newsheadlines

Airport Body Scan Risks

Part 1: How Airport Terahertz Waves Tear Apart Human DNA

Part 2: Naked Scanners May Increase Cancer Risk

How Airport Terahertz Waves Tear Apart Human DNA

Friday, October 30, 2009

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

'Naked' scanners may increase cancer risk

By Kate Schneider

Article posted May 20 2010, 11:38 PM

US scientists are warning that radiation from controversial full-body airport scanners has been dangerously underestimated and could lead to an increased risk of skin cancer - particularly in children. University of California biochemist David Agard said that unlike other scanners, the radiation from these devices is delivered at low energy beam levels, with most of the dose concentrated in the skin and underlying tissue.

“While the dose would be safe if it were distributed throughout the volume of the entire body, the dose to the skin may be dangerously high,” Dr Agard said. "Ionizing radiation such as the X-rays used in these scanners have the potential to induce chromosome damage, and that can lead to cancer."

Of further concern is that a failure in the device – like a power or software glitch - could cause an intense radiation dose to a single spot on the skin. The warnings come ahead of the planned rollout of the scanners in Australia next year as part of the Federal Government’s crackdown on airport security.David Brenner, the head of Columbia University’s Centre for Radiological Research, says the concentration on the skin – one of the most radiation-sensitive organs of the body – means the radiation dose is actually 20 times higher than the official estimate.

Dr Brenner says the most likely risk from the airport scanners is a type of skin cancer called basal cell carcinoma, which mainly occurs on the head and neck and is usually curable. The researcher was consulted to write guidelines for the security scanners in 2002 but said he would not have signed the report had he known the devices were going to be used so widely.

"There really is no other technology around where we're planning to X-ray such an enormous number of individuals," he said. “While individual risks will be extremely small, the population risk has the potential to be significant.”

The research also shows children are more vulnerable to radiation damage, because they have more cells dividing at any one time than when fully grown and a radiation-induced mutation can lead to cancer in adulthood. Officials from the US Transportation Security Administration and the Food and Drug Administration have tried to allay concerns by saying that it would take thousands of trips through the scanners to equal the dose from one X-ray scan in a hospital.

The recent concerns raised by Dr Brenner at the US Congressional Biomedical Caucus have not been officially addressed. Dr Agard and fellow doctors John Sedat, a molecular biologist and the group's leader; Marc Shuman, a cancer specialist; and Robert Stroud, a biochemist and biophysicist, addressed their concerns to Dr John Holdren, science adviser to US President Barack Obama. The scientists are calling for more research to be undertaken before the use of the scanners becomes commonplace. Dr Brenner believes millimetre-wave scanners that use radio waves instead of X-rays would be better to use because they have no known radiation risks.

Full-body scanners no stranger to controversy. The full-body scanners have already caused controversy, with privacy concerns including whether scanned images may breach child pornography laws in various countries.
They have also been criticised as ineffective, with warnings they would be unlikely to detect many of the explosive devices used by terrorism groups.

In other trouble earlier this month, a US airport security screener was suspended for assaulting a colleague who joked about him having small genitalia after he walked through a scanner. And in March a UK airport security worker said she would sue her bosses after a colleague leered at her “naked” image in a scanner.