|Fig. 1: Image of Airport Security at the Denver International Airport in Denver, CO. (Source: Wikimedia Commons)|
After multiple airport bombings, the 9/11 tragedy and incidents like a passenger hiding plastic explosives in his underwear onto a flight, airports worldwide have implemented full body scanners at the TSA a security checkpoints in order to increase airport safety for all travelers.  Many people were immediately concerned that the full body scanners were violating their privacy rights. TSA promised to make the images less graphic to remove their faces as well as not save the images on the computers.  Not only are TSA invading people's privacy regarding their body parts, but all of their objects must go though radiative millimeter wave detection. The long security lines, as seen in Fig. 1, and being forced to take out laptops, liquids, and shoes off might also seem as the worst parts of security but the radiation exposure to the full body has been viewed as the most dangerous part of security. Many travelers most likely have no idea about the radiation exposure and probably do not care because they are only being scanned for a few seconds.  However, the trips through the scanner add up especially if you travel consistently for business purposes so it is important for frequent flyers to know the possible dangers of the full body scanners.
Surprisingly, the scanners use very little radiation. Most TSA scanners use millimeter waves rather than x-rays. Millimeter waves are less than a small portion of energy that is transmitted from a cell phone. Millimeter waves have the capability of heating up one's skin lightly. 
People continue to use devices that contain radiation like cell phones, as well as take X-rays for broken bones, so being exposed to radiation in general is something that it difficult to completely avoid. Unlike direct transmission of radiation throughout parts of the body in a typical X-ray, the millimeter radiation just reflects off the person while the image is being taken. Therefore, the radiation is barely absorbed on the skin, which is the most superficial part of the body.  However, people are still worried about the possible chance of skin cancer, but also other concerns like birth defects and abnormalities that can be greatly increased by the exposure to radiation.
Light absorption of radiation is highly quantum. The wavelength of the light determines the energy quantum, which is then deposited into the electron and the light is absorbed in one impulse.  Only electrons can interact with light in this way. If the quantum for our full body scanner is a 50 kV X-ray, which is essentially a tiny wavelength, then that is equivalent to 50,000 electron volts.
The equation for energy of a photon is: 
where hc = 1.24 × 10-4 eV cm. So for the millimeter wave, it is:
The energy 1 electron volt is the boundary between light that is quantum-mechanically dangerous and light that is quantum-mechanically benign. This is because it takes 1 electron volt to break a chemical bond. This is the range of ultraviolet light.  Therefore, millimeter waves cannot break chemical bonds. As a result, the exposure of radiation from the scanners should not be too concerning for travelers.
Is the safety of our entire world worth the risk of exposure to radiation and end up possibly causing cancer? With TSA pre check and ClearMe, airports have allowed travelers to skip the full body scanners as well as breeze through all of the other annoyances of security. Travelers with TSA pre check just walk through the original airport security devices, the metal detectors, without receiving any of the radiation. Users have to pay around $80 per year but if you are still paranoid about the radiation wave exposure, it may be worth the cost to prevent the potential cancer risks.
© Payton Chang. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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