New full-body airport security scanners using X-rays generate much lower doses than normal background radiation, a draft report compiled by international agencies says.
Such devices, which cost about 10 times as much as conventional airport scanners, are likely to go into much wider use since a Nigerian man alleged to have had explosives hidden undetected in his underwear boarded a US plane heading to Detroit on December 25.
While normal annual background radiation per person runs to about 3,000 microsieverts — a unit used to measure radiation exposure — the body scan delivers 0.1 to 5 microsieverts, the report, compiled by a group of international bodies including the European Commission and the UN nuclear agency said.
"This (risk) is very small," Renate Czarwinski, head of radiation safety and monitoring at the International Atomic Energy Agency (IAEA) in Vienna, said on Friday.
"Every application of X-ray systems should be justified… you have to weigh the benefits and the probable harm. The benefit, for security, is very high," she said.
There are two types of full-body scanner — one which uses high frequency radio waves and one using X-rays — and only the latter machine would expose passengers to the ionising radiation such as that used in medical X-rays, Czarwinski said.
Although the dosages are small, the inter-agency report said exposures should be carefully monitored.
"In order to appropriately assess the full radiological protection impact of scanner use, the manner in which passengers will be selected should be known," it said.
The scanners, used to see under clothes and identify unusual objects, may have detected the hidden explosives the Nigerian is alleged to have carried on board the jet but their use has been limited mainly because of cost and privacy concerns.