Study type: Medical/biological study (experimental study)

Microwave radiation, in the absence of hyperthermia, has no detectable effect on synapsin I levels or phosphorylation med./bio.

By: Browning MD, Haycock JW
Published in: Neurotoxicol Teratol 1988; 10 (5): 461-464
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Aim of study (acc. to author)

To determine whether microwave exposure might be neurotoxic, the effects of microwave exposure on the protein synapsin I have been studied.

Background/further details

Synapsin I is a neuron-specific phosphoprotein that is present in all neurons, where it is located to the presynaptic terminal and it is associated with synaptic vesicles. Calcium-dependent phosphorylation of synapsin I in synaptosomes isolated from rats exposed to microwaves was also examined. The phosphorylation of synapsin I reflects numerous components of the presynaptic aspect of neuronal transmission.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2 GHz
Modulation type: CW
Exposure duration: continuous for 30 min
Exposure 2: 2 GHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
Exposure 3: 2.08 GHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
Exposure 4: 2.8 GHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
Exposure 5: 2.8 GHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
Exposure 6: 500 MHz
Modulation type: AM
Exposure duration: continuous for 30 min
Exposure 7: 450 MHz
Modulation type: AM
Exposure duration: continuous for 30 min
Exposure 8: 2.4 GHz
Modulation type: CW
Exposure duration: almost continuous, 23 h/day, for 1 week

Exposure 1

Main characteristics
Frequency 2 GHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Setup The animals were lightly restrained in aerated Lucite holders with polystyrene foam sides and positioned parallel to the E-field.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 20 mW/cm² maximum measured - 1, 5, 10, 20 mW/cm²
Additional parameter details

For each frequency condition, the order of power densities was randomized.

Measurement and calculation details

Power density was measured using electromagnetic radiation monitors.

Exposure 2

Main characteristics
Frequency 2 GHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Pulse width 10 ms
Repetition frequency 6,000 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 20 mW/cm² maximum measured - 1, 5, 10, 20 mW/cm²

Exposure 3

Main characteristics
Frequency 2.08 GHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Pulse width 10 ms
Repetition frequency 6,000 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 50 mW/cm² maximum measured - 1, 5, 10, 20, 50 mW/cm²

Exposure 4

Main characteristics
Frequency 2.8 GHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Pulse width 10 ms
Repetition frequency 6,000 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 50 mW/cm² maximum measured - 1, 5, 10, 20, 50 mW/cm²

Exposure 5

Main characteristics
Frequency 2.8 GHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Pulse width 10 ms
Repetition frequency 500 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 50 mW/cm² maximum measured - 1, 5, 10, 20, 50 mW/cm²

Exposure 6

Main characteristics
Frequency 500 MHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type AM
Modulation frequency 16 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 20 mW/cm² maximum measured - 1, 5, 10, 20 mW/cm²

Exposure 7

Main characteristics
Frequency 450 MHz
Type
Charakteristic
Exposure duration continuous for 30 min
Modulation
Modulation type AM
Modulation frequency 16 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 15 mW/cm² maximum measured - 1, 5, 15 mW/cm²

Exposure 8

Main characteristics
Frequency 2.4 GHz
Type
Charakteristic
  • guided field
Exposure duration almost continuous, 23 h/day, for 1 week
Additional info Guy, A. W.; Chou, C. K. System for quantitative chronic exposure of populations of rodents to UHF fields. In: Johnson, C. C.; Shore, M. L., eds. Biological effects of electromagnetic waves: Selected papers. HEW Publication (FDA) 77-8011; 1975:38-42.
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber The circular waveguide system was described by Guy and Chou [1975]. The TE11 mode was excited by two radial probes located 90° apart and driven with a phase difference of 90°.
Setup Animals were unrestrained in cages.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 1 W/kg - determined by power loss - -
SAR 2 W/kg - determined by power loss - -
Measurement and calculation details

The SAR was determined by the measured difference between input and output power and the mass of the animal.

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)

Neither acute nor chronic exposure to microwaves had any detectable effect on synapsin I levels. At intensities below that required to produce mild hyperthermia, no effects of microwave exposure were seen on synapsin I phosphorylation. Short-term exposure to microwaves at power densities that produced modest hyperthermia significantly decreased the calcium-dependent phosphorylation of synapsin I, but this effect was not seen after chronic, hyperthermic exposure.

Study character:

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