Controversy rages over the introduction of full body scanners at UK airports for a number of reasons, privacy, cost and whether or not they will actually detect the type of threat involving explosives held in/on the body.

However, many people seem concerned about the health risks to travelers being exposed to radiation which penetrates body tissue to a depth of 2cm.

What makes the scanners controversial is that they use radiation to generate their images. And that has some wondering whether they might be dangerous, particularly for children and pregnant women. Children are more sensitive to radiation than adults. The Stuart report into Mobile Phone health risks recognised this, recommending that children under 16 should not use mobile phones.

Using the same exposure parameters in full body scanners as used on an adult may result in larger doses to the child. It is common knowledge within the medical profession that exposure to x-rays and to emissions from CT scanners pose a health risk in the long and short term, with implications for cancer developing in some patients. The benefits of the need to scan have to be weighted against the risk by the physician ordering the scan.

In Germany as far back as 2008, the government there decided that there was no evidence to show that full body scanners would pick up items hidden in body cavities and chemicals used in explosives. Furthermore, they came to the conclusion that the risk to the privacy and health of the traveler was greater than the benefits for security, not to mention any possible as yet unknown health risks. However, political pressure throughout Europe seems to be ignoring both the privacy and health issues involved, with the EU making decisions over installation in Eurozone airports later this week.

Following Gordon Brown’s announcement last week, BAA, which operates six airports in the UK, said that the full-body scanners will be introduced as soon as is practical. Heathrow is expected to be the first to receive the new technology, which is scheduled for installation within the next few weeks. 

It is understood that the manufacturer of one of the scanner types, Eqo scanner, has already received an order from BAA. It works by bouncing millimetre waves onto a person from a 2m-high panel. The variations in reflection generate a 3D image that the company claims can reveal any kind of hidden material threat.

However, speaking on Radio 4’s Today programme, Ben Wallace, Tory MP and former employee of security group Qinetiq, warned that the millimetre-wave technology would probably not have picked up the low-density explosives used in the foiled Christmas Day attack and that any such technology should be used as part of a layered approach.
Prof Chris Mayhew from Birmingham University believes that the government should take a chemical approach to address these concerns. His team is currently working on a scanner based on soft chemical ionisation that he claims will be able to detect low-density explosives without posing any health risks to passengers.

‘The only way you’re going to detect explosives unambiguously is to use some kind of chemical sensor,’ said Mayhew. ‘We’re are working on a standalone instrument that uses PTR-MS [proton transfer reaction time-of-flight mass spectrometry] to do this… We believe this could a better way to go.’

PTR-MS works by using charged molecules of water (H3O+) that donate their proton to the explosive agent on contact. Once the agent is ionised, its mass increases by one atomic unit and can be highlighted as a threat. According to Mayhew, the system can detect very small traces of explosives that can’t be seen by the human eye. ‘I think Gordon Brown’s announcement was a knee-jerk reaction,’ he said. ‘There are still concerns over the effectiveness and safety of full-body scanners and some sort of discussion should be had before they are put into all airports.’

An alternative system has been produced by US-based group Rapiscan. The system uses X-ray reflections that bounce off a person’s skin to produce 3D full-body images. Based on backscatter technology, the system is able to see an image of the person 0.5mm below the surface of their skin and takes in the region of 7-8 seconds to produce a full-body analysis.

Terry Whittock, vice-president of sales at Rapiscan, said: ‘Millimetre-wave scanners, from our experience and understanding, are in some way lacking when it comes to aviation security. Our backscatter machine was designed purely for the kind of threat that was discovered a week and a half ago… Although we haven’t tested the exact material used, we have full confidence that it will be able to detect it.’

While the company claims that backscatter technology improves the quality of images, the detection rate and health concerns over the frequent use of X-rays on passengers is still under contention by academics throughout Europe.
However, Canadian media has reported that what makes millimeter wave scanners superior to X-rays and other older imaging technologies is the fact that they emit only the tiniest amount of energy -- even lower than your cellphone or your TV's remote control.

At least one expert believes there is nothing to worry about.

"I would have no safety concerns about going through one of these scanners at the airport. Not even slightly," Daniel Mittleman, a physics professor in the Electrical and Computer Engineering faculty at Rice University in Houston, Texas. told Canadian TV News website.

The scanners to be used in Canadian airports use a relatively new form of imaging, something called millimeter wave technology (other scanners, using backscatter technology are being used installed some airports in the U.S.).
L-3 Communications, the makers of the devices to be used in Canada, says the scanners are safe and harmless, noting that they emit only non-ionizing radiation. Ionizing radiation is the most worrying kind of radiation, and is emitted by such things as X-rays and the ultraviolet light of the sun. That form of radiation, with prolonged exposure, can disrupt DNA and cause tissue damage.

Both scanners, unlike conventional X-rays, can strip away layers of clothing, accurately mapping the contours of the body, any prosthetics beneath the skin, as well as clothing and metallic and non-metallic objects.

Developers say the level of radiation used by backscatter scanners is so minimal there are no major health concerns, while the in the USA their Transportation Security Agency says millimeter wave technology involves a fraction of the radio waves used in a cell phone.

Privacy campaigners say the scanners produce "naked" images of passengers which represent an unnecessary violation. They say the process is humiliating, and despite pledges that the images will not be stored or used elsewhere, it could be open to abuse -- particularly with scans of celebrities.

Although the U.S. Transportation Security Agency, which is installing the scanners in many U.S airports, insist the equipment does not capture details of face or produce images of a quality that can be deemed compromising, opponents say the technology is still capable of this and may be utilized in the future.

But there are additional complications involved in the sue of these scanners.

Those wearing pacemakers or mechanical heart valves for example would have  to explain to the airport staff that they cannot go through the scanner because it affects the frequency and can stop such devices working which could kill some people. Similarly those with certain types of surgical implants are unable to go through airport scanners because they would then have to go back to hospital to have them reset.

Perhaps the last word comes from a comment by a reader of a U.S based news website:

"These body scanners don’t detect explosives. They detect anomalies. The expense is not worth it—it’s another heroic measure that is simply replacing common sense and intelligence. Bomb-sniffing dogs are (yes, it’s true) far more effective in actually DETECTING explosives, chemicals, etc. Meanwhile, if you have a colostomy bag or implant, plan on spending a lot of time in the airport being questioned and searched!"

Source: Guardian On Line / CNN / Canadian TV News / The Engineer