Radiofrequency field emitted by mobile phones and alteration of the blood-brain barrier: how strong is the experimental evidence?
Résumé
It is known that high power, thermal radiofrequency radiation (RFR) can alter the blood-brain barrier (BBB) permeability with a brain av eraged specific absorption rate (BASAR) threshold evaluated at around 100 W/kg (1). Mobile communication technologies are using RFR with exposure guidelines for public local exposure at 2 W/kg, far lower than the threshold previously mentioned. However, in a paper recently published (2) the occurrence of BBB leakage and brain damage (presence of dark neurons) has been reported 50 days after a single 2-hour exposure of rats to a GSM-900 signal. In that investigation however, biais could have occurred as, for instance, exposed animals were mixed in terms of age (12- to 26-week old) and gender, while those differences were not taken into account in the analysis. Moreover, other groups have published contradictory results (3). Our group undertook a confirmation study of the Salford experiments within an international collaborative programme including technical improvements. Our study includes the detection of dark neurons, alteration of the permeability of the BBB and apoptosis 14 or 50 days after GSM-900 exposure. The exposure setup was the loop antenna that allows for head-only exposure. Five groups of 16 Fisher 344 rats (14 -week old) were exposed to GSM-900 during 2 hours at various SAR levels (0, 0.14 and 2.0 W/kg), or were used as cage control or positive controls. Positive controls were treated with kainic acid (10 mg/kg) or by cold injury (dry ice during 5 minutes). After exposure, rats were kept alive during 14 or 50 days to study brain damages. Then, they were anesthetized with urethane (i.p. 1.5 mg/kg), perfused with PBS and fixed with paraformaldehyde 4% (PAF 4%). Brains were extracted and put in cold PAF 4% during the following night, then placed in cold sucrose 20% during 2-3 days, frozen with isopentane and placed at -80°C. Coding was done on brains. Frozen brains were cut in 3 different areas (frontal, median and posterior). Slides were stained with cresyl violet and FluoroJade B to detect the presence of dark neurons. Apoptosis was investigated using the TUNEL method and endogenous albumin visualized using immuno-histochemical labeling as a marker of leakage of the blood -brain barrier. Preliminary data on 2 to 4 rats per group do not suggest that GSM-900 exposure could induce alterations in the brain of rats. The experiments will be completed and a review on this topics, including our contribution, will be presented