My problem with this study--which I have not seen--based upon this news story is whole body  dosage was used.  The vast majority of radiation doesn't penetrate more than half an inch into the flesh so a great deal less than "whole body" is being exposed.  If I were a frequent flier/air crew (who already get double the dosage of radiation at high altitude per year as "normal" people) or even more a TSA agent standing around the x-ray machines all day I would not like the frequent exposure.  Radiation damage is cumulative.  There is no such thing as a safe dosage.  Just acceptable tradeoffs.