Letters to the Editor  |   February 2011
Pandora's Boxes: Questions Unleashed in Airport Scanner Debate
Author Affiliations
  • Harry Severance, MD
    Emergency Medicine Resident
    Professor of Emergency Medicine University of Tennessee at Chattanooga
Article Information
Cardiovascular Disorders / Imaging / Professional Issues
Letters to the Editor   |   February 2011
Pandora's Boxes: Questions Unleashed in Airport Scanner Debate
The Journal of the American Osteopathic Association, February 2011, Vol. 111, 87-119. doi:
The Journal of the American Osteopathic Association, February 2011, Vol. 111, 87-119. doi:
To the Editor:  
Like the chaos unleashed by the mythical Pandora's box, the decision of the Transportation Security Administration (TSA) to begin installing advanced imaging technology in airports has led to the public being bombarded by conflicting information about the new “full-body scanners.” The two types of scanning technology being implemented are, primarily, “backscatter” models, which use low levels of ionizing radiation, and, less commonly, “millimeter wave” models, which use radio frequencies from 30 GHz to 300 GHz.1 
The ionizing radiation of backscatter models is potentially carcinogenic to human tissues, and radiation doses are cumulative to tissues that are repeatedly exposed. The radio frequencies of millimeter wave models are not currently considered to be inherently carcinogenic. However, there is much more information available about backscatter systems, which were introduced in 1992, than about the newer millimeter wave systems, which are still not widely used in airports.2 
The debate over these scanning technologies in the news media has centered primarily on traveler privacy issues related to the images produced. The debate has focused only secondarily on the safety of the traveling public exposed to such scans and on the effectiveness of these technologies in detection. We believe that issues of traveler privacy and machine effectiveness are best discussed in other venues. In the present letter, we address concerns related to the safety of scanner radiation. Because the Department of Homeland Security views the body scanner issue to be a sensitive matter of national security, we anticipate that there is some information concerning these technologies that is not available to us. 
From the available literature that we reviewed, we found that radiation dosing from a single backscatter scan is reported as ranging from 0.005 mrem to 0.009 mrem.3,4 By comparison, a passenger on a cross-country flight receives approximately 3 mrem of radiation, and the dose from a single chest radiograph is 10 mrem.3 Backscatter systems have not proven to be harmful, according to several authorities, including the TSA, the US Food and Drug Administration's Center for Devices and Radiological Health, the National Institute of Standards and Technology,5 The Johns Hopkins University Applied Physics Laboratory,6 the Center for Radiological Research at Columbia University,7 the United Kingdom's Health Protection Agency,8 and the American College of Radiology.9 The American College of Radiology has reported that “a traveler would require more than 1,000 backscatter scans in a year to reach the effective dose equal to one standard chest x-ray.”9 
There are 3 backscatter models that are currently manufactured for security screening. American Science and Engineering Inc of Billerica, Massachusetts, produces the SmartCheck10; Rapiscan Systems of the United Kingdom produces the Secure 100011; and Tek84 Engineering Group of San Diego, California, produces the Ait84.12 Of these devices, Rapiscan Systems' Secure 1000 is the most commonly used. In an interview published in the Los Angeles Times in November 2010, Peter Kant, Rapiscan Systems' executive vice president of global government affairs, stated that his company produced 211 of the 385 image scanners then in use at the 68 airports in which such machines had been deployed.13 (According to the TSA Web site, there were 486 image scanners at 78 airports as of January 2011.14) Based on the previously cited report by the National Institute of Standards and Technology,5 it appears that Rapiscan Systems' Secure 1000 has been designed with appropriate safeguards for widespread deployment. 
Despite the published reports that support the safety of backscatter technology,5-9 scientists at the University of California, San Francisco15 have recently raised questions about how radiation exposures were calculated in the reports—raising doubts about the accuracy of the dose-per-scan data.3,4 These scientists have also raised questions regarding whether backscatter scanning would pose an added health risk for individuals who are genetically susceptible to particular cancers.15 These safety issues certainly require further research. Moreover, we have been unable to find any reports of backscatter technologies being subjected to large-scale clinical outcomes studies or other medical testing with either human or animal subjects. 
As we previously noted, questions regarding the effectiveness of scanner technologies are best left to other venues. Nevertheless, all medical decisions involve considerations of risks vs benefits. If a procedure carries a potential risk (such as radiation exposure) and if the procedure's benefits are in question, such facts would be important to know in making medical decisions, including the decision on whether an individual agrees to be scanned. 
In April 2010, The Vancouver Sun published a revealing interview with Rafi Sela, former chief security officer at the Israel Airport Authority and a 30-year veteran in airport security and defense technology who helped design security measures at Ben Gurion International Airport in Tel Aviv.16 Mr Sela was quoted as saying, “I don't know why everybody is running to buy these expensive and useless [full-body scanner] 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.”16 
In regard to millimeter wave technology, Ben Wallace, a member of the British Parliament who worked on millimeter wave scanners for the defense research organization QinetiQ, was quoted in a January 2010 Mail Online article as saying, “The millimeter wave technology is harmless, quick and can be deployed overtly or covertly. But it cannot detect chemicals or light plastics.”17 This limitation could prove to be a serious obstacle in the widespread adoption of millimeter wave technology in airport security. 
Of course, the adoption by terrorists of alternative strategies designed to bypass both backscatter and millimeter wave machines—such as bodypacking—could render both types of scanners irrelevant. Although concerns about the effectiveness of these devices may one day make the issue of safety mute, such questions persist today. 
In summary, it is our sense that—given the current state of scientific knowledge—backscatter radiation scans may be safe, with appropriate built-in safeguards to allow these machines to be deployed for everyday use by appropriately trained personnel. However, large-scale clinical testing of these devices has not yet been performed, and there are legitimate questions concerning the effectiveness of these machines in accomplishing the task for which they were designed. Therefore, using the logic of the risk-benefit ratio, it might be prudent to obtain more information on clinical exposure and more confirmation of device effectiveness before exposing large segments of the population to these full-body scanners. 
Ryan KL, D'Andrea JA, Jauchem JR, Mason PA. Radio frequency radiation of millimeter wave length: potential occupational safety issues relating to surface heating. Health Phys. 2000;78(2):170-181.
Hamilton J. New airport body scans don't detect all weapons. National Public Radio Web site. January 14, 2010. Accessed January 19, 2011.
Layton J. Do “backscatter” X-ray systems pose a risk to frequent fliers? HowStuffWorks Web site. February 27, 2007. Accessed January 19, 2011.
Z Backscatter. American Science and Engineering Inc Web site. Accessed January 19, 2011.
Cerra F. Assessment of the Rapiscan Secure 1000 Body Scanner for Conformance with Radiological Safety Standards. Arlington, VA: Transportation Security Administration. July 21, 2006. Accessed January 19, 2011.
The Johns Hopkins University. Radiation Safety Engineering Assessment Report for the Rapiscan Secure 1000 in Single Pose Configuration. Version 2.0. Laurel, MD: The Johns Hopkins University Applied Physics Laboratory; August 2010. NSTD-09-1085. Accessed January 19, 2011.
Reinberg S. Airport full body scanners pose no health threat: experts. Bloomberg Businessweek. January 8, 2010. Accessed January 19, 2011.
Body scanning at airports. UK Health Protection Agency Web site. Accessed January 19, 2011.
ACR statement on airport full-body scanners and radiation. American College of Radiology Web site. January 2010. Accessed January 19, 2011.
SmartCheck personnel inspection systems. American Science and Engineering Inc Web site. Accessed January 19, 2011.
People screening. Rapiscan Systems Web site. Accessed January 19, 2011.
Body scanner. Tek84 Engineering Group Web site. Accessed January 19, 2011.
Martín H. Maker defends airport full-body image scanners. Los Angeles Times. November22 , 2010.
Advanced imaging technology (AIT). Transportation Security Administration Web site. Accessed January 19, 2011.
Knox R. Scientists question safety of new airport scanners National Public Radio Web site. May 17, 2010. Accessed January 19, 2011.
Schmidt S. Full-body scanners are waste of money, Israeli expert says. The Vancouver Sun. April 23, 2010. body scanners waste money Israeli expert says/2941610/story.html. Accessed January 19, 2011.
Body scanner wouldn't have foiled syringe bomber, says MP who worked on new machines. Mail Online. January 3, 2010. Accessed January 19, 2011.