Backscatter chatter

There’s been talk recently of using new “backscatter” machines for passenger screening to detect explosives and other dangerous items that a metal detector would miss. Most of the commentary has been about the threat to privacy, since the machines essentially look through your clothes. That’s to be dealt with by degrading the images to a certain extent.

I’m not too worried about privacy. After all, how much privacy and dignity do we really have left at airport checkpoints these days any way. On the other hand, backscatter is produced by radiation. In other words passengers will be going through X-ray machines. Patients are getting exposed to some alarmingly high doses of radiation from CT without anyone taking notice, so I wondered about the effects of backscatter on frequent fliers like me who might go through them hundreds of times every year.

I got some reassurance from a Health Physics Society article, which reports that it would take 200 screening scans in one year to reach the federally-defined Negligible Individual Dose. The Nuclear Regulatory Commission considers it safe to hit at least 25 times this number, or 5000 scans per year.

Meanwhile Rapiscan, a maker of backscatter systems, says each full-body scan is equivalent to what a person gets in five minutes from background environmental radiation.

I’m not an expert on this topic but from what I’ve read so far I’m not as alarmed as I thought I might be.

December 13, 2006

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