Radiation literature survey

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This is a retrospective cohort study which investigated the association between radon and UV exposure and skin cancer. A total of 5.2 million people were included in the study, which contained a total of 2,989 skin cancer deaths primarily due to malignant melanoma. The individuals’ residential exposures to radon and UV were assessed using exposure prediction models which were based on environmental data. The study found that residential radon exposure increased the risk of skin cancer, when combined with UV or independently. The authors found that both radon and UV exposure are relevant risk factors for skin cancer.

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The strength of this study was its sample size – it used the famous Swiss National Cohort which consists of more than 5 million people and has been used for numerous studies.

The study assessed individual exposures to radon and UV based on modelled exposures at the place of residence of the subjects The study contained inherent disadvantages of this type of study design i.e. great potential for exposure misclassification as there are many behavioural factors that affect personal exposure to radon and UV compared to residential exposure. Nevertheless the exposure assessment was more convincing for radon compared to UV.

In conclusion, the methods employed were good for this type of study and were a better predictor of the radon skin cancer relationship compared to the UV skin cancer comparison.

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This is an Australian prospective cohort study that investigated the effect of wireless (mobile and cordless) phone use and cognitive function in children. A total of 412 children from 36 schools in Melbourne and Wollongong were followed for a period of up to 28 months. The information on socio-demographics and wireless phone use was obtained via questionnaires. The change in various cognitive outcomes (evaluated via computer-based tests) between the start of the study period and the follow-up at the end was assessed. The study found limited evidence that increased wireless phone use was associated with cognitive function.

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The World Health Organization (WHO) has previously identified in their radiofrequency (RF) research agenda that studies into children’s behavioural and neurological outcomes associated with RF electromagnetic fields (EMF) exposure are of high priority (http://whqlibdoc.who.int/publications/2010/9789241599948_eng.pdf?ua=1).  

ARPANSA recently published an RF research agenda, where it serves as an interim solution to identifying priority research needs for Australia, as the WHO’s 2010 research agenda has become dated. Prospective cohort studies of children and adolescents investigating exposure to RF EMF and various outcomes including cancer and behavioural and neurological disorders remain high in priority. The ARPANSA RF research agenda is available at Radiofrequency Electromagnetic Energy and Health: Research Needs.

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This is a cohort study which investigated any association between exposure to extremely low frequency (ELF) magnetic fields early in life and asthma in children. A total of 92,676 child and mother pairs were included in the study. The children’s exposures were estimated at the mothers’ residences during pregnancy and at the children’ residences from birth until diagnosis/end of follow up (estimations were based on distance from  transmission lines and transmission line configuration details).The study did not find any statistically significant results that indicated an increased risk of asthma in children exposed to different levels of ELF magnetic fields. The authors concluded that there is no association between ELF magnetic fields exposure and asthma in children.

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One of the major limitations of epidemiological studies investigating residential ELF magnetic fields exposure lies with the tiny proportion of study participants being exposed above the normal background level i.e. above .3 or .4 microtesla (µT). This leads to a low statistical power to reliably detect any association. ELF magnetic fields above .3 or .4 µT were shown by some epidemiological studies to be associated with childhood leukaemia – association that has not been established up until now. For example, the study by Sudan et al found that the proportion of subjects exposed above .2 µT was only 0.05%.

The Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) in its opinion on potential health effects of exposure to electromagnetic fields in 2015 reported that there were recent studies that found an increased risk of asthma in the offspring associated with exposure to ELF magnetic fields during pregnancy. One major study that found this was a prospective cohort study conducted by Li et al (2011). SCENIHR concluded that even though recent studies for the first time have shown an association between ELF magnetic fields exposure and asthma, the results need to be reproduced to evaluate their significance for risk assessment. It was interesting to note that the study by Sudan et al was designed to replicate the study by Li et al; however the study by Sudan et al did not reproduce the results found by Li et al.

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This is a case-control study which investigated the link between exposure to ionising radiation from natural sources and childhood leukaemia. A total of 2,700 cases (diagnosed during the period 2002-2007) and 30,000 controls were included in the study. The exposure to radon, gamma, and total radiation were estimated using environmental exposure data, based on the child’s municipality at time of diagnosis. Overall, the study did not find any association between childhood leukaemia and exposure to natural background radiation, hence providing no support to the hypothesis that residential exposure to natural background radiation increases the risk of childhood leukaemia.

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Commentary by ARPANSA:

This study by Demoury et al did not find an association between childhood leukaemia and exposure to natural background radiation, whereas two older studies by Kendall et al in Switzerland and Spycher et al in the UK both found an increased risk of childhood leukaemia at a dose of 1 millisievert per year  over 10 years or so. It should be noted that the study by Demoury et al did not rule out a slight association with gamma radiation at the time of birth – which is in line with the findings in the Swiss and UK studies.

All of these three studies are well conducted and are large enough to provide a statistically significant result however differences in the methodology are likely accounting for the difference in results. The two biggest methodological issues in all three studies were (a) the assessment of exposure which was based on residence estimation and not individual dosimetry, and was estimated differently in all three and (b) all three studies used retrospective registry information.

Since all three studies used registry information, other lifestyle, genetic or environmental factors (requiring interview to be determined) were not accounted for. Nevertheless the registry information eliminates the potential for recall bias. Bias due to unknown confounding factors is very unlikely to explain the entire observed effect.

In conclusion, there is currently mixed results on whether background radiation is associated with childhood leukaemia and further research is needed in this area.

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This paper reviewed some hypothesised mechanisms of how skin cancers may develop. There was a landmark paper published in 1977 that first hypothesised that melanoma was caused by intermittent solar ultraviolet (UV) exposure (brief episodes of exposure to high-intensity UV) and that non-melanoma skin cancers were caused by progressive accumulation of sun exposure. Taking into account the knowledge since 1977, the authors suggested that while the intermittent sun exposure is still relevant, they elaborated on a new hypothesis called the dual pathway hypothesis (i.e. sun exposure early in life combined with intermittent sun exposure) for melanoma skin cancers.

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In 1992 the International Agency for Research on Cancer (IARC) evaluated all the available evidence in relation to solar UV radiation and cancer. Based on “sufficient” evidence of carcinogenicity in humans and animals, IARC classified solar radiation as “carcinogenic to humans” (Class 1).

In 1994, the World Health Organization (WHO) conducted an in-depth review of the scientific literature concerning the effects of UV radiation exposure on human health and the environment.

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This human provocation study investigated whether exposure to negative media reports surrounding RF devices induce electromagnetic hypersensitivity (EHS). A total of 65 participants were randomly shown a video which contained either a negative report (promoted adverse health effects of RF) or a neutral report. They were subsequently given stimulus to their hands and were asked to rate the pain level, in both conditions: no exposure and sham-exposed. It was found that participants who were shown the negative report tended to perceive themselves as being more sensitive to EMF. The authors suggested that negative media reports on RF devices (such as those broadcasted on TV) can cause one to perceive normal somatosensory sensation as being more intense, which leads to the development of nocebo effects.

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This meta-analysis investigated the association between mobile phone use during pregnancy and behavioural problems in the offspring. Five cohorts from five different countries were included in the study, resulting in a total of 83,884 mother-child pairs. The information on mobile phone use was obtained via questionnaires – asked during pregnancy in three cohorts and asked when the children were seven years old in two cohorts. The children’s behaviour was analysed when their age was between four and seven years. For overall behavioural and emotional problems, no statistically significant association was found. There was an increased risk of hyperactivity/inattention problems with increased use of mobile phone during pregnancy (medium mobile phone users: odds ratio, OR = 1.11, 95% confidence intervals, 95% CI = 1.01 – 1.22; high users: OR = 1.28, 95% CI = 1.12, 1.48). The authors concluded that maternal mobile phone use during pregnancy may increase the risk of behavioural problems in the offspring.

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The 2015 review by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) on “Potential Health Effects of Exposure to Electromagnetic Fields” discussed epidemiological and animal studies on adverse developmental effects of radiofrequency (RF) fields. The SCENIHR review mentions that numerous animal studies have clearly shown that RF fields cause developmental effects at exposure levels that are sufficiently high to cause significant increase in core maternal temperature (greater than 1 degree Celsius). However the SCENIHR review mentions that there were no adverse effects on development from RF fields at non-thermal exposure levels, even with the inclusion of more recent human and animal data. The SCENIHR review concluded that the weight of the evidence is strong against an effect on development at low level RF, such as when using a mobile phone. The results reported by Birks et al need further investigation.

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This cohort study looked into whether exposure to ELF MF at the workplace causes central nervous system (CNS) disease. There were a total of 32,006 men eligible for the investigation that were followed during 1982-2010. The exposure to ELF MF was assessed via a job-exposure matrix. The CNS diseases investigated included dementia, motor neuron disease, Parkinson’s disease, multiple sclerosis and epilepsy. The study found a statistically significant association between dementia and high exposure to ELF MF of 1 microtesla and above (incidence rate ratio = 1.44, 95% CI = 1.20-1.73).

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This is a systematic review that aimed to investigate the association between Parkinson’s disease and some common exposures in the workplace. The investigation was mainly on exposure from pesticides but electromagnetic fields (EMF) were also included. The meta-analysis of a total of 10 studies relevant to occupational EMF exposure did not find any increased risk of the disease.

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This case-control study investigated the risk of preterm birth associated with living close to high voltage powerlines. A total of 285 women were included in the study, consisting of 135 cases (women with spontaneous preterm birth) and 150 controls (women with term birth). The exposure was assessed via the distance of the maternal home to the high voltage powerlines (exposed ≥ 600 meters, not exposed < 600 m). Spontaneous preterm birth and birth defect were associated with the mother living less than 600 meters from high voltage powerlines. The authors concluded that living close to high voltage powerlines may increase the risk of preterm birth.

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