Life threatening software bugs?

I thought the internet panic over the new TSA pat-downs and body images was a bit of an overreaction. It turns out that the pat-down may be much better than the alternative, going through the back scatter imaging system. It seems the science is very untested on the risks of this system, and those risks could be quite real.


Check out this letter from concerned scientists to the government urging more testing.

Some key points they make:
– people compare the level of radiation to exposure in a chest x-ray or cosmic rays. But this is a totally different radiation. By design it doesn’t penetrate the skin — so while a chest x-ray just flies through you, this all just stops in the skin.
– all the analysis compares the dosage to your whole body mass — but that’s not relevant. It may all stop and stay in a thin outer layer of your skin, and be a very high dose for that mass. We don’t know, because it has not been tested.
– there is one key piece of data to measure the risk: Flux (photons per unit of area and time). That data is not available and may not have been measured!
– if you are in any of these groups you should be especially concerned: over 65, female, a child, HIV+, pregnant, or have testicles. At least 18-64 year old eunuchs are low risk.

Consider this: the dose level of radiation in the system is controlled by software. How often, in your experience, does software contain bugs? Knowing how hard it is to hire great software engineers, how good do you think the programmers are at Rapiscan Systems in Woodland Hills, CA? Have you ever been using a computer and had it unexpectedly hang up for a second? Better hope this hardware and software doesn’t hang for a second while scanning you. Since it scans your whole body with a high energy beam in a few seconds, if it hung for a second mid-scan, it would deliver a very intense dose to one small area of your body.

If ATMs can fail, can an X-ray scanner?

But hey, they probably got the software and hardware all right on the first release, that happens a lot. Not really worth the hassle of extensively testing these systems before rolling them out.

Of course we are constantly risking our lives on the reliability of software systems — in your car, flying a plane, chest X-rays… but most of those systems are pretty thoroughly tested and cautiously rolled out. And deliver a lot more benefit to you for the risk you are taking than going through a back scatter scan.

Consider that you know for sure that you are not a terrorist about to hijack a plane: so a more accurate security screening delivers absolutely no value to you. I think I’ll probably opt for the pat-down experience instead, and let them beta test this technology on others.

Thanks to Bryan Cantrill for educating me on this and saving me some radiation.

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Written by Josh Hannah
Josh Hannah joined Matrix Partners after a career as a serial entrepreneur (Betfair, eHow, wikiHow.) Read more about Josh.
  • Roger Rohrbach

    My brother-in-law is an MD who has worked for the House Oversight Committee. He points out that Rebecca Smith-Bindman, the preeminent national outside expert on radiation safety, did not sign the letter with her UCSF colleagues. His opinion is that this type of radiation is most likely bounced off the skin.

    The FDA response addresses some of the concerns voiced in UCSF letter. In particular, the skin dose is shown to be approximately twice the effective dose. As has been noted, the latter is orders of magnitude less than that delivered by most common medical and dental x-ray procedures.

    On the other hand, the issue of chemical bond breaking due to the Compton effect, which may lead to melanoma, is not directly addressed in the FDA response. As a layperson, I can't tell whether this is because, given the low dosage (1/89,000 of the National Council on Radiation Protection's annual recommended limit) it is simply not an issue. I hope so!

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