Angela Aiuto, Timothy Aaron, Evan Fredericksen

Angela Aiuto, Timothy Aaron, Evan Fredericksen

4/27/2011

Professor Magnes

Is Backscatter Imaging Technology really worth it?

Controversy erupted in 2010 when the use of full body scanners was introduced to enhance security measures in airports. Implemented by the Transportation Security Administration (TSA), full body scanners are devices that produce “naked” images of passengers through the use of radio waves and X-rays. According to the TSA, the technology is supposed to be able to detect plastic and chemical explosives similar to that used by “underwear bomber” Umar Farouk Abdulmutallab in December 2009. Critics, however, suggest that full-body scanners may not have detected Abdulmutallab’s explosives, calling the overall effectiveness of the technology into question. Moreover, due to the fact that the technology exposes the subject of the scan to radiation, the possibly negative health effects have been called into question as well. In this essay we seek to conduct an investigation of the novel advanced-imaging-technology, focusing on the backscatter system in particular, to draw conclusions about the technology’s efficacy in light of widespread privacy and health concerns.

The basic premise behind backscatter x-ray systems holds that they must be effective in detecting contraband that other screening methods cannot. To this end, the system works differently than traditional x-ray scanners. A normal-ray device functions by bouncing x-rays into the object from which it’s trying to get an image. Various materials will either allow the x-rays to pass straight through them or they will absorb them, creating an image. Generally, Elements with fewer protons scatter more x-ray protons while elements with more protons tend to absorb x-ray protons. Similar to traditional x-rays, a backscatter system bounces x-ray beams into the object that it is scanning. Unlike normal x-rays, however, backscatter x-rays rely on differently objects scattering x-ray photons differently, allowing for a far more detailed scan of organic material. Backscatter x-rays produce a two-dimensional image, so two pictures are simultaneously taken of someone’s front and back.[1]

The resulting image, when completely unfiltered, creates a revealing image of the human body. A picture of Susan Hallowel Director of the Transportation Security Administration's research lab, shows her nude body, with contraband clearly visible.[2] The Transportation Security Administration filters the images that it takes down to one that is much less revealing. The issue with the filtered images is that they do not reveal potential contraband nearly as well as a fully unedited picture. While the debate about backscatter imaging has generally been framed as its functionality as a highly effective security screening device against privacy and health concerns, it should be noted that backscatter x-rays are not infallible in detecting contraband on a person. The image produced does not penetrate the skin, so someone could potentially smuggle through a weapon or explosive by storing it in a bodily cavity for further use. Backscatter x-rays do not even detect everything that is simply strapped to a person; a recent study in the Journal of Transportation Security says that “It is very likely that a large (15–20 cm in diameter), irregularly-shaped, cm-thick pancake [of PETN explosive] with beveled edges, taped to the abdomen, would be invisible to this technology. ... It is also easy to see that an object such as a wire or a boxcutter blade, taped to the side of the body, or even a small gun in the same location, will be invisible."[3]

Although AIT provides both a safe and more effective means of detecting hidden weapons, it has raised some privacy concerns. Perhaps most troubling is the potential for images to be wrongfully stored and distributed by security personnel after a passenger has passed through the scanner. It is the highly detailed nature of AIT imaging, and particularly backscatter imaging—in which facial features and other anatomical elements are often clearly visible, potentially rendering passengers recognizable—that raises the possibility of privacy violations. Civil liberties groups have voiced concerns that images produced by AIT scanners will wind up on the Internet; still others have pointed to potential law violations in the implementation of the scanners in airports. The most prominent example comes from the United Kingdom, where the Guardian found that “the rapid introduction of full body scanners at British airports threatens to breach child protection laws which ban the creation of indecent images of children.” (Travis)

In the past, the Transport Security Administration (TSA) has insisted that all images produced by AIT are not—and cannot—be stored or recorded, and instead are deleted shortly after they are viewed. In February 2010, however, a letter from Gale D. Rossides, Acting Administrator of the TSA, revealed that all machines used by the agency must be able to store and distribute images for “testing, training, and evaluation purposes.” (McCullagh) In August of the same year, the U.S. Marshals Service confessed to saving tens of thousands of AIT images on at the security checkpoint of a Florida courthouse. (McCullagh) Indeed, the greatest privacy concerns of AIT were realized when the technology blog Gizmodo.com posted pictures of backscatter scans that it had acquired form the U.S. Marshals Serivce through the Freedom of Information Act. (Johnson)

One potential solution to these problems is to obfuscate the passenger’s body through the use of a privacy algorithm. This technology converts a detailed, two-dimensional backscatter scaninto a “chalk outline” of the passenger’s body and any particular threats that may be on his or her person. In this way, passengers’ facial features and private areas are obscured, though threats remain outlined, and in a sense, highlighted. (Cavoukian, 225) Pictured below are an original backscatter image (left) and an example of a backscatter image that has been run through a privacy algorithm (right); both were provided by Cavoukian.

Other potential solutions to the privacy issues posed by the use of backscatter machines in airports rely on operational policy. For instance, in order to prevent the wrongful saving and distribution of backscatter images, airport authorities should prohibit staff from engaging in such activities. Cavoukian suggests that airport authorities conduct independent audits in order to ensure that employees are adhering to such regulations. (Cavoukian, 9) A separate suggestion focuses on controlling under what conditions personnel view the backscatter images. Cavoukian writes, “Airport authorities in Canada and the U.S. have created separate image viewing rooms (in remote back rooms) where security personnel cannot see the scanned passengers before or after the scans, and do not have access to passenger details. These personnel are also banned form bringing photographic devices (including cellphones) into the viewing area and are prohibited from connecting storage or communication devices to the machine.” (Cavoukian, 9) This extremely thorough approach would perhaps be most effective in preventing the wrongful saving and distribution of backscatter images.

Because backscatter technology uses ionizing radiation that reflects off of the subject’s body, both scientists as well as the general public have questioned whether such technology is safe for human exposure. Despite the widespread stigma surrounding nuclear radiation, however, backscatter technology does not negatively affect the health of humans.

The reason people raise questions about the health effects of backscatter technology is because the word “radiation” appears in its description. The fear of radiation originated in the wake of World War Two when the horrifying aftermath of the atomic bombs dropped on Hiroshima and Nagasaki were witnessed worldwide. In view of the aftermath, political opposition towards all forms of radiation developed due to increased pressures from the scientific community. Moreover, empirical studies on the effects of radiation were performed on fruit flies to assess the negative impacts of radiation. Scientists observed mutation in the cells of fruit flies that were exposed to radiation and drew conclusions that presented radiation in a negative light. Because of both the stigma placed on radiation and the results of the experiments performed on fruit flies, the International Commission on Radiological Protection implemented a no-threshold of acceptance police on radiation. However, years later we are using radiation as a security mechanism to the disapproval of many.[4]

Although radiation is a word that elicits alarmed responses, there are safe levels of radiation to which a human may be exposed. Through tests on humans, researchers have deduced that a single, whole-body dose of 150mSv (millisieverts, the unit used to measure radiation) or 15 rem (roentgen equivalent mammal/man) of radiation is not harmful to the human body.[5] Moreover, the Health Protection agency in Great Britain has advanced that human exposure to less than 300 mSv is safe.[6] Not only do these numbers pertain to healthy individuals, they also pertain to children, pregnant women, and people with medical implants.[7]

Backscatter radiation levels remain well within the safe limits of human radiation exposure. During each scan, which takes only a few seconds, airport passengers are exposed to about .05mSv (5 microrem) of radiation. This number is 3 million times lower than the safe, single-dose of 15 rem.[8] Even if one is not convinced by these numbers, which could mean nothing to a layperson, backscatter radiation put into perspective against the natural radiation that one receives both during flight and throughout everyday life will help demonstrate that the technology’s radiation levels are negligible.

Humans are exposed to infinitely more amounts of radiation living their daily lives and flying on planes than they are by undergoing backscatter scans. Some examples will help illuminate this point. On a one-way flight from Frankfurt to New York, passengers are exposed to about 35 Sv of radiation compared to the backscatter dose of about .1 Sv.[9] Put into perspective, the radiation a human is exposed to during a backscatter scan is equivalent to the radiation a human is exposed to during about two minutes of flying on an airplane. Moreover, in 42 minutes of living one’s everyday life, a person is exposed to more radiation from natural sources than that used in a backscatter scan.[10]

Gaining knowledge of the hard, empirical data and having it put into perspective, it is clear that backscatter radiation is not detrimental to the health of human beings. Approved by many organizations and institutions including the Food and Drug Administration, the Center for Devices and Radiological Health, the National Institute for Standards and Technology, John’s Hopkins University Applied Physics Laboratory, and the Transportation Security Administration, the general public should be assured that backscatter technology is safe.[11]

Although concerns about ill health effects from backscatter imaging technology appear to be unwarranted, the issue of privacy certainly is not. In light of political grandstanding following the September 11th attacks, airport security tools must be closely examined to determine whether their security-enhancing effects are outweigh any disadvantages inherent with screening technology. Backscatter x-ray technology does not seem to pass this muster. Its capability to produce near-nude images of passengers, coupled with avoidance measures that determined terrorists could take, indicate that this technology may not have been worth the massive investment that the American government made.

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[2]

[3]

[4]Cuttler, Jerry M. "Is Airport Body-Scan Radiation a Health Risk?" PubMed (2011). Print.

[5]Cuttler, Jerry M. "Is Airport Body-Scan Radiation a Health Risk?" PubMed (2011). Print.

[6]"Airport Full Body Scanners and Pregnancy - Query Bank." Royal College of Obstetricians and Gynecologists. 2011. Web. 27 Apr. 2011. <

[7]"TSA: Safety." TSA | Transportation Security Administration | U.S. Department of Homeland Security. Web. 27 Apr. 2011. <

[8]Cuttler, Jerry M. "Is Airport Body-Scan Radiation a Health Risk?" PubMed (2011). Print.

[9]Hupe, Oliver. "X-ray Security Scanners for Personnel and Vehicle Control: Dose Quantities and Dose Values." European Journal of Radiology (2007): 237-41. Print.

[10]"Products for Security Screening of People." U S Food and Drug Administration Home Page. Web. 27 Apr. 2011. <

[11]"Fact Sheet: Advanced Imaging Technology (AIT) Health & Safety." Homeland Security. Office of Health Afairs. Web. <