This document summarizes research on the dielectric properties of red blood cells (RBCs) and how they are affected by exposure to extremely low frequency (ELF) magnetic fields. It discusses polarization mechanisms in biological materials and how dielectric properties are measured. Several studies found that prolonged exposure of rats to 50Hz magnetic fields with intensities of 0.2-3 mT caused structural changes to hemoglobin in RBCs, increasing their relative permittivity and conductivity over time. This suggests exposure may damage RBC function and metabolism, with downstream effects on organs. In conclusion, analyzing dielectric properties provides insight into electromagnetic field interactions with cells and how exposure may affect physiological processes.

1. To My Father

2. Presented by / Fatma Abd-Elhamied Ahmed
Supervisor / Dr. Sally Eldeghaidy

3. Also they provide information that helps in
understanding the interaction between electromagnetic
fields and biological systems.
Why we are Interested in Studying the
Dielectric Properties of Tissues??
Analysis of dielectric properties of cells as a whole and the
cells structure parts (membrane, cytoplasm, etc) provide
valuable knowledge about different cell structures, function
and metabolic mechanisms.

4. Outline
A review on the effect of (ELF) magnetic field on the
dielectric properties of RBCs
Polarization mechanisms
Measurements of dielectric properties
Dielectric spectroscopy for soft tissues
The dielectric properties of tissues will be discussed
in details including:

5. Dielectric Polarisation
When an electric field is applied to a dielectric material,
electric charges slightly shift from their average equilibrium
positions causing dielectric polarization
A dipole is formed,
and the material is
said to be
polarized
After the electric
field is turned off
Before the
application of
electric field
Electric field is
applied

6. The polarization (P) is related to the applied electric field (E) by
where ε0 is the electric constant, and χ is the electric
susceptibility of the medium.
The x is related to the relative permittivity by
EP χε0=
1−= rεχ

7. Dielectric Polarisation
Mechanisms in Biological Material
Several mechanisms contribute to the dielectric
properties of tissues and other biological materials.
• The main mechanisms giving rise to dielectric
polarization is tissue are:
• Dipole polarisation
• Interfacial polarisation
• Counter-ion polarisation
Depending on the material and frequency range of
interest one or another might predominate in its
influence.

8. Dipole Polarisation
This mechanism of polarization is particular to polar
molecules, such as water, and many proteins. In the
absence of an external electric field, the permanent
dipole moments are oriented at random directions
Water molecule

9. When an externally electric field is applied, on polar
molecules, permanent dipoles (each with dipole
moment M) will reorient and experience a rotational
force (F), defined by the torque:
)sin(θτ MF=
where θ is the angle between
the dipole moment and the field.

10. The relaxation time in dipole polarization can be
obtained by considering the diffusion of the molecules
in a viscous medium:
where η is the viscosity (Poise), a is the molecule
radius, T is the absolute temperature, and k is
Boltzmann’s constant . The relaxation time t ranges
from picoseconds for small dipolar molecules such as
water, to microseconds for large globular proteins in
aqueous solution.
kT
a3
4πη
τ =

11. Interfacial Polarisation
This mechanism arises from the heterogeneity of the
material leading to changes in the distribution of electric
fields within the material at different frequencies.
This effect is caused mainly due to cell membrane.
Characteristics “charging effects”.

12. At low frequencies, the current flows around the
spheres “cells” because of membrane's high impedance.
As the frequency is increased, progressively more
current flows through the cells.
 At very high frequencies, the membranes are short-
circuited owing to their capacitance, and no longer
impede current flow. The permittivity and conductivity will
be close to those of the media that are contained by and
surround the spheres.

13. The relaxation time is given by:
)
1
2
1
(
ia
maC
σσ
τ +=
Where a is the radius of the spheres, Cm is the capacitance
of the membrane and σa , σi are the conductivities of the
outer and inner media.

14. Counter-ion Polarisation
The polarisation originates from ionic diffusion effects
(displacements of ions) near cell surfaces and the formation of
counter-ion or electric double layers during the presence of
electric field.
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Electric fieldElectric fieldNo Electric fieldNo Electric field
appliedapplied

15. The relaxation time can be calculated by:
kT
ea
µ
τ
2
2
=
where a is the radius of the sphere, e is the
elementary charge, and μ is counter-ion mobility.

16. How Dielectric Properties can be
Measured?
The response of a material to an applied electric field
is described by its permittivity (ε) and conductivity (σ)
'''
0
rrr
r
jεεε
ε
ε
ε
−=
=
∗
Dielectric constant
storage
Dielectric
loss
1−=j

17. LRC meter is usually used to measure the capacitance
and resistance for the sample under study at various
frequencies.
The permittivity is calculated for each frequency, using
Where d, is the inter-electrode distance, A is the area of electrode
measured from the cell used, and ε0 is the permittivity of free space.
A
Cd
0
'
ε
ε =

18. The loss tangent (tanδ), the dielectric loss (ε’’) and
the AC conductivity σ are calculated from the relations
where, f is the frequency applied, and R is the resistance
of the specimen.
'tan''
2
1
tan
εδε
π
δ
=
=
fRC
0''2 εεπσ f=

19. The Dependence of Permittivity
and conductivity on frequency.
The general trend for the permittivity to decrease as
frequency increases, while the conductivity increases
with increasing the frequency.

20. The Dielectric spectroscopy
for Soft Tissues
Schawn defined three
frequency regions for the
dielectric properties of
biological materials from the
observed main dispersions of
the conductivity and the
permittivity.
Conductivity increases with
increasing the frequency,
while the permittivity
decreases over a wide range

22. Major dispersions in biological
Matter

23. Example for Dielectric properties
of Different Tissue Types.

24. The Effect of ELF Magnetic Field on
RBCs
Changes in RBC’s biophysical properties will affect its
capability for carrying and transporting oxygen (O2), and
therefore on its metabolic functions.
The failure in metabolic function of the RBCs is directly
reflected in highly active critical organs, such as heart
muscles, brain and bone marrow.
Why did we choose RBC?
Therefore, RBCs were chosen as a good example for the changes
that may occur as a result of exposure to ELF magnetic field

25. The Structure and Function of RBCs
They are biconcave shape with a
flattened centre, giving an
increase in surface area
Their main function is carrying and
transporting O2 to all body parts

26. They consists of 4 polypeptide
subunits, each contain a heme
group
Each haemoglobin molecule is
able to carry up four oxygen
molecule at it's maximum capacity

27. Review on the Effect of ELF
Magnetic Field on RBCs
The effect of prolonged exposure of animals to 50 Hz
magnetic field with intensity of 0.2 mT on the RBC’s
haemoglobin molecular structure was investigated for 4
groups (6 rats each) for 15, 30, and 45 days. The 4th
group
was used as control. The field was turned on continuously
for the groups under exposure.
The dielectric measurements permittivity (ε) and
conductivity (σ) were made in the frequency range from 0.1
to 10 MHz.
Ali et al, Bioelectromagnetics 24:535-545 (2003)

28. Results
Control
15 days exposure
30 days exposure 45 days exposure

29. These results indicate that the prolonged exposure of the
animals to 50 Hz magnetic field of intensity 0.2 mT caused
structural changes in their Hb molecules, which may affect
their properties and hence the RBC’s physiological functions

30. In another study, the exposure to 50 Hz MFs of intensity
3 mT, showed similar results to the previously shown.
However, in this study the exposure time was shorter, 8
hours/day for two, three and four successive weeks.
The dielectric measurements, εr and σ were calculated in
a frequency range of 12 Hz – 0.1 MHz.
The relative permittivity and conductivity of Hb showed
an increase in response to the exposure of the magnetic
field.
SHALABY, and SHAWK. ROMANIAN J. BIOPHYS., Vol. 16, No. 3,
P. 169–180, (2006).

31. Similar results were confirmed in more recent studies.
In these studies [1,2]
, the effect of 50 Hz MF was
investigated at intensities:
 1.8 mT (frequency range 20 Hz to 0.1 MHz) for a duration
of 8 hours/day for 1, 2, 3, and 4 weeks [1]
.
 And at 0.3 mT (frequency range 50 Hz to 0.2 MHz). The
animals were continuously exposed to magnetic field for 21
days another group for 45 days[2]
.
[1] Rageb and Sallam. Egypt.J.Biophs.Engng., 8:15-24, (2007)
[2] Baieth and Morsy. Egypt.J.Biophs.Engng., 8:1-13, (2007),

32. Conclusions
Analysis of dielectric properties of cells as a whole and the cells
structure parts provide valuable information about different cell
structures, function and metabolic mechanisms.
• It helps in understanding the interaction between
electromagnetic fields and biological systems.
• Recent studies showed that the exposure of 50 Hz magnetic
field with intensities 0.2, 0.3, 1.8 and 3 mT caused structural
changes in Hb molecules, which may affect their properties
and hence the RBC’s physiological functions. This also
consequently damage other organs such as liver and other
critical organ.

33. Acknowledgment
I would like to thank all staff members, and
colleagues for all their help and support during the
last four years.
In particular, I would like to thank
 Prof. Mostafa Kamel, head of the departments.
Prof, Yehia Abbas,
 Prof. Magdy Elshry,
and Prof. Wahib Attia.
Dr. Sally Eldeghaidy