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 tumors 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 ionize
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
The evidence that terahertz radiation damages biological systems is
"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
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.