I could not locate a link to the original peer-reviewed publication in order to analyze the actual measurements made and their methodology, but I have to say that using two active airport scanners is not particularly impressive.

Also, as Ink pointed out, radiation is not necessarily ionizing, so comparing total radiation is meaningless. And as Petaluma points out, the increase in population skin cancer can be important, considering they are providing no benefit whatsoever, and therefore should have no risk whatsoever at the very least (not just low risk).

Mostly, this still does not remove the fact that the scanners are ineffective (false negatives) and lead to too many false positives (particularly in persons with private issues or medical devices that are no concern of the TSA at all).