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January 02, 2010

Full body scans, x-rays, and cancer

There's been a lot of talk about full body scans the wake the abortive Christmas Day crotch bombing. Naturally, any of the biggest scanning proponents also sell full body scanners.

A lot of people are nervous about technology that allows TSA screeners to see them naked.

But nobody seems to be asking about the potential health risks of bombarding passengers with x-rays. Not all full body scanners use x-rays, but the TSA has already ordered some that do.

The thing is, X-rays are carcinogenic. That's why your hygienist gives you a lead apron leaves the room when you get dental x-rays.

(Correction: Nevermind about the mammogram example. Thanks to commenters Kittywampus and Butdoctorihatepink for setting me strait.)

No doubt the risks associated with airport screenings are very low, but the relevant question is about the cost/benefit ratio. We shouldn't have to put up with any additional risk unless there's a significant marginal benefit. Even under the status quo, deaths from airplane terrorism are exceedingly rare.

Nate Silver estimates that odds of an air traveler being involved in a terrorist event on any given flight at less than 1 in 10 million. So, if scans caused even a tiny increase in cancer risk among the millions of people who fly every year, the technology could end up killing more people than it saved.

Presumably, it takes a lower dose of x-ray radiation to penetrate clothing than it does to visualize structures deep inside the body. On the other hand, the risks from x-ray exposure are cumulative. Safety guidelines must take into account the risks for frequent fliers. Maybe it's perfectly safe to get scanned once a year, but what if you fly every week? Full-body scans could become an occupational health and safety issue, since so many frequent fliers are traveling for work. 

Maybe scanners are perfectly safe. However, these devices should be subject to the same rigorous safety testing as a medical device. We shouldn't just take the word of the high priced hucksters who are touting them on CNN.


a wonderful incentive to fly less.

Just to continue the derail about mammography, but radiation exposure WAS a concern of the USPSTF. It is true, digital technology and progress in general has decreased the amount of radiation in an individual mammogram. UpToDate says that one mammogram contains the amount of radiation a typical person would get in three months of background radiation. So, the individual dose of one is not that significant in the grand scheme of things. However, repeated doses make a difference, and it makes a difference if they are started a decade earlier. Especially if it is a poor tool for premenopausal, dense breasts, and repeat mammograms will be ordered, along with those unnecessary biopsies. Cumulative exposure is the key. Which would be the key for airport full body scanners, too.

(OK, I know this post isn't about mammograms, but since I already admitted this was a derail, and I am only answering a previous comment...) Also, the reason the USPSTF changed its recommendation on mammograms had little to do with simple anxiety. Mammograms are a poor screening tool for women from age 40 to 50. They will get MORE biopsies because of this, and no less mastectomies. Mammograms do not prevent cancer, at all. They are simply an imperfect visualization tool. Reputable experts think repeated mammograms, especially on women with dense breasts who start early and then live a long time, may actually cause more cancers than they diagnose in that particular group of younger, low risk women.

I am not against mammograms as a screening tool in appropriate populations that it is effective for. If you are high risk, go for it. If you are over 50, go for it. This is not about simple anxiety or "the government" not wanting to cover the cost of "your life", at all (Cost was not even considered, and it's an independent organization, not the government. And, mammograms in this age group did not save significant lives. Here is a great article by an ob/gyn on the subject, and here is one I wrote about it, and why people in public health and oncologists are supporting the new recs).

More procedures is not always better. At the doctor or at the airport.

OK, off my soapbox.

squashed -

There are two kinds of machines: millimeter wave and X-rays.

I think Phantom has been clear that it's not about the statistics of safety, but the appearance of safety. Phantom feels safer, even if the actual numbers don't show a difference.

And that's why we make mothers drink their own breast milk or have TSA agents fondle the breasts of young women, or have grandma remove her prosthetic leg before boarding. These things give the appearance of making us safer.

Other folks have pointed out similar situations, last time I flew, i was wearing a business suit and had a briefcase. I'm a white balding guy that was born and raised in the USA, so I was pulled aside at each airport and searched. Meanwhile I watched men that were tall dark middle easterners with heavy accents, walk by with hardly any attention paid to them.

It's all about the appearance of safety. And i think that's what Phantom is trying to express.

Yes, body scans are VERY important to protect the 21st century from the 11th. It is critical to have technology and processes and systems that remove all personal responsibility and human behavior from the world that flies on airplanes and dashes about administering the "real" world."

Stand in line quietly, walking through the portal and board the machine that keeps you perfectly sealed from any and all anywhere as you go about the careful and perfect existence. Until you die peacefully in a glittering hospital cared for by the process and machines there administered by the benign and kind overseers who keep you safe from all the others.

Stand quietly in the line and let the others take care of it all. The system works. Trust the system and the overseers. You have no say in the matter.


You miss every possible point

The numbers are only one metric - judgment has to enter into it. The nature of an evolving threat has to be considered as well.

Some years back, a Muslim terrorist planted a bomb in the luggage of his pregnant " girlfriend ". But guys like you would probably have been upset at any inspection of pregnant women.

There are those who will hide bombs in their clothing, in their bodies, and who will plant bombs on anyone including your grandma and in a one year old's diaper.

This is what those who try to keep you safe have to contend with. I'd like to know what you would do differently.

Eric Jaffa said...

There are two kinds of machines: millimeter wave and X-rays.

Yes, there is new, full body X-ray scanner. Which IMO is gigantic stupidity and will be a ginarmous class action lawsuit waiting to happen.

X-ray can ionize molecules, no matter how "low" they say it is. It damage cellular molecules and DNA machineries. aka CANCER. (They say it will be low doze. but too low of an energy, you wouldn't see anything usefull. What's the point. X-ray strength is ability to penetrate all the way inside human body. You want to see inside of human body cavity.)

Anyway, they are not going to "calculate" how many exposure a passenger receive during a trip across various international airports, let alone during a person lifetime. They just gonna keep spraying everybody with X-ray, and I guarantee you out of several hundred millions passanger, a couple will develop cancers.

On top of that, the whole thing still doesn't solve plane suicide bomber. One can simply insert semi rigid condom filled with liquid explosive and none of these machine will be able to detect. (granted making effective and stable liquid explosive is very hard and beyond al qaeda ability.)

Phantom, those bombs can be detected by the existing X-ray machines and metal detectors with only slight modifications. Many of the restrictions currently in place could be replaced with less onerous but equally safe restrictions. The TSA needs to ask itself the question of whether its purpose is to maximize security or discomfort. Right now, it maximizes discomfort.

For example: the shoe-removal rule comes from the fact that the metal detectors have a 10-centimeter blind spot at the bottom, providing Richard Reid with an opportunity. The security regulations could have required airports to place block or ramps at the bottom of the metal detectors, to prevent people from walking in the blind spot; alternatively, they could have required security officers to watch carefully to make sure people lift their feet high enough to avoid the blind spot. Instead, they require people to remove their shoes - while the blind spot seems to still be there.

For another example: the X-ray scans are capable of detecting explosives and chemical compounds. There is no reason to open all bags, especially not when the security officers don't even look that closely inside. Nor is there a reason to ban liquids - just ask people to put all liquids through the X-ray scan. Water would clear the check, bi-liquid explosives wouldn't.

Even the old process could be made more convenient - for instance, in Singapore, you only have to go through security at the gate where you board, which requires purchasing more metal detectors and X-ray machines but makes passengers' lives easier by turning two lines to one.

Best case scenario: thanks to technology that eliminates any possibility of bringing hidden explosives on board an airplane, the next terrorist flies to the US without explosives.

At which point he buys explosives and sets off a bomb in a crowded place like a shopping mall, where there is far less security.

I don't think the problem is with explosive inside bags that one is solved long time ago, but anything attached on or inside human body.

You can't use X-ray technology to detect explosive inside bag on human body. It's too harsh and will cause cancer. The same amount of energy that cause nucleous ionization and give signal if material is explosive or not, will also crunch DNA strand. I am pretty sure it'll be a nightmare if 500 millions air passengers suddenly start developing cancer 20 yrs from now.

On the other hand anal probe for every passenger is pretty disagreeable.

again, we are talking about bomb material inserted into body cavity, not just strapped on to body.

I just want to point out that you get a dose of radiation from flying itself. I don't know how many millirem of exposure one gets from a typical flight. A little googling shows something like .3 mrem/hour of flight time. What's the dose from a full body scan? It's probably more than the flight. Anyone have a number?

Why bother with the full body scan? Another modest proposal - fly naked. The real problem here is modesty, is it not? Hell, we could even have "hot" flights with only sexy naked people. We'd have screeners for hotness, of course. Think of the business opportunities. :-) (for the humor-impaired - I am not serious)

Per wikipedia, someone being scanned with a backscatter x-ray machine will get exposed to 0.005 - 0.009 millirems of radiation. While you're actually in the air, you're exposed to about .3 millirems per hour. Unless I'm doing the math wrong, that means that a full body scan is equivalent to the additional radiation exposure of 1-2 minutes of flight time. I have a hard time believing that it's a significant danger.

A study conducted by Boian Alexandrov (and colleagues) at the Center for Nonlinear Studies at Los Alamos National Laboratory in New Mexico indicated that terahertz radiation has the potential to literally rip apart or unzip double-stranded DNA. This, in turn, creates bubbles that could interfere with critical processes (like DNA replication and gene expression).

I don't really don't mind being exposed nude for the TSA pervs, but having my DNA unraveled ... that's another issue altogether!!

THANK YOU for posting this. If given the choice between being scanned or having to undergo a strip search, I would pick the latter. I've had to endure far more invasive situations in my life. I've been trying to look into if that's an option and have come up with nothing.

soft plastic and liquid are not visible to any scanner. that got to be pad down. but then one can insert it in body cavity, like I said.

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