Studies of pulsed 900/1800 MHz RF-fields on the permeability of
the blood-brain barrier in rats.
1
Bertil R.R. Persson, 1Lars Malmgren, 2Arne Brun, and 2Leif G. Salford.
1
Department of Radiation Physics, 2Division of Experimental Neurooncology,
Department of Neurosurgery; Lund University Hospital, SE-221 85 Lund, Sweden
Abstract: No indication of increased brain tumour
growth in rats exposed to electromagnetic fields, while
increased blood-brain barrier permeability of albumin
has been recorded in rats exposed to electromagnetic
fields used in wireless communication.
INTRODUCTION
The effects of RF electromagnetic fields upon the
blood-brain barrier (BBB) and upon tumour growth in
the mammalian brain have been studied since 1980’s in
our laboratory. We have thus collected an extensive
experimental experience in this field. Our studies on the
effects of pulse-modulated microwaves at 915 MHz
upon brain tumour growth have not disclosed any
growth-promoting effects in our rodent models [1]. The
same RF electromagnetic fields have been revealed to
cause significantly increased leakage of albumin through
the BBB of exposed rats as compared to non-exposed
animals – in a series of more than one thousand [2].
Follow-up studies have been made with real GSM-900
and GSM-1800 exposures.
EXPOSURE EQUIPMENT
Rectangular coaxial transmission lines in form of TEMcells as shown if Figure 1 are used for studies on the
biological effects of plane wave RF electromagnetic
fields exposures up to 1 GHz. Exposures at higher
frequencies are performed in an anechoic chamber,
which simulates a free-space environment at microwave
frequencies. The size of our chamber is chosen such that
it can be used for far field exposures at frequencies over
1.5 GHz as well.
Figure1: The TEM-cells we used in our investigations
on non-thermal biological effects of electromagnetic
fields are shown is this photograph.
leak into the brain tissue and is demonstrated as brown
areas around the vessels as shown in Figure 3. The
most remarkable observation in our studies is the fact
that SAR values lower than 1 mW/kg give rise to a
more pronounced albumin leakage than higher SAR
values Figure 4. If the reversed situation were at hand,
we feel that the risk of cellular telephones, basestations and other RF emitting sources could be
managed by reduction of their emitted energy. The
situation that the weakest fields, according to our
findings, are the biologically most effective, poses a
major problem. The most pronounced BBB-opening
effect of the cellular telephone may not be in the most
superficial layers of the brain, but several centimetres
deep in central cerebral structures! It cannot be
excluded that these weak effects may influence nonusers in the vicinity of the cellular phone users.
POTENTIAL HEALTH EFFECTS
RESULTS
The brains were perfused with saline for 3-4 minutes,
and thereafter perfusion fixed with 4% formaldehyde for
5-6 minutes. Whole coronal sections of the brains were
dehydrated and embedded in paraffin and sectioned at 5
µm. Albumin and fibrinogen were demonstrated
immunohistochemically and classified as normal versus
pathological leakage. In Figure 2 is shown a normal
unexposed brain. After exposure to microwaves albumin
Several summaries of epidemiological studies
concerning neurological diseases and EMF have been
published [3]. The results from these studies do not
indicate any distinct correlation between EMF and the
risk of Alzheimer's disease and Parkinson's disease.
There is, however, a slight indication of a connection
between highly exposed individuals and increased risk
concerning these diseases. The biological hypothesis
concerning EMF and these diseases are still missing
[3,4]. The conclusive results from those studies indicate,
however, a significant increased risk of ALS
(amyotrophic lateral sclerosis) is found in groups with
occupation related to high EMF exposure. The risk
seems to increase with exposure, which indicates a doseresponse relation. A possible mechanism for increased
risk of ALS is EMF induced production of antibodies
that induce premature ageing of the large nerve cells that
are affected in ALS. The disturbed function of the Ca-
Figure 2: Brain of non-exposed control rat.
channels in these cells is probable involved in the
ageing process [5-7]. The enhanced permeability of the
blood brain barrier found in rats exposed to
microwaves might also be involves in the mechanism
of induction of neurological disease [2]
These findings motivate further studies in order
to determine the level of health risks involved from
low-level human exposure to microwaves.
CONCLUSION
We have demonstrated that microwave exposure
produces an unequivocal effect on the BBB in Fischer
rats. The clinical importance of this finding, however,
is disputable. Our method for detection of albumin is
extremely sensitive and reveals even minute amounts
of albumin leaking through the BBB, so small that they
may be harmless to the brain. However, the potential
health hazards of the opening the BBB during
exposure to wireless communication demands further
investigation.
It cannot be excluded that the increased
permeability of BBB may promote the development of
autoimmune and neuro-degenerative diseases, and we
conclude that the suppliers of mobile communication –
and our politicians – have an extensive responsibility
to support the exploration of these possible risks for
the users and the society.
REFERENCES
Figure 3: Pathological leakage around vessels
demonstrated by immuno-staining against albumin.
Figure 4: Blood-brain barrier permeability of albumin in
rats exposed to 915 MHz microwaves with different
modulation frequencies at SAR values 4x10-4-8x10-3
W/kg [2].
[1] Salford, L. G., Brun, A., and Persson, B. R. R., "Brain
tumour development in rats exposed to electromagnetic
fields used in wireless cellular communication.,"
Wireless Networks, vol. 3 pp. 463-469, 1997.
[2] Persson, B. R. R., Salford, L. G., and Brun, A., "BloodBrain Barrier permeability in rats exposed to
electromagnetic fields used in wireless communication.,"
Wireless Networks, vol. 3 pp. 455-461, 1997.
[3] Bergqvist, U., Brante, T., Fransson, K., Hansson Mild,
K., Hillert, L., Johansson, O., Rönnbäck, L., Sandström,
M., and Stenberg, B., "Elektromagnetiska fält,
elöverkänslighet
och
neurologisk
sjukdom-en
kunskapsöversikt," Arbete och Hälsa, vol. 23 1998.
[4] Feychting, M., Pedersen, N. L., Svedberg, P., Floderus,
B., and Gatz, M., "Dementia and occupational exposure
to magnetic fields," Scand.J Work Environ.Health, vol.
24 pp. 46-53, 1998.
[5] Johansen, C. and Olsen, J. H., "Mortality from
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vol. 148, no. 398, pp. 404, 1998.
[6] Savitz, D. A., Chekoway, H., and Loomis, D. P.,
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[7] Savitz, D. A., Loomis, D. P., and Tse, C.-K. J.,
"Electrical occupations and neurodegenerative disease:
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References
[1] L. G. Salford, A. Brun and B. R. R. Persson, Brain tumour development in rats exposed to electromagnetic fields
used in wireless cellular communication. Wireless Networks 3, 463-469 (1997).
[2] B. R. R. Persson, L. G. Salford and A. Brun, Blood-Brain Barrier permeability in rats exposed to electromagnetic
fields used in wireless communication. Wireless Networks 3, 455-461 (1997).
[3] U. Bergqvist, T. Brante, K. Fransson, K. Hansson Mild, L. Hillert, O. Johansson, L. Rönnbäck, M. Sandström and
B. Stenberg, Elektromagnetiska fält, elöverkänslighet och neurologisk sjukdom-en kunskapsöversikt. Arbete och Hälsa
23, (1998).
[4] M. Feychting, N. L. Pedersen, P. Svedberg, B. Floderus and M. Gatz, Dementia and occupational exposure to
magnetic fields. Scand J Work Environ Health 24, 46-53 (1998).
[5] C. Johansen and J. H. Olsen, Mortality from amytrophic lateral sclerosis, other chronic disorders, and electric
shocks among utility workers. Am J Epidemiol 148, 404 (1998).
[6] D. A. Savitz, H. Chekoway and D. P. Loomis, Magnetic field exposure and neurodegenerative disease mortality
among electric utility workers. Epidemiology 9, 398-404 (1998).
[7] D. A. Savitz, D. P. Loomis and C.-K. J. Tse, Electrical occupations and neurodegenerative disease: analyses of
U.S. mortality data. Arch Environ Health 53, 71-74 (1998).
[8] B. R. R. Persson, L. Malmgren, L. G. Salford and A. Brun. Health: Studies on Growth of Brain-Tumours
and on the Blood-Brain Barrier in Rats Exposed to 900/1800 MHz Rf-field. COST 244, Bordeaux 19-20
April.
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Ref Type: Abstract
[9] L. G. Salford, B. R. R. Persson and A. Brun, Neurological Aspects on Wireless Communication. In Non-Thermal
Effects of RF Electromagnetic Fields vol. ICNIRP 3/97. (Ed. J. H. Bernhardt, R. Matthes and M. H. Repacholi) pp. 131144, International Commission of Non-Ionizing Radiation Protection and World Health Organization, Proc. Sem on
Biol. Eff. Non-Therm. Pulsed and Amplitude Modulated RF EM Fields and Related Health Risks, Munich Germany
Nov 20 and 21, 1966 1997.
[10] L. G. Salford and B. R. R. Persson, Neurological Aspects of Exposure to Radiofrequency Fields. In
Communication Technology in the Community. Irish Government, Dublin, Ireland 1998.