Body Scanners: Do They Emit Radiation?

Airport body scanners have been a topic of concern for travellers, with many worrying about their radiation exposure. While some scanners emit low levels of backscatter X-ray ionizing radiation, others use millimeter-wave non-ionizing radiation. The former can cause biological damage, while the latter is limited to moving atoms in a molecule or causing them to vibrate. The US Food and Drug Administration (FDA) has the authority to set standards for machines that produce radiation, and the FDA requires that all machines be correctly calibrated and maintained. The radiation exposure from airport security scans is considered relatively small, and the risk of health effects is very low. However, there are still concerns about the impact of radiation on vulnerable groups such as pregnant women and children, and the potential for defects or software errors in the machines to cause an intense dose of radiation.

Millimeter wave scanners emit non-ionizing radiation

Millimeter wave scanners use a special type of microwave, known as millimeter wave radiation, to detect objects hidden underneath a person's clothing. Millimeter waves are ideal for scanning as they are large enough to pass through most materials, such as clothing. The waves are directed at the subject and the reflected energy is then interpreted to create a 3D image. This image is sent to a remote monitor for analysis.

The amount of energy emitted by millimeter wave scanners is extremely low. In fact, it is thousands of times less than the energy emitted by a cell phone. The waves are also much larger than X-rays, which are a form of ionizing radiation. As such, millimeter wave scanners are considered very safe and are widely used in airports across the world.

In the United States, the Food and Drug Administration (FDA) has federal authority to set standards for machines that produce radiation, including millimeter-wave scanners. The FDA requires that all machines are correctly calibrated and maintained to ensure safety.

Backscatter x-ray scanners emit ionizing radiation

Backscatter X-ray scanners are an advanced imaging technology that has been used to perform full-body scans of airline passengers to detect hidden contraband, such as weapons, tools, liquids, narcotics, and currency. They are one of two types of full-body scanners used by the Transportation Security Administration (TSA) in the United States, the other being millimeter wave scanners.

Backscatter X-ray scanners work by detecting the radiation that reflects off the target being scanned, as opposed to traditional X-ray machines, which detect the variation in X-ray intensity transmitted through the target. This reflected radiation is then used to form an image. This technology is particularly useful for imaging organic material and can operate even if only one side of the target is available for examination.

The potential harm caused by ionizing radiation depends on the dose. At low doses, radiation causes biological damage, but cells can repair this damage rapidly. At moderate doses, cells can be permanently changed, becoming cancerous or leading to other abnormalities. At even higher doses, cells cannot be replaced quickly enough, resulting in serious health problems.

While the doses of radiation from backscatter X-ray scanners are very low, there is still a potential risk, especially for frequent flyers. The risk is further compounded by the additional radiation exposure from air travel, which is higher at the altitudes of commercial flights due to greater proximity to the sun.

To address these concerns, the TSA has implemented several measures to ensure the safety of passengers. The TSA's backscatter X-ray scanners meet strict federal standards set by the U.S. Food and Drug Administration (FDA) for machines that produce radiation. The scanners are regularly tested and maintained to ensure they comply with safety standards. Additionally, the TSA has also explored alternative technologies, such as millimeter wave scanners, which do not use ionizing radiation.

Privacy concerns

Privacy has been a major concern for passengers and various organizations since the introduction of full-body scanners at airports. The scanners, which were introduced to enhance security and detect contraband, have been criticized for being too revealing and invasive.

The Transportation Security Administration (TSA) in the United States initially defended the use of full-body scanners, stating that the images could not be stored and were only seen by a security worker who did not interact with the passenger. However, reports emerged that tens of thousands of scanner images were improperly saved and disseminated, raising doubts about the TSA's assurances. There were also concerns that employees could alter the settings of the machines to remove privacy safeguards.

The American Civil Liberties Union (ACLU) likened the scans to virtual strip searches, and the Electronic Privacy and Information Center (EPIC) filed a lawsuit against the Department of Homeland Security, alleging that the scans violated the Fourth Amendment, the Privacy Act, the Religious Freedom Restoration Act, and the Video Voyeurism Prevention Act. Religious groups also expressed their opposition to the scans.

Due to the privacy concerns, the TSA removed the backscatter scanners, which produced detailed body images using low-dose X-rays, from all US airports by June 2013. The manufacturer of these scanners, Rapiscan, was unable to fix the privacy issues, despite being given a deadline by Congress. The remaining scanners in use produce a generic outline instead of a naked image, addressing privacy concerns while still allowing for effective security screening.

To further protect travellers' privacy, newer technologies such as Millimeter Wave (MMW) body scanners display alerts on a generic mannequin instead of showing the actual scan image. This helps operators locate suspicious items without revealing personal details. MMW imaging is also non-ionizing, making it safer and more suitable for personnel surveillance.

Health concerns

There are two types of full-body scanners used at airport security: backscatter x-ray scanners and millimeter wave scanners. Backscatter x-ray scanners use ionizing radiation, while millimeter wave scanners use non-ionizing radiation.

Backscatter X-Ray Scanners

Backscatter x-ray scanners use low-dose x-rays, similar to those used in medical imaging, to generate a detailed image of the body. The potential health risk of these scanners lies in their use of ionizing radiation, which can cause biological damage depending on the dose. At low doses, cells can repair the damage caused by radiation rapidly. However, at moderate doses, cells can be permanently changed, leading to cancer or other abnormalities. While the doses of ionizing radiation emitted by backscatter x-ray scanners are very low, the cancer risk merits consideration, especially for frequent flyers and vulnerable subgroups such as children.

Millimeter Wave Scanners

Millimeter wave scanners use non-ionizing electromagnetic radiation, similar to that used by wireless data transmitters. The health risks posed by these machines are still being studied, and the evidence is mixed. While they do not generate ionizing radiation, there may still be potential biological effects, as the radiation can interact with the entire body, individual organs, or large molecules. However, the risk is generally considered acceptable due to the low intensity and penetration depth of the millimeter waves during the short scan duration.

Overall Health Risk Assessment

The radiation exposure from airport security scanners is extremely small, and the cancer risk has been described as "truly trivial." The risk of health effects from backscatter x-ray scanners and millimeter wave scanners is considered very low. However, there is ongoing debate and a lack of long-term studies on the potential health impacts of these technologies, particularly for frequent flyers and vulnerable subgroups.

Safety measures

The use of body scanners in airports has raised concerns about the safety of such devices, particularly regarding radiation exposure and privacy. Here are some of the key safety measures and considerations related to airport body scanners:

Radiation Exposure:

• Ionizing Radiation: Some airport body scanners use ionizing radiation, which has enough energy to remove electrons from atoms. This type of radiation is used in medical X-rays and can have potential health effects, especially at high doses. However, the dose received from airport body scanners is extremely low and is comparable to the radiation exposure during a short flight.
• Non-Ionizing Radiation: Millimeter-wave scanners, commonly used in the United States, fall under this category. They use non-ionizing radiation, similar to radio waves, which does not have enough energy to remove electrons from atoms. These scanners emit far less energy than a cell phone and are considered safe for passengers.
• Regulations and Standards: The U.S. Food and Drug Administration (FDA) sets standards for machines that produce radiation, including airport body scanners, to ensure they operate within safe limits. The FDA requires proper calibration and maintenance of the scanners to adhere to these standards.
• Alternative Screening Methods: For individuals who are concerned about radiation exposure or are more vulnerable to its effects, such as pregnant women, alternative screening methods are available. These include pat-down searches or metal detectors, which use non-ionizing radiation and do not expose individuals to additional radiation.

Privacy:

• Image Privacy: Body scanners can generate detailed images of passengers, raising privacy concerns. Measures have been implemented to address this, such as blurring faces, using generic body outlines, and separating security personnel from passengers to protect their privacy. Additionally, the Transportation Security Administration (TSA) has stated that the scanners cannot store or export images and has taken steps to prevent this from occurring.
• Opt-Out Options: Passengers who are uncomfortable with body scanners have the option to opt-out. They can request alternative screening methods, such as a pat-down search, which does not involve radiation exposure.
• Independent Testing and Assessment: There have been calls for additional independent testing and assessment of body scanners to verify their safety and address concerns about potential malfunctions or software errors that could impact privacy and radiation exposure.

Frequently asked questions