"Some scientists argue the danger (from back-scatter x-ray devices, the ones the TSA is rolling out) is exaggerated. They claim low levels stimulate the repair mechanism in cells, meaning that a little radiation might actually be good for the body." (Grokked from Tobias Buckell) The first part of that last sentence is true. X-ray radiation is ionizing radiation, in this case it means that when this radiation does damage to your DNA, it breaks the DNA chain. Your DNA can repair itself from such damages. This is called "dark repair" (in contrast to UV/non-ionizing radiation which causes the hydrogen atoms at the edges of your nucleotides - T and A IIRC - to kick into a higher energy level creating new hydrogen bonds between adjacent nucleotides, which can be repaired by a process called "light repair"). So, yes, the damage can stimulate the "dark repair" process. However, to say this is "good for the body" is complete and utter bullshit.
One, it costs you energy, your DNA needs to make the proper enzymes, and the repair isn't always correct. See, this is exactly the mechanism that causes X-rays to cause cancer. If your DNA remains broken, the cell is broken and won't function properly which leads it (in most cases) to apoptosis (or programmed cell death). However if that "dark repair" mechanism switches out some nucleotides while it's repairing that damage, which is possible (the "repair" is just meant to rejoin the DNA), that way can lay cancer.
Just in case you think the government establishes regulations willy-nilly, as in what the conservative Republicans want you to think, don't miss this line: "'Establishing a mandatory standard takes an enormous amount of resources and could take a decade to publish,' said Dan Kassiday, a longtime radiation safety engineer at the FDA." And then there is this line, "… since the mid-1990s, Congress has directed federal safety agencies to use industry standards wherever possible instead of creating their own," and this one: "The government used to have 500 people examining the safety of electronic products emitting radiation. It now has about 20 people. In fact, the FDA has not set a mandatory safety standard for an electronic product since 1985."
Feel safe, yet?
Well, you know, these things (the scanners) should be inspected for safety? Right? "Instead, annual inspections are done by Rapiscan, the scanners’ manufacturer." Because you can trust the person selling you the equipment to let you know when there's a problem with that equipment. Especially when that problem may not appear for years and may not be discernible from the background levels of cancer (see earlier comment about Chernobyl and how many cancers it may have caused).
"Some TSA screeners are concerned about their own radiation exposure from the backscatters, but the TSA has not allowed them to wear badges that could measure it…" Good thing we're not allowing them to form unions. There's a line here about, "if there's no reason to worry, why not let them wear exposure badges?" You know, if you haven't done anything wrong…
It's a good article with lots of info about how the government really works, and the influence of money in politics, the security theater, and just what your representatives (on all sides) are willing to sell your health out to get.