Radiation literature survey

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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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This is an animal study that investigated the effects of mobile phone and Wi-Fi use on some hormones and oxidative stress levels. A total of 72 rats (32 pregnant at the start and subsequently yielded 40 offspring) were divided into four groups: 1 control group and 3 exposed groups to radiofrequency (RF) radiation at 900, 1800 and 2450 megahertz (MHz), at specific absorption rate (SAR) of 0.1 W/kg (25% higher than the exposure limit for members of the public), for 60 minutes per day for a total of 9 weeks. The authors found that RF may alter hormone concentrations and oxidative stress levels in pregnant rats and their offspring.

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This is a case-control study conducted in the UK to investigate the association between the extremely low frequency (ELF) magnetic fields (MF) from high-voltage underground cables and the risk of childhood cancer. A total of 55,525 children (cases) under the age of 15 diagnosed with childhood tumours in England and Wales were identified during the period 1962 – 2008. The cases were compared to a total of 116,815 controls matched for age, sex and the district of birth for their ELF MF exposure. The ELF MF exposure was calculated based on the distance between the nearest underground cables and the premises where the mother resided at child’s birth. The authors found no elevated risk of childhood leukaemia and no clear pattern of risks for other childhood cancers, with all levels of ELF MF exposure.

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For decades now, the question on whether ELF MF exposure is attributed to the risk of childhood leukaemia continues to be investigated. Based on some positive epidemiological findings between higher than normal MF and an increased risk in childhood leukaemia ELF MF was classified as “possibly carcinogenic for humans” in 2002 by the International Agency for Research on Cancer.

To date, the study by Bunch et al. is the largest epidemiological study on the effects of ELF MF exposure resulting from underground high voltage power lines. The study did not find any association between ELF MF exposure and childhood cancers. It is expected that homes near underground power lines will not have higher than normal MF.

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This is a cross-sectional study that investigated whether adverse expectations (nocebo effects) related to electromagnetic fields (EMF) are the cause to the ailments of people claiming to have electromagnetic hypersensitivity (EHS). Forty EHS individuals were interviewed (11 men and 29 women) about their symptoms. The study found that most participants had the health symptoms for a period of time before they made the connection between their ill symptoms and EMF exposure (usually through the media). The author was of the opinion that nocebo effects may reinforce the attribution to EMF exposure however they may not always be the cause of EHS.

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This animal study looked into the effects of ELF MF exposure on the melatonin levels in calves. Eight young calves were divided into two groups: control and exposed group. The experiment was done twice, one in summer and one in winter. For each experiment, four calves were exposed to ELF MF at the intensity of 0.39 – 0.41 microtesla (µT) which is around 250 times below the current international guidelines for public exposure (which is 200 µT), for 35 days, and saliva samples were taken regularly. It was found that in the exposed group the melatonin level was reduced in winter and increased in summer. The authors hypothesised that the ELF MF exposure may have a different effect on the melatonin level depending on the season.

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This is an animal study that investigated whether exposure to ELF MF results in adverse health effects (as revealed by a blood test). A total of 128 rats were randomly assigned into a sham group or exposed group. Exposure was at a frequency of 50 Hertz and at a MF of 100 µT (half the limit of current international guidelines for public exposure), for 20 hours a day, for three months. The analysis of the blood samples did not reveal any differences between the two groups. The authors concluded that ELF MF exposure does not affect the rats’ blood characteristics.

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This is a case-control study that investigated the association between electric shocks or ELF MF exposure and Amyotrophic Lateral Sclerosis (ALS). A total of 4,709 cases and 23,335 controls were included in the study. The exposures were assessed based on the occupations using job-exposure matrices. Overall, there were no associations between occupational ELF MF or electric shocks and ALS. For subjects less than 65 years old, electric shocks were associated with ALS (odds ratio (OR) of 1.22, 95% confidence interval, 95% CI = 1.03, 1.43). It was also found that for welders less than 65 years old, the OR was 1.52 (95% CI = 1.05, 2.21). The authors concluded that there is no overall higher risk of ALS in electrical occupations and provided only a weak support for association between electric shocks and ALS.

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This animal study investigated whether mobile phone use causes harm to the brains of juvenile rats, in order to relate the results to children and adolescents. Eighteen rats were divided into three groups: not exposed, sham-exposed and exposed to RF radiation. Exposure was at a frequency of 900 megahertz (MHz), for 1 hour per day, for 30 days at a specific absorption rate (SAR) of 0.024 Watts per kilogram (W/kg) which is 1.2% of the public exposure limit. The analysis on the rats’ brains extracted from the exposed group revealed a lower nerve cells count. The authors suggested that RF exposure may adversely affect the brain of children and adolescents.

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