Radiation literature survey

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This is a review of the literature on the studies that investigated the risk of brain tumours and mobile phone use. A total of 22 scientific papers were included in the review. The majority of the studies did not find an increased risk with mobile phone use. However some studies (such as INTERPHONE study and CERENAT study) showed increased risk of gliomas (which is the second most common type of brain tumour) among the heavy mobile phone users. The authors concluded that the evidence is so far inconsistent on gliomas and inconclusive on other brain tumour types.

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This case-control study investigated the association between exposure to extremely low frequency (ELF) magnetic fields (MF) and three types of childhood cancers (leukaemia, central nervous system tumour and malignant lymphoma). This study was an extension of an older study to include recent cases. A total of 1570 cases and 4341 controls were included in the present study (covering 1987-2003), for a grand total of 3277 cases and 9129 controls for the combined period of 1968-2003. The analyses on the three cancers combined revealed that for the group exposed to elevated level of MF (defined as 0.4 microtesla, µT or greater) the odds ratio (OR) was 0.88 (95% confidence interval, 95% CI = 0.32-2.42) in the present study and 1.63 (95% CI = 0.77-3.46) in the combined period. The authors concluded that the increased risk associated with elevated MF exposure found previously OR 5.72 (CI 1.40-23.36) could not be confirmed based on the present study.

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The study by Pederson et al includes only very small numbers of cases and controls who are exposed to elevated MF; there were only 11 cases and 19 controls that were exposed to elevated MF in the combined period of 35 years. The exposure to ELF MF in the study was assessed using the distance of the subject’s residence to electrical supply infrastructure. This method of exposure assessment may have misclassified the exposure status of the subjects in the study.

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This cross-sectional study investigated the association between RF radiation and the risk of type 2 diabetes mellitus. Two schools with a total of 159 students were included in the study. Both schools were about 200 metres from the mobile phone base stations (operating at a frequency of 925 MHz) and students were exposed for 6 hours daily, 5 days a week. The RF exposure was measured in one school to be 9.601 nW/cm² (around 0.002% of the public exposure limit), which was roughly 5 times higher than the level at the other school. Although the authors reported that the students at the school with higher RF exposure had a significantly higher incidence of type 2 diabetes mellitus, the parameter used to measure the disease was not very different between the two schools.

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This human provocation study looked into the effects of radiofrequency (RF) exposure on sleep quality. Thirty young male participants were subjected to three nights of each exposure condition: sham, GSM (900 megahertz, MHz), and WCDMA/UMTS (2 gigahertz, GHz). The exposure was for the whole night (8 hours), with the specific absorption rate (SAR) set to reach but not exceed 2 watts per kilogram (W/kg) which is the limit for general public exposure in the Australian RF Standard. In 90% of the subjects, one or more sleep parameters were significantly different during GSM or WCDMA/UMTS exposure when compared to the sham exposure. However there was no consistent pattern in sleep parameter changes among the subjects. The authors found that in about 30% of the subjects there was a prolonged period of one of the sleep stages (rapid eye movement sleep) during the RF exposure, although this result does not indicate a sleep disturbance.

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Studies investigating the effects of RF exposure on sleep quality have so far given inconsistent results. This study by Danker-Hopfe et al. also reviewed the main findings of many other studies done in this area, where the majority of the studies did not find any effects. Findings of some studies were conflicting with each other – two studies reported reduced sleep latency but one study reported prolonged sleep latency. A previous study by Danker-Hopfe et al. in 2010 did not find any effects on sleep quality (reported in June 2010’s literature report).

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This is a human provocation study that investigated whether RF exposure influences brain activity and ability to sustain attention. A total of 56 students participated in the study involving electroencephalographic recording and psychomotor testing whilst being exposed to Wi-Fi or sham. The exposure was at a frequency of 2.4 gigahertz (GHz), and a maximum peak SAR of around 15 mW/kg at the head region. This exposure level is around 0.75% of the general public exposure limit in the Australian RF Standard. The authors found that no effects on brain activity and attention were observed as a result of RF exposure.

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This is a cross-sectional study that investigated whether nocebo responses are responsible for the increases in health complaints surrounding the construction of high voltage power lines (HVPL). Questionnaires were distributed to residents in close proximity of HVPL (up to 500 metres away) and to residents living further away (500-2000 metres away). A total of 1254 responses were received in 4 stages: when the construction was carried out, construction completed but not yet operational, 2 months after operation, and 7 months after operation. The authors found that putting HVPL into operation can lead to subjective symptoms through stronger negative beliefs about the health risks, which is explainable by nocebo effects.

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This is a systematic review that investigated the association between tinnitus and exposure to electromagnetic fields (EMF), particularly in people who claim to have electromagnetic hypersensitivity (EHS). A total of 45 relevant studies were evaluated. Some studies reported significantly higher prevalence of tinnitus in EHS participants. One major study suggested that tinnitus is associated with intensive use of mobile phone for a prolonged period (4 years or more). However the rest of the major studies evaluated did not report any effects or any direct association between EMF exposure and tinnitus.

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Meta-analysis of epidemiological studies that investigated the association between extremely low frequency (ELF) electromagnetic fields (EMF) and cancer risk. A total of 42 case-control studies involving 13,259 cases and 100,882 controls were included. The overall analysis of the pooled data found that there is a small increased cancer risk (odds ratio, OR = 1.08; 95% confidence interval, 95% CI = 1.01-1.15). In subgroup analyses increased risks were shown in interview-based studies compared to measurement-based studies, in North American studies compared to European studies and residential studies compared to occupational studies. The authors concluded that there is an association between ELF EMF exposure and cancer.

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The study by Zhang et al is one of the first meta-analysis to include all of the eligible case-control studies on ELF EMF exposure and cancer. Although the authors found an overall statistically significant association, the association is very small. Furthermore the authors assign subjects as being exposed at lower exposure levels, which could account for the results. Another methodological problem with this paper is that it combines both occupational and residential studies for the overall result; although separate associations are also provided.

The overall evidence for an association between ELF magnetic field exposure and the risk of female breast cancer as well as adult brain cancer and leukaemia is weak and remains inadequate (see World Health Organization’s Environmental Health Criteria no. 238, http://www.who.int/entity/peh-emf/publications/Complet_DEC_2007.pdf). The exception is with leukaemia in children, the new epidemiological studies published after the WHO’s review are continuing to be consistent with earlier findings of a possible increased risk of childhood leukaemia with exposures higher than typically encountered by the public (Scientific Committee on Emerging and Newly Identified Health Risks). However, it is not known how magnetic fields could cause childhood leukaemia. In addition, other research including studies on cells and animals has not confirmed these results. On balance, the evidence related to childhood leukaemia is not strong.

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This animal study investigated whether the RF exposure, ringtone and vibration associated with mobile phone use results in anxiety-like behaviour and oxidative stress. A total of 25 rats were randomly divided into 5 groups: 1 group sham-exposed and 4 groups exposed to RF emitted from GSM mobile phones (at frequencies of 900/1800 MHz) with the phones’ ringing mode on silent, vibration, ringtone, and combination of vibration and ringtone. The exposure was for 10 minutes per day for 4 weeks. The authors found that the RF exposure or in combination with vibration and/or ringtone produced an effect on anxiety-like behaviour and oxidative stress in young rats.

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This animal study investigated whether the low-level exposure to ELF magnetic fields (MF) (alone and when combined with ionising radiation) has any effects on survival, growth and development of offspring during pregnancy and after birth. Mice were divided into 4 groups: sham-exposed, exposed to ELF-MF, exposed to X-rays (dose of 1 Gray), and exposed to both ELF-MF and X-rays. The ELF-MF exposure was at 50 Hz, 65 µT (32.5% of the public exposure limit from the current international guidelines), 24 hours/day for 30 days. The authors found that no effects were detected after continuous exposure to ELF-MF alone, whereas effects were observed with combined exposures to ELF-MF and X-rays.

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