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When we got to the scanner, I opted out. Then they opted out.

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Re: When we got to the scanner, I opted out. Then they opted out.

#181

Post by blahblahblah »

yummyfajitas wrote: post #85
ohyes wrote: post #75

Earlier quoted context omitted.

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 This says BS is about .006-.009 mrem: http://science.howstuffworks.com/innovation/backscatter.htm Keep in mind that under cer…

(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…

The situation is analogous to what happens when a CT machine malfunctions. The basic design of a CT machine has an x-ray source on a rotating ring. The patient lays down on a table and the table is moved through the center of the ring at constant velocity for the duration of the scan. The overall motion of the x-ray source relative to the patient is helical. If the movement mechanism jams and the table stops moving, the pattern of motion collapses into a circle and the patient receives an excessive radiation dose focused in the region of the body that is in the center of the ring when the table stops. The received dose is a function of the time until the operator notices the malfunction and stops the scan.

With a backscatter x-ray system, the person stays motionless and the x-ray source moves. If the x-ray source stops moving, the person receives an excessive dose wherever the source happens to be pointing when it gets stuck. The dose received is, again, a function of how long it takes for the operator to notice the malfunction.

With a microwave backscatter system, the radiation used is in the RF range and, therefore, not ionizing. However, if the microwave source stops moving because of malfunction, a portion of the body experiences higher than normal SAR. If the SAR is high enough, significant localized heating may occur, causing burns on the person.

Re: When we got to the scanner, I opted out. Then they opted out.

#182

Post by kayhi »

yummyfajitas wrote: post #122
seanc wrote: post #95

Earlier quoted context omitted.

No, it's all about bit errors and error correction. Highly concentrated radiation is more likely to cause multiple errors to a particular DNA strand, which can defeat the error correction and cause a mutation. The same radiation distributed through the body will cause fewer errors per strand and be corrected.

It's been a long time since I studied dosimetry, but I was under the impression this was only significant at high doses. Do you have evidence otherwise?

The key issue is the actual wavelength being used. I have yet to see this number published. If you knew the wavelength of the X-ray then you could attain a good estimate of the radiation dose. It is well established that X-rays cause protein damage (in vitro) at 1-1.5 Angstroms which is certainly smaller than what is being used in the is case. The wavelength at which radiation damage does not occur would be interesting to determine.

Re: When we got to the scanner, I opted out. Then they opted out.

#183

Post by jerf »

yummyfajitas wrote: post #178
jerf wrote: post #153

Earlier quoted context omitted.

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? Th…

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…

Millions to billions, no, but would anybody notice if it never properly turned off? That would be in the thousands.

Again, not really worried about this, I'm more concerned by the blithe acceptance of the idea that nothing can possible go wrong.

Re: When we got to the scanner, I opted out. Then they opted out.

#184

Post by something »

jessriedel wrote: post #150
something wrote: post #109

Earlier quoted context omitted.

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.

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 poi…

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.

Re: When we got to the scanner, I opted out. Then they opted out.

#185

Post by Tuna-Fish »

Symmetry wrote: post #38
batasrki wrote: post #15

Earlier quoted context omitted.

Well, firstly, the fact that the TSA employee didn't challenge that statement tells me that either that employee isn't properly informed or he/she knows more than what is publicly known. I'm gonna go on a limb and say it's the former rather than latter. Secondly, it shouldn't be a question of whether the machine is x-ray or millimeter wave. Both of those emit radiation and until there's definitive proof that one or b…

We actually have a very good idea how much damage x-rays and millimeter waves do to the human body, since we've been dealing with both technologically for many years. Because x-rays are used in medical devices that have to be approved by the FDA, we've developed some very good ideas about what sort of doses are harmful and which aren't. The damage done by the x-ray scans used by the TSA do indeed produce damage, meas…

The health concern raised about the backscatter x-ray devices is that the rays they use are very low-energy compared to the x-rays we are used to. Because of this, the entire radiation dose will be concentrated on the first millimeter or so of your skin, which means that the radiation dose your skin absorbs from the device will be considerably higher than the dose it absorbs from flying.

Re: When we got to the scanner, I opted out. Then they opted out.

#186

Post by delackner »

Anyone care to do the math on what it would cost in excess fuel to add enough metal shielding to the fuselage to offer passengers "new and improved: no x-rays!" flights? (Only mostly not serious).

With more widespread awareness of x-ray exposure during a normal flight, I wonder if we will see any people so agitated that they wear stuff like this: http://www.medvena.com/protection_clothing_maco_en.html

Re: When we got to the scanner, I opted out. Then they opted out.

#187

Post by Locke1689 »

burgerbrain wrote: post #129
mrkurt wrote: post #116

Earlier quoted context omitted.

That picture is the millimeter wave scanner, which doesn't use radiation. The backscatter scanners are the xray type and are the majority of the scanners in airports.

You didn't pay very close attention in physics class did you? Millimeter wavelength electromagnetic waves are still radiation as much as any other wavelength.

So? If you think that all parts of the EM spectrum have the same effect then you didn't pay very close attention in physics class.

Propping up pseudoscience bullshit like "it's radiation!" is the same reason why we have to deal with morons complaining about wifi signal.

Ugh /former physics minor

Re: When we got to the scanner, I opted out. Then they opted out.

#188

Post by burgerbrain »

Locke1689 wrote: post #187
burgerbrain wrote: post #129

Earlier quoted context omitted.

You didn't pay very close attention in physics class did you? Millimeter wavelength electromagnetic waves are still radiation as much as any other wavelength.

So? If you think that all parts of the EM spectrum have the same effect then you didn't pay very close attention in physics class. Propping up pseudoscience bullshit like "it's radiation!" is the same reason why we have to deal with morons complaining about wifi signal. Ugh /former physics minor

>think that all parts of the EM spectrum have the same effect

Absolutely nowhere did I indicate that.

It does use radiation, and radiation is for the most part, and in this case, completely harmless.

I would assert that not understanding that all EM waves are radiation, including visible light, is the reason we have to deal with morons complaining about wifi signals.

/former physics major, and current title dropper

Re: When we got to the scanner, I opted out. Then they opted out.

#189

Post by Confusion »

jrockway wrote: post #164
dpatru wrote: post #130

Earlier quoted context omitted.

If everything is configured properly, the dosimeters would read normal. If not, isn't it better to find out as soon as possible?

No. Imagine if a few workers were being overdosed. The TSA would get sued and they'd have to find some other way to annoy us. No data, no lawsuit.

Using dosimeters works in many places where they use equipment that produce X-rays. On occasion, an incident happens. This may lead to a lawsuit, but still a lawsuit much smaller in scope than when workers are being overdosed over longer periods of time and them finding out in a few years.

Re: When we got to the scanner, I opted out. Then they opted out.

#190

Post by IsaacSchlueter »

yummyfajitas wrote: post #142
ohyes wrote: post #136

Earlier quoted context omitted.

It is hard to think that a flashlight or cellphone would have a power supply strong enough to do that much damage. (Although actually, metal halide lamps can sometimes cause UV radiation burns if they are damaged... http://archpedi.ama-assn.org/cgi/content/full/158/4/372 ). As long as the backscatter machine doesn't run on Double A's, my fears are actually more reasonable than yours. The backscatter machine presumabl…

My desk lamp also uses an electrical plug to connect to power. It isn't inconceivable that it could receive more power than intended and blind me! By the way, an order of magnitude or two more radiation than intended would be equivalent to a dental xray. Look, I'm not saying your fear is physically impossible. I'm just saying I can't think of a very many machines (radiation sources or otherwise) for which anything si…

And if it does, it's your responsibility.

Your desk lamp doesn't emit X-Rays, you don't force droves of people to stand underneath it, and no oncologists ever told me to be wary of your desk lamp until it has received further study.

So, yeah. Not the same thing. Not even remotely. In fact, your analogy is a bit silly.

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