Hintzsche H, Stopper H. Micronucleus frequency in buccal mucosa cells of mobile phone users. Toxicol Lett. Dec 24, 2009 Ahead of print.

Studies of the effects of radiofrequency (RF) radiation on DNA provide contradicting results. Some studies have shown an effect of RF radiation on gene expression while others have not. As to genotoxic effect detected by some investigators, the majority of studies could not confirm it. Micronuclei test is one of the widely used tests for measuring DNA damage. It quantifies the occurrence of micronuclei, small nuclear bodies that contain broken chromosome fragments. Because the oral cavity is located within the area of RF exposure emitted from mobile phones, the micronuclei test in buccal mucosa cells is suitable for analyzing potential effects of this exposure. The only previous study applying the micronuclei assay to evaluate genomic instability in buccal cells (Yadav and Sharma, 2008) has shown an increase in micronuclei in mobile phone users compared to non-users, and an increasing trend with increasing overall period of exposure.

The objective of this study was “to verify whether those results could be confirmed in a different population using a larger cohort and counting double the amount of cells to increase statistical power and using a different, DNA-specific staining procedure.”

A questionnaire was filled out by potential participants about duration of daily mobile phone use, overall period of exposure and usage of head-sets. Information on demographic characteristics, body height and weight, smoking, medication use and nutritional habits was also obtained. Non-users were matched to users on age. Samples from 131 individuals (2,000 cells per individual) were evaluated by two scorers.  For staining, a DNA-specific staining procedure using a-tubulin-antibody and chromomycin A3 was used.

There were no significant differences in micronuclei frequency depending on gender, age, body mass index and smoking status. The number of fragmented nuclei did not depend on these factors except for gender (significantly greater number of fragmented nuclei in males, p<0.05). No significant differences were observed in micronuclei frequency or fragmented nuclei depending on headset use/non-use, overall period of mobile phone use (<5, 5-10, 10+ years). No differences in micronuclei frequency were detected in relation to hours per week of mobile phone use. There was a decreasing trend in the number of fragmented nuclei with duration of mobile phone use (hours per week). By grouping the study subjects into 3 groups, it was shown that the number of fragmented nuclei was higher in subjects using a mobile phone for 1-2 hours/week than in those using it less or using it more.

Interpretation and Conclusion
In contrast to the study by Yadav and Sharma (2008), this study has not detected any effect of duration of mobile phone use either in terms of weekly use or overall period of mobile phone use in years. The authors find it difficult to explain the fluctuant results for fragmented nuclei and suggest a high variability of this endpoint as a possible explanation. The different results of the two studies could be explained by higher statistical power of the present study and different staining techniques.

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