Auteurs
Eberhardt JL,  Persson BRR, Brun AE,  Salford LG, Malmgren LOG. (2008). Blood-Brain Barrier Permeability and Nerve Cell Damage in Rat Brain 14 and 28 Days After Exposure to Microwaves from GSM Mobile Phones  Electromagnetic Biology and Medicine, 27( 3):215 – 229.

Background
The authors investigated the effects of global systems for mobile communication (GSM) microwave exposure on the blood brain barrier (BBB). The BBB restricts the transport of substances from the general blood circulation into and from the brain and if damaged becomes less selective to the passage of substances from the blood. This could lead to entry of toxic substances from the blood to the brain. The indicator for BBB being less selective is the up normal presence of albumin (small protein) in the brain. The authors have been studying the effects of exposure to electromagnetic fields in both the continuous wave form and those used in the GSM communications and found earlier that BBB becomes less selective after exposure to radiofrequency (RF) fields.

Objective
The general aim of the study was to see the effects of exposure to GSM from mobile phones on BBB and nerve cell damage in rat brains. More specifically, the objectives were (1) to follow the presence and distribution of albumin in rat brain; (2) to follow the details of the development and progression of neuronal damage; (3) and to investigate the effects of low exposure level (SAR 0.12 mW/kg) in a rat model after a recovery time of 14 and 28 d after a single 2-h exposure to 900MHz radiation from GSM.

Methods
Ninety-six male and female Fisher rats were divided into 8 exposed groups (4 exposures at whole body SAR of 0.12, 1.2, 12 or 120 mW/kg and 2 different recovery times after exposure (14 or 28 days). Two control groups each composed of 16 rats were not exposed (sham-exposed) and kept for recovery for 14 or 28 days. Rats were exposed using the traverse electromagnetic transmission (TEM-cell). Those cells were known to generate uniform electromagnetic fields for standard measurements. A genuine GSM mobile phone with programmable power output was connected to the TEM-cells. Rats in the experiment groups as well as the controls were sacrificed after either 14 or 28 days of exposure and the extravasations of albumin, its uptake by neurons and occurrence of damaged neurons was assessed.

Results
The results showed that albumin extravasations and uptake by neuronal cells was enhanced 14 days after exposure but not after 28 days. Neuronal damage, on the other hand, took place after 28 days of exposure. More importantly, neuronal albumin uptake was significantly correlated with occurrence of damaged neurons. An interesting finding of this study is that neuropathological changes occurred at SAR levels as low as 0.12 W/kg, a value which is far below the current recommended limit value for the exposure of the head (2 W/kg) according to the guidelines from the International Commission for Non-Ionizing Radiation (ICNRP). What was more striking is that albumin leakage at this exposure level was even more pronounced than at higher SAR exposure levels. This caution against the recommendations that reduction of emitted energy from cellular phones, base-stations, and other RF-emitting devices could protect against their harmful effects since the current study indicated that weakest fields could be more biologically damaging.

The significance of BBB damage (indicated by albumin leakage into the brain) is demonstrated by the correlation between albumin uptake and occurrence of dark neurons 28 days after exposure. The caution against findings of this study is that they were not corroborated by other studies of similar methodology and whether those findings can be extrapolated to humans. 

Conclusion
It was noted by the authors that bystanders could be exposed to RF fields through a passive GSM exposure, but also groups being exposed when being a distance away from base-stations. It was concluded that additional research is warranted before changes to recommendations for future exposure limit values taking into account non thermal effects of RF fields from mobile communications on the human brain activit

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