TSA scanners: Some safety questions linger

Opinion Zone,Max Borders
The TSA recently announced the bureaucracy will introduce new software to obscure the embarrassing crevices, curves and cottage cheese areas once revealed by full body scanners. Humiliation is one thing. Danger is quite another. 

TSA hasn’t done enough to quell fears about radiation. Orlando, New York and other municipalities have either introduced, or are considering, local bans of the scanners. Should we be worried? I consider myself someone who is not particularly susceptible to paranoia. But I think it makes sense to look more closely at the science.

Let me preface all of this by saying I am not a scientist. I appeal to more knowledgeable experts in physics and radiology, but I also welcome more thorough scientific opinion and commentary from all quarters. I write this because this conversation should not be over.

I’m going to offer a layman’s explanation for why I think these devices could be dangerous. I hope that they are safe. But we should all be doing our homework. Based on what I’ve been able to determine, I’ll be opting for the grope next time I travel.

About the Science

There are two basic types of radiation that can be used for imaging: ionizing and non-ionizing.

Ionizing - The first includes so-called “soft” and “hard” X-rays. “Backscatter” machines use soft X-rays. People generally get the “hard” form when they visit the doctor. Of course, medical techs wear lead shielding or stand behind a lead wall when they operate these machines. The patient gets a dose of these hard X-rays, some of which are absorbed by the body while others reflect back onto the film -- providing an image. This involves risk -- but it’s pretty low relative to the health benefits. Most tissue is transparent to hard X-rays. But a radiologist’s job is to minimize the likelihood that any absorbed X-rays will introduce free radicals that could damage your DNA. In any case, because most hard X-rays pass through the body, what does get absorbed is scattered among billions of cells. 

With “soft” X-rays, the difference lies not only in frequency of the energy emission, but in how much gets absorbed by the skin. We know somewhat less about the effects of soft X-rays on health, because these devices are effectively useless for medical imaging. But we know enough about the dangers that patients and technicians are shielded from soft x-rays, which are created at the same time as hard x-rays. Their “negative image” is formed in a film that is behind/underneath the patient. The absence of absorbed x-rays leave those regions of the imaging field unexposed and transparent in the film. Although good information on the health effects of soft X-rays is less abundant, we know it can cause cancers. Ironically, it can treat skin cancers, but that application focuses solely on the cancerous cells as the rays kill everything in its path.

Still, it would seem at first blush that TSA scanners using soft radiation might be no more dangerous than a visit to the doctor. Even if travelers are getting a full dose of soft x-rays, you may be thinking “so what? The problem is low doses of hard X-rays absorbed in billions of cells, say in your chest, represent a negligible risk. But what about a dose distributed in a much smaller body mass -- your skin (only millions of cells)? 

As a rough (and perhaps inexact) analogy: think about the difference between broiling a chicken at 500 degrees for three minutes and baking it at 300 degrees for three minutes. Which one will cause more skin damage to the chicken? In any case, we shouldn’t let the term “soft” lead us astray. Because the skin is far less transparent to soft X-rays (which allows TSA to take the unflattering nude pictures), the exposure concentrates in the skin. That means the exposure per unit of tissue mass could be more than 100 times that of hard X-rays. That said, the government insists the dose is so low people should not be concerned about this type of exposure.

Non-ionizing. The second basic type of radiation includes “millimeterwave” radiation. This radiation has been proposed for some body scanners, called “MW” scanners. A subset of these use Terahertz frequency waves. According to folks at the Center for Non-Linear Studies at the Los Alamos National Laboratory, radiation at these frequencies can cause strands of DNA essentially to “unzip” -- even at low intensity levels -- through what is known as “destructive resonance.” This phenomenon has only been modeled but, as far as we know, not tested. MIT’s Technology Review reports:

Alexandrov and co have created a model to investigate how THz fields interact with double-stranded DNA and what they've found is remarkable. They say that although the forces generated are tiny, resonant effects allow THz waves to unzip double-stranded DNA, creating bubbles in the double strand that could significantly interfere with processes such as gene expression and DNA replication. That's a jaw dropping conclusion.

We should mention that the center conducted this research to explain why, in some instances, studies showed considerable genetic damage and in others little or none. The modelers believe they have now explained the discrepancy. Their model is the only scientific explanation that can support laboratory observations for DNA unzipping, which is not theoretical.

You can think of destructive resonance as similar to opera singers voices breaking wine glasses at certain frequencies. In this case, the MW waves strike the DNA at just the right frequency, damaging the double helix. So it’s not conclusive that the MW scanners are any safer for human beings than soft x-rays. The consequences of destructive resonance to human health are not fully understood. But mutagenic disease (cancers and autoimmune disorders) caused by the inability of unzipped DNA to properly express its genetic materials could actually more severe than the damage caused by ionizing radiation. 

Remember, ionizing radiation will just tear strands at one point in your DNA.  If only one strand is torn, the other health strand can repair it before the cell replicates.  That’s why a radiologist is focuses on insuring that the statistically likelihood is maximized that no cell in your body will absorb two x-rays (tearing both strands), which would leave it unable to repair itself. Obliterating whole fragments of your DNA through resonant processes is far more severe. There will be absolutely no chance for self-repair in that instance, because so much of the DNA molecule has been destroyed.

Mishandling Your Genes

The problem with any form of radiation, ionize or non-ioning, is that either form can damage your DNA. Of course, DNA damage can cause cancer or reproductive problems (including birth defects) -- particularly in people who have diseases that retard or compromise the DNA repair mechanism. 

Because TSA personnel are not required to wear lead shielding, we have to wonder whether they could be undergoing thousands of exposures per day of something dangerous. We don’t know -- that is, unless we’re willing simply to take the word of the TSA and the companies that produce the scanners. Government officials claim these machines are “well within [safety] standards.” But if they are, how can we verify this independently?

We might also be concerned about quality control. As Andrew Schneider writes:

To ensure the doses are as low as billed, it is imperative to calibrate the machines accurately and monitor their performance carefully.
A spike in the intensity of the scanning beam, or a slowdown or pause in the timing of its sweep across a body, could cause significant radiation damage, according to a radiologist and two radiological health physicists.

In other words, how can the government guarantee that any given scanner is working as it should?

Risks versus Benefits

One of the most unfortunate aspects of the TSA scanner controversy is that the technical specs of the scanners have not been made available to the public. Nor, to my knowledge, are scanners being made available for independent testing. We’re simply supposed to trust the word of the TSA, the FDA, and hand-picked radiation “experts” that the scanners are safe. This lack of transparency (no pun) is both frightening and illiberal considering the dangers these machines could pose to public health. At the moment, these machines are ‘black boxes.’

In testimony to the City of Austin, physicist and nanotechnology expert Pierre de Rochemont claimed that backscatter radiation could increase the incidence of skin cancer by “225,000 per year, causing an additional 1,700 fatalities per year.” 

For the sake of discussion, let’s just stipulate that this estimate is overblown and cut it in half. Scanners would thus only cause 850 fatalities per year. How many people per year is the TSA saving? Let’s also factor out the enormous costs of the bureaucracy itself, the missed flights, the humiliation and the inefficiency now built into our air travel system, and the number of people who now only drive instead of fly (which is far more dangerous). From a purely statistical-utilitarian standpoint, does TSA expect to save more than 850 people per year? How many did TSA save last year?

Max Borders is a writer living in Austin. He blogs at Ideas Matter.
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