Autores

Belyaev IY, Markovà E, Hillert L, Malmgren LOG, Persson BRR. Microwaves from UMTS/GSM mobile phones induce long-lasting inhibition of 53BP1/-H2AX DNA repair foci in human lymphocytes (p n/a). Bioelectromagnetics Ahead of print Oct 6 2008.

Background
Non-ionizing radiofrequency microwave exposures are influenced by many parameters. Researchers have noted that microwaves can in some specific exposure circumstances inhibit repair of DNA damage. It is unclear what the mechanisms of these effects are but they could be the result of interaction between DNA and proteins. A previous study by the same authors found that microwaves from GSM induce changes in chromatin conformation (an indicator of stress response to genotoxic challenge) and inhibit DNA repair after one hour of exposure.

Objective
The authors wanted to investigate the effects of UMTS in comparison to the effects of GSM microwaves within 72 post exposure.  GSM mobile phones emit microwaves at narrow signals in the range of 200 KHz. In comparison, radiation from UMTS mobile phones emit wide band 5 MHz signals, which hypothetically may result in higher biological effects since they may include ‘effective’ frequency windows, presumably around 1-10 MHz. The authors wanted to test this hypothesis. Another purpose of the study was to compare the response of cells from individuals hypersensitive to EMF radiation and normal healthy individuals.

Methods
Blood samples were obtained from five healthy donors and five individuals who believe they are hypersensitive to electromagnetic field (EMF) radiation. Lymphocytes were isolated 30 minutes after drawing blood. Two lymphocyte samples from matched hypersensitive and healthy persons were simultaneously exposed to either GSM (905 or 915 MHz) using GSM 900 or UMTS (1947.4 MHz) test mobile phone. Exposure was conducted for 1 hour. The output of each phone was connected to the coaxial cable to the correspondent traverse electromagnetic line (TEM) cell. Control cells were exposed in the same TEM cells with microwave power off. More than 50% of cells had SAR values between 20 and 40 mW/kg. The endpoints measured were:

1-Changes in the conformation of chromatin were measured by the method of anomalous viscosity time dependencies (AVTD) assay. This is a sensitive assay to measure genotoxic effects and stress response.

2-Inhibition of DNA damage repair and induction of DNA damage was measured by immunostaining of DNA repair protein localization.

Results
Results showed that irradiation with 905 MHz GSM resulted in statistically significant conformational change of chromatin in cells from three donors.  While radiation from UMTS resulted in significant condensation only in cells from one donor, these data suggest that the effects on chromatin are frequency dependent. An interesting finding on chromatin conformation is that results did not differ significantly between hypersensitive and normal individuals.   

Similarly, irradiation of lymphocytes induced a statistically significant DNA damage in cells analyzed from 1 hour up to 72 hours after irradiation with 915 MHz but not with 905 MHz. Again, there was no statistically significant difference in DNA damage induction between normal and hypersensitive individuals.  Also, radiation from both UMTS and GSM produced a consistent reduction in DNA damage repair in both normal and hypersensitive individuals. The interesting finding from this study is that effects of microwaves from UMTS mobile phones on inhibition of DNA damage repair continued for up to 3 days after the initial one hour exposure.   

Discussion and Conclusion
This study showed that inhibition of DNA repair foci and chromatin conformation in human lymphocytes was affected by specific GSM/UMTS non-thermal levels from mobile phones. Intensities were below the safety standards of the International Commission on Non-ionizing radiation Protection (ICNIRP). The results also supported the hypothesis of higher biological effects of UMTS signals compared to GSM signals since the inhibitory effects of UMTS microwaves on DNA damage repair lasted for more than 72 hours, even longer than the stress response following heat shock. Results do not indicate any significant differences in effects between subjects who were healthy and those who reported hypersensitivity.



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