Radiation literature survey

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This study was trying to examine the reliability of the incidence data from the Swedish Cancer Register. The incidence data from the Swedish National Inpatient Register (IPR) and Causes of Death Register (CDR) were studied and compared to the Cancer Register data for the time period 1998-2013. The authors comment that the Cancer Register may miss a number of cases, due to brain tumours of unknown type are either not reported to the Cancer Register or when reported they could potentially be classified as other brain cancer types, and also due to general decline of autopsies where diagnosis can be made at time of death. The authors concluded that the Swedish Cancer Register is not reliable to be used to dismiss results in epidemiological studies on the use of wireless phones and brain tumour risk.

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This in vitro study investigated the effects of ELF-MF exposure on the regulation of clock genes in the cell line. This cell line was exposed to ELF-MF at the frequency of 50 Hz, at a level of 0.1 millitesla (mT) which is at the public exposure guideline in Australia. The authors reported that the ELF-MF exposure caused some effects, mainly altering the expression of the clock genes that may affect the circadian rhythm. This study supported the hypothesis that ELF-MF may be able to affect circadian physiological process..

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This animal study examined whether microwave radiation causes any cognitive impairment and effects on the heat shock protein level (usually released when cells are in stress). Rats were either not exposed or exposed to microwave radiation at three different frequencies (900, 1800 and 2450 megaherts, MHz), for 2 hours per day, for 180 days. The specific absorption rate (SAR) used for the exposure was thousands of times below the Australian exposure limit. The authors found that there was a slight decline in cognitive function and an increase in the heat shock protein level.

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This animal study looked into the effects of radiofrequency (RF) radiation on the rat testicle. Rats were exposed to RF, at 900 MHz, for 1 hour a day, for 30 days at a level of around 6% of the Australian public exposure limit. The authors were of the opinion that exposure to low level RF can cause injury in testicular tissue.

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This animal study investigated whether exposure to extremely low frequency (ELF) magnetic fields (MF) affects the repair rate of DNA damage after ionising radiation (IR) exposure from X-ray. Pregnant mice were either exposed to ELF-MF only (at a level of 300 microtesla, µT which is three times the public exposure guideline in Australia), IR only (at a level of 100 milligray, mGy), and combination of both ELF-MF and IR. The authors concluded that ELF-MF exposure does not induce DNA damage nor does it affect the repair rate of DNA damage caused by IR exposure.

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This ecological study looked into whether the incidence of brain cancer in New Zealand increased in the 16-year period up to 2010. During that period there were 4,212 cases of malignant brain tumours that were diagnosed in people aged10 years or older. Overall there was a decrease in brain cancer during the period, except in females aged 30-49. There was a statistically significant increase of 2.98% in glioma at ages over 70 in the male group, which the authors suggested to be due to improved diagnostic technologies.

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Although ecological studies are limited in proving whether a certain risk factor causes disease they are useful to rapidly test a hypothesis using existing data sets.

In this study the popular hypothesis on whether mobile phone use is associated with brain cancer is tested in the New Zealand population.The study by Kim et al found an overall decrease in brain cancer incidence. This is not a surprise as many ecological studies done in other developed countries did not find increases in overall incidence of brain cancers, for example studies in Scandinavian countries (reported in December 2009), United States (reported in July 2010), and England (reported in January 2011).

It is however important to note that ecological studies such as the one done by Kim et al is highly unlikely to detect an effect if there is a long latency period with the brain cancer i.e. more than 10 to 15 years (if it were induced by mobile phone use).

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This is a case-control study that looked into the association between childhood leukaemia and exposure to ELF-MF. A total of 745 cases were matched to 1475 controls. The ELF-MF exposure was determined via measurements in the child’s bedroom. Analyses using arithmetic mean of the magnetic field readings found an odds ratio (OR) of 1.87 (95% CI = 1.04-3.34) for exposure within 0.1-0.2 µT; however the analyses for exposure of more than 0.2 µT did not find a statistically significant OR.

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This in vivo study investigated whether exposure to low level radiofrequency (RF) fields from mobile phones causes adverse health effects. The head region of the rats was exposed to at 900 megahertz (MHz) RF field (frequency used for GSM mobile phones), at power density level of 608 milliwatts per square metre (roughly one tenth of the public exposure limit), for 45 minutes. The authors suggested that a single 45-minute session of low level RF exposure may lead to a retarded learning and a deficit in spatial memory.

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This case-cohort study investigated the association between occupational exposures and Parkinson’s disease (PD). Over 58,000 men and over 62,000 women were followed for over 17 years, resulting in 402 male and 207 female PD deaths. Exposures to pesticides, solvents, metals, diesel motor emissions, electric shocks and extremely low frequency magnetic fields (ELF-MF) were included in the study. Elevated risk was reported for high exposure to ELF-MF (Hazard ratio = 1.54, 95% CI = 1.00-2.36) (the authors do not provide any information on what constitutes a high exposure). The authors conclude that the weight given to these findings is limited by the absence of a trend with either duration or cumulative exposure.

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Few studies have reported on a positive association between occupational exposure to ELF-MF and PD, but it is possible that electric shock is responsible for the association, as has been suggested for other neurodegenerative diseases especially Alzheimer’s disease.

Due to the small number of PD cases studied in this paper, any correlation between ELF-MF exposure and PD cannot be confidently linked. This is because PD is a chronic, but not a fatal disease so there is a strong suggestion that substantial under-reporting of PD on death certificates has occurred. Since the study relies on the information on death certificates to find the cases, under-reporting could reduce the power to detect associations. Limited number of high-exposed cases especially among women is another limitation of this study.

A report by the Scientific Committee on Emerging and Newly Identified Health Risks in 2013 found that there are few new epidemiological studies on neurodegenerative diseases and they did not provide convincing evidence of an increased risk of these diseases related to ELF-MF exposure. Whether exposure to ELF-MF affects the development or progression of neurodegenerative diseases remains unclear and further epidemiological and experimental studies are required.

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This in vivo study investigated the impact of melatonin treatment when exposure to microwave radiation occurs. Rats were exposed to a 900 MHz RF field, 160 volts per metre (roughly 1.5 times the occupational exposure limit), for 4 hours a day, for 20, 40 and 60 days. Rats were divided into four treatment groups (rats not exposed/control, rats treated with melatonin, rats exposed, and rats exposed and treated with melatonin). The treatments were examined for oxidative stress, as it is the key mechanism on how microwave causes tissue injury. Overall, the melatonin treatment led to a decrease in oxidative stress.

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