Study type: Medical/biological study (experimental study)

Simultaneous response of brain electrical activity (EEG) and cerebral circulation (REG) to microwave exposure in rats med./bio.

By: Thuroczy G, Kubinyi G, Bodo M, Bakos J, Szabo LD
Published in: Rev Environ Health 1994; 10 (2): 135-148
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Aim of study (acc. to author)

The study was related to the following questions: 1) Does a weak modulated or continuous wave (CW) electromagnetic field cause measurable effects on systemic and/or localized regulation mechanism in the CNS? 2) Is there any correlation between the field activated systemic and/or localized regulatory mechanisms and the changes in CNS activity? 3) Does evaluation of measured biopotentials provide more information about the effects on the CNS of modulated and continuous wave (CW) electromagnetic field irradiation? In two different experiments on rats 1) before and after 10 min, whole body exposures to 2.45 GHz CW microwaves, and 2) during 30 min exposures to 4 GHz amplitude modulated microwaves (partial body exposure), the effects on the CNS were observed simultaneously with those on the cardiovascular system.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Modulation type: CW
Exposure duration: continuous for 10 min
  • power density: 10 mW/cm² unspecified (at the head)
  • SAR: 2.3 mW/g average over mass (whole body)
  • SAR: 8.3 mW/g average over mass (brain) (± 1.7 mW/g)
  • SA: 1.23 Ws/g average over mass (whole body)
  • SA: 4.98 Ws/g average over mass (brain) (± 1.02 Ws/g)
  • power density: 30 mW/cm² unspecified (at the head)
  • SAR: 6.9 mW/g average over mass (whole body)
  • SAR: 25.1 mW/g average over mass (brain) (± 5.2 mW/g)
  • SA: 4.14 Ws/g average over mass (whole body)
  • SA: 14.94 Ws/g average over mass (brain) (± 3.05 Ws/g)
Exposure 2: 4 GHz
Modulation type: CW
Exposure duration: continuous for 30 min
brain localized exposure
  • power: 300 mW
  • power density: 8.44 mW/cm² unspecified
  • SAR: 8.44 mW/g average over mass (brain) (± 2.7 mW/g)
  • SA: 15.12 Ws/g average over mass (brain) (± 4.9 Ws/g)
  • power: 600 mW
  • power density: 16.88 mW/cm² unspecified
  • SAR: 16.8 mW/g average over mass (brain) (± 5.4 mW/g)
  • SA: 30.24 Ws/g average over mass (brain) (± 9.8 Ws/g)
  • power: 1,500 mW
  • power density: 42.4 mW/cm² unspecified
  • SAR: 42 mW/g average over mass (brain) (± 13.5 mW/g)
  • SA: 75.6 Ws/g average over mass (brain) (± 24.5 Ws/g)
Exposure 3: 4 GHz
Modulation type: AM
Exposure duration: continuous for 30 min
brain localized exposure
  • power: 300 mW
  • power density: 8.44 mW/cm² unspecified
  • SAR: 8.44 mW/g average over mass (brain) (± 2.7 mW/g)
  • SA: 15.12 Ws/g average over mass (brain) (± 4.9 Ws/g)
  • power: 600 mW
  • power density: 16.88 mW/cm² unspecified
  • SAR: 16.8 mW/g average over mass (brain) (± 5.4 mW/g)
  • SA: 30.24 Ws/g average over mass (brain) (± 9.8 Ws/g)

Exposure 1

Main characteristics
Frequency 2.45 GHz
Type
Charakteristic
Exposure duration continuous for 10 min
Additional info whole body exposure
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber anechoic room of 2.55 m x 1.8 m x 2.9 m
Parameters
Measurand Value Type Method Mass Remarks
power density 10 mW/cm² unspecified measured - at the head
SAR 2.3 mW/g average over mass estimated whole body -
SAR 8.3 mW/g average over mass measured and calculated brain ± 1.7 mW/g
SA 1.23 Ws/g average over mass estimated whole body -
SA 4.98 Ws/g average over mass measured and calculated brain ± 1.02 Ws/g
power density 30 mW/cm² unspecified measured - at the head
SAR 6.9 mW/g average over mass estimated whole body -
SAR 25.1 mW/g average over mass measured brain ± 5.2 mW/g
SA 4.14 Ws/g average over mass estimated whole body -
SA 14.94 Ws/g average over mass measured brain ± 3.05 Ws/g
Measurement and calculation details

The incident power to the horn antenna (G = 14 dB) was measured continuously using a directional coupler and a power meter. The spatial pattern of power density was measured using a radiation monitor. The SAR in the brain cortex was measured at 30 mW/cm² (30 s) using a thermocouple placed perpendicularly to the E-field and inserted 5 mm deep into the brain tissue of anaesthetized animals. From these data the SAR values at 10 mW/cm² were calculated.

Exposure 2

Main characteristics
Frequency 4 GHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 30 min
Additional info brain localized exposure
Modulation
Modulation type CW
Exposure setup
Exposure source
Setup The irradiation was performed in a waveguide setup TE-cell. A standard WR waveguide was extended up to 100 x 60 mm and connected through a horn to the waveguide.
Parameters
Measurand Value Type Method Mass Remarks
power 300 mW - measured - -
power density 8.44 mW/cm² unspecified measured - -
SAR 8.44 mW/g average over mass measured and calculated brain ± 2.7 mW/g
SA 15.12 Ws/g average over mass measured and calculated brain ± 4.9 Ws/g
power 600 mW - measured - -
power density 16.88 mW/cm² unspecified measured - -
SAR 16.8 mW/g average over mass measured and calculated brain ± 5.4 mW/g
SA 30.24 Ws/g average over mass measured and calculated brain ± 9.8 Ws/g
power 1,500 mW - measured - -
power density 42.4 mW/cm² unspecified measured - -
SAR 42 mW/g average over mass measured and calculated brain ± 13.5 mW/g
SA 75.6 Ws/g average over mass measured and calculated brain ± 24.5 Ws/g
Measurement and calculation details

The incident, reflected and transmitted powers were measured using directional couplers and power meters. Power density in the cross section of the TE-cell was measured through a slot using a small (3 mm) loop antenna at 1 cm depth from the top wall. The spatial pattern of SAR distribution in the brain cortex was measured at 2 W (56 mW/g SAR) CW (15 s) using a thermocouple placed perpendicularly to the E-field and inserted 5 mm deep into the brain tissue of anaesthetized animals with their heads placed toward the generator. The average SAR values versus the incident powers were calculated from these data.

Exposure 3

Main characteristics
Frequency 4 GHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 30 min
Additional info brain localized exposure
Modulation
Modulation type AM
Modulation frequency 16 Hz
Modulation depth 70 %
Additional info

sine wave
Exposure setup
Exposure source
  • same setup as in E2
Parameters
Measurand Value Type Method Mass Remarks
power 300 mW - measured - -
power density 8.44 mW/cm² unspecified measured - -
SAR 8.44 mW/g average over mass measured and calculated brain ± 2.7 mW/g
SA 15.12 Ws/g average over mass measured and calculated brain ± 4.9 Ws/g
power 600 mW - measured - -
power density 16.88 mW/cm² unspecified measured - -
SAR 16.8 mW/g average over mass measured and calculated brain ± 5.4 mW/g
SA 30.24 Ws/g average over mass measured and calculated brain ± 9.8 Ws/g

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

The total power of EEG spectra increased after whole body 2.45 GHz continuous wave (CW) exposure (30 mW/cm²) for 10 min. No changes occured at 10 mW/cm². The cerebral blood flow increased after 10 mW/cm² irradiation. The power of EEG delta (0.5-4 Hz) waves was increased by thermal level of brain localized 4 GHz continuous wave (CW) irradiation (at 42 mW/g SAR) simultaneously with the rheoencephalogram amplitude as an index of cerebral blood flow. Amplitude modulation at 16 Hz (8.4 mW/g SAR) was associated with increased power of EEG beta (14.5-30 Hz) waves but changes in the cerebral blood flow were not observed. CW exposure at 8.4 mW/g increased the cerebral blood flow, but did not change EEG spectra.

Study character:

Study funded by

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