Scanners 'are threat to privacy not health'

Full body scanners being introduced at airports to tighten security pose little risk to passengers but raise concerns about privacy, according to a radiology expert.

The scanners are being introduced at Heathrow and Manchester airports from this month, and will be rolled out across the country following the attempted bombing of a US airliner on Christmas Day.

But concerns have been raised that they could expose individuals to dangerous levels of radiation and infringe privacy because of the detailed images produced, leading to the coining of the term "virtual strip search". Writing in the British Medical Journal, Professor Mahadevappa Mahesh, chief physicist and associate professor of radiology at John Hopkins University, says worries about safety are misplaced.

The scanners use either radio waves or low intensity X-rays called "backscatter systems" to generate an image. Radio waves pose no threat and the radiation dose from backscatter systems is so low – less than 0.1 microsievert per scan – that a traveller would have to pass through the scanner 1,000 to 2,000 times to receive the same dose as a chest x-ray, and 2,500 to 5,000 times in a year to exceed the annual safe US limit.

Current calculations show that back scatter systems are safe even for infants and children, pregnant women, and people with genetic sensitivity to radiation. But quality checks of scanners and routine maintenance are essential, Professor Mahesh says. Operators also need radiation safety training to avoid any inadvertent exposure.

Privacy issues were highlighted by reports that the naked image of the Bollywood star Shahrukh Khan was printed and circulated by scanner operators at Heathrow airport. The reports were denied by the British Airports Authority.

Professor Mahesh says concerns about privacy can be mitigated by ensuring the system cannot store images, and by having the image viewing stations at remote locations rather than beside the scanners.