Radiation literature survey

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This is a systematic review of eight epidemiological studies investigating the association between physiotherapists’ occupational exposure to radiofrequency (RF) electromagnetic fields from shortwave and microwave diathermy devices and adverse pregnancy outcomes. The reproductive outcomes analysed included: spontaneous abortion, delayed time to pregnancy of more than 6 months, altered gender ratio, low birth weight, still birth and congenital malformations in the physiotherapists’ offspring. The authors identified that the lack of data on the intensity and duration of RF exposure and the distances to diathermy devices, to be the major flaw in most of the reviewed studies. The authors concluded that the findings of the reviewed studies for adverse reproductive outcomes are not consistent enough to draw a causal relationship with RF exposure from diathermy devices and that further research is warranted.

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This in vivo study investigated whether perinatal (immediately before and after birth) exposure to ELF magnetic fields is associated with autism spectrum disorders (ASD). In the study male mice were either exposed or sham-exposed to a 1 mT 50 Hz magnetic field continuously during the last week of gestation and for 7 days after delivery. The exposed mice demonstrated reduced social interaction. The authors conclude that these results are supportive of a causal link between exposure to ELF and ASD.

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This case-control study investigated whether occupational exposure to ELF magnetic fields and electrical shocks are related to mortality from amyotrophic lateral sclerosis (ALS). In the study the occupational exposure to ELF magnetic fields and electrical shocks was compared between 5,886 cases (that died of ALS between 1991 and 1999) and 57,667 controls. Exposure to ELF magnetic fields and electrical shocks was assessed via the same JEM used by van der Mark et al. There was a statistically significant positive association between occupational magnetic fields greater than 0.3 µT and ALS mortality (odds ratio, OR = 1.09, 95% confidence interval, CI = 1.00-1.19). There was a statistically significant protective effect between electrical shocks and ALS mortality (OR = 0.73, 95% CI = 0.67-0.79). The authors report that ELF magnetic fields and electrical shocks are inversely related to ALS mortality.

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This case-control study investigated whether occupational exposure to ELF magnetic fields and electrical shocks are related to Parkinson’s disease. In the study the occupational exposure to ELF magnetic fields and electrical shocks was compared between 444 cases of Parkinson’s disease (diagnosed between 2006 and 2011) and 876 controls. Exposure to ELF magnetic fields and electrical shocks was assessed via a JEM. The authors report no association between ELF magnetic fields and electrical shocks and Parkinson’s disease.

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This is a case-control study investigating whether occupational exposure to extremely low frequency (ELF) magnetic fields is associated with brain tumours. In the study the occupational exposure to ELF magnetic fields was compared between 3,761 cases of brain tumour (1,939 glioma, 1,822 meningioma) diagnosed between 2000‑2004 and 5,404 controls. Exposure to ELF magnetic fields was assessed using a job-exposure matrix (JEM). There was no association between lifetime cumulative ELF exposure and glioma or meningioma. However, there was a positive association between cumulative exposure to ELF magnetic fields 1‑4 years prior to the diagnosis date and glioma (odds ratio (OR) 1.67, 95% confidence interval (CI) 1.36-2.07). The authors conclude that the results showed a positive association between occupational exposure to ELF magnetic fields in the recent past and glioma.

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In 2002, the International Agency for Research on Cancer (IARC) classified ELF magnetic fields as “possibly carcinogenic to humans” (http://monographs.iarc.fr/ENG/Monographs/vol80/volume80.pdf). The classification was based on “limited” epidemiological evidence for an association between prolonged exposure to higher than normal residential ELF magnetic fields and childhood leukaemia. However, this association is not supported by laboratory or animal studies and no credible theoretical mechanism has been proposed.

Subsequent to the IARC classification a number of epidemiological studies have investigated whether occupational exposure to ELF magnetic fields is associated with adult cancers and in particular breast cancer, leukaemia and brain tumours. Results from these studies have been largely inconsistent. In 2007 the World Health Organization assessed the evidence and found that overall the evidence for an association between occupational exposure to ELF magnetic fields and cancer remains inadequate
(www.who.int/peh-emf/publications/Complet_DEC_2007.pdf).

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This case-control study investigated whether living close to high voltage power lines is associated with childhood cancer. The study compared the residential distance to high voltage power lines between 53,515 children diagnosed with cancer between 1962 and 2008 (the cases), and 66,204 matched controls. The risk for leukaemia when living within 200 m of a power line compared to living more than 1000 m away was higher in the 1960s (odds ratio, OR, 4.5, 95% confidence interval, CI, 0.97 – 20.83) compared to the 2000s (OR 0.71, 95% CI 0.49‑1.03). The authors conclude that the declining risk for childhood leukaemia over time is unlikely to arise from any physical effect of the power lines (such as exposure to electric and magnetic fields) and is more likely to be the result of changing population characteristics among those living near power lines.

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This in vivo study investigated whether exposure to RF EMF emitted by mobile phones affects auditory function by altering the neurotransmitter glycine. In the study rats were exposed to a 835 MHz RF signal at a specific absorption rate of 4 W/kg or sham for three months. The authors report differences in the glycine activity between the exposed and non-exposed rats which are indicative of auditory dysfunction.

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This is a report by researchers from the Swedish Radiation Safety Authority about an RF measurement programme conducted in rural, urban and city areas of Sweden. Measurements were conducted from a moving car (travelling at no more than 30 km/h) and covered the frequency range used by broadcast television and radio services as well as mobile phone networks. The median power density was found to rise with increasing population density being 16 microwatts per square meter (µW/m²) in rural areas, 270 µW/m² for urban and 2400 µW/m² in the cities. All measurement values were found to be well below the general public exposure limits of the guidelines (PDF 526kb) published by the International Commission on Non-Ionizing Radiation Protection. In each of the three settings the main contributor to RF exposures was found to be mobile phone base stations.

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This case-control study investigated the association between mobile phone use and brain tumours in adults. The study compared mobile phone use between 447 cases of brain tumour (253 glioma and 194 meningioma) that were diagnosed between 2004-2006 and 892 matched controls. There was no statistically significant association between regular phone use and brain tumour. However, the authors found statistically significant positive associations for heavy use, when considering life-long cumulative call duration of more than 896 hours (odds ratio, OR=2.89; 95% confidence interval, CI 1.41 to 5.93 for glioma and OR=2.57; 95% CI 1.02 to 6.44 for meningioma), and when considering more than 18,360 number of calls for glioma (OR=2.10; 95% CI 1.03 to 4.31). The authors conclude that these results support other findings concerning a possible association between heavy mobile phone use and brain tumours.

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The INTERPHONE project, which is coordinated by the International Agency for Research on Cancer (IARC), is a multi-national series of case-control studies (from 13 different countries including Australia) testing whether using mobile phones is associated with an increased risk of various cancers in the head and neck. The INTERPHONE studies were conducted using the same methods to enable the data to be pooled for analysis.

A pooled analysis of the INTERPHONE studies for malignant brain tumours (glioma and meningioma) showed no overall association (INTERPHONE Study Group, 2010 (PDF 187kb). There were suggestions of an association (most pronounced for glioma) in the group representing individuals with the highest cumulative call time. The authors note that limitations of the methodology prevent conclusions of causality being drawn from these observations.

In May 2011 IARC assessed the possible carcinogenicity of radiofrequency electromagnetic fields (RF-EMF). Based on positive associations found in INTERPHONE and some other epidemiological studies between glioma and acoustic neuroma and exposure to RF-EMF from wireless phones (mobile and cordless phones) IARC has classified RF EMF as “possibly carcinogenic to humans” (also known as Group 2B carcinogen) (see June 2011 report). The classification by IARC does not provide estimates of what risk of cancer might by posed by any given level of exposure to RF fields. An assessment of this and other possible health effects is currently being conducted by the World Health Organization.

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This review describes the epidemiological evidence on glioma including the incidence of the disease and possible risk factors. Glioblastoma, the most common type of glioma has an age-adjusted incidence rate in Australia of 3.4 annual cases per 100,000 people. Exposure to high levels of ionising radiation has been shown to increase the risk of glioma. The authors mention that the potential influence of mobile phone use has also been examined with inconclusive results.

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