Auteurs
Söderqvist F, Carlberg M, Hardell L. Use of mobile telephones and serum S100B levels: A descriptive cross-sectional study among healthy Swedish adults aged 18-65 years. Sci Total Environ. Ahead of print November 4, 2008.

Background
A long-standing concern over radiofrequency fields (RF) emitted by mobile phones is their potential effects on the blood-brain barrier (BBB).  The BBB controls the passage of molecules between the brain and the blood thus is essential to maintain an optimal environment for nervous system function. In the late 1970s, it was found that RF affected the BBB in rats and studies conducted since then have been contradictory.

Objective
The goal of this study was to investigate the effects of long and short-term exposure to RF on the BBB and is the first study to investigate this relationship in humans.

Methods
When the BBB is disrupted, the protein S100B is released into the blood. One thousand adults living in Örebro, Sweden were randomly asked to participate in the study. Subjects were asked to give a blood sample and to fill in a questionnaire on their use of mobile phones (mobile phones and cordless desktop phones (DECT)). Subjects described their usage history, both over a longer period of time and on the day they provided the blood sample, and identified the type of mobile phone they owned. The questionnaire also included questions on employment history, other sources of exposure (X-rays, chemicals or radiation therapy), and on health and lifestyle factors including health conditions known or suspected to influence the BBB.  

Results
Three hundred and fourteen subjects participated in the study. S100B levels were higher among women and among those who gave a blood sample in the morning as opposed to later in the day while other lifestyle factors and previous RF exposures did not influence S100B levels. Subjects were considered unexposed to RF fields if their total mobile phone or DECT use was less than that of three quarters of the subjects. Exposed and unexposed subjects had the same blood levels of S100B, regardless of type of phone used (mobile analogue, digital, UMTS or DECT) or years since first mobile phone use. When blood S100B levels were measured on a continuous scale as opposed to a dichotomous scale, longer time since first use of UMTS mobile phones increased S100B levels in men but not in women. The effect of short-term exposure to RF fields was assessed by comparing those who had used mobile phones on the day they gave blood to those who had not. No difference in blood S100B levels was found between the two groups, regardless of how S100B levels were measured. However, in those with the longest time between use of DECT and giving blood on the same day, S100B levels were lower than in those who had used DECT closer to the time of giving blood on the same day. This result was nearly statistically significant.

 

Interpretation and Limitations
The finding of increased levels of S100B in men with a longer time since first UMTS phone use is based on a small number of subjects (49) with relatively low levels of blood S100B and therefore need to be confirmed in future studies. The short-term effects of mobile phones on S100B levels should be further tested under conditions where stress and other confounding factors can be better controlled. The limitations of this study are the low response rate, the potential inaccuracy of self-reported data on mobile phone use, the validity of S100B levels as a marker of BBB dysfunction, and the time lapse between mobile phone use and blood draw which may have limited the ability to detect a short-term association between mobile phone use and S100B levels.

Conclusion
Long or short-term use of mobile telephones was not associated with elevated levels of S100B, a marker of BBB function.


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