Airport Body Scanners: How They Work And What They See

Airport full-body scanners are security devices that detect objects on or inside a person's body without physically removing their clothes or making physical contact. They use Advanced Imaging Technology (AIT) to create a full-body scan, with two types of scanners in use: millimeter wave scanners and backscatter X-ray scanners. Millimeter wave scanners use non-ionizing electromagnetic radiation to detect metallic and non-metallic objects, while backscatter X-ray scanners detect radiation reflecting from the body. These scanners are designed to enhance security and improve the efficiency of screening processes at airports worldwide.

Millimeter wave scanners

Millimeter-wave scanners are one of three distinct technologies used in full-body scanners at airports. They use non-ionizing electromagnetic radiation in the extremely high-frequency radio band, which is a lower frequency than visible light. This type of radiation is harmless and is similar to that used by wireless data transmitters, including Wi-Fi devices like your phone or tablet.

Millimeter-wave scanners can detect a wide range of metallic and non-metallic threats, including weapons, explosives, and other objects, concealed under layers of clothing. They can also detect items hidden in body cavities. The technology works by sending millimeter waves toward a passenger's insides. These waves pass through clothing and reflect off the passenger's skin and any concealed objects. The reflected waves then bounce back an image, which is interpreted by the machine.

The scanners are designed to protect passenger privacy. With older machines, officers located away from the checkpoint could see under clothing, but newer machines use automated target recognition software to produce a generic outline of a person, highlighting areas that may require additional screening. Passengers are required to remove items from their pockets, as well as accessories like belts and jewelry, to ensure these are not flagged as suspicious.

Millimeter-wave scanners have been implemented in airports across the world, including in the United States, Canada, the Netherlands, Italy, Australia, and the United Kingdom. They are also used in mass-transit systems in some countries.

Backscatter X-ray scanners

The safety concerns regarding backscatter X-ray scanners are centred around the use of ionizing radiation. X-rays are a form of ionizing radiation, which can remove electrons from atoms and alter the structure of biological molecules. Manufacturers claim that the radiation dose from a single scan is extremely low, around 0.02 to 0.03 microsieverts, similar to the radiation one would be exposed to in an hour from natural sources. The National Council on Radiation Protection and Measurements, The Health Physics Society, and the American College of Radiology have stated that there is no specific evidence that full-body scans are unsafe. However, some radiation safety authorities disagree, stating that there is no safe threshold dose of radiation below which there is no increased risk of cancer.

Privacy concerns

Full-body scanners at airports have raised several privacy concerns. The scanners produce detailed, three-dimensional images of individuals, which some security experts have likened to a physically invasive strip search. In some countries, these scanners create images of virtual strip searches on persons under the age of 18, which may violate child pornography laws. For instance, in the UK, these scanners may be contravening the Protection of Children Act of 1978 by creating pseudo-images of nude children.

In the past, the TSA used Rapiscan backscatter machines, which produced a stream of low-energy X-rays, causing concerns about safety, privacy, and effectiveness. These machines were also found to be cumbersome and expensive. The older machines, which are no longer used, allowed officers located away from passengers to see under their clothing. This led to a lawsuit in 2010 to stop body scanning in Australia.

Additionally, there are concerns about the radiation risks posed by the scanners, with TSA employees identifying cancer clusters allegedly linked to radiation exposure while operating the scanners. A Johns Hopkins University study revealed that radiation zones around the scanners could exceed the "General Public Dose Limit". Despite these concerns, the machines are considered safe by some, with the energy emitted by millimeter-wave technology being reportedly 10,000 times less than what is permitted by standard cellphones.

Health concerns

In 2010, the German Federal Office for Radiation Protection (BfS) conducted measurements on two active full-body scanners using millimetre wave technology to estimate the expected radiation exposure to screened individuals. The measurements showed that both systems give rise to low exposures to high-frequency electromagnetic fields, and health effects are not expected. The US Centers for Disease Control and Prevention (CDC) notes that we are exposed to this type of non-ionising radiation every day at low levels.

Despite these assurances, concerns have been raised about the potential health risks of full-body scanners, particularly for vulnerable groups such as children, pregnant women, and the elderly. Experts have questioned the safety of the scanners and noted that radiation exposure from devices like full-body scanners increases individuals' cancer risk. A study by Johns Hopkins University found that radiation zones around body scanners could exceed the "General Public Dose Limit". Additionally, the National Institute of Standards and Technology (NIST) has warned airport screeners to avoid standing next to full-body scanners, and the TSA has admitted to bungling airport body-scanner radiation tests.

In response to these concerns, the TSA asserts that the machines have been adequately tested by various organisations and that the risk of harm is trivial. However, some experts, including professors at the University of California, San Francisco, have called for more independent testing to be conducted. They argue that it is premature to expose the entire population to the scanners without further due diligence and independent testing.

Effectiveness

The effectiveness of airport full-body scanners has been a topic of debate, with various stakeholders offering differing opinions. On one hand, the Transportation Security Administration (TSA) maintains that full-body scanners are "highly effective" at detecting explosives and weapons hidden under clothing, including non-metallic items such as plastic explosives. This capability addresses a critical security gap in traditional metal detectors. The TSA considers these scanners the "most effective and least intrusive" method of searching travellers for hidden weapons.

However, critics argue that the scanners are not entirely effective and pose health and privacy risks. Some studies and classified research suggest that the machines might miss carefully concealed plastic explosives, indicating potential security vulnerabilities. Additionally, the scanners have been associated with concerns about radiation exposure, particularly the now-discontinued backscatter X-ray machines, which were found to expose travellers to a non-negligible amount of radiation, potentially increasing cancer risks.

To address privacy concerns, the TSA has implemented privacy software that displays a generic human body outline instead of a detailed image. This software maintains detection capabilities while reducing the invasiveness of the scanning process.

While the effectiveness of full-body scanners in enhancing security is generally accepted, the extent of their contribution is questioned. The TSA has faced criticism for its failure rate in detecting weapons during investigations, and some suggest that alternative methods, such as passenger profiling or the use of bomb-sniffing dogs, could be more effective.

The deployment of full-body scanners also involves significant financial considerations. The TSA has already invested over $100 million in the technology and plans to spend hundreds of millions of dollars more to outfit nearly every airport security lane. This substantial investment underscores the perceived importance of full-body scanners in enhancing airport security.

In conclusion, while full-body scanners have been touted as an effective tool in airport security, particularly for detecting non-metallic threats, concerns about their effectiveness, health impact, privacy, and cost persist.

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