There has been much hyperactive reaction to the new Transportation Safety Agency (TSA) screening procedures utilizing whole-body scanners or, alternatively if you refuse the scan, so-called "enhanced" pat-downs likened to near-sexual assaults. Most of it is ill-informed and over-reactive. My purpose here is to inject a bit of calm factual discussion into the maelstrom of rhetoric whirling around this issue. Hopefully, the result will be a little better understanding.
First, the overall problem of airport security should be addressed. The precipitous implementation of airport body scanners, a major cause of the negative reaction, was brought about by the so-called "underwear bomber," Umar Farouk Abdulmutallab, and his failed attempt to set off a small amount of explosive--think a McDonald's salad dressing packet--concealed in his tighty-whities. This Newman's Own "bomb" passed undetected through the existing security screening, eliciting a frantic government reaction. Also at issue, of course, is the billions in taxpayer money spent on developing the scanners.
The fact is, no physical screening technology or procedures, short of naked body examinations including parts and places you don't want to think about, will detect all potential hidden explosives. Even then, some idiot fanatic will find a way to swallow a ticking bomb made of X-ray-transparent materials. So, impressive as this brilliant new technology may be, it won't guarantee safety from dedicated terrorists. The question then becomes, is it worth it? The answer is, no-one knows. Personally, I doubt it.
Now, what is it and how does it work? There are two types of Whole Body Imaging (WBI) technologies in place. They are backscatter and millimeter-wave. The first uses low-level X-rays to image the body. This passes through clothing and into you, but a portion reflects off of your skin, or "backscatters", technically called "Compton scattering." This radiation does penetrate the skin, but a small amount reflects and is detected by a bank of detectors. The data are computer processed to create a whole-body image. Frontal and rear images are usually obtained simultaneously. The resulting two-part image is of the subject's skin surface, all of it, in excruciating fine detail. The processing software blanks out facial features.
It must be acknowledged that this is X-ray radiation, which is ionizing radiation. That is, it penetrates cells and can modify or damage their DNA. Hence, it is designated by the government--EPA?, CDC?, CPSC? I'm not sure who--as a non-threshold carcinogen. This means no level is low enough to be 100% safe. Even though the amount of radiation is relatively small, the energy is focused on the skin and adds to the normal background radiation we receive every day.
Background radiation is diffused throughout the body, while backscatter X-rays are focused on the skin and penetrate a short distance below. Damage from ionizing radiation is permanent, and therefore is cumulative. Consequently, despite assurances from the TSA and others, radiation from airport backscatter body scanners is not totally innocuous. There is some risk of genetic damage to the skin and the tissue beneath. Again, the question is, is it worth it?
The other technology is millimeter wave. This method utilizes Extra-High Frequency (EHF) radiation in the range of 30 GHz-- think microwave on steroids--to create an image. EHF radiation will penetrate clothing but reflects off of skin which it does not significantly penetrate. Thus, there is no risk of genetic damage but it can burn. At the levels employed by the airport scanners, this is highly unlikely unless you fall asleep in one. Unfortunately, this safer technology is the less common. I'm not sure why, but it might be the state of development or perhaps the cost.
The following drawings show the typical configurations of the two types of WBI scanners.
Backscatter Scanner Millimeter Wave Scanner
So, what's the bottom line? WBI scanners in airports are an invasion of privacy and grossly immodest, if that matters anymore. There is a serious question of medical privacy for persons with ostomies and breast prostheses from cancer surgery. Since these items can appear suspicious in the scans, invasive pat-down, sometimes with exposure and close physical examination, is usually required which can cause problems. I don't think I need go into detail. (TSA is currently re-examining their procedures in light of this problem.)
The health risk from backscatter scans is small. There is a possibility of genetic damage, especially for people whose health is already compromised. Although we are exposed to ionizing radiation every day, this is an additional exposure exacerbated by the focused nature of the radiation. So, there is an undeniable small risk, especially with repeated exposure as the effect is cumulative. There is no known risk from millimeter-wave scanning, unless you believe that cell phones cause brain cancer.
Note: The above statements reflect my opinion, some knowledge and interpretation of published information on the subject. The purpose of this post is only to inform. It is not to be construed as any sort of medical advice as I am not medically trained. There are, however, qualified authorities (which excludes the ACLU) on both sides of this issue, some of whom convincingly assert a medical risk from backscatter X-ray scanners.
Finally, I leave you with a quote from Rafi Sala, an Israeli airport security expert who helped design security at Ben Gurion International Airport: "I don''t know why everybody is running to buy these expensive and useless machines. I can overcome the body scanners with enough explosives to bring down a Boeing 747. ... That's why we haven't put them in our airport."
El-Al, Israel's airline, relies on sophisticated profiling techniques. They haven't had a terrorist incident since 1970, and that one failed.
My reaction, for what it's worth, is that this is just another over-reactive wasteful government boondoggle that will do virtually nothing to improve airline security. Although the health risk is slight, the benefit is even less. There is a greater risk from baggage and cargo than from individuals. Many in the jihadist community are a good bit more clever than the hapless "underwear bomber" and will simply devise other methods and technology to defeat whatever screening equipment we create. It is not possible to anticipate every possible terrorist tactic so long as people, luggage and cargo are allowed aboard and the ground crew and flight crew have unscreened access. (Pilots have just been exempted from WBI screening because of union objection. They and ground crew are subject only to identity verification.)
The solution is not in fancy hardware but in intensive profiling as implemented by the Israelis, looking to detect demeanor and actions, and yes, including background and origin, that betray the suicide bomber attempting to board. Nervousness is much harder to hide than explosives. This screening process should also be applied to anyone who has access to the aircraft on the ground.
But I'm whistling in the windstorm. It will never happen here in the indulgent, politically-correct, overly-sensitive U.S.A. Until ..... .