Chapter
5
Researching Non Thermal RF Hazards
Non thermal effects such as calcium ion
efflux, blood/brain barrier, melatonin, alterations in EEG, etc., have been
observed for low-intensity modulated radio frequency fields. The biological
significance remains unclear as to exactly how biological effects resulting
in adverse health effects in people. There have been a number of studies
looking for DNA damage from non thermal rf exposures. Some studies have
shown DNA damage at lower than cell phone handsets!
5.12
The energy quanta of radiation at 0.9 and
1.8 GHz equal 4 and 7 µeV, respectively (1 µeV is a
millionth of an eV). Both these values are extremely small compared with the
energy of around 1 eV needed to break the weakest chemical bonds in genetic
molecules (DNA). This is
why the scientific community in general is stuck on a thermal threshold (SAR),
it being impossible. Therefore, history is simply repeating itself,
popular belief is close to be proven incorrect. Ever more proof is
coming to light a
microwave effect truly exist. It's a scary thought to think that RF
radiation effects bioatomic resonant frequencies damaging DNA directly,
which might effect mechanisms of
Cellular Mitosis
becoming a precursor for cancer.
5.13
Radio frequency radiation could, however,
produce other effects. In general, detectable changes can arise only if the
effect of the electric field within the biological system exposed to RF
fields is not masked by thermal noise.
Thermal noise or random motion, also known as Brownian motion, is due to the
thermal energy that all objects possess at temperatures above absolute zero.
In solids, the atoms vibrate and in gases and liquids they move erratically
to and fro following very frequent collisions with other atoms. So all
components of biological tissue – ions, molecules and cells – are in
constant motion. The thermal energy of each component has an average value
of about kT, where
k, Boltzmann’s constant, is 86 µeV
per degree and T is the
absolute temperature measured in kelvin, K (T
= 273 + t,
where t is the
temperature in degrees centigrade). The value of T
is about 300 K at body temperature so that
kT is 26 meV and, if this is
much larger than the energy of the motion produced by the electric field,
any effect of the field will be completely masked (not detected by any
component of the biological tissue). This comparison with thermal noise
should then provide a good measure of the minimum electric field necessary
to produce detectable biological effects. It should be noted, however, that
if there was a special case in which the biological system were resonantly
sensitive at the frequency of the electric field and rather insensitive to
fields at other frequencies, the comparison would need to be made with the
thermal motion taking place at frequencies close to the resonant frequency.
If the resonance was very sharp, this would be very much smaller than the
total thermal noise, so that quite small electric fields might produce
detectable effects in resonant systems of this type, should they exist in
biological tissue.
5.14
This argument can be used, for example, to
see whether non-thermal effects could arise from the motion of the ions
discussed above. The ions are driven to and fro by an oscillating electric
field, although the extent of the motion is severely reduced by the
viscosity of the surrounding liquid. For a field of 100 V/m the movement is
in fact less than 10–14 m – the
diameter of an atomic nucleus – and the energy associated with this motion
is less than that of the thermal motion of the ion by about a factor of 1015*.
This is so small that it can safely be concluded that this ionic motion
could not result in any non-thermal biological effects. The expression (in
the footnote) shows that the energy increases with the mass of the charged
object, although, for E =
100 V/m, it would still appear to be small at these frequencies compared
with thermal noise for objects such as cells of average size which have
radii around 10 µm (Adair, 1994). Adair notes, however, that it could become
significant for larger cells with correspondingly greater masses.
5.15
Another mechanism involving cells concerns the
attraction between them in the presence of an electric field (Schwan, 1985;
Adair, 1994). The electric field polarises the cell, that is to say
* The velocity of the ion is
µE = µE0 sin(2πνt), where µ, the mobility, is about
10–7 m2/(V/s) for chloride, the ion of highest mobility, and ν, the
frequency, is 0.9 or 1.8 GHz. This leads to a maximum displacement of µE0/2πν
which, for an electric field E0 = 100 V/m, equals 2 x 10–15 m and
10–15 m at frequencies of 0.9 and 1.8 GHz, respectively. So the average
kinetic energy of an ion of mass m in this field is mµ2E0
2/4 or mµ2E2/2, where E is the rms value of the
electric field. For a chloride ion this energy is equal to about 10-17 eV,
or about 10–15 kT.
charges in the cell move
so that one side of it becomes positive with respect to the other. The cell
is then an electric dipole (like a tiny torch battery) and attracts
similarly polarised cells. For typical cells and frequencies below about 100
MHz, the energies involved are calculated to become comparable to thermal
noise in electric fields of E
= 300 V/m. The energies are calculated to become appreciably
less for RF fields, but Adair (1994) suggests that, since these values would
depend on the detailed structure of the biological elements involved, the
possibility of biological effects for fields of this size cannot be
excluded.
5.16
Other possible biological effects are associated
with cell membranes and the movement of currents through the membrane in
either direction. Membranes are known to have strongly nonlinear electric
properties (Montaigne and Pickard, 1984). When a voltage is applied across
the membrane, the current that flows is not always proportional to the
voltage. Part of this no linearity may, in fact, be due to the effect of the
electric field on the proteins in the membrane or nearby, which assist the
flow of the product currents through the membrane. The membrane also acts as
a rectifier. If a voltage is connected across the ends of a wire, the size
of the current that flows depends solely on the magnitude of the voltage: if
the polarity of the voltage is reversed, the current changes direction but
its size is unchanged. However, if the polarity of the voltage applied
across a rectifier is reversed, the current changes direction but now its
size also changes. So, if an oscillating voltage (electric field) is applied
across a rectifier, the total current that flows when the field is in one
direction is not balanced by the current when the field is in the other: an
AC field produces a net DC current and hence a net flow of products through
the membrane. However, the response times of the ion gates are very much
slower than the period of microwave frequencies and, using data obtained
from measurements on membranes (Montaigne and Pickard, 1984), it has been
shown that, for electric fields of 200 V/m, the relative change in the
membrane potential is very small (Adair, 1994; see also Foster, 2000a).
Therefore no biological effects seem likely from this mechanism.
5.17
Many other mechanisms have been proposed by
which significant biological effects from RF fields might arise, but very
few, if any, appear to stand up to critical analysis of the sort presented
above (Foster, 2000b). One, for which there is recent experimental support
(Bohr and Bohr, 2000), is that microwave radiation might cause proteins to
unfold (denature). The experiments were carried out in a modified microwave
oven at 2.45 GHz, a frequency comparable to the likely torsional modes of
the protein. The intensity was not specified, but seems likely to have been
above ICNIRP guidelines. The experiments were very recent and have not yet
been replicated. Another mechanism that has continued to create interest is
based on the assumption that biological systems might interact resonantly
with microwave fields. This possibility was initially discussed by Fröhlich
(1968, 1980) and his work has had a considerable impact (see, for example,
Penrose, 1994; Pokorny and Wu, 1998).
5.18
Fröhlich was interested in the mechanism through
which the chemical energy taken into the body (food) was channeled into
highly ordered processes, such as cell building, rather than into heat. His
model involves the mechanical vibrations of large molecules or components of
biological tissue and the way they interact with each other, which he argued
could lead to the existence of a band of frequencies into which energy could
be absorbed, plus a particular "coherent state" of vibration. He also
considered whether quite small oscillating electric fields might put energy
into this state and hence trigger significant biological changes; that it is
to say, whether a living biological system might behave in a manner roughly
similar to a radio receiver. A radio can detect and amplify an extremely
small signal against a background of very much larger signals. It does this
when the operator tunes a resonant circuit to the frequency of the carrier
wave. The resonant circuit essentially responds only to electromagnetic
waves of frequencies (including those generated by thermal noise – see
paragraph 5.13) within a narrow bandwidth. The power needed to amplify these
waves comes from the power supply of the radio. A number of solid state
systems behave in similar ways, such as narrow-band optical amplifiers,
which are the basis of lasers.
5.19
The Fröhlich model has stimulated a range
of other work. However, so far there appears to be no direct experimental
evidence, and no convincing indirect experimental evidence, for the
existence of Fröhlich’s coherent state in biological systems. Moreover, the
present theoretical treatments of the model do not provide estimates for the
magnitude of the electric fields needed to produce biological effects.
Fröhlich suggested that the findings of a number of experiments carried out
at frequencies of 40 GHz and above on systems such as
E coli bacteria and yeast cultures
(see Fröhlich, 1980) might be (indirect) evidence for his model, since these
frequencies lie in the range where cell membranes are expected to resonate
mechanically. Four recent attempts to reproduce some of this work have
failed to do so (E coli:
Athey and Krop, 1980; Santo, 1983; yeast cultures: Furia
et al, 1986; Gos
et al, 1997), although there have
been further reports from Balyaev and colleagues that appear to endorse the
earlier research (E coli:
Balyaev, 1992). A recent appraisal of all this work (Foster, 2000a) notes
that the experiments present formidable technical
problems and that, while their results may be statistically significant, it
may not always be possible to eliminate systematic errors. In view of this
appraisal, it is not possible to conclude that this work provides support
for the existence of resonant absorption by biological tissue.
5.20
Hyland (1998) has suggested that the
mechanism proposed in Fröhlich’s model might lead to biological effects from
electromagnetic fields at the appreciably lower frequencies of mobile
phones. This would require the presence of components in the biological
tissue with sharp resonant vibrational modes in this frequency range. The
frequencies are lower than those expected for most components, although
theoretical work (Kohli et al,
1981; Van Zandt, 1986; Porkny and Wu, 1998) suggests that DNA polymers and
elements of fibre structures (cytoskeletons), such as microtubules and actin
filaments, could have modes in this range. However, since these components
are surrounded by relatively viscous fluids, their mechanical vibrations
would normally be expected to be very highly damped. Thus, resonance's they
might have out of solution would be almost completely smeared out when they
are immersed*. Certainly no
evidence of resonant absorption†
was found from DNA in solution (Gabriel
et al, 1987), although this might
not rule out the possibility that it occurs under the conditions in which
DNA exists in tissue.
5.21
CONCLUSION This work on DNA should be repeated
under conditions more closely matched to those in tissue and similar
measurements should be made on microtubules and actin filaments.
5.22
Another hypothesis is that the interaction
with biological tissue depends on the coherence of the electromagnetic
fields (see paragraph 4.36). Experimental evidence in support of this idea
has been given by Litovitz et al
(1993, 1997a,b) but not yet independently replicated.
5.23
In summarising the physical basis for
non-thermal effects, it is convenient to consider separately the situations
near to the antenna of a mobile phone and near to a base station.
* Water provides an example of
this effect. Water vapour shows strong resonant absorption but the
resonances are smeared out in liquid water and absorption occurs over a wide
range of frequencies. Scott (1984) and Van Zandt (1986) have, however,
proposed models to explain why this might not happen for DNA in solution.
† Earlier work on DNA in
solution appeared to show strong resonant absorption in this range (Edwards
et al, 1984). It was shown, however, that this could have been the
result of an experimental artefact (Foster et al, 1987) and, as
noted, the work of Gabriel et al (1987), carried out on samples
chosen to be as close as possible to those of Edwards et al, failed
to see any such effects. In this work, three different techniques were used
in two different laboratories and the results were essentially identical. It
can be concluded, therefore, that DNA in solution does not have resonant
modes that couple to microwaves in this range.
Mobile phones
5.24
In Chapter 4 it was noted that the
maximum size of the electric
fields produced in the head by the antenna of a mobile phone is around 100
V/m, although the fields inside the brain would be appreciably less. For
fields of this size the mechanisms most likely to produce non-thermal
biological effects would be through the movement of large cells (paragraph
5.14) or through the attraction between neighbouring cells (paragraph 5.15).
At this stage, although there is no experimental evidence to support these
mechanisms, the possibility that both of these could produce effects cannot
be excluded (Adair, 1994).
