Air passengers should be made aware of the health risks of airport body screenings and governments must explain any decision to expose the public to higher levels of cancer-causing radiation, an inter-agency report said.

Pregnant women and children should not be subject to scanning, even though the radiation dose from body scanners is “extremely small,” said the Inter-Agency Committee on Radiation Safety report, which is restricted to the agencies concerned and not meant for public circulation. The group includes the European Commission, International Atomic Energy Agency, Nuclear Energy Agency and the World Health Organization.

A more accurate assessment about the health risks of the screening won’t be possible until governments decide whether all passengers will be systematically scanned or randomly selected, the report said. Governments must justify the additional risk posed to passengers, and should consider “other techniques to achieve the same end without the use of ionizing radiation.”

President Barack Obama has pledged $734 million to deploy airport scanners that use x-rays and other technology to detect explosives, guns and other contraband. The U.S. and European countries including the U.K. have been deploying more scanners at airports after the attempted bombing on Christmas Day of a Detroit-bound Northwest airline flight.

“There is little doubt that the doses from the backscatter x-ray systems being proposed for airport security purposes are very low,” Health Protection Agency doctor Michael Clark said by phone from Didcot, England. “The issue raised by the report is that even though doses from the systems are very low, they feel there is still a need for countries to justify exposures.”

3-D Imaging

A backscatter x-ray is a machine that can render a three- dimensional image of people by scanning them for as long as 8 seconds, the report says. The technology has also raised privacy issues in countries including Germany because it yields images of the naked body.

The Committee cited the IAEA’s 1996 Basic Safety Standards agreement, drafted over three decades, that protects people from radiation. Frequent exposure to low doses of radiation can lead to cancer and birth defects, according to the U.S. Environmental Protection Agency.

Most of the scanners deliver less radiation than a passenger is likely to receive from cosmic rays while airborne, the report said. Scanned passengers may absorb from 0.1 to 5 microsieverts of radiation compared with 5 microsieverts on a flight from Dublin to Paris and 30 microsieverts between Frankfurt and Bangkok, the report said. A sievert is a unit of measure for radiation.

European Union regulators plan to finish a study in April on the effects of scanning technology on travelers’ privacy and health. Amsterdam, Heathrow and Manchester are among European airports that have installed the devices or plan to do so.

The U.S. Transportation Security Administration has said that it ordered 150 scanners from OSI Systems Inc.’s Rapiscan unit and will buy an additional 300 imaging devices this year. The agency currently uses 40 machines, which cost $130,000 to $170,000 each, produced by L-3 Communications Holdings Inc. at 19 airports including San Francisco, Atlanta and Washington D.C.

To contact the reporter on this story: Jonathan Tirone at jtirone@bloomberg.net