Study type: Medical/biological study (experimental study)

Effect of immobilization and concurrent exposure to a pulse-modulated microwave field on core body temperature, plasma ACTH and corticosteroid, and brain ornithine decarboxylase, Fos and Jun mRNA med./bio.

By: Stagg RB, Hawel LH, Pastorian K, Cain C, Adey WR, Byus CV
Published in: Radiat Res 2001; 155 (4): 584-592
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Aim of study (acc. to author)

To determine if a near field radiofrequency exposure could induce a stress response.
The aims of this study were 1) if the loose-tube restraints (some movement allowed) necessary for accurate near field radiofrequency exposures could cause a stress response in animals, 2) if near field radiofrequency exposures to the head could induce a stress response in animals above that observed in sham-exposed immobilized animals, and 3) if a threshold level for brain near field radiofrequency exposure could be identified using a series of molecular stress markers.

Background/further details

The effects of the loose-tube immobilization with and without prior conditioning were investigated.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1.6 GHz
Modulation type: pulsed
Exposure duration: continuous for 2 h
  • SAR: 0.6 W/kg average over time (brain)
  • SAR: 1.6 W/kg average over time (brain)
  • SAR: 5 W/kg average over time (brain)

Exposure 1

Main characteristics
Frequency 1.6 GHz
Charakteristic
Exposure duration continuous for 2 h
Modulation
Modulation type pulsed
Packets per second 11
Additional info

Iridium protocol
Exposure setup
Exposure source
Distance between exposed object and exposure source 5 cm
Chamber Carousel containing 10 cylindrical PVC tubes arranged radially around a central antenna (see reference article).
Setup Animals were loosely restrained in the PVC cylindrical tubes. Clear acrylic pins were placed vertically behind the animal to prevent backward mobility. Only five animals at a time were placed in every other tube for symmetry. The field-exposure and the sham-exposure carousels were located in the same rack.
Parameters
Measurand Value Type Method Mass Remarks
SAR 0.6 W/kg average over time calculated brain -
SAR 1.6 W/kg average over time calculated brain -
SAR 5 W/kg average over time calculated brain -
Measurement and calculation details

A detailed model of near field distribution and SARs prepared by Kuster and Schoenborn (publication id 1510) was used to set the antenna input powers at levels that established the desired time-averaged SARs in the rats' brains.

Reference articles

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 data revealed that Iridium-modulated microwave fields at brain SAR levels up to 5 W/kg did not induce a stress response in terms of elevated core body temperature, plasma ACTH and corticosteroids, or brain ODC, Fos and Jun mRNA levels in rats immobilized in loose-tube restraints (compared to sham-exposed loose-tube immobilized animals).
However, the non-tube-trained rats did experience a significant stress response when placed into the tube restraint apparatus. This stress response was seen clearly as short-term (less than 2 h) increases in plasma ACTH and corticosterone levels and a transient, small increase in core body temperature. Adaptation by prior conditioning (tube training) lessened the extent and duration of the stress-related marker elevations.
In conclusion, the pulse modulated digital Iridium radiofrequency field at SAR-values up to 5 W/kg is incapable of altering these stress-related responses. This conclusion is further supported by the use of a radiofrequency field exposure apparatus that minimized immobilization stress.

Study character:

Study funded by

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