Academic literature on the topic 'Electromagnetic field emitter'

As mobile phone connections approach two billion worldwide and become steadily more available and affordable, demands for scientific studies on the effect of such EMFs on human functioning similarly increase. The current thesis systematically investigated the effects of acute mobile phone exposure on human brain activity and performance using an in-vivo approach. The research question comprised the following parts: First, is human neural function sensitive to acute mobile phone exposure? Second, if so, what processes are affected? Third, if so, do these neural changes affect gross measures of performance or behaviour? A review of the previous literature found that there was some, but not conclusive evidence that mobile phone exposure affects neural function and some aspects of human performance, and that the studies in question required replication with reliable and realistic dosimetry, double-blinding and additional technical tests to ensure that the experimental set-up was free of artefact contamination. A pilot study was conducted to provide an indication of possible future results, assist in the formation of hypotheses for the main study, and highlight what technical issues required attention before the main study could begin. Results of the pilot study indicated that EMFs emitted by GSM900 mobile phones may alter human brain activity during an auditory task, particularly in proximity to the phone. Both early sensory and later more cognitive ERP components were significantly altered during active compared to sham exposure. Results also suggested that mobile phone exposure may hinder human performance, with longer RTs during the active exposure relative to the sham exposure. However, due to the small sample size of the pilot investigation and questions remaining as to possible technical limitations of the study, these results were treated with caution and used primarily in the formation of future hypotheses for the larger experimental study. Subsequent technical tests provided improvement and validation of the experimental set-up and exposure delivery system, and ensured that future research would be free from such technical limitations. These tests included the characterisation of spectral emissions by the test phone; ensuring that EMFs emitted by the test phones would not interfere with, nor distort, data from the response pad or that processed by the electrode leads; determining whether electrode leads cause an increase or decrease in SAR; and examining the issue of experimenter interference. These tests enabled the conclusion that a positive finding from the large experimental trial would be due to the active exposure of the mobile phone, or in the case of a null finding, would not be due to insufficient or unreliable exposure. Applying the knowledge gained from these technical tests, the main study aimed to provide results of a definitive nature by employing a sample size of 120 sufficient statistical power to detect relatively subtle effects, and a stringent methodological design to account for past limitations. The main study also increased the scope of investigation beyond that achieved in previous research by including endpoints related to sensory processing (auditory and visual tasks), higher cognitive processing (cardsorting task), performance (reaction time and accuracy) and cortical activation (EEG alpha power). To increase this scope even further, within these tasks, the study used data from each scalp electrode and offered insights into the effect of laterality (ipsi- versus contralateral in relation to the exposure source), psychological arousal, perception of transmission, and between-subject factors such as age, gender, previous mobile phone use and hemisphere exposed (right versus left hemisphere exposure). The results of the main study suggested that acute exposure to GSM900 mobile phone significantly reduced levels of psychological arousal, particularly in relation to selfratings of Energy. Results also indicated that only minutes of active exposure can lead to enhanced alpha EEG activity during active exposure relative to sham exposure. Interestingly, this effect was found to be transient, decreasing below sham levels after ten minutes of active exposure and up until ten minutes after exposure cessation. These exposure-induced changes in EEG alpha power were here interpreted as representing an overall reduction in integrative brain function, possibly caused by the physiological response to neural interference or altered synaptic transmission. Acute exposure did not alter human brain activity in the form of the early sensory or later cognitive ERP responses during an auditory or visual task, or EEG synchronisation during a higher cognitive task. The findings also suggested that resultant behaviour, as indexed by RT and accuracy, is unaffected by exposure. Conversely, exploration into specific groups within the sample resulted in some interesting interactions, which raised the possibility that active mobile phone exposure may affect individuals differently as a function of age, gender and which hemisphere is exposed. Specifically, the auditory processing of older individuals was particularly vulnerable to the detrimental effects of mobile phone exposure compared to their younger counterparts. Results of the visual task suggested that the performance of females may also be particularly vulnerable to the detrimental effects of active exposure, compared to males. Overall, the present study has confirmed that there are mobile phone-related bioeffects at the low levels that mobile phones are permitted to operate at. Although various effects have been observed, there is no indication from the present results that cumulative effects or any health consequences exist as this was not the focus of the research. It is argued that future investigation into mobile phone-related bioeffects should apply more sophisticated methodologies to the investigation of acute exposure on EEG alpha power and higher cognitive functioning, as well as larger sample sizes and fewer carefully planned comparisons in order to detect small effects. Further investigation into exposure-induced effects on different groups according to age, gender and which hemisphere is exposed should also be a priority.

Thesis (PhD) - Swinburne University of Technology, Brain Sciences Institute, 2007.<br>Doctorate of Philosophy, Brain Sciences Institute, Swinburne University of Technology - 2007. Typescript. "April 2007".

The use of mobile phones is continually increasing throughout the world, with recent figures showing that there are currently more than 2 billion mobile phone users worldwide. However, despite the recognised benefits of the introduction and widespread use of mobile phone technologies, concerns regarding the potential health effects of exposure to the radiofrequency electromagnetic fields emitted by mobile phone handsets have similarly increased, leading to an increase in demand for scientific research to investigate the possibility of health effects related to the use of mobile phones. An increasing amount of radiofrequency bioeffects research related to mobile phone use has focussed on the possible effects of mobile phone exposure on human brain activity and function, particularly as the absorption of energy in the head and brain region is much higher than in other body regions, which is a direct result from the close proximity of the mobile phone to the head when in normal use. In particular, the use of sleep research has become a more widely used technique for assessing the possible effects of mobile phones on human health and wellbeing, and is particularly useful for providing important information in the establishment of possible radiofrequency bioeffects, especially in the investigation of potential changes in sleep architecture resulting from mobile phone use. A review of the previous literature showed that a number of studies have reported an increase in the electroencephalogram spectral power within the 8 � 14 Hz frequency range in both awake and sleep states following radiofrequency electromagnetic field exposure. In regards to sleep, the enhancements reported have not been entirely consistent, with some early studies failing to find an effect, while more recent studies have reported that the effect differs in terms of particular frequency range. However, in general the previous literature suggests that there is an effect of mobile phone emissions on the sleep electroencephalogram, particularly in the frequency range of sleep spindle activity. In addition to changes in spectral power, changes in other conventional sleep parameters and the production and secretion of melatonin have also been investigated, however, there has been little or no consistency in the findings of previous studies, with the majority of recent studies concluding that there is no influence of mobile phone radiofrequency fields on these parameters of sleep or melatonin. Following a detailed review of the previous research, the current study was developed with the aim to improve on previous methodological and statistical limitations, whilst also being the largest study to investigate mobile phone radiofrequency bioeffects on human sleep. The principle aims were thus to test for the immediate effects of mobile phone radiofrequency electromagnetic fields on human sleep architecture and the secretion of the pineal hormone, melatonin. The experiment included 50 participants who were randomly exposed to active and sham mobile phone exposure conditions (one week apart) for 30 minutes prior to a full night-time sleep episode. The experimental nights employed a randomised exposure schedule using a double-blind crossover design. Standard polysomnography was used to measure subsequent sleep, and in addition, participants were required to provide urine samples immediately following exposure and upon waking in the morning. A full dosimetric assessment of the exposure system was also performed in order to provide sufficient details of the exposure set-up used in the current thesis and to account for the lack of detailed dosimetric data provided in the majority of previous studies. The results of the current study suggest that acute exposure to a mobile phone prior to sleep significantly enhances electroencephalogram spectral power in the sleep spindle frequency range compared to the sham exposure condition. The current results also suggest that this mobile phone-induced enhancement in spectral power is largely transitory and does not linger throughout the night. Furthermore, a reduction in rapid eye movement sleep latency following mobile phone exposure was also found compared to the sham exposure, although interestingly, neither this change in rapid eye movement sleep latency or the enhancement in spectral power following mobile phone exposure, led to changes in the overall quality of sleep. Finally, the results regarding melatonin suggested that, overall, overnight melatonin secretion is unaffected by acute exposure to a mobile phone prior to sleep. In conclusion, the current study has confirmed that a short exposure to the radiofrequency electromagnetic fields emitted by a mobile phone handset immediately prior to sleep is sufficient to induce changes in brain activity in the initial part of sleep. The consequences or functional significance of this effect are currently unknown and it would be premature to draw conclusions about possible health consequences based on the findings of the current study.