EFFECT OF GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM) MICROWAVE EXPOSURE ON BLOOD-BRAIN-BARRIER PERMEABILITY IN RAT

We investigated the effects of global system for mobile communication (GSM) microwave exposure on the permeability of the blood-brain barrie r using a calibrated microwave exposure system in the 900 MHz band. Ra ts were restrained in a carousel of circularly arranged plastic tubes and sham-exposed or microwave irradiated for a duration of 4 h at spec ific brain absorption rates (SAR) ranging from 0.3 to 7.5 W/kg. The ex travasation of proteins was assessed either at the end of exposure or 7 days later in three to five coronal brain slices by immunohistochemi cal staining of serum albumin. As a positive control two rats were sub jected to cold injury. In the brains of freely moving control rats (n = 20) only one spot of extravasated serum albumin could be detected in one animal. In the sham-exposed control group (n = 20) three animals exhibited a total of 4 extravasations. In animals irradiated for 4 h a t SAR of 0.3, 1.5 and 7.5 W/kg (n = 20 in each group) five out of the ten animals of each group killed at the end of the exposure showed 7, 6 and 14 extravasations, respectively. In the ten animals of each grou p killed 7 days after exposure, the total number of extravasations was 2, 0 and 1, respectively. The increase in serum albumin extravasation s after microwave exposure reached significance only in the group expo sed to the highest SAR of 7.5 W/kg but not at the lower intensities. H istological injury was not observed in any of the examined brains. Com pared to other pathological conditions with increased blood-brain barr ier permeability such as cold injury, the here observed serum albumin extravasations are very modest and, moreover, reversible. Microwave ex posure in the frequency and intensity range of mobile telephony is unl ikely to produce pathologically significant changes of the blood-brain barrier permeability.