5 ms·

edit: s/mwbs/bs/g; per comment below Well, X-rays cause cancer. BS uses X-rays So it is a cancer risk. And it is a little more founded than someone randomly s

by ohyes 16y ago

edit: s/mwbs/bs/g; per comment below Well, X-rays cause cancer. BS uses X-rays So it is a cancer risk. And it is a little more founded than someone randomly saying' this causes cancer'. In terms of risk... This says dental x-rays are about 2-3 mrem: http://www.physics.isu.edu/radinf/dental.htm http://www.physics.isu.edu/radinf/dental.htm This says BS is about .006-.009 mrem: http://science.howstuffworks.com/innovation/backscatter.htm http://science.howstuffworks.com/innovation/backscatter.htm Keep in mind that under certain models (the 'no-threshold model'), any amount of exposure (even a tiny amount) to an X-ray is a slight increase in the chance that that person will get cancer. Now you might think that because dental x-rays are about 300 times more powerful than BS, dental x-rays have a much higher chance to cause cancer. Sure, individually, my chances of getting cancer from a BS are much lower than my chances of getting cancer from a dental x-ray. It is even higher from daily background radiation, or from the radiation that you get from flying in an airplane. But everything is about context. How many people fly each day? 2 million or so? How many people do we propose to put through the BS machine? All of them? (I assume the intent is to eventually replace the metal detectors with these). If you are putting 2 million people through the BS each day, that is actually large amount of radiation exposure. Probabilistically, someone will get cancer from the BS. There are certain types of radiation that you can avoid (x-raying your foot for fun! backscatter machines), and there are certain types of radiation that you cannot avoid (background cosmic). I don't see how the argument that it is 'nothing' in comparison to other forms of radiation really stands up, in that I could potentially avoid backscatter radiation, whereas I couldn't conceivably avoid the other types. (This doesn't take into account other real issues, like 'what if the machine breaks down and we start blasting people with focused beams of radiation'... while trained to run the machine, I doubt that the TSA people are trained to maintain the machine, or would even know if something had gone horribly wrong with it).

yummyfajitas 16y ago
(This doesn't take into account other real issues, like 'what if the machine breaks down and we start blasting people with focused beams of radiation'... What if my flashlight breaks down and I start blasting people with focused beams of laser light? What if my cell phone breaks down and the microwaves melt the brains of everyone within 6 feet of me? I don't know a great deal about the engineering of MWBS, but I see no reason to believe that your fear is any more likely than mine. Most machines just don't work that way. Do you have evidence that MWBS is different?
- jerf 16y ago
  It is not a theoretical concern: http://en.wikipedia.org/wiki/Therac-25 http://en.wikipedia.org/wiki/Therac-25
  - tedunangst 16y ago
    Therac was designed to send a concentrated beam of radiation into somebody. That was the machine's purpose. Are the scanners designed or even capable of doing the same?
    - jerf 16y ago
      You're playing the role of skeptic, but you're not going far enough. How would I actually answer that question? You could have said the same thing about the Therac; of course it can't blast that much radiation, there's no good reason for it. Yet, here we are. What evidence do you have that it is actually not possible for the machines to dangerously malfunction, and how much confidence can actually be placed in it? Those telling us it is safe don't have entirely clean hands on the topic, they've lied about other things like picture retention policies and capabilities before. You're making an appeal to incredulity. I would not actually be that incredulous to discover that the machines do indeed have some sort of flaw that would permit them to blast out more radiation than intended. After all, it's happened before. That said, I don't necessarily consider it likely, either, what I find far more problematic is that this is merely one consistent piece in a larger puzzle of unconcern about the real safety of the public. For the same reasons we ought to be able to examine our voting machines, we ought to be able to examine these machines.
      - yummyfajitas 16y ago
        The Therac was designed to blast dangerous amounts of radiation. It had two modes of operation - "deadly radiation" and "VERY deadly radiation". A software bug caused it to go into "VERY deadly radiation" mode when it should have been only in "deadly radiation" mode. A smaller radiation source, like that of an x-ray backscattering scanner, does not need to have a "deadly radiation" mode. And it's highly unlikely that a hardware failure can accidentally turn "10x weaker than chest x-ray" mode into "deadly radiation mode". The more likely failure mode will be something along the lines of "6x weaker than chest x-ray mode". It's just highly unlikely that any device will accidentally emit millions to billions of times more energy than it was designed to.
jessriedel 16y ago
Here's the key idea: your cross-country flight exposes you to 2-5 mrem. MWBS is about 0.01 mrem. It's trivial.
- something 16y ago
  the UCSF letter explains why this is not a valid comparison. the ambient radiation absorbed in flight and the radiation of the mwbs are not in the same part of the spectrum so they are not comparable using simple agregate statistics. the stopping power of your (or any) body is function of the energy of the incident radiation (or particle) and this not considered in the mrem comparison.
  - jessriedel 16y ago
    If you demand that human trials be done for every possible permutation of conceivable risk---throwing out as incomparable all data that is taken in even remotely different circumstances--then you can claim health risks about every single thing. And it's pretty much impossible to satisfy you because of the cost of human trials. The concerns raised in the UCSF letter are strained beyond belief. Further, a number of points (like the breast-cancer bullet point) are clearly there to influence emotions rather than critical reasoning. I'll just explain this one. As the UCSF letter states, the radiation is being deposited on a volume smaller than usual by a factor possibly as large as "one to two orders of magnitude". That means that at absolute worst this is like radiation dose of 1 mrem (still less than the flight tiny compared to your yearly dose), and that's assuming that all of the risk of cosmic radiation comes from skin cancer (which is wildly wrong).
    - something 16y ago
      i agree that demanding perfect testing is ridiculous in most scenarios, especially when talking about human trials. however, that's not what i'm suggesting should happen. i also don't deny that the UCSF letter has a sensationalist or alarmist tone. i'm not touting their concerns, just suggesting it as a place that explains the difference between cosmic xrays and the xrays in these scanners. i guess my point is that it's very easy to mislead people that have no appreciation for these very real differences. glossing over details and nuance that have not yet been proven insignificant, and doing so with the goal of making concerned people stop asking questions about their own safety- that's not cool. when it's our own government it's even less cool. there are so many issues swirling around this subject- privacy, security, safety, fear, "terror"... i guess i'm just wanting the science of the safety to be completely objective, open, reviewed, failsafes and failure modes known... all that jazz. as a member of the public it seems like these things were just thrown out there. the tsa is covering their butt by doing whatever is possible, a few scanner manufacturers are having a good year, and we're just supposed to leave it like that, keep calm, carry on... i can't say that makes me feel great.
Steuard 16y ago
Backscatter X-ray scanners use X-ray photons. Millimeter-wave scanners use far-infrared/microwave photons. To the best of my knowledge, nobody's every shown that microwaves or infrared light cause cancer: the photons just don't have enough energy to cause that kind of cell damage. (Yes, this is quibbling about what was probably just an error in definition; I think your comments are right as applied to backscatter X-ray scanners. But if we keep our language straight, our arguments against these blasted things will be that much harder to dismiss.)
- ohyes 16y ago
  Yes, of course you are right, I was just looking at it from a perspective of the x-ray scanners. I have no idea about the microwave based scanners.

by ohyes 16y ago

yummyfajitas 16y ago

(This doesn't take into account other real issues, like 'what if the machine breaks down and we start blasting people with focused beams of radiation'... What if my flashlight breaks down and I start blasting people with focused beams of laser light? What if my cell phone breaks down and the microwaves melt the brains of everyone within 6 feet of me? I don't know a great deal about the engineering of MWBS, but I see no reason to believe that your fear is any more likely than mine. Most machines just don't work that way. Do you have evidence that MWBS is different?

jerf 16y ago
It is not a theoretical concern: http://en.wikipedia.org/wiki/Therac-25 http://en.wikipedia.org/wiki/Therac-25
- tedunangst 16y ago
  Therac was designed to send a concentrated beam of radiation into somebody. That was the machine's purpose. Are the scanners designed or even capable of doing the same?
  - jerf 16y ago
    You're playing the role of skeptic, but you're not going far enough. How would I actually answer that question? You could have said the same thing about the Therac; of course it can't blast that much radiation, there's no good reason for it. Yet, here we are. What evidence do you have that it is actually not possible for the machines to dangerously malfunction, and how much confidence can actually be placed in it? Those telling us it is safe don't have entirely clean hands on the topic, they've lied about other things like picture retention policies and capabilities before. You're making an appeal to incredulity. I would not actually be that incredulous to discover that the machines do indeed have some sort of flaw that would permit them to blast out more radiation than intended. After all, it's happened before. That said, I don't necessarily consider it likely, either, what I find far more problematic is that this is merely one consistent piece in a larger puzzle of unconcern about the real safety of the public. For the same reasons we ought to be able to examine our voting machines, we ought to be able to examine these machines.
    - yummyfajitas 16y ago
      The Therac was designed to blast dangerous amounts of radiation. It had two modes of operation - "deadly radiation" and "VERY deadly radiation". A software bug caused it to go into "VERY deadly radiation" mode when it should have been only in "deadly radiation" mode. A smaller radiation source, like that of an x-ray backscattering scanner, does not need to have a "deadly radiation" mode. And it's highly unlikely that a hardware failure can accidentally turn "10x weaker than chest x-ray" mode into "deadly radiation mode". The more likely failure mode will be something along the lines of "6x weaker than chest x-ray mode". It's just highly unlikely that any device will accidentally emit millions to billions of times more energy than it was designed to.

jessriedel 16y ago

Here's the key idea: your cross-country flight exposes you to 2-5 mrem. MWBS is about 0.01 mrem. It's trivial.

something 16y ago
the UCSF letter explains why this is not a valid comparison. the ambient radiation absorbed in flight and the radiation of the mwbs are not in the same part of the spectrum so they are not comparable using simple agregate statistics. the stopping power of your (or any) body is function of the energy of the incident radiation (or particle) and this not considered in the mrem comparison.
- jessriedel 16y ago
  If you demand that human trials be done for every possible permutation of conceivable risk---throwing out as incomparable all data that is taken in even remotely different circumstances--then you can claim health risks about every single thing. And it's pretty much impossible to satisfy you because of the cost of human trials. The concerns raised in the UCSF letter are strained beyond belief. Further, a number of points (like the breast-cancer bullet point) are clearly there to influence emotions rather than critical reasoning. I'll just explain this one. As the UCSF letter states, the radiation is being deposited on a volume smaller than usual by a factor possibly as large as "one to two orders of magnitude". That means that at absolute worst this is like radiation dose of 1 mrem (still less than the flight tiny compared to your yearly dose), and that's assuming that all of the risk of cosmic radiation comes from skin cancer (which is wildly wrong).
  - something 16y ago
    i agree that demanding perfect testing is ridiculous in most scenarios, especially when talking about human trials. however, that's not what i'm suggesting should happen. i also don't deny that the UCSF letter has a sensationalist or alarmist tone. i'm not touting their concerns, just suggesting it as a place that explains the difference between cosmic xrays and the xrays in these scanners. i guess my point is that it's very easy to mislead people that have no appreciation for these very real differences. glossing over details and nuance that have not yet been proven insignificant, and doing so with the goal of making concerned people stop asking questions about their own safety- that's not cool. when it's our own government it's even less cool. there are so many issues swirling around this subject- privacy, security, safety, fear, "terror"... i guess i'm just wanting the science of the safety to be completely objective, open, reviewed, failsafes and failure modes known... all that jazz. as a member of the public it seems like these things were just thrown out there. the tsa is covering their butt by doing whatever is possible, a few scanner manufacturers are having a good year, and we're just supposed to leave it like that, keep calm, carry on... i can't say that makes me feel great.

Steuard 16y ago

Backscatter X-ray scanners use X-ray photons. Millimeter-wave scanners use far-infrared/microwave photons. To the best of my knowledge, nobody's every shown that microwaves or infrared light cause cancer: the photons just don't have enough energy to cause that kind of cell damage. (Yes, this is quibbling about what was probably just an error in definition; I think your comments are right as applied to backscatter X-ray scanners. But if we keep our language straight, our arguments against these blasted things will be that much harder to dismiss.)

ohyes 16y ago
Yes, of course you are right, I was just looking at it from a perspective of the x-ray scanners. I have no idea about the microwave based scanners.