Quantum Thoughts

Terahertz Waves Affect DNA

Posted on: October 31, 2009

The way terahertz waves are absorbed and emitted is often used to determine the chemical composition of a material. the have a small skin depth so they don’t travel far inside the body, but lately they are often used breast tumours spotting as well as non invasive inspections.

Moreover, 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?

Technology review says that

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.

Full paper from Cornell here  arxiv.org/abs/0910.5294.

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1 Response to "Terahertz Waves Affect DNA"

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.

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