4 ms·

Actual web page: http://www.public.asu.edu/~atppr/bodyscan.html http://www.public.asu.edu/~atppr/bodyscan.html Actual article: https://docs.google.com/viewer?u

by aphyr 16y ago

Actual web page: http://www.public.asu.edu/~atppr/bodyscan.html http://www.public.asu.edu/~atppr/bodyscan.html Actual article: https://docs.google.com/viewer?url=http://www.public.asu.edu/~atppr/RPD-Final-Form.pdf&pli=1 https://docs.google.com/viewer?url=http://www.public.asu.edu... The first thing you'll learn in radiation safety is that the nature of the dose matters a lot. Sometimes you're A-OK if you can survive the initial dose. Other doses are accumulative. It depends on the energy of the radiation, the tissue's scattering cross-section, the time, and the flux, among other things. This means that the Sievert (a unit of biological impact due to radiation) is only meaningful in the context of the dose geometry. It's great for talking about a chest X-ray, where the dose is spread out over a big volume of tissue. Where it's unclear is in the case of rapidly-thermalizing or compton-scattered particles: like backscatter. Look at the graph in that article. Something like half of the energy is deposited in the first couple centimeters of tissue. We haven't done this before, and don't have a good model for the long-term effects. My guess? This kind of exposure is a hell of a lot worse for melanomas than a chest X-ray delivering the same energy. Claiming compliance to a metric like the ANSI limits is meaningless. Edit: Oh, and the concern raised over the beam stopping and delivering a couple Sv to a quarter-sized patch of skin is definitely scary. We did exactly that to several people with medical cyclotrons. Edit: I should also mention that tissues have varying tolerance to radiation. Rapidly-dividing cells tend to be hit the hardest, which is why your stomach lining, skin, and hair slough off after acute ionizing rad exposure. Your skin, stomach, lungs, breast and thyroid are also the most frequent to undergo cancer in radiation-linked longitudinal studies. See, for example, http://pats.atsjournals.org/cgi/content/full/5/9/934 http://pats.atsjournals.org/cgi/content/full/5/9/934

jdp23 16y ago
And according to David Brenner of Columbia University: Recent research ... indicates that about 5 percent of the population — one person in 20 — is especially sensitive to radiation. These people have gene mutations that make them less able to repair X-ray damage to their DNA. Two examples are the BRCA-1 and BRCA-2 mutations associated with breast and ovarian cancer, but scientists believe many more such defects are unknown. http://www.npr.org/templates/story/story.php?storyId=126833083 http://www.npr.org/templates/story/story.php?storyId=1268330...
joe_the_user 16y ago
Fabulous post. Even if the thing is absolutely, perfectly safe as designed, if you keep in mind human error, mechanical failure, individual physiology, and variations in flying frequency, it's not to see this as actually significantly more likely to cause death than terrorism.
stcredzero 16y ago
George Bush International doesn't have this yet. I'm going to opt out of scanning for my flight back from Pittsburgh, however.
- fexl 16y ago
  I'll be opting out as well, karma be damned.
uvdiv 16y ago
This is a grossly irresponsible abuse of statistics. What's even stranger is that the author agrees. In his paper (conclusions, page 15): >The major public health effect of concern at low doses of ionizing radiation is cancer. There is clear evidence of cancer induction at effective dose above about 200 mSv. Below an effective dose of about 100 mSv radiogenic cancer mortality risk estimates for all cancers is highly uncertain. 16 It is not possible to determine reliably whether a radiogenic risk is present in an X-ray screening population because of the high spontaneous incidence of cancer and multifactorial nature of disease causation 17. >Use of collective dose to estimate public health impacts when large populations are exposed to trivial doses is inappropriate and not reasonable. The assumptions implicit in the collective dose calculation conceal large biological and statistical uncertainties.16 If an individual passenger is not harmed by X-ray screening then the population isn’t either. "Inappropriate and not reasonable". Yet on his webpage (not submitted to peer review), he does exactly that.
- nubian 16y ago
  > Use of collective dose to estimate public health impacts when large populations are exposed to trivial doses is inappropriate and not reasonable. First, let's make sure we are clear about the difference between collective (for a population) and cumulative (adding up repeated doses for an individual). Second, "inappropriate" and "not reasonable" tend to be weasel words with regard to scientific findings. The real issue is that the effects of small doses haven't been rigorously studied, unlike with high doses. Rather than actually study them, we see brusque dismissals.

by aphyr 16y ago

jdp23 16y ago

And according to David Brenner of Columbia University: Recent research ... indicates that about 5 percent of the population — one person in 20 — is especially sensitive to radiation. These people have gene mutations that make them less able to repair X-ray damage to their DNA. Two examples are the BRCA-1 and BRCA-2 mutations associated with breast and ovarian cancer, but scientists believe many more such defects are unknown. http://www.npr.org/templates/story/story.php?storyId=126833083 http://www.npr.org/templates/story/story.php?storyId=1268330...

joe_the_user 16y ago

Fabulous post. Even if the thing is absolutely, perfectly safe as designed, if you keep in mind human error, mechanical failure, individual physiology, and variations in flying frequency, it's not to see this as actually significantly more likely to cause death than terrorism.

stcredzero 16y ago

George Bush International doesn't have this yet. I'm going to opt out of scanning for my flight back from Pittsburgh, however.

fexl 16y ago
I'll be opting out as well, karma be damned.

uvdiv 16y ago

This is a grossly irresponsible abuse of statistics. What's even stranger is that the author agrees. In his paper (conclusions, page 15): >The major public health effect of concern at low doses of ionizing radiation is cancer. There is clear evidence of cancer induction at effective dose above about 200 mSv. Below an effective dose of about 100 mSv radiogenic cancer mortality risk estimates for all cancers is highly uncertain. 16 It is not possible to determine reliably whether a radiogenic risk is present in an X-ray screening population because of the high spontaneous incidence of cancer and multifactorial nature of disease causation 17. >Use of collective dose to estimate public health impacts when large populations are exposed to trivial doses is inappropriate and not reasonable. The assumptions implicit in the collective dose calculation conceal large biological and statistical uncertainties.16 If an individual passenger is not harmed by X-ray screening then the population isn’t either. "Inappropriate and not reasonable". Yet on his webpage (not submitted to peer review), he does exactly that.

nubian 16y ago
> Use of collective dose to estimate public health impacts when large populations are exposed to trivial doses is inappropriate and not reasonable. First, let's make sure we are clear about the difference between collective (for a population) and cumulative (adding up repeated doses for an individual). Second, "inappropriate" and "not reasonable" tend to be weasel words with regard to scientific findings. The real issue is that the effects of small doses haven't been rigorously studied, unlike with high doses. Rather than actually study them, we see brusque dismissals.