4 ms·

This comparison is meaningless. The risk of cancer is caused by DNA errors. Your cells are constantly checking and repairing your DNA for mutations and damage.

by aphyr 16y ago

This comparison is meaningless. The risk of cancer is caused by DNA errors. Your cells are constantly checking and repairing your DNA for mutations and damage. They can usually repair or detect a low error rate, like the kind you get from living at high altitude, in a house with a minor radon source, or flying on a plane. What they can't deal with as well is a sudden burst of many errors. Backscatter X-ray scanners deliver their entire dose to a tissue region in a few microseconds. That's the kind of exposure we're talking about, and it has an entirely different biological impact.

Confusion 16y ago
Where 'an entirely different biological impact' may just as well mean 'no impact at all': it may even turn out to prevent melanomas. While everyone is busy losing themselves in radiation hysteria, where facts are only guessed at, the government is laughing their ass off, because everyone lost sight of the actual problem: that these machines are assumed to improve safety in the first place. The radiation scare is an enormous red herring that mainly harms the public perception of 'radiation', that wasn't too good to begin with, for all the wrong reasons.
- aphyr 16y ago
  We know that short-term small doses of X rays results in increased probability of developing skin cancer. We know that prolonged exposure to low-level radiation sources increases your probability of developing skin cancer. We know that acute high doses of ionizing radiation leads to your skin falling off. Skin cancers are abnormally elevated in radiologists, survivors of Hiroshima who experienced even relatively low doses, radioisotope miners, and people who are treated with X rays for skin conditions. I'll hazard a guess here and say there's close to zero probability that backscatter machines are lowering your risk of cancer. Don't get me wrong: I love radiation. I think Cherenkov glow is the coolest thing about working in a reactor. I've handled more sources than I probably should have by this point in my life. At the same time, we should be honest that there is probably a small risk, and it is probably higher than currently stated.
  - Confusion 16y ago
    We know that short-term small doses of X rays results in increased probability of developing skin cancer. An increase that is so minute that we don't mind the dentist or doctor X-raying us. An increase that is so minute that we would accept it, if it actually reduced our chances of dying due to a terrorist attack. The radiation is not the problem: it is the intended goal that we have no reason to believe in. We know that prolonged exposure to low-level radiation sources increases your probability of developing skin cancer Do we? Not WiFi or the low-energy spectrum of the sun. What energy is 'low' in this respect?. And how long is 'prolonged exposure'? These claims are undoubtedly true for some values of the aforementioned quoted terms, but are they relevant here? Do most of the people repeating this stuff even wonder about that? Again, the problem is a slightly increased risk. But why is that increased risk a problem in the first place? I'll hazard a guess here and say there's close to zero probability that backscatter machines are lowering your risk of cancer. And I agree. But the "we don't know for sure" argument is pretty shallow, when we accept certain risks on a daily basis and when we all know certainty doesn't exist and we all take aspirin to prevent a second heart-attack, even though a thousand doctors will argue with another thousand doctors about whether that actually works, all citing studies supporting their side, and the net effect is quite small even according to the side affirming it works.
    - aphyr 16y ago
      Preface: I totally agree with your argument that risks must be weighed against outcomes. I also believe that even if the scanning technology were totally safe, it would be objectionable on privacy grounds. I think we're going about the whole problem of security backwards. :) An increase that is so minute that we don't mind the dentist or doctor X-raying us. Actually, we do. There are good reasons we impose strict limits on your medical X-ray exposure annually, and why you wear a lead vest or use collars to protect other tissue. There's also a good reason the radiologist stands outside the other room to press the button. Two x-rays a year is not significantly mutagenic. Fifty? Then you start getting nervous. Not WiFi or the low-energy spectrum of the sun. What energy is 'low' in this respect?. And how long is 'prolonged exposure' UV exposure from solar radiation is one of the biggest melanoma risks. A few orders of magnitude up the frequency scale, X rays for far shorter durations also have mutagenic effects on skin tissue. It's possible that low-energy X rays, falling in the middle of that energy range, also cause cancer. We don't know for sure yet because we don't regularly expose people to them. (I should mention that just because the X rays are low energy does not mean their effects scale linearly. Medical X rays are well above the Compton shoulder. IIRC (not enough time to check now) they're thermalizing slowly in heavy tissues as opposed to bouncing inelastically off the surface layers. Depending on the scattering cross-section for those energies, the backscattered X rays could be more ionizing. Total conjecture... I haven't done this for a while.) Again, the problem is a slightly increased risk. But why is that increased risk a problem in the first place? You're absolutely right. We have no good characterization of the risk. Radiation biometrics is fucking hard. I only want to argue that our current risk statement is inaccurate and poorly understood (for instance, we don't even know the angular flux of these machines), and offer some potential reasons why the risk might be higher than currently stated.
uvdiv 16y ago
>What they can't deal with as well is a sudden burst of many errors. Actually that is false, as far as low doses: >When you are asked whether there is a critical time period over which 1 rem of dose may have a greater biological impact than it might otherwise have, the answer is "No." One rem of dose is sufficiently low that whether it was delivered within one second or spread over a year or more, we would not expect any difference in biological effects. https://hps.org/publicinformation/ate/q8325.html https://hps.org/publicinformation/ate/q8325.html (For comparison, 1 uSv = 0.1 mrem). >The risk of cancer is caused by DNA errors. Your cells are constantly checking and repairing your DNA for mutations and damage. They can usually repair or detect a low error rate But in this dose regime, ionization events are so rare, that they are so far apart that no cell experiences more than one. There is no variation in error rate.
- nubian 16y ago
  Let me quote from your own source: "There have been numerous biological experiments conducted, with nonhuman organisms, that demonstrate that the rate at which radiation dose is delivered can affect the extent of biological response. Thus a sufficiently high dose delivered over a period of a few minutes may be expected to have a greater biological impact than the same dose spread over a year." The only question is what constitutes a "sufficiently high" dose, due to extrapolation. See 5). THEIR OWN POSITION PAPER on backscatter scanners recommends per-screening and per-year (time limit!) maximums FAR below the threshold that they claimed wasn't a problem in the first place -- see 8). 4) Further, the terse "no" answer looked disingenuous. The cited position paper link was broken but I tracked it down. It appears to be "Radiation Risk in Perspective", PS010-2 (which I assume is the updated version of PS010-1). It has nothing to say about doses over short time periods. http://www.hps.org/hpspublications/positionstatements.html http://www.hps.org/hpspublications/positionstatements.html 5) The issue seems to be that there is very little data about low-dose exposures, so regulations are based on extrapolation from high-dose exposures. See http://www.ncrponline.org/PDFs/TST_NRC%20_04-08-08.pdf http://www.ncrponline.org/PDFs/TST_NRC%20_04-08-08.pdf (third slide) 6) What it does say is this: "the Health Physics Society recommends against quantitative estimation of health risks below an individual dose of 5 rem in one year or a lifetime dose of 10 rem above that received from natural sources." 7) The whole point of their objection was that we lack the empirical evidence to extrapolate from high doses to low doses. Then the article you cite does exactly that. They go from saying, "we lack proof that the answer is X" to saying, "the answer is ~X". 8) The recommended standard "limits the reference effective dose delivered to the subject to 0.25 microsieverts (25 microrem) per screening. Additionally, a screening facility should not expose any individual to more than 250 microsieverts (25 millirem) reference effective dose in a year." "Use of Ionizing Radiation for Security Screening Individuals" PS017-1 http://www.hps.org/hpspublications/positionstatements.html http://www.hps.org/hpspublications/positionstatements.html How they can go from saying in the first paper, "However, below 5–10 rem (which includes occupational and environmental exposures), risks of health effects are either too small to be observed or are nonexistent" to supporting a maximum of 0.025 rem per year is entirely unclear. Except that the Health Physics Society seems to have turned into a pro-industry spokesgroup. The current president works for Dade Moeller, who are embroiled in a number of controversies, to put it lightly. A lot of extremely damaging information is cited in the original link below. ""Hirsch then zeroed in on Dade Moeller’s radiation plan and on the controversial company itself, whose namesake testified back in the 1990s that money spent on cleaning up Cold War-era nuclear facilities was being wasted since there would be a cure for cancer." Original comment: http://news.ycombinator.com/item?id=1889673 http://news.ycombinator.com/item?id=1889673

by aphyr 16y ago

Confusion 16y ago

Where 'an entirely different biological impact' may just as well mean 'no impact at all': it may even turn out to prevent melanomas. While everyone is busy losing themselves in radiation hysteria, where facts are only guessed at, the government is laughing their ass off, because everyone lost sight of the actual problem: that these machines are assumed to improve safety in the first place. The radiation scare is an enormous red herring that mainly harms the public perception of 'radiation', that wasn't too good to begin with, for all the wrong reasons.

aphyr 16y ago
We know that short-term small doses of X rays results in increased probability of developing skin cancer. We know that prolonged exposure to low-level radiation sources increases your probability of developing skin cancer. We know that acute high doses of ionizing radiation leads to your skin falling off. Skin cancers are abnormally elevated in radiologists, survivors of Hiroshima who experienced even relatively low doses, radioisotope miners, and people who are treated with X rays for skin conditions. I'll hazard a guess here and say there's close to zero probability that backscatter machines are lowering your risk of cancer. Don't get me wrong: I love radiation. I think Cherenkov glow is the coolest thing about working in a reactor. I've handled more sources than I probably should have by this point in my life. At the same time, we should be honest that there is probably a small risk, and it is probably higher than currently stated.
- Confusion 16y ago
  We know that short-term small doses of X rays results in increased probability of developing skin cancer. An increase that is so minute that we don't mind the dentist or doctor X-raying us. An increase that is so minute that we would accept it, if it actually reduced our chances of dying due to a terrorist attack. The radiation is not the problem: it is the intended goal that we have no reason to believe in. We know that prolonged exposure to low-level radiation sources increases your probability of developing skin cancer Do we? Not WiFi or the low-energy spectrum of the sun. What energy is 'low' in this respect?. And how long is 'prolonged exposure'? These claims are undoubtedly true for some values of the aforementioned quoted terms, but are they relevant here? Do most of the people repeating this stuff even wonder about that? Again, the problem is a slightly increased risk. But why is that increased risk a problem in the first place? I'll hazard a guess here and say there's close to zero probability that backscatter machines are lowering your risk of cancer. And I agree. But the "we don't know for sure" argument is pretty shallow, when we accept certain risks on a daily basis and when we all know certainty doesn't exist and we all take aspirin to prevent a second heart-attack, even though a thousand doctors will argue with another thousand doctors about whether that actually works, all citing studies supporting their side, and the net effect is quite small even according to the side affirming it works.
  - aphyr 16y ago
    Preface: I totally agree with your argument that risks must be weighed against outcomes. I also believe that even if the scanning technology were totally safe, it would be objectionable on privacy grounds. I think we're going about the whole problem of security backwards. :) An increase that is so minute that we don't mind the dentist or doctor X-raying us. Actually, we do. There are good reasons we impose strict limits on your medical X-ray exposure annually, and why you wear a lead vest or use collars to protect other tissue. There's also a good reason the radiologist stands outside the other room to press the button. Two x-rays a year is not significantly mutagenic. Fifty? Then you start getting nervous. Not WiFi or the low-energy spectrum of the sun. What energy is 'low' in this respect?. And how long is 'prolonged exposure' UV exposure from solar radiation is one of the biggest melanoma risks. A few orders of magnitude up the frequency scale, X rays for far shorter durations also have mutagenic effects on skin tissue. It's possible that low-energy X rays, falling in the middle of that energy range, also cause cancer. We don't know for sure yet because we don't regularly expose people to them. (I should mention that just because the X rays are low energy does not mean their effects scale linearly. Medical X rays are well above the Compton shoulder. IIRC (not enough time to check now) they're thermalizing slowly in heavy tissues as opposed to bouncing inelastically off the surface layers. Depending on the scattering cross-section for those energies, the backscattered X rays could be more ionizing. Total conjecture... I haven't done this for a while.) Again, the problem is a slightly increased risk. But why is that increased risk a problem in the first place? You're absolutely right. We have no good characterization of the risk. Radiation biometrics is fucking hard. I only want to argue that our current risk statement is inaccurate and poorly understood (for instance, we don't even know the angular flux of these machines), and offer some potential reasons why the risk might be higher than currently stated.

uvdiv 16y ago

>What they can't deal with as well is a sudden burst of many errors. Actually that is false, as far as low doses: >When you are asked whether there is a critical time period over which 1 rem of dose may have a greater biological impact than it might otherwise have, the answer is "No." One rem of dose is sufficiently low that whether it was delivered within one second or spread over a year or more, we would not expect any difference in biological effects. https://hps.org/publicinformation/ate/q8325.html https://hps.org/publicinformation/ate/q8325.html (For comparison, 1 uSv = 0.1 mrem). >The risk of cancer is caused by DNA errors. Your cells are constantly checking and repairing your DNA for mutations and damage. They can usually repair or detect a low error rate But in this dose regime, ionization events are so rare, that they are so far apart that no cell experiences more than one. There is no variation in error rate.

nubian 16y ago
Let me quote from your own source: "There have been numerous biological experiments conducted, with nonhuman organisms, that demonstrate that the rate at which radiation dose is delivered can affect the extent of biological response. Thus a sufficiently high dose delivered over a period of a few minutes may be expected to have a greater biological impact than the same dose spread over a year." The only question is what constitutes a "sufficiently high" dose, due to extrapolation. See 5). THEIR OWN POSITION PAPER on backscatter scanners recommends per-screening and per-year (time limit!) maximums FAR below the threshold that they claimed wasn't a problem in the first place -- see 8). 4) Further, the terse "no" answer looked disingenuous. The cited position paper link was broken but I tracked it down. It appears to be "Radiation Risk in Perspective", PS010-2 (which I assume is the updated version of PS010-1). It has nothing to say about doses over short time periods. http://www.hps.org/hpspublications/positionstatements.html http://www.hps.org/hpspublications/positionstatements.html 5) The issue seems to be that there is very little data about low-dose exposures, so regulations are based on extrapolation from high-dose exposures. See http://www.ncrponline.org/PDFs/TST_NRC%20_04-08-08.pdf http://www.ncrponline.org/PDFs/TST_NRC%20_04-08-08.pdf (third slide) 6) What it does say is this: "the Health Physics Society recommends against quantitative estimation of health risks below an individual dose of 5 rem in one year or a lifetime dose of 10 rem above that received from natural sources." 7) The whole point of their objection was that we lack the empirical evidence to extrapolate from high doses to low doses. Then the article you cite does exactly that. They go from saying, "we lack proof that the answer is X" to saying, "the answer is ~X". 8) The recommended standard "limits the reference effective dose delivered to the subject to 0.25 microsieverts (25 microrem) per screening. Additionally, a screening facility should not expose any individual to more than 250 microsieverts (25 millirem) reference effective dose in a year." "Use of Ionizing Radiation for Security Screening Individuals" PS017-1 http://www.hps.org/hpspublications/positionstatements.html http://www.hps.org/hpspublications/positionstatements.html How they can go from saying in the first paper, "However, below 5–10 rem (which includes occupational and environmental exposures), risks of health effects are either too small to be observed or are nonexistent" to supporting a maximum of 0.025 rem per year is entirely unclear. Except that the Health Physics Society seems to have turned into a pro-industry spokesgroup. The current president works for Dade Moeller, who are embroiled in a number of controversies, to put it lightly. A lot of extremely damaging information is cited in the original link below. ""Hirsch then zeroed in on Dade Moeller’s radiation plan and on the controversial company itself, whose namesake testified back in the 1990s that money spent on cleaning up Cold War-era nuclear facilities was being wasted since there would be a cure for cancer." Original comment: http://news.ycombinator.com/item?id=1889673 http://news.ycombinator.com/item?id=1889673