Are airport body scanners a radiation risk?

Going through a body scanner
Image caption Backscatter X-ray scanners which emit low doses of ionising radiation are being trialled at some airports.

A consultant refused to go through the full-body scanner at Manchester Airport this week, claiming it was potentially dangerous to his health.

Tony Aguirre, a specialist at Huddersfield Royal Infirmary, said he was not prepared to take the risk of being exposed to X-rays.

"X-rays are known to cause cancer and I think somebody will get cancer from this body scanner whether it's me or someone else," he said.

Mr Aguirre was barred from boarding his flight and took a flight from Liverpool instead, where scanners are not used.

Does he have a point? Is there a medical risk involved in being scanned?

A recent report from the British Institute of Radiology and the Royal College of Radiologists found the dose from an airport scan is 100,000 times lower than the average annual dose of radiation we get from natural background radiation and medical sources.

Dr Peter Riley, consultant radiologist and lead author of the report, said the risk was tiny.

"You can't say there isn't any risk. Some people will be at risk - perhaps two or three out of all the people who fly every year, but it wouldn't put me off flying."

In fact, the radiation dose from flying in a plane at 35,000ft is five microsieverts per hour. That is at least 100 times more than the dose received from a scan in an airport X-ray scanner - 0.02 to 0.03 microsieverts.

Even allowing for two or three scans per examination, this is about the same as people receive from natural background radiation in one hour (0.1 microsieverts).

Gene mutations

We are, of course, exposed to radiation all the time in the form of radon, a natural radioactive gas. It is in the ground, in our homes and in the air we breathe.

But it seems that not all radiation experts are in complete agreement about the risk posed by airport scanners.

Last year Dr David Brenner, head of Columbia University's centre for radiological research, urged researchers to carry out more tests to look at the way the scanners affected specific groups, like children and passengers with gene mutations.

He also proposed missing out the head and neck from the scanning process to avoid increasing the risk of a type of skin cancer.

Dr Tony Nicholson, from the Royal College of Radiologists, says it is all a question of risk and benefit.

"There is a very tiny risk involved but that risk has to be put into context with all the other radiation we are exposed to.

"You wouldn't walk through the scanner if there isn't a reason for doing so, but they are designed to catch terrorists so we don't have a choice."

The airport security scanners now being trialled at Manchester, Gatwick and Heathrow airports are called backscatter X-ray scanners and they emit low doses of ionising radiation.

Image caption The growing use of CT scans has increased our exposure to radiation in the past 10 years

They were first introduced in 2003 to combat what was seen as a growing terrorist threat.

Not every passenger has to go through the body scanners. They go through a metal detector first and then get directed to the body scanner or the exit.

Although Dr Riley's report concludes that the radiation risk from these scanners is minuscule, it does recommend that other scanning techniques should be considered.

In French airports, for example, an instrument called a wave body scanner is used to scan passengers.

Instead of being exposed to ionising radiations, travellers are exposed to an electromagnetic field from which there are "no proven health risks", the report says.

The report also recommends there should be signs warning people that they are about to be scanned and more guidance on how many times individuals should be asked to go back and forth through the scanners.

Yet the greater concern must be the UK public's increased exposure to radiation from medical procedures over the past decade.

The Health Protection Agency estimates that about 46 million medical and dental X-ray examinations were carried out across the UK in 2008, an increase of 10% since 1997.

The agency also reported a 140% increase in CT examinations over the same period.

Professor Richard Wakeford, a radiation epidemiologist, says that in 2009 the average US citizen was getting more radiation from medical processes than from natural background radiation.

The UK is certainly nowhere near that scenario yet, but Prof Wakeford is still concerned.

"The phenomenal increase in radiation from diagnostic medical sources shows no signs of abating at the moment - particularly with more technologically advanced procedures.

"CT scans are just a whole series of X-rays slicing through you."

If Dr Aguirre was trying to make a point by refusing to submit to a body scan at Manchester Airport, his energies might be best directed elsewhere.

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