Since the brain is also exposed to the microwaves, changes in auditory functions could be caused by action at the level of the inner ear and/or central auditory pathways. The experiments were aimed at monitoring separately peripheral (by DPOAE measurements) and central auditory functions (auditory brainstem responses) after microwave exposure of the animals.
In the in vivo experiment, groups of eight guinea pigs had their left ear exposed to GSM microwaves and distortion product otoacoustic emissions (DPOAEs) were measured and auditory brainstem response thresholds were monitored.
In vitro, the two organs of Corti of 15 newborn rats were isolated and placed in culture.
Modulation type: pulsed
Exposure duration: repeated daily exposure, 1 h/day, 5 days/week, for 2 months
Modulation type: pulsed
Exposure duration: continuous for 24 h
|Chamber||An eight-compartment setup was constructed from RF absorbing panels avoiding interference among antennas.|
|Setup||Guinea pigs were held in a holding device composed of two sliding-yoke PVC tubes each with a V notch providing a hole for the neck in order to keep the head outside the tube and maintained straight by a sliding ring adjusted over the nose of the animal. The animal body could lie comfortably on a platform inside the tube assembly. The antenna was fixed horizontally at the level of the external auditory canal of the left ear in contact with the edge of the pinna.|
|Additional info||Sham exposure took place under the same conditions but in the absence of RF field.|
|Chamber||Two pieces of wire-patch cell (WPC) apparatus (see reference article) were used to expose the organs of Corti (OCs) in Petri dishes. Each WPC was placed in its own incubator for true blind operation.|
|Setup||The WPC consisted of two parallel square metallic plates with the bottom one being powered with RF through a coaxial line passing through the top one. Four poles at the four corners between the plates allowed for optimal tuning of the device.|
|Additional info||For each rat, one OC was exposed, and the other one was sham-exposed.|
The data showed no difference in DPOAE amplitudes or in auditory brainstem response thresholds between the exposed and non-exposed ears/groups.
Corti organs all appeared normal at this stage of development.
These data provided no evidence that microwave irradiation, at the levels produced by mobile phones, caused damage to the inner ear or the auditory pathways in the animals.