Thursday July 26 2007
A study examining people who believe that mobile phone masts make them feel unwell has found that it is likely that any symptoms are all in the mind, BBC News and other sources reported.
Up to 5% of the general population believe themselves to be affected by electro- or radiosensitivity and experience flu-like symptoms, headaches, lethargy and nausea when exposed to various electrical appliances.
The reports state that the three-year study of 44 electrosensitive volunteers and 114 control volunteers, found that the people who thought that they were electrosensitive experienced symptoms when they were placed near to a mobile phone mast and told that it was "switched on".
However, when the tests were repeated with the volunteers not knowing whether the masts were switched on or off, there was no relationship between their symptoms and the mobile phone signals. This, the newspapers suggest, may mean that any health effect of mobile phone masts is all in the mind.
This small, short-term study cannot prove that mobile phone signals have no harmful effects on the individual or what these effects may be. We can also draw no conclusions from these results on what would be experienced if an individual were to live near a telecommunications mast for many years.
Where did the story come from?
The study was conducted by Dr Stacy Eltiti and Professor Elaine Fox with colleagues of the University of Essex and published in the peer-reviewed journal Environmental Health Perspectives. The researchers received technical support from Red-M and the National Physical Laboratory. The research was funded by the Mobile Telecommunications and Health Research Programme grant number RUM 20.
What kind of scientific study was this?
This was a case control study conducted in two parts: the first was 'provocation' where participants were aware that they were being exposed to mobile phone signals, the second part was double blind, where researchers and participants were unaware of when the mobile phone mast was switched on or off.
The laboratory study compared 56 electrosensitive volunteers who claimed to suffer symptoms as a result of exposure to radiofrequency electromagnetic fields (rf-emf), with 120 control volunteers. Each volunteer participated in four, once weekly testing sessions. The first test was open provocation, in which the volunteer was seated near to an experimental mobile phone mast and told whether it was switched on or off, and if it was on, which type of mobile phone signal, Global System for Mobile communications (GSM) or Universal Mobile Telecommunications System (UMTS), it was sending out. The responses of the volunteers were tested by a questionnaire of their symptoms (e.g. anxiety, discomfort) and by taking measurements of blood pressure, heart rate and skin conductance.
During the following three sessions both the volunteer and researcher were unaware whether the mast was sending out no signal, a GSM signal or a UMTS signal. The volunteers were asked to guess, according to how they felt, whether the mast was sending out a signal, and how confident they felt in their answer. Exposure lasted for about 90 minutes. Of the original study members, results were only available for 44 case and 114 control volunteers.
What were the results of the study?
The study found that during the first test, when volunteers were told which signal was operating, electrosensitive volunteers experienced symptoms when both mobile signals were on, while the controls experienced more symptoms with the UMTS system.
During the blind tests, there was no increase in the number or severity of symptoms experienced with either mobile signal in either group, however there were reports of greater levels of arousal during the UMTS exposure in electrosensitive volunteers. The researchers found no difference in measures of blood pressure, heart rate or skin conductance throughout the tests.
What interpretations did the researchers draw?
The researchers conclude that GSM mobile signal exposure had no effect upon well being. Although there appeared to be heightened arousal level with UMTS exposure, they suggest that this may be due to the order in which the signals were emitted: a greater number of electrosensitive participants received UMTS exposure in session two when the greatest levels of arousal were experienced. They suspect that study participants may have had more natural anxiety in this early stage of the study.
What does the NHS Knowledge Service make of this study?
This study raises interesting points and appears to demonstrate the importance of carrying out blinding in scientific research tests.
However, caution is needed in interpreting these results.
- This small study cannot prove that mobile phone signals have no harmful effects on the individual or what these effects may be.
- This was also only short-term exposure; no conclusions can be drawn from these results on what would be experienced if an individual were to live near a telecommunications mast for a large number of years.
Care must be taken in dismissing the symptoms described by sensitive individuals as "all in the mind". The real psychological symptoms observed in the 'sensitive' individuals recruited to this study require further analysis even if the link between mobile phone masts has not been proven.