November 28, 2010
— Open Blogger Jason Bell, a biochemist working in biophysics.

Chromosome Damage From Radiation
On the significance of the type of radiation used:
The TSA has been stating that the X-rays used in the back scatter machines use 'soft' X-rays, which are defined as radiation between 0.12-12 keV (or kilo electron volts) and are generally stopped, or absorbed, by soft tissue or low density matter. 'Hard' X-rays are between 12-128 keV and are absorbed by dense matter like bone. According to the TSA safety documents, AIT uses an 50 keV source that emits a broad spectra (see adjacent graph from here). Essentially, this means that the X-ray source used in the Rapiscan system is the same as those used for mammograms and some dental X-rays, and uses BOTH 'soft' and 'hard' X-rays. Its very disturbing that the TSA has been misleading on this point. Here is the real catch: the softer the X-ray, the more its absorbed by the body, and the higher the biologically relevant dose! This means, that this radiation is potentially worse than an a higher energy medical chest X-ray.
(Emphasis mine.) He has several concerns about the power of the machines in question:
- Based on the limited engineering schematics released in the safety documents, the machines could be easily reconfigured to perform through-the-body X-rays, and the hardware has the capability to output high doses of radiation though failure or both authorized and unauthorized reconfiguration of software and hardware.
- The X-ray beam is being rastered across the body--that is, scanned in lines from side to side, top to bottom, like a TV screen. If the machine fails or gets stuck during a pass, there is a possibility a person's eye, testicle, or hand, for example, could receive a dangerous dose of X-rays.
- This possibility gives rise to certain questions: What is the failure rate of these machines? What is the failure rate in an operational environment? Who services the machine? What is the decay rate of the filter? What is the decay rate of the shielding material?
- Also, what is the variability in the power of the X-ray source during the manufacturing process? The Johns Hopkins Applied Physics Laboratory noted a significant disparity in their test models--which were supposed to be adjusted to exact specifications.
On the widely publicized claim that radiation from the machines amounts to the same exposure one would receive after two to three minutes of flight:
With respect to errors in the safety reports and/or misleading information about them, the statement that one scan is equivalent to 2-3 minutes of your flight is VERY misleading. Most cosmic radiation is composed of high energy particles that passes right through our body, the plane and even most of the earth itself without being absorbed or even detected. The spectrum that is dangerous is known as ionizing radiation and most of that is absorbed by the hull of the airplane. So relating non-absorbing cosmic radiation to tissue absorbing man-made radiation is simply misleading and wrong.
Much more at the link, including questions raised by scientists about the lack of testing and safety data provided by the government and/or the manufacturers and the lack of independent testing and data. He also points out how stingy the release of information has been, with many things redacted in the material that has been made available. Why?
Link via BoingBoing.
Posted by: Open Blogger at
08:01 PM
| Comments (109)
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Posted by: Laurie David's Cervix at November 28, 2010 08:17 PM (6bDVD)
Posted by: eman at November 28, 2010 08:17 PM (kn74g)
Posted by: Jean at November 28, 2010 08:19 PM (CPefM)
Posted by: torulewye at November 28, 2010 08:20 PM (yL0f4)
Posted by: Guy Fawkes at November 28, 2010 08:20 PM (JcRgg)
Posted by: parisparamus at November 28, 2010 08:22 PM (B+w8R)
Posted by: Andrew Sullivan at November 28, 2010 08:25 PM (wMXoq)
Posted by: eman at November 28, 2010 08:25 PM (kn74g)
Posted by: buzzion at November 28, 2010 08:25 PM (oVQFe)
Posted by: humphreyrobot at November 28, 2010 08:26 PM (EiH7n)
Posted by: Swanny at November 28, 2010 08:27 PM (lyOKm)
Posted by: Dr Jekyl at November 28, 2010 08:27 PM (wMXoq)
Posted by: humphreyrobot at November 28, 2010 08:28 PM (EiH7n)
Posted by: eman at November 28, 2010 08:29 PM (kn74g)
Posted by: Dr Jekyl at November 28, 2010 08:29 PM (wMXoq)
If the shutters and safety interlocks fail, the radiation blasts out.
Do the TSA workers wear dosimeters?
They should. Travelers should too.
Posted by: eman at November 29, 2010 12:25 AM (kn74g)
I believe it was discussed the other day that the TSA workers are actually forbidden from wearing anything to indicate that they might be getting overexposed to harmful radiation. I'm betting that its because the higher ups know that if there is any indication that the scanners could be dangerous people will refuse to go through them.
Posted by: buzzion at November 28, 2010 08:31 PM (oVQFe)
Posted by: Dr Jekyl at November 28, 2010 08:31 PM (wMXoq)
Posted by: Smorgasbord at November 28, 2010 08:32 PM (JBB4K)
Posted by: Russ at November 28, 2010 08:34 PM (bMxOC)
Posted by: eman at November 28, 2010 08:34 PM (kn74g)
Posted by: humphreyrobot at November 28, 2010 08:35 PM (EiH7n)
Posted by: eman at November 28, 2010 08:36 PM (kn74g)
Posted by: Alaska trash at November 28, 2010 08:37 PM (GCl5B)
Posted by: Dr Jekyl at November 28, 2010 08:37 PM (wMXoq)
Do the TSA workers wear dosimeters?
Somebody said the other day that they weren't allowed to wear them. I wonder if that's the case or whether they just don't supply them (and service them).
Posted by: rdbrewer at November 28, 2010 08:37 PM (7hPoF)
Posted by: butch at November 28, 2010 08:41 PM (RMiT+)
Posted by: eman at November 28, 2010 08:42 PM (kn74g)
TSA worker don't wear a dosage badge, protective clothing, or stand behind protective shielding when the machine is in operation.
How much radiation are people getting exposed to just standing around?
Since radiation exposure is a cumulative affect sort like people who are always
tanning and get skin cancer or looking like an old leather couch.
Posted by: YIKES! at November 28, 2010 08:43 PM (zSAp9)
Most cosmic radiation is composed of high energy particles that passes right through our body, the plane and even most of the earth itself without being absorbed or even detected.
He's being a bit hinky himself when it comes to matters of radiation dose. The particles that slide on through the Earth are chargeless neutrinos and no one but no one takes any dose from them or quotes any numbers as such. Now, you *do* get a substantially higher dose at altitude than you do the typical 120 mRem/year (and the health physicists are quite careful to note that that dose is at sea level). Metal shielding does help to some extent but nowhere does Bell cite any numbers that make any meaningful comparison. Later in his article, he cites some numbers about dose to TSA workers from the scanners themselves but it's never clear just which set of numbers he using are, in fact, correct. And the ones he uses differ by a factor of ten. And even though Bell notes that for all intents and purpose, TSA workers are working with radiation producing devices, he uses the civilian population 100 mRem/yr dose limit, rather than the higher values used by radworkers.
This whole affair is turning into a gigantic mess in terms of meaningful information and Bell's not particularly helping the situation here.
Posted by: Additional Blond Agent at November 28, 2010 08:43 PM (SHKl9)
Posted by: rdbrewer at November 29, 2010 12:36 AM (7hPoF)
Forgive the Android phone spelling on the street.
Dennis Prager and Michael Fumento, the later being the former's kind of science panic go to guy (to de-bunk them). Prager doesn't have a problem with the machines because the images they supposedly generate are impersonal (you don't know who the person is); and Fumento, who is pretty good imho, kind of signed onto the few minutes of flying dose equivalent theory.
I emailed a link to this post to DP and his producer, and hopefully this scientists blog post will get to DP somehow.
(OT: there appears to be a Prager-Palin alliance building, which somewhat surprises me, and delights me at the same time; alas DP isn't a Romney fan ;-( )
Posted by: ParisParamus at November 28, 2010 08:43 PM (gMzAL)
Posted by: humphreyrobot at November 28, 2010 08:46 PM (EiH7n)
Posted by: eman at November 28, 2010 08:46 PM (kn74g)
Posted by: ParisParamus at November 28, 2010 08:46 PM (gMzAL)
Posted by: John Pistole at November 28, 2010 08:49 PM (7hPoF)
Posted by: eman at November 28, 2010 08:51 PM (kn74g)
Also, when you think of failure rates, most medical scanners don't get used SEVERAL THOUSAND times a day.
As I've said about 100 gazillion times, they're securing the smallest risk area at airports and ignoring everything else, THAT'S the problem.
Posted by: Merovign, Strong on His Mountain at November 28, 2010 08:53 PM (bxiXv)
I wonder what they use to guide the beams, to raster them. I mean, f/x, in the old tube-type TV days you'd occasionally see a picture that stopped scanning, with a line across the middle or just a dot. And you'd see that every time you switched the TV off--for a few seconds, anyway. Tube-type TVs used magnets to guide an electron beam. So. Like I said, I wonder what guides the X-ray beam. Something mechanical?
And. I wonder how easy it is to twiddle the machine settings, whether accidentally or on purpose.
I wouldn't want to stand by one for long hours. At least until they're thoroughly tested.
Posted by: John Pistole at November 28, 2010 08:55 PM (7hPoF)
Posted by: KG at November 28, 2010 08:55 PM (2pDBV)
Posted by: Interesting Connections at November 28, 2010 08:55 PM (rwFPp)
Oh, he asks "What is the decay rate of the filter?" Maybe the beam is rastered with a screen of some sort. Bet it's some sort of spinning cylander with slits cut in it overlain with another filter that has a single slit that moves ("scans") up and down. As the point the two slits intersect a beam emerges.
Posted by: John Pistole at November 28, 2010 08:59 PM (7hPoF)
Wow, watch the lawsuits happen.
Posted by: Interesting Connections at November 28, 2010 08:59 PM (rwFPp)
Posted by: rdbrewer at November 28, 2010 09:04 PM (7hPoF)
Posted by: rdbrewer at November 28, 2010 09:25 PM (7hPoF)
Posted by: humphreyrobot at November 28, 2010 09:39 PM (EiH7n)
Posted by: Oilfield Dude at November 28, 2010 09:55 PM (Cx5cx)
I know what you meant, but that was really funny; evokative of the STOS episode where computers simulate the battles of an war, and then the appropriate number of people are executed.
Posted by: ParisParamus at November 28, 2010 10:02 PM (gMzAL)
Posted by: Oilfield Dude at November 28, 2010 10:07 PM (Cx5cx)
Posted by: Oilfield Dude
You would be more convincing if you weren't glowing and didn't have the tentacles....
Posted by: Laurie David's Cervix at November 28, 2010 10:34 PM (6bDVD)
Posted by: s☺mej☼e at November 28, 2010 10:43 PM (glsV4)
But seriously folks....
The size of the exposed population is the big factor. The number of people working with radiation sources like you are, what - in the thousands? While there are over 800 million airline passengers in the US each year, most of them scanned, most of them twice. Call it 1.5 billion scans each year. Now how many people are going to be in the machine when it glitches, or they just happen to get a critical hit on the right bit of genome. Tens. hundreds, thousands?
Posted by: Laurie David's Cervix at November 28, 2010 10:44 PM (6bDVD)
Also, I assume folks like you are properly trained and are using carefully maintained equipment.
Now look at the mechanical failure rate of commercial aircraft, the most thoroughly scrutinized equipment at airports. With all that oversight, engines still blow up, wings still fall off. Now think of how much less TLC the people who maintain the scanners are going to use.
Posted by: Laurie David's Cervix at November 28, 2010 10:52 PM (6bDVD)
Posted by: Boots at November 28, 2010 11:06 PM (neKzn)
Posted by: Boots
Discovery during the lawsuits should take care of it....
Posted by: Laurie David's Cervix at November 28, 2010 11:12 PM (6bDVD)
Posted by: Oilfield Dude at November 28, 2010 11:35 PM (Cx5cx)
Posted by: Mr. TSA Smiley-Face Guy at November 29, 2010 12:18 AM (u5eVT)
"Backscatter" is a very misleading term that makes the untrained think the X-rays are "bouncing off the skin". They are not, they interact with ther atoms in the skin and cause an electron to be ejected and a photon to be produced which is then used as the source for the "picture". In nuclear terms this is called Compton's Scattering.
As I said the other day, if a "evil" private business were doing this they would be in jail.
Posted by: Vic at November 29, 2010 12:34 AM (e4sSD)
Don't forget that these things are hitting your eyes as well. Those are very radiation sensitive organs.
Posted by: Vic at November 29, 2010 12:35 AM (e4sSD)
I understand what your saying, but I still think it's a bit overblown. Even if those detectors went Chernobyl on you, you're only exposed for 30 seconds max. I don't think you'll be turning into Captain Pollution with those weak stats. Plus TSA workers don't need training. They're expendable!
Posted by: Oilfield Dude at November 29, 2010 03:35 AM (Cx5cx)
And what about all the people standing around in line waiting for their turn? What about all the TSA personnel near the machines. Its not as if the X-ray is a guarranteed directed beam to the person in the machine. Actual medical professionals that stand behind the X-ray machines and still put up a lead wall between them and it demonstrates that. There are going to be a lot of frequent flyers going through these machines on a regular basis.
Since you're in the oil industry yeah you're dealing with potential radiation from whatever is in the oil. That's usually been analyzed by others to determine the amount. Its not like you're suddenly going to come on a chunk of enriched uranium. There is some idea of what your exposure level is going to be. Can you guarrantee the X-Ray exposure level from these machines?
Posted by: buzzion at November 29, 2010 12:37 AM (oVQFe)
Exposure to radiation from Uranium is negligible unless you eat it or breath it, then you will have problems long term. Uranium is an alpha emitter and apha particles are stopped/shielded by even a piece of paper. It is an internal hazard only.
X-Rays are penetrating. Hell, you would be safer if they were exposing you to pure U-235 in the airport.
Posted by: Vic at November 29, 2010 12:55 AM (e4sSD)
Posted by: TimInVirginia at November 29, 2010 01:51 AM (CfTuh)
I'm an electrical engineer with a bit of experience in high-energy physics. If the machine is capable of producing "soft" X-rays and scanning, it's capable of producing a lot more output if the scan ever fails, and there's no failsafe to shut down the beam. A properly designed and tested machine would be a safe as possible while still doing the job. Medical devices are vetted by the FDA for years - and billions in costs - before getting deployed. Were these machines so tested?
Above all, ANY unnecessary exposure to X-rays or other ionizing radiation is a bad idea. Forcing people into these machines is very irresponsible - but them what's the government for?
Finally, isn't there a little conflict with the Fourth Amendment? Unreasonable search this is, if there ever was one.
Posted by: Chuck Kuecker at November 29, 2010 01:56 AM (LgHPp)
Posted by: Vic at November 29, 2010 02:02 AM (e4sSD)
Accidents involving nuclear medicine are a lot more common than people think. We used to get monthly reports from the NRC detailing all the industry accidents for the previous month and usually these reports were all dominated by unintentional dose to a patient caused by miscalculation of prescribed dose.
What I found ironic was that the hospital in question would be "cautioned" or given some kind of a slap on the wrist fine a few thousand dollars for accidents involving exposures of several hundred rem to specific organs.
This is opposed to some "paperwork" violation at a power plant where the utility would be fined a hundred thousand dollars.
Posted by: Vic at November 29, 2010 02:16 AM (e4sSD)
Most people do not have a problem with the scanners because they trust technology more than people. They not only prefer a scanner over a pat down they would rather walk through a scanner than get a complete background check and an interview just to get on a plane.
Posted by: Terrye at November 29, 2010 02:56 AM (9iEV2)
A side-effect of this is that now, scientific information on things like these back-scatter machines is mistrusted. I have no idea if they are safe or not, because I don't trust the government to tell us the truth, and the company has a vested interest in saying they are safe in order to get more sales and avoid lawsuits.
This uproar over the machines' safety is a direct result of science being manipulated for political purposes. As someone who worked in science years ago, I find this ery upsetting. Furthermore, what ELSE is being twisted or downright lied about? We have no idea.
Posted by: Miss Marple at November 29, 2010 03:11 AM (Fo83G)
Posted by: Another Bob at November 29, 2010 03:40 AM (UghWd)
Long before Wikileaks, given the Obama administration's fabricated government figures and propaganda, why anyone would believe any official statement or report is not logical.
This possibility gives rise to certain questions: What is the failure rate of these machines? What is the failure rate in an operational environment? Who services the machine? What is the decay rate of the filter? What is the decay rate of the shielding material?
Those questions assume that the machines are functioning under ideal circumstances. This past week, I've heard experts express complete misgivings over the scanner machines given that lay employees, not experts, are the ones using them on the public. Point being, a very minor maladjustment results in major damage on the human bodies. And the laymen haven't a clue when the machines are maladjusted.
Posted by: maverick muse at November 29, 2010 03:45 AM (H+LJc)
–TJ Radcliffe
Posted by: RoboMonkey at November 29, 2010 03:46 AM (mdDbk)
Posted by: xavier at November 29, 2010 03:47 AM (ROLH/)
There it is.
Posted by: maverick muse at November 29, 2010 03:52 AM (H+LJc)
Posted by: maverick muse at November 29, 2010 03:54 AM (H+LJc)
I heard a TSA person explaining the safety of this machine to a very, very skeptical older lady. She wasn't making progress, judging by the raised eyebrows and body language.
It would be something if after having had to deliver this spiel to thousands of unwilling passengers, they are the ones who had problems in the future.
It'll be interesting to see.
Posted by: Who Knows at November 29, 2010 04:11 AM (QLiYt)
Posted by: Museisluse© at November 29, 2010 04:49 AM (DTfXb)
Posted by: torabora at November 29, 2010 04:59 AM (grzsD)
Posted by: al at November 29, 2010 05:06 AM (4nxhP)
Posted by: John Edwards at November 29, 2010 05:42 AM (grzsD)
I'm a radiation oncologist who works with radiation-producing machines (linear accelerators) and radioactive isotopes every day, and I call bullshit on this.
The strength of the x-rays in the scanners is what we would call "superficial", in other words it is essentially entirely absorbed in your skin and never gets to deeper tissues. The higher energy x-rays do pass through you and are more problematic because they do have the potential to cause radiation damage to deeper tissues. While it is true that the "soft x-rays" are absorbed more by the body (because they are weaker in energy), it is total BS to say that they are going to be more damaging than the higher energy x-rays. The guy says that cosmic rays are
Yes, you will get more radiation exposure in your flight than from the scanners. In fact, flight crews in Europe are classified as radiation workers. You will also get more simply by living in high altitude locations like Colorado, which has a background radiation more than twice that of places at sea level, or by living in places with higher amounts of radioactive minerals in the rocks (i.e. the Rocky Mountains).
Posted by: MM at November 29, 2010 05:54 AM (EtH1K)
Posted by: SarahW at November 29, 2010 05:55 AM (Z4T49)
Posted by: SarahW at November 29, 2010 06:01 AM (Z4T49)
Whoops, forgot to finish the one sentence.
The guy says that cosmic rays aren't absorbed by you or are absorbed by the airplane. While there will be some filtration by the airplane hull, aluminum of the thickness used in airplane hulls will only filter out the weakest cosmic rays, leaver the higher energy to pass through you and yes, get absorbed by your body. Despite all of this exposure, flight crews do not display any evidence of elevated rates of fertility or malignancies. In fact, there are parts of the world, like the Kerala coast in India that have background radiation levels of 260mSv (Chest x-ray gives you 0.06mSv) which is 200x that of normal background radiation. People living there are, if anything, healthier than the general population.
Posted by: MM at November 29, 2010 06:07 AM (EtH1K)
Posted by: MM at November 29, 2010 06:12 AM (EtH1K)
With this administration I do not trust a single number they use anywhere. All of them are liars.
And BTW, I hate GD European dose measurements.
Posted by: Vic at November 29, 2010 06:51 AM (e4sSD)
If I'm flying, personal safety ... even if only perceived ... trumps personal rights every time.
It's mindless dumbfuckery like this that emboldens the government to trample on your rights.
Posted by: Warden at November 29, 2010 07:01 AM (V6HDd)
OK hypothetically the scanners contain radioactive material, unless you refuse to be x-rayed then you get a pat down/sexuallly molested. So what happens if a hidden butt bomb is detonated by a homocide bomber inside the scanner? will this explosion become a small dirty radiological bomb?
Is the TSA actually helping terrorist to set off such a dirty device by providing the material at each airport boarding line?
Posted by: HEP-T at November 29, 2010 07:08 AM (ZPZ3z)
Posted by: Jack's complete lack of suprise at November 29, 2010 07:12 AM (F/4zf)
This would cause even more gloating and schadenfreude than the speed-trap cops who got testicular cancer from their radar guns.
Posted by: RoboMonkey at November 29, 2010 07:15 AM (mdDbk)
If the shutters and safety interlocks fail, the radiation blasts out.
theses online
Posted by: Freddy at November 29, 2010 07:17 AM (qKSBv)
And forget the term "backscatter" radiation. That is another misleading term ginned up by the makers of these devices to make them seem harmless.
Posted by: Vic at November 29, 2010 07:22 AM (e4sSD)
Posted by: SarahW at November 29, 2010 07:54 AM (Z4T49)
Posted by: Chuck Kueker at November 29, 2010 05:56 AM
They aren't even releasing all the information they do have on them. Go to the link and take a look at the redacted page.
It's redacted, you know, because X-rays are TOP SECRET.
Posted by: rdbrewer at November 29, 2010 08:09 AM (TLdeF)
The strength of the x-rays in the scanners is what we would call "superficial", in other words it is essentially entirely absorbed in your skin and never gets to deeper tissues.
So? Don't you like your skin?
Posted by: rdbrewer at November 29, 2010 08:15 AM (TLdeF)
Posted by: Henry Bowman at November 29, 2010 08:50 AM (+gIcK)
MM, you aren't who you represent yourself to be if you think that treating a cancer with targeted radiation and general exposure of the scalp, including precancerous tissure to xrays is somehow therapeutic.
That's shockingly dishonest at the very least.
Yeah, that's right. What the hell do I know?
Posted by: MM at November 29, 2010 09:00 AM (EtH1K)
The terrible consequences of a software logic flaw, unintended or malicious, is described in Set Phasers On Stun. There was a logic flaw in a Therac 25 X ray system control program allowing a huge overdose of X-rays. The guy who was lethally irradiated used that phrase jokingly, but it still killed him dead.
Posted by: chuckR at November 29, 2010 09:55 AM (XLu7l)
And I misled in what way exactly?
Radiation is used to treat skin cancer, particularly in cosmetically sensitive areas like the central face, and on the scalp as well if the lesion is large and the surgical excision would leave a large defect. I wouldn't treat the entire scalp for a skin cancer, just the lesion in question with a 1.5cm margin if it is a basal cell. I am not arguing the physics of how low-energy x-rays work, I know how they work because I have used them. I am arguing the biological significance of the dose that these scanners put out as well as trying to correct some erroneous information put out by a guy who not a radiation physicist, nor a radiation biologist (yes, that is a an actual field) and who was trying to put things in the most alarmist manner possible to try to scare people.
Posted by: MM at November 29, 2010 10:03 AM (EtH1K)
Frequent flyers and flight personnel will have dosimeters that will be in the red. Will the defects and sterilty cuased by these machines be covered under Obamacare?
Once again bad law and bad technology will render bad results.
Posted by: Anna Puna at November 29, 2010 12:59 PM (HYy2l)
Thanks in knowledge ikinci el eþya
Posted by: Chris at December 05, 2010 01:45 PM (sd9Ri)
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Posted by: nerdygirl at November 28, 2010 08:08 PM (UAftU)