Medical/biological study (experimental study)

Non-Thermal Effect of Microwave Radiation on Human Brain med./bio.

By: Hinrikus H, Bachmann M, Tomson R, Lass J

Published in: Environmentalist 2005; 25 (2-4): 187-194

Aim of study (acc. to author)

This study focused on the comparison of 450 MHz microwave exposure effect at different frequency modulations on human EEG.

Background/further details

Thirteen healthy subjects (4 male and 9 female) in the age of 21-30 years participated. During the experiments the participants were lying in a relaxed position in dark room, eyes closed and ears blocked.
Frequency modulations were selected from the EEG frequency spectrum: 7, 14, and 21 Hz.

Endpoint

effects on the neurological system: effects on EEG

Exposure

- microwaves

Exposure	Parameters
Exposure 1: 450 MHz Modulation type: pulsed Exposure duration: intermittent, 1 min off/1 min on, for 10 min per frequency	power density: 0.16 mW/cm² (at the skin) SAR: 0.0095 W/kg (in the brain)

Exposure 1

Main characteristics

Frequency	450 MHz
Type	electromagnetic field
Exposure duration	intermittent, 1 min off/1 min on, for 10 min per frequency

Modulation

Modulation type	pulsed
Duty cycle	50 %
Additional info	pulse rates of 7, 14, and 21 Hz

Exposure setup

Exposure source	quarter-wave antenna (13 cm)
Distance between exposed object and exposure source	10 cm
Setup	The antenna was located at 10 cm from the skin on the left side of the head.
Sham exposure	A sham exposure was conducted.
Additional info	During each 30-min test session (one only per day), the exposure conditions and the succession of the modulation frequencies were double-blind and randomly assigned by a computer. All subjects passed the exposure and sham protocols twice.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	0.16 mW/cm²	-	measured	-	at the skin
SAR	0.0095 W/kg	-	calculated	-	in the brain

Measurement and calculation details

The power density at the skin was estimated from calibration curves depending on distance obtained under real experimental conditions using a field strength meter, and the stability of the MW level was monitored during the experiments. The SAR inside the brain was calculated based on the power density at the skin on the left side of the head. The results of numerical calculations based on the digital anatomical model taking into account the frequency dependence and possible variations of tissue dielectric value and conductivity yielded a more reliable estimation of the whole body and localized SAR than the initially used formula SAR = σE²/2ρ [Hurt et al., 2000; Gajsek et al., 2001]. The levels of power density and SAR calculated by both methods were so low that thermal effects are unlikely.

Reference articles

Gajsek P et al. (2001): Parametric dependence of SAR on permittivity values in a man model
Hurt WD et al. (2000): Variability in EMF permittivity values: implications for SAR calculations

Exposed system:

human
partial body: left side of the head

Methods Endpoint/measurement parameters/methodology

effects on the neurological system: changes of the EEG rhythms (evaluation of theta wave, alpha wave, beta waves (beta1 (15-20 Hz) and beta2 (22-40 Hz))

Investigated system:

investigation on living organism

Investigated organ system:

brain/CNS

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

The microwave exposure at 14 Hz and 21 Hz frequency modulation caused significant increase in beta1 waves and alpha waves. It can be noticed that the microwave exposure caused significant effect when the frequency modulation was higher or comparable with EEG rhythm frequency.

Study character:

medical/biological study
experimental study
full/main study
double blind study

Study funded by

Estonian Science Foundation (ETF), Estonia

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