Yes, this dose emanating from the top of the machines will result in scatter analogous to skyshine as well as primary dose to those standing above it. Here's a link to clarify the phenomenon, it's found in megavoltage therapy environments:
http://www.whiterockscience.com/moritz/aex.html
In a nuts , it's scatter radiation from a primary gamma beam (or in this case our friendly X-ray machine) from atmospheric dispersion.
How much dose this results in is a function of the technique used to produce the backscatter images. The more I read, the more I'm willing to bet that those aren't consistent either. For reference, I've inserted a quick dose calc based on the dose rates we use in radiotherapy. In reality, the dose rates seen with these scanners is an order of magnitude lower (10-20 mGy)
If anyone is interested, you can follow either this pdf which walks through the calculations:
http://www.aapm.org/meetings/07ss/do...STRUCTURES.pdf
or........... suffer through reading a thesis about it as I do:
http://www.cvmbs.colostate.edu/erhs/...der_Thesis.pdf
Again: Of note.......those calcs are done on megavoltage machines (6-18Mev) whereas the scans done on these machines use energies 3 orders of magnitude lower. That translates to dose rates in the 10 mGy range instead of the 10cGy range used in the calcs. Good thing is that the physical interaction mode does not change. Extrapolate carefully!!
From both examples we can see that doses are in the nSv/uR range. The problem is the volume of scans that a worker is exposed to over the course of a workday (I don't know the exact amount but I'm guessing it's pretty high.....300-400 perhaps?), and their proximity to the machine during those scans. ulative dose can become problematic in that case.
, even an X-ray tech walks out of the door or behind a wall before yelling "X-ray!!!". TSA employees stand next to the controls the entire time.
You essentially have a non-licensed operator(s) in charge of operating machinery that imparts dose to people. I don't understand why this is allowed. Quite disturbing tbh.

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