Airport Body Scanning Raises Radiation Exposure, Committee Says

9 07 2010

Airport Body Scanning Raises Radiation Exposure, Committee Sa

By Jonathan Tirone – February 5, 2010

Feb. 5 (Bloomberg) — 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

www.bloomberg.com

See Also: Radiation Safety Group Says Naked Body Scanners Increase Risk Of Cancer





How Terahertz Waves Tear Apart DNA

1 11 2009

How Terahertz Waves Tear Apart DNA

A new model of the way the THz waves interact with DNA explains how the damage is done and why evidence has been so hard to gather

Great things are expected of terahertz waves, the radiation that fills the slot in the electromagnetic spectrum between microwaves and the infrared. Terahertz waves pass through non-conducting materials such as clothes , paper, wood and brick and so cameras sensitive to them can peer inside envelopes, into living rooms and “frisk” people at distance.

The way terahertz waves are absorbed and emitted can also be used to determine the chemical composition of a material. And even though they don’t travel far inside the body, there is great hope that the waves can be used to spot tumours near the surface of the skin.

With all that potential, it’s no wonder that research on terahertz waves has exploded in the last ten years or so.

But what of the health effects of terahertz waves? At first glance, it’s easy to dismiss any notion that they can be damaging. Terahertz photons are not energetic enough to break chemical bonds or ionise atoms or molecules, the chief reasons why higher energy photons such as x-rays and UV rays are so bad for us. But could there be another mechanism at work?

The evidence that terahertz radiation damages biological systems is mixed. “Some studies reported significant genetic damage while others, although similar, showed none,” say Boian Alexandrov at the Center for Nonlinear Studies at Los Alamos National Laboratory in New Mexico and a few buddies. Now these guys think they know why.

Alexandrov and co have created a model to investigate how THz fields interact with double-stranded DNA and what they’ve found is remarkable. They say that although the forces generated are tiny, resonant effects allow THz waves to unzip double-stranded DNA, creating bubbles in the double strand that could significantly interfere with processes such as gene expression and DNA replication. That’s a jaw dropping conclusion.

And it also explains why the evidence has been so hard to garner. Ordinary resonant effects are not powerful enough to do do this kind of damage but nonlinear resonances can. These nonlinear instabilities are much less likely to form which explains why the character of THz genotoxic
effects are probabilistic rather than deterministic, say the team.

This should set the cat among the pigeons. Of course, terahertz waves are a natural part of environment, just like visible and infrared light. But a new generation of cameras are set to appear that not only record terahertz waves but also bombard us with them. And if our exposure is set to increase, the question that urgently needs answering is what level of terahertz exposure is safe.

Ref: arxiv.org/abs/0910.5294: DNA Breathing Dynamics in the Presence of a Terahertz Field

http://www.technologyreview.com/blog/arxiv/24331/