Basic summary: the radiation exposure from these newish full-body x-ray scanners is small, and really nothing to be worried about. Nekkid pix and/or TSA groping is a different issue.
Here's a really fabulous discussion from twitter about the TSA's new backscatter x-ray full-body imaging systems, and the radiation risks from the delivered dose, captured 11/17/2010, about noon PST, roughly 2-3hrs after the conversation occurred. I've curated it here to make it a bit more readable, and have maybe cleaned up a typo or two.
Here's a really fabulous discussion from twitter about the TSA's new backscatter x-ray full-body imaging systems, and the radiation risks from the delivered dose, captured 11/17/2010, about noon PST, roughly 2-3hrs after the conversation occurred. I've curated it here to make it a bit more readable, and have maybe cleaned up a typo or two.
PhysicistLisa's "rant" starts here: http://is.gd/hi8Ic
@PhysicistLisa Lisa M
Ok friends it's rant time though I prefer think of it as educating with numbers.
If you believe that the new TSA policies are necessarily invasive, please don't weaken your case by spouting off about radiation dose
Making easily falsifiable statements will hurt your case, particularly if this goes to court. It is a lie that the doses are "unknown"
Prominent experts in the field of radiation science HAVE done dose calculations of these scanners and estimate them at .005-.009 mrem
Now let's just say... just say for the sake of conservatism (what I do at my job every day) that this is off by an order of magnitude
So we pick the highest estimate and mark it off by 1 order of magnitude, at 0.09 mrem...
By moving from Atlanta to Colorado, I upped my annual dose by 52 mrem per year. because there is more uranium in the soil here and more cosmic radiation dose as I am at a higher elevation.
This means that I would have to stand in that scanner 578 x's to make up the difference in radiation dose between 1 yr in CO vs. [1 yr in] GA
and that's making an assumption of an order of magnitude error by people who are absolute experts in the area of dose calculation
If you think that the privacy concerns should be fought, you are potentially harming the eventual court case by allowing emotionally charged non-science to be considered at all on the agenda. Please consider standing out against this. it will help your case in the long run.
Making any one part of an argument look foolish when faced with facts will make people think about how much they believe the rest of it.
PhysicistLisa Lisa M
A few people have brought this article to my attention http://gizmodo.com/5692198/ @mik3cap @popsciguy
I stand by the numbers i have stated and also by the statement that the doses calced by *outside groups* DO consider the dose is to the skin
normalizing the dose calc to a whole body dose is a common practice for compliance with fed regs, however there are regs for organ dose too
If you read the letter of concern note that there is no actual numbers presented for the extra risks discussed.
as a professional, i do not trust sources that discuss "dangers" with no numbers or calculations associated with them.
and i think that reading his addendums to the article at the bottom really says a lot.
Though imo saying the "cancer risks are not well understood"is a lot like saying "the effects of vaccines on autism are not well understood"
FYI, i hadn't read that article before because i broke up with Gizmodo a while ago for their tendency to not present the fact
PhysicistLisa Lisa M
and honestly... i thought about putting it all in a blog post and i still might, but if i link a blog you're a lot less likely to read it :)
-----
@bird2brain John McKee
@PhysicistLisa How does the scan compare with the subsequent flight? Also, Aren't there two types of scanners? THANKS!
PhysicistLisa Lisa M
.@bird2brain the estimate of 6 hours flight is generally accepted to be 2 mrem, so the dose from the scanner is much less than the flight
.@bird2brain yes, millimeter wave scanners are non-ionizing (like cell phone or MRI) & backscatter rad are ionizing (like an x-ray or CT)
.@bird2brain 2 different kinds of rad with two completely different sets of potential and theoretical health effects
----
Physicsguru Curtis Meisenheimer
@PhysicistLisa Isn't the issue more of the type of radiation, ie X-ray vice gamma. Therefore, the dose is absorbed locally in the skin...
@PhysicistLisa as opposed to whole body radiation exposure?
PhysicistLisa Lisa M
.@Physicsguru x-ray and gamma are both e-mag ionizing radiation, just x are emitted by electrons and gamma is emitted by the nucleus
.@Physicsguru dose calculated to the skin or any other organ is normalized to a whole body equivalent for compliance with regulation
.@Physicsguru the fact that this is a skin dose *has* been considered.
----
GeekStuffOG Matt Cipoletti
@PhysicistLisa just to be clear we are saying that the radiation portion of the argument is hulaballoo but the privacy issues are legit?
PhysicistLisa Lisa M
@GeekStuffOG yes. that is what i'm saying. i just hate seeing a legitimate argument being marred by bad science
----
jduvel Jason Duvel
@PhysicistLisa ...what about pilots who may be scanned multiple times per day depending on their flights, and for many years? ...
PhysicistLisa Lisa M
.@jduvel well you saw my numbers... compared to their flights the scanners are not really a concern for pilots. It's an increasing trend to badge pilots (give them an external radiation dose monitor) so they know the dose they are getting in a year.
----
PhoinixArt Phoinix
@PhysicistLisa Question: Would there be added risk associated with air-crew continually using them? Adding onto their doses from flying etc?
PhysicistLisa Lisa M
@PhoinixArt compared to the dose they get from the flight itself, it would take a long time for it to add up to a couple extra flights
----
thefoodgeek Brian J. Geiger
@PhysicistLisa So the argument about the radiation being absorbed into a small percentage of the body volume is likewise irrelevant?
PhysicistLisa Lisa M
.@thefoodgeek it's not irrelevant, it's accounted for in the dose calculations that have been done, despite what the media has told you
----
GlennF Glenn Fleishman
@stradling @PhysicistLisa It’s not that I dispute the science. I dispute the veracity of the scanner makers. Dose calcs ≠ clinical msrments
PhysicistLisa Lisa M
@GlennF i'm not basing my numbers off of the scanner makers my numbers are from outside groups like the Health Physics Society @stradling
@GlennF and the experiments that have been done so far show doses less than calculated.
----
bird2brain John McKee
@PhysicistLisa But the backscatter is still not much of a concern?
PhysicistLisa Lisa M
@bird2brain in my professional opinion? no i would not worry about the dose from backscatter radiation.
----
jduvel Jason Duvel
@PhysicistLisa Though even using your order of magnitude # with 4 scans a day and 200 days of flying comes up to 72 mrem/year.
PhysicistLisa Lisa M
@jduvel which is lower than the dose to the public of 100 mrem/yr enforced by 10CFR20. Radiation workers are allowed a higher dose even
----
popthestack Ryan Martinsen
@PhysicistLisa can you post your sources for the studies you've read?
PhysicistLisa Lisa M
@popthestack http://www.public.asu.edu/~atppr/RPD-Final-Form.pdf
----
PhysicistLisa Lisa M
@particle_person i don't think that there's any credible calculations that would say this technology will cause a few extra deaths a year
@particle_person but your point is an interesting philosophical one. i don't know enough about terrorists risk rates to say for sure
markbeadles Mark Beadles
@PhysicistLisa Agreed about individual radiation risk, but is aggregate radiation risk > aggregate terror risk?
PhysicistLisa Lisa M
@markbeadles i don't know enough about aggregate terror risk to comment for sure but anyone who's telling you that the scanners are going to kill multiple people a year are not using defensible calculation technique
----
Physicsguru Curtis Meisenheimer
@PhysicistLisa Understandable. Isn't mm-wave superior since it isn't ionizing? Or do they lose resolution?
PhysicistLisa Lisa M
@Physicsguru i'm not entirely sure. over all there is no proven risk to low levels of non-ionizing so safer, in essence yes.
----
treelobsters Tree Lobsters!
@PhysicistLisa How much extra radiation exposure does someone get from flying at 30000 feet? i.e. is it more or less than the scanner
PhysicistLisa Lisa M
@treelobsters 2 mrem for a 6 hour flight. much more
----
GeekStuffOG Matt Cipoletti
@PhysicistLisa anyopinion on safety for pregnant women?
PhysicistLisa Lisa M
@GeekStuffOG your dose would be much higher on the plane ride itself. read here http://www.ncbi.nlm.nih.gov/pmc/articles/PMC153688/
@GeekStuffOG that addresses the us and canada's stance on flying during pregnancy.
@GeekStuffOG the fact of the matter is that it is mostly skin dose and the baby isn't actually that close to the surface
----
Finguz Paul Finlay
@PhysicistLisa So "I don't like the invasion of privacy and the fewer mrems the better, no matter how small the dose" isn't unreasonable? :)
PhysicistLisa Lisa M
@Finguz i think that worrying about .009 mrem is a little unreasonable honestly. The things you do in a day that alter you by .009 mrem...
@Finguz i completely stand by the right to privacy though. i just worry people will weaken their court case when they are inevitably made to look foolish on the stand if they start to bring up the rad dose...
----
GlennF Glenn Fleishman
@PhysicistLisa @stradling Experiments by whom? Who provided #s used for calculations? My assumption starts with notion that scanner...
PhysicistLisa Lisa M
@GlennF the ones i have been able to actually read the full calculations by are by Arizona State University and the Health Physics Society
[there's actually a quite a bit of dialogue between @GlennF and @PhysicistLisa - I encourage you to check it out]
