Biological Effects - RF/Microwave Interaction with Biological Tissues - page 111

nonrandom variations of a survival in control groups, determining two-
directional embryo response to millimeter-wave exposure [76].
A theoretical model has been proposed for evaluation of the dielectric
properties of the cell nucleus between 0.3 and 3 GHz as a function of its nucleic
acids concentration. It is based on literature data on dielectric properties of
DNA solutions and nucleoplasm. In skeletal muscle cells, the SAR ratio
between nucleoplasm and cytoplasm is found to be larger than 1 for a nucleic
acids concentration above 30 mg mL -1 . A nearly linear relationship has been
found between this concentration and this nucleo-cytoplasmic SAR ratio.
Considering the nanoscale of the layer of condensed counterions and bound
water molecules at the nucleic acid-solution interface, the power absorption
per unit volume has been evaluated at this precise location. It has been found
to be between one and two orders of magnitude above that in the surround-
ing solution and in muscle tissue as a whole. Under realistic microwave expo-
sure conditions, however, these SAR inhomogeneities do not generate any
significant thermal gradient at the scale considered here. Nevertheless, the
question arises of a possible biological relevance of nonnegligible and prefer-
ential heat production at the location of the cell nucleus and of the nucleic
acid molecules [77].

3.5 LOW-LEVEL EXPOSURE AND ELF COMPONENTS

The effects of low-level RF and microwave exposure of brain tissue and animal
behavior, more specifically the effects on the BBB (protein permeability and
saccharide permeability), on calcium ion exchange in brain tissue and on
animal behavior were extensively reviewed in 1986 [78]. The study offers a
comprehensive critical discussion of the relevance of the experimental data
derived from a number of studies to the health and safety of exposed people
as well as a number of references.

3.5.1 Microwave Syndrome

For humans exposed to very low power densities (between a few microwatts
per square centimeter and a few milliwatts per square centimeter), East Euro-
pean epidemiological studies [13, 79, 80] have revealed a variety of reversible
asthenic problems that constitute the hypothetical microwave syndrome
(headache, perspiration, emotional instability, irritability, tiredness, somno-
lence, sexual problems, loss of memory, concentration and decision difficulties,
insomnia, and depressive hypochondriac tendencies). There was, however, no
control group. Furthermore, these complaints are very subjective and their
evaluation is difficult in the absence of well-established dosimetric data.
Indeed, individuals suffering from a variety of chronic diseases may exhibit
the same dysfunction of the central nervous and cardiovascular systems.
Hence, it is extremely difficult, if not impossible, to rule out other factors in