... 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
via Technology Review: Blogs: arXiv blog: How Terahertz Waves Tear Apart DNA.
Friday, October 30, 2009
True Spooky: Terahertz Waves Tear Apart DNA?
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2 comments:
Dr.Daniel Mittleman of Rice University, who has been involved in thz research for many years responds to the DNA damage claim on my blog. In particular read the last paragraph. I believe the claim terahertz damages DNA is very weak, in light of the facts.
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I have seen that report about the idea of DNA damage by THz radiation. I remain skeptical. The experimental evidence for any kind of THz-induced damage (other than merely by heating) is so far not repeatable. This recent paper is purely theory, assuming a very specific and detailed model for the dynamics of a DNA chain which may not correspond to reality. The way that they include the solvent damping (i.e., the effects of all those water molecules lying around) is not clear. In fact there doesn’t seem to be any accounting for the fact that the water is going to absorb most of the incident field, which might heat up the water but would have no other effect on the solvated DNA. I can’t say that they’re wrong, but being an experimentalist, I am going to need to see experimental results before I buy this mechanism.
The bottom line here is that the world is awash in THz radiation. Every room-temperature object is emitting THz radiation just by virtue of being at room temperature. In fact, the power (per unit bandwidth) in that ambient THz field is larger than the power in most (though not all) artificial THz sources. This makes it hard to imagine how a typical (weak) THz source could give rise to any biological effects. It could be that this mechanism is relevant to real-world situations, but I think the burden of proof remains in the camp of those who say there is a non-thermal effect.
Randys right. Thz is just another term for far infrared and were awash with it. The new scanners have the ability to see through the "fog" but their powers are much lower (1000 times) than what you get from a person and far less than a light bulb emits in the Terahertz region. Its all down to a technicque called lock in detection.
its probabally true this effect but the headline should read "Natrually occuring radiation shown to be essential to DNA replication mechanisms" but that wouldnt grab the headlines.
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