Finnie JW, Blumbergs PC, Cai Z, Manavis J. Expression of the water channel protein, aquaporin-4, in mouse brains exposed to mobile telephone radiofrequency fields. Pathology. Apr 26, 2009. Ahead of print.
Because mobile phones are held close to the brain, potential neurological effects from mobile phone exposure are of particular concern. There is some evidence that repeated and high intensity radiofrequency (RF) electromagnetic radiation exposure from mobile phones can cause biological effects in neural tissue that could be detrimental to health. However, the evidence is insufficient and conflicting, which prevents regulatory authorities from making firm conclusions on the safety of mobile phones. Many studies investigating the neurological effects of mobile phone exposure have looked at increased blood-brain barrier (BBB) permeability as a marker of neuronal injury. In response to increased BBB permeability, the protein aquaporin-4 (AQP-4), which serves to control the flow of water across the BBB, increases its presence and enhances water clearance from the brain into the bloodstream.
The objective of the study was to determine whether exposure to mobile phone RF fields, either acutely or long-term, produces an increase in AQP-4.
The field strength in the exposure system was 4 W/Kg. This was much higher than the allowable human exposure limit in Australia (0.4 W/Kg). Mice were either acutely exposed for 60 minutes or exposed long-term on 5 successive days per week for 104 weeks. In both studies, there was an exposed group (10 mice), sham-exposed group (10 mice), and a non-exposed, freely moving cage control group (10 mice) to control for any stress-related effects of being confined during exposure. In addition, a positive control group was given a toxin known to cause increased production of AQP-4 in rodent brains. At the end of the experiment, mice were sacrificed and their brains were examined for the presence of AQP-4 by two independent pathologists.
In mouse brains exposed to the toxin, AQP-4 was abundant. In contrast, AQP-4 levels in mouse brains from exposed, sham-exposed, and freely moving, cage control groups were much less, and were similar across the three groups at both time intervals.
Interpretation and Limitations
This study found no difference in the presence of AQP-4 between exposed and non-exposed (sham and cage control groups) in both short- and long-term exposed brains. These results are in accordance with previous studies that used different markers of BBB disruption following RF exposure. This study is one of the few assessments of the neurological effects of long-term (i.e. 2 years) exposure to RF fields. This study is limited by the small number of mice studied.
The authors concluded that exposure of mouse brains to mobile phone RF fields of short or long duration did not produce any detectable changes in the production of AQP-4, suggesting that there was no significant increase in BBB permeability.