Originally Posted by Ron Bennett

To chime in regarding the X-Ray backscatter scanners, the risk of going through such machines isn't necessarily the nominal amount of radiation, but the potential exposure to much higher levels in the event of a malfunction...

Readup on the Therac-25 saga ... http://en.wikipedia.org/wiki/Therac-25 ... it's a warning of what can go wrong even with seemingly well designed machines - not the only case either, since there have been numerous other x-ray diagnostic machines that have experienced nasty problems.

Point is that radiation dose can't be guaranteed except by hardware interlocks, robust design, and much testing - it's likely the X-Ray backscatter machines the TSA are deploying are built by the lowest bidder with little testing in regards to overdosing...

A related issue is X-Ray concentration ... while the TSA touts the X-Ray exposure as being very low, which may very well be true, that neglects to take into account that exposure is likely not going to be uniform - some portions of a person's body may be exposed to far higher levels due to the design of the machine, one's individual body shape, and their position and time in the machine.

Ron