4 ms·

>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 crit

by 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
- uvdiv 16y ago
  >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). >...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. Where they support that 0.025 rem/year recommendation, they explain that the point is to keep "individual doses as low as reasonably achievable (ALARA) while achieving the desired objective." (Same source, PS017-1). And you mischarcterize their claims. HPS does not claim <5 rem doses are "not a problem" -- they said the effects are such are "either too small to be observed or nonexistent". (It does not follow that a health effect too small to be epidemologically noticable is "not a problem"). "Too small to be observed" is NOT a quantifier of significance; it is an explanation for the lack of empirical observations. That position statement (PS010-2) is a recommendation against quantiative estimation of the effects of <5 rem radiation doses, not an assertion of their absolute safety. >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. It does not appear to have been referenced for that purpose.
  - nubian 16y ago
    > It does not appear to have been referenced for that purpose. Your comment referenced it for that purpose. Your comment about dose per unit time not mattering referenced an article which referenced their position paper which didn't support what the article said. Hence the article was simply the opinion of the author. > (And you mischarcterize their claims. HPS does not claim <5 rem doses are "not a problem" -- they said the effects are such are "either too small to be observed or nonexistent". (It does not follow that a health effect too small to be epidemologically noticable is "not a problem"). "Nonexistent" sounds like "not a problem" to me. "Too small to be observed" is the same. How is a problem that causes no observable effects a problem? That's the practical definition of "not a problem". And if dose per unit time doesn't matter, then their per-screening and annual limits for these small doses wouldn't matter. They are contradicting themselves. Further, as mentioned, they are not an independent safety group. They are an industry group for the pro-nuclear lobby. This is like relying on the Business Software Alliance (BSA, a front group for Microsoft and other large software corporations) for opinions on the harmful nature of DRM, copyright laws, etc.
aphyr 16y ago
Good point uvdiv: if the ionization events are sufficiently rare in both cases we ought to be able to treat them as cumulatively equivalent. I guess it would depend on the error correction time and the size of the affected nucleotide sequence, especially in a double-break error. The dose delivered by these scanners is probably well-below that threshold. My remaining concern would be that the biological effects of this particular energy regime are as-of-yet uncharacterized.

by uvdiv 16y ago

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

uvdiv 16y ago
>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). >...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. Where they support that 0.025 rem/year recommendation, they explain that the point is to keep "individual doses as low as reasonably achievable (ALARA) while achieving the desired objective." (Same source, PS017-1). And you mischarcterize their claims. HPS does not claim <5 rem doses are "not a problem" -- they said the effects are such are "either too small to be observed or nonexistent". (It does not follow that a health effect too small to be epidemologically noticable is "not a problem"). "Too small to be observed" is NOT a quantifier of significance; it is an explanation for the lack of empirical observations. That position statement (PS010-2) is a recommendation against quantiative estimation of the effects of <5 rem radiation doses, not an assertion of their absolute safety. >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. It does not appear to have been referenced for that purpose.
- nubian 16y ago
  > It does not appear to have been referenced for that purpose. Your comment referenced it for that purpose. Your comment about dose per unit time not mattering referenced an article which referenced their position paper which didn't support what the article said. Hence the article was simply the opinion of the author. > (And you mischarcterize their claims. HPS does not claim <5 rem doses are "not a problem" -- they said the effects are such are "either too small to be observed or nonexistent". (It does not follow that a health effect too small to be epidemologically noticable is "not a problem"). "Nonexistent" sounds like "not a problem" to me. "Too small to be observed" is the same. How is a problem that causes no observable effects a problem? That's the practical definition of "not a problem". And if dose per unit time doesn't matter, then their per-screening and annual limits for these small doses wouldn't matter. They are contradicting themselves. Further, as mentioned, they are not an independent safety group. They are an industry group for the pro-nuclear lobby. This is like relying on the Business Software Alliance (BSA, a front group for Microsoft and other large software corporations) for opinions on the harmful nature of DRM, copyright laws, etc.

aphyr 16y ago

Good point uvdiv: if the ionization events are sufficiently rare in both cases we ought to be able to treat them as cumulatively equivalent. I guess it would depend on the error correction time and the size of the affected nucleotide sequence, especially in a double-break error. The dose delivered by these scanners is probably well-below that threshold. My remaining concern would be that the biological effects of this particular energy regime are as-of-yet uncharacterized.