Airport body scanners have a potentially greater risk of cancer than previously thought, a scientist has warned.
The devices emit radiation up to 20 times more powerful than it was believed.
Dr David Brenner, head of the centre for radiological research at Columbia University in New York, said that the concentration of the radiation on skin could pose a greater risk of cancer than expected.
The risk is due to inability of a body to repair X-ray damage to its cells.
"If all 800 million people who use airports every year were screened with X-rays then the very small individual risk multiplied by the large number of screened people might imply a potential public health or societal risk," the Telegraph quoted Brenner as saying.
"The population risk has the potential to be significant," he added.
However, Civil Aviation Authority spokesman insisted that all the health regulations by the Department for Transport and Health Protection Agency have been considered for the device's use.
"Under current regulations, up to 5,000 scans per person per year can be conducted safely," he added.