Autores

Mizuno Y, Moriguchi Y, Hikage T, Terao Y, Ohnishi T, Nojima T, Ugawa Y. Effects of W-CDMA 1950 MHz emitted by mobile phones on regional cerebral blood flow in humans. BioelectromagneticsMay 27, 2009. Ahead of print.

Background

Widespread use of mobile phones has led to discussions about possible interactions of the electromagnetic field (EMF) with the human body; particularly the brain.  A number of studies have attempted to investigate how the absorbed EMF emitted by mobile phones affects the brain by using techniques such as electroencephalography (EEG) and positron emission tomography (PET).  Among them, 4 studies have performed PET to investigate the effects of mobile phone-related EMF on regional cerebral blood flow (rCBF) in humans.  Activations and deactivations in rCBF are reported in terms of Brodmann areas (BAs); regions of the cortex defined based on its organization of cells.  Although all 4 of the previous studies detected significant changes in rCBF either during or after EMF exposure, the BAs in which the changes were observed are inconsistent.  Furthermore, all 4 studies used second generation (2G) phones and no neuroimaging studies have been done for third generation (3G) systems in wide use today.

Objective
The purpose of this study was to investigate the effects of 3G mobile phone signals on the human rCBF.

Methods
Study participants were 9 healthy, right-handed, male volunteers.  Cerebral blood flow was measured by PET before, during, and after real or sham EMF exposure.  Each subject underwent 12 scans in total, half for the EMF exposure condition and half for the sham exposure condition.  Only the subject was blind to the exposure condition, not the experimenter.  Two scans were taken at baseline.  Real or sham exposure lasted 30 minutes.  Scan 3 was taken 10 minutes after the start of exposure, scan 4 was taken 10 minutes after scan 3.  Scan 5 was taken immediately after exposure and scan 6 was taken 10 minutes after scan 5.  The interval between real and sham exposures was at least 1 week.  The antenna emitting EMF was mounted to the right side of the subject’s head.

Results
Statistical analysis showed no significant effects of EMF from the 3G system on rCBF.  None of the contrasts, real/during - real/before, real/before – real/during, real/after – real/before, or real/before – real/after, compared with the corresponding sham conditions revealed significant changes in rCBF.  Several clusters of BAs showed significant increases in rCBF after real EMF exposure; however similar clusters of increases in rCBF were also found after sham exposure.

Interpretation and Limitations
The results of this study indicate that EMF emitted from 3G mobile phones does not significantly change rCBF during or after 30 min exposure.  This is in contrast to results from earlier studies which used 2G exposure systems.  It is currently unknown which exposure parameters (e.g. frequency of EMF, specific absorption rate, internal electric field strength, etc.) are most important to EMF effects on the brain, and the 2G and 3G systems differ with respect to these parameters.  Using power calculations, the authors determined that this study did not have enough subjects to detect even a large effect.  Improvements to neuroimaging methods are recommended to remedy the problem of low power.  Furthermore, this study was not set up to investigate the long-term effects of mobile phone exposure.

Conclusion
This study found no effects of EMF emitted from 3G mobile phones on rCBF.



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