19 November 2010

"It's not a grope. It's a Freedom Pat."

Bruce Schneier has a massive load of links on the TSA's new toys.

This one stood out:
There's talk about the health risks of the machines, but I can't believe you won't get more radiation on the flight. Here's some data:
A typical dental X-ray exposes the patient to about 2 millirems of radiation. According to one widely cited estimate, exposing each of 10,000 people to one rem (that is, 1,000 millirems) of radiation will likely lead to 8 excess cancer deaths. Using our assumption of linearity, that means that exposure to the 2 millirems of a typical dental X-ray would lead an individual to have an increased risk of dying from cancer of 16 hundred-thousandths of one percent. Given that very small risk, it is easy to see why most rational people would choose to undergo dental X-rays every few years to protect their teeth.

More importantly for our purposes, assuming that the radiation in a backscatter X-ray is about a hundredth the dose of a dental X-ray, we find that a backscatter X-ray increases the odds of dying from cancer by about 16 ten millionths of one percent. That suggests that for every billion passengers screened with backscatter radiation, about 16 will die from cancer as a result.
Given that there will be 600 million airplane passengers per year, that makes the machines deadlier than the terrorists.
Let's just repeat that: backscatter screening devices are more deadly than terrorists.

And that doesn't take into account the number of people who will decide to opt for highway travel rather than the safer air travel.

(BTW Whether you get more radiation on he flight is immaterial: that is an unavoidable consequence of flying, whereas the x-rays in screening are entirely avoidable.  Stairs are one of the most statistically dangerous things in your homes, but they are unavoidable.  We still ban many much less dangerous items from homes.  This is not incongruous.)

I am passing this information on to the fair Mrs. SB7, a multiple-time survivor of melanoma.  Of course the alternative is some minimum wage thug pawing at her delicate bits, which I admit to not being terribly comfortable with either.

It should also scare us that the makers of these machines,and their partners in DC have decided that it is unncessary to release full details of their health effects.  You think they'd let SB7 Corp. get away with sweeping the effects of a new radiation device under the rug like this? Perhaps I'm being cynical, but maybe it has something to do with the likes Michael Chertoff, and George Soros, not to mention scads of lobbyists and Obama donors, getting rich off these things.

2 comments:

  1. SB7,

    The problem with the epidemiological estimate that Schneir quotes is that there are too many unknowns. The LawProf author of the estimate, Michael Dorf, writes that "it is quite possible that the effects rise with exposure in an at least a roughly linear way" and then, based on that possibility, assumes linearity.

    In fact, the danger of backscatter machines could quite possibly be much lower or much higher.

    (Great blog, by the way. Thanks.)

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  2. Very good point.

    The very fact that we have to make such broad assumptions, that we don't even know if the effects are sublinear or superlinear, scares me. It's not just that they're dangerous, it's that no one really knows how dangerous. That unknown is worrisome.

    A set of reasonable assumptions -- possibly incorrect assumptions, but as AFAIK reasonable ones -- makes these things roughly as dangerous as terrorism, and no one seems to have considered that before installing them. That says a lot about TSA's process and motivation.

    I think a lot of people go overboard with OMG-Radiation-Cancer!!! scares whenever there's a new device, but in this case, until we know more, I'm likely to steer clear of these things. If I see some reliable numbers that they're safer than estimated, then great. But until then I'm steering clear.

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