RaginPlainsman

Rush Holt (D-NJ) isn't just a congressman, he's also a physicist. And for a while he has been questioning both the effectiveness and the safety of x-ray backscatter scanners. He just sent a letter to the TSA about it.

From the press release:

Earlier this year, the Congressional Biomedical Caucus - of which Holt is a co-chair – hosted a briefing by Dr. David Brenner of Columbia University on the potential health effects of “back scatter” x-ray devices. According to Dr. Brenner, the devices currently in use and proposed for wider deployment deliver to the scalp “20 times the average dose that is typically quoted by TSA and throughout the industry.” Dr. Brenner has pointed out that the majority of the radiation from X-ray backscatter machines strikes the top of the head, which is where 85 percent of the 800,000 cases of basal cell carcinoma diagnosed in the United States each year develop. ...

“I appreciate the challenges we face in trying to prevent terrorists from boarding American airliners. That same background also gives me an understanding of why TSA’s current obsession with fielding body imaging technology is misguided, counterproductive, and potentially dangerous,” Holt writes.

MsTravelBug

Thanks for posting this info. I've been disappointed to see that my local TV stations are glossing right over the health risks of the scanners. I guess it's "sexier" to focus on the privacy issues.

While I respect those who object to the scanners on that basis, reporting that focuses on that issue makes it easy to dismiss the objectors as overly modest or prudish. People who aren't worried about the privacy issue might re-think their opinion of the scanners if they had more information about the health risks.

exbayern

I was stunned to read on another forum that a physician (a radiologist) didn't recommend that pregnant women use AIT, and another poster (a shop clerk) disputed her recommendation.

AUS2008

That post sounds familiar.

Here's the scoop. I am a radiologist. Though quite admittedly not as thoroughly versed in all of the radiation physics and radiobiology as some other posters on here (JanetDoe comes to mind--she sounds quite intelligent).
The American College of Radiology (ACR) says that, based on the info they have, they think it is a small enough dose to not be of concern, so they (currently) are not recommending that people avoid the backscatter machines. But they are getting their info from TSA.

But personally, having read articles, comments and letters by the UCSF professors, Dr. Rez in Arizona, and Dr. Brenner from Columbia, understand their questioning of just how this *reported* dose was derived and their call for further study. It seems there are enough people out there questioning the amount of radiation that further investigation certainly is necessary, and I do not know if any dose adjustments would cause the ACR to change their position. In fact, I emailed Dr. Brenner about this just last week, but we didn't go into much detail, and he basically stated that a single walk through isn't really of concern. He did not go into any issues from multiple exposures regarding frequent fliers or the flight crew. And he is not part of ACR, so can't comment to that.(It was sort of a non-answer, but I don't expect he has a lot of time for individual emails these days.)

Intuitively, what is bugging me is that radiologists and the ACR are heading in a direction of dose REDUCTION for patients. Granted, that is with diagnostic xrays, but still, an overall reduction. So it disturbs me that, on the other hand, it is "OK" for potentially MILLIONS of people will get these little added doses. And of course, this radiation, no matter how small, is NOT necessary. They could use MMW. Or the puffers. Or just the WTMD and check our bags. It has been pretty effective, really.

Also, I agree with the above-mentioned scientists' concern about where this dose is delivered. Think about what is close to the skin: eyes, skin, thyroid, breasts, genitals. And a fetus is not all that much deeper, depending on stage of pregnancy, and also more susceptible to radiation. Notice we don't tend to do xrays on pregnant women unless we absolutely have to--and shield their bellies if so? And from what I understand, these lower energy beams go to the skin and underlying surface and STOP. Not passing all the way through the body like medical imaging. Wonder what they are doing to the cells and DNA?

So, for me, and for the people I care about...I do not recommend them. Maybe after there is more info on the dose and who is keeping the machines calibrated? (the image itself isn't what bugs me, though I understand those concerns as well) I mean, I do fly. Often. And I don't stress about the cosmic radiation dose.

AUS2008

Not to mention...on that other forum, people say that having a TSA agent see you "naked" or grope you is JUST LIKE having a physician with many years of post-graduate education and medical training see you naked or examine you. Hope Nappy doesn't arm them with speculums next.

bdschobel

Rush Holt is my representative, and it's just about time he spoke out! I've been writing and calling his office for weeks about this, with no personal response yet.

Bruce

This letter really is spectacular! Excerpt:He's got my vote!!! ^^^

Bruce

pmocek

This hit Boing Boing this afternoon, so lots of people are hearing about it. "Scientist: X-ray scanners deliver `20 times the average dose that is typically quoted by TSA.'," Mark Frauenfelder, 12:38 PM Monday, Nov 22, 2010

kerflumexed

Good to see the Holt letter getting some traction - it is extremely well written. Also AUS2008 thanks for the good post on this.

I too wonder about calibration and independent verification and audit that each machine truly works the way it is supposed too.

Can the individual operator change any of the settings? Can it be dialed up for a better picture? While not a direct analog, these things and some of the issues remind me of the Therac-25 which is a classic case study in the limits and perils of software control and the user-interface.

Bill

OakParkFlyer

I'm glad to see more questioning about the health consequences of this type of xray. The TSA and other sources continue to quote the amount of radiation received being so small that it is equivalent to 2 minutes of cosmic radiation received in flight. However they don't offer any data around how the body absorbs the backscatter radiation versus cosmic, which goes right through you.

This xray comparison is apples and oranges. The TSA had Johns Hopkins measure the amount of radiation, and verify it complies with standards published by other agencies for exposure, but no one is tying it all together and looking at the long-term impact of delivering low power/low dose xrays to the soft tissues.

That makes me think of how the USDA is responsible for the health and cleanliness of chickens, but the FDA is responsible for the food safety of the eggs... That's worked out so well recently.

Olton Hall

Same with me. No response from his people either. I am glad he has come out with this.

Boggie Dog

So if getting screened by Backscatter perhaps that tinfoil hat ain't such a bad idea.

DoingHomework

But I know you had some radiation physics at some point, right? When they say the radiation penetrates 1/10 inch of the skin they mean, if they are physicists, the penetration depth where the intensity (or electric field strength possibly) has been reduced by about 63% (e^-1). The remaining 37% keeps going progressively deeper. There is also the issue of evanescent waves and constructive interference deeper in the body that are not issues with conventional medical imaging technology.

I avoid medical xrays when not necessary. I make sure the lead apron covers my genitals for dental xrays and I take note of where the gun points and insist it be repositioned when it points into my head or toward my neck glands unnecessarily. So, call me paranoid, and I'm not really, but I do not see the need to submit to a scan just to fly.

Don't worry the people keeping the machines calibrated are probably the ones who could not get jobs as screeners...

It's scary both that this is the best reassurance our government can give and that is reassures anyone.

100 watts of electromagnetic radiation at 1600 kHz (radio waves) goes through your body all the time.
100 watts of electromagnetic radiation at 500 nm wavelength (light) will hardly keep you warm.
100 watts of the same radiation made coherent in a laser would burn right through you and anything your tried to block it with including an airplane.
soft xrays are about a billion times higher frequency and lower power than light bulbs.
Cosmic rays have energies billions of times higher, so high they pass right through the body without interacting, for the most part.

So what does any on this have to do with the TSA? Nothing. I wish they would stop spitting out the worthless information about radiation levels being like what you are exposed to in the sky. It makes about as much sense as saying you are exposed to higher power (optical) radiation from the cabin lights...and you are. But that won't hurt you!

If they want make those kinds of claims they should open it up to peer review like every other scientific endeavour. And don't say SSI - we do peer review on top secret weapons systems! This is purely political.

CPT Trips

Too bad our elder Senator is escorting Nappy!

janetdoe

I think AUS2008's point was that the entire dose of low-energy x-rays dissipate their energy inside the body, causing damage in the form of free radicals, and in contrast, a significant percentage of high-energy x-rays will pass straight through your body without interacting with any tissue or creating any damage. (After, all, the way you read a diagnostic x-ray is by looking at how much of the beam passed through the body...) I think you two are in total agreement.

Also - where/how did you get 1/10 of an inch? I wasn't sure if you were throwing that out as an example or saying it was published. My back-of-the-envelope calculations (based on a NIST model for soft tissue) say it's more like 1 inch - the vast majority of the energy penetrates the skin. But I would like to check my scribbling against an expert's real data.

Please take everything that I say with a grain of salt. My field of study demands an understanding of how radiation interacts with matter, but radiobiology is definitely a whole new ballpark for me!!

SparkyRadar

Another common sense article/blog about backscatter here:

http://www.tjradcliffe.com/?p=114