Airport Body Scanners: What's In A Name?

Full-body scanners, also known as advanced imaging technology (AIT), are used at airports to detect objects on or inside a person's body for security screening purposes, without physically removing clothes or making physical contact. They use one or more antennas that move around a person's body to construct a 2D or 3D image. The two main types of full-body scanners in use are backscatter X-ray machines and millimeter wave scanners.

Millimeter wave scanners

One of the key advantages of millimeter wave scanners is their ability to respect privacy while still providing detailed imaging. While early versions of the technology displayed detailed images of the surface of the skin, current scanners utilise Automatic Target Recognition (ATR) software to generate a generic body outline while highlighting potential threat areas. This addresses concerns about "virtual strip searches" and protects the privacy of individuals being scanned.

In terms of safety, millimeter wave scanners emit non-ionizing radiation, which has significantly lower energy levels than ionizing radiation. This means it does not have enough energy to cause cancers or other biological damage beyond localized heating and associated chemical changes. However, the potential health effects of millimeter wave radiation are still being studied, and some individuals continue to express concerns about the technology.

Overall, millimeter wave scanners have become an important tool for airport security, offering efficient and effective threat detection while also respecting the privacy and safety of travellers.

Backscatter X-ray scanners

Backscatter X-ray technology is based on the Compton scattering effect, a form of ionizing radiation. Unlike traditional X-ray machines, backscatter X-rays detect radiation that reflects off objects to form an image. This radiation bounces off weapons, explosives, or other threats concealed under clothing or against the skin, allowing for their detection. The backscatter pattern is dependent on the material property and is particularly effective for imaging organic material.

The scanners produce low-energy X-rays, which have a wavelength of approximately 0.0000000001 meters or 0.0000001 millimeters. These X-rays penetrate clothing and bounce off the skin, returning to detectors on the machine's surface. The resulting images can be photo-like and reveal both the presence and position of organic components, making them easy to interpret.

Advanced Imaging Technology (AIT)

AIT scanners are walk-through systems that allow for faster and more efficient security screening. They can detect both metallic and non-metallic objects, addressing security concerns that arose after airliner bombing attempts in the 2000s. The technology can identify threats such as weapons, explosives, and other dangerous items, enhancing the safety of air travel.

Millimetre wave scanners emit low-energy, high-frequency radio waves that bounce off the body and return to the machine, creating an image that reveals hidden objects. This type of radiation is considered safer than ionizing radiation, as it has insufficient energy to remove electrons from atoms. Instead, it causes atoms in molecules to vibrate or move around, similar to the way wireless data transmitters operate.

The use of AIT scanners has sparked debates about health risks and privacy. While some authorities assert that there is no evidence of health hazards, others argue that long-term studies on the effects of millimetre wave scanners are lacking. Additionally, public outrage over nude images created by earlier body scanners led to a lawsuit in 2010, prompting the development of privacy-preserving AIT technology.

Today, AIT scanners are widely adopted in North American and European airports, contributing to enhanced security and a more seamless travel experience. The technology continues to evolve, aiming to strike a balance between safety and privacy for travellers.

Privacy concerns

Airport body scanners, also known as full-body scanners, have been the subject of much debate and discussion when it comes to privacy concerns. These scanners, which started supplementing metal detectors at airports in 2007, have faced criticism and raised questions about the balance between security and privacy.

One of the main privacy concerns surrounding full-body scanners is the level of detail they can reveal about an individual's body. While the scanners are designed to detect potential threats, they can also show intimate details, such as prosthetics, breast prostheses, prosthetic testicles, colostomy bags, and catheters. This has led to worries about potential embarrassment and harassment, especially for the transgender community. Some people argue that using a full-body scanner without probable cause is akin to a strip search and violates basic human rights.

In response to these concerns, authorities have implemented measures to protect passengers' privacy. For example, the Transportation Security Administration (TSA) in the United States has stated that their scanners do not store images of passengers. Additionally, some scanners now use generic outlines of a human form, often referred to as a "gingerbread man" or "paper doll," to indicate the location of potential threats without revealing detailed images of an individual's body.

Another concern relates to the radiation emitted by the scanners. While most scanners use non-ionizing radiation, which is considered safe and similar to the radiation from a cell phone, there were worries about older scanners that used ionizing radiation. Between 2009 and 2013, the TSA employed Rapiscan backscatter machines, which produced low-energy X-rays, raising concerns about potential health risks and increased radiation exposure. As a result of these concerns, pilot and flight-crew unions successfully lobbied to change the requirements, and the TSA transitioned to using Millimeter Wave AIT scanners, which do not use ionizing radiation.

While the newer scanners have addressed some privacy and health concerns, the debate continues as the technology evolves. Some people still worry about the potential long-term effects of regular exposure to even low levels of non-ionizing radiation. Additionally, there are concerns about the accuracy of the scanners, as the ones proposed for use in Australia have shown a high rate of error. This has led to discussions about the balance between security and privacy, with ongoing efforts to enhance security while also respecting and protecting the privacy of individuals.

Health concerns

Airport body scanners have been the subject of some health concerns and debates. The primary concern relates to the safety of backscatter X-ray scanners, which, unlike millimetre wave scanners, use ionizing radiation. Ionizing radiation has sufficient energy to knock electrons out of atoms, a process known as ionization. While the doses of ionizing radiation emitted by backscatter X-ray scans are extremely low, there is a potential risk of biological damage at low doses, with cells rapidly repairing this damage. At moderate doses, cells can be permanently altered, potentially becoming cancerous or leading to abnormalities such as birth defects.

Several authorities, including the National Council on Radiation Protection and Measurements, The Health Physics Society, and the American College of Radiology, have stated that they are unaware of any evidence that full-body scans are unsafe. However, other radiation experts, including the International Atomic Energy Agency and Nuclear Energy Agency, recommend against using ionizing radiation on specific populations like pregnant women and children. Opponents of backscatter X-ray technology argue that there have been no long-term studies examining the health effects of these scanners.

In response to these concerns, the Transportation Security Administration (TSA) in the United States has transitioned exclusively to millimetre wave Advanced Imaging Technology (AIT) scanners, which do not employ ionizing radiation. Millimetre wave scanners use non-ionizing radiofrequency waves, emitting far less energy than a cell phone. These scanners are considered safe for individuals with pacemakers and those with surgical metal implants or breast implants.

Additionally, the TSA has implemented measures to protect the privacy of individuals undergoing scanning. The scanners create a generic human-like representative figure on the screen, indicating the location of potential threats without exposing the details of the person's body. The TSA has also made it impossible for scanners in airports to save or export images, addressing concerns about the improper storage and dissemination of scanned images.

While millimetre wave scanners are widely used in the United States and Canada, some airports have also adopted supplementary technologies, such as infra-red thermal conductivity scanners, to identify individuals with elevated temperatures, particularly during the COVID-19 pandemic.

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