays to cause disease.

Edit: Because you deleted your comment, other readers now have no clue what I responded to. :/

> Sv is 1 joule of radiation absorbed for every kg of a person's weight, but that 1 joule could come from alphas, betas, gammas, or x-rays. It may be a fixed amount of energy, but whether it comes from photons or electrons or positrons or helium nuclei is _IMPORTANT_.

No, that's factually incorrect. You're thinking of the gray (Gy), which is 1 J/kg no matter what. 1 J of gamma absorbed is 1 Gy and 1 Sv, but 1 J of alpha absorbed is 1 Gy and 20 Sv. 1 Sv of neutrons is only 0.1 Gy.

It doesn't help that they are dimensionally equivalent, so there's a proliferation of unit converters which consider the conversion to be 1.0 always.

> Unless someone works with radiation, I cannot imagine how anyone's skin is constantly bombarded by these types of particles.

Depends. Some people have granite countertops in their kitchens which give off Radon, an alpha emitter. (Not all granite does this.)