Radiation literature survey

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This statement by the International Commission on Non-ionizing Radiation Protection (ICNIRP) provides information on areas where further research is needed on exposure to extremely low frequency (ELF) electric and magnetic fields (EMF) and health. Specific areas where future research should focus on as recommended by ICNIRP include neurodegenerative disorders, pain perception, childhood leukemia, ELF EMF dosimetry, and the possible mechanisms by which ELF EMF can cause adverse health effects. The paper also provides guidance to researchers on how to conduct research to fill these gaps.  

GAPS IN KNOWLEDGE RELEVANT TO THE “GUIDELINES FOR LIMITING EXPOSURE TO TIME-VARYING ELECTRIC AND MAGNETIC FIELDS (1 HZ–100 KHZ)”

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Power lines and other electricity supply infrastructure, such as transformers and substations, as well as other electrical sources such as electrical wiring and common appliances produce ELF EMF. For further information on ELF EMF and health, see the ARPANSA fact sheet: Electricity and health. The scientific evidence does not establish that exposure to ELF EMF found around the home, the office or near power lines and other electrical sources is a hazard to human health. However, it is important to continue research in this area and ARPANSA supports ICNIRP’s recommendations for future research.

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This cohort study investigated the risk of central nervous system (CNS) cancers among the atomic bomb survivors of Hiroshima and Nagasaki based on their estimated radiation exposure. Between 1958 and 2009, there was 285 cases of CNS cancers out of a cohort of 105,444 atomic bomb survivors with radiation dose estimates. The study examined the risk of these cancers as excess relative risk (ERR) per gray (Gy) (ERR/Gy). The authors reported ERR/Gy for glioma as 1.67 (95% confidence interval (CI) 0.12 to 5.26), for meningioma 1.82 (95% CI: 0.51 to 4.30), for schwannoma 1.45 (95% CI − 0.01 to 4.97), and for all CNS tumours combined 1.40 (95% CI: 0.61 to 2.57). Further, the authors reported a trend of increasing rates of CNS tumours with increased radiation exposure, with an apparent linear dose response. The authors concluded that the radiation exposure from the atomic bombs is associated with elevated risks of CNS tumours in general, and was significant for glioma and meningioma. There was a higher but non-significant association with schwannoma. 

Radiation risk of central nervous system tumors in the Life Span Study of atomic bomb survivors, 1958–2009

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The study reported a significant association with CNS tumours. However, the results also highlight the difficulty of examining the risk of radiation exposure at low levels, especially when examining the occurrence of rare diseases such as CNS tumours. Interestingly, in this study the unexposed control group was reported to have a higher rate of CNS cancers overall than that of the exposed groups with assigned dose of less than 1 Gy. The study attempts to show that at low radiation doses there is still a linear dose response; however, the limitations and inconsistencies in this study prevent this conclusion. Overall, the results of this study are unclear at low levels. This is consistent with the position held by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) that states at low levels (less than 100 milligray) the possible increased risk of cancer from radiation exposure is uncertain (UNSCEAR, 2017).

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This meta-analysis examined the possible link between parental occupational exposure to extremely low frequency magnetic fields (ELF MF) and the risk of childhood leukaemia in their children. The study considered 11 case-control studies, which when combined included 9723 cases of childhood leukaemia and 17099 controls. Parents had their occupational exposure to ELF MF estimated using a job-exposure matrix. The study found no increased risk of either acute lymphoblastic leukaemia or acute myeloid leukaemia at any exposure level of the parents. For maternal exposure during pregnancy of greater than 0.2 microtesla the odds ratios (OR) for their offspring developing acute lymphoblastic leukaemia was OR 1.00 (95% confidence interval (CI) 0.89 to 1.12) and for acute myeloid leukaemia OR 0.85 (95% CI 0.61 to 1.16). The authors concluded that this study provided no evidence of an association between parental occupational exposure to ELF MF and childhood leukaemia.

Parental occupational exposure to low-frequency magnetic fields and risk of leukaemia in the offspring: findings from the Childhood Leukaemia International Consortium (CLIC)

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The findings of this meta-analysis are consistent with a previous study by (Reid et al, 2011) who also found no increased risk of acute lymphoblastic leukaemia with parental occupational exposure to ELF MF. The international guidelines for exposure to ELF MF set by the International Commission on Non-ionizing Radiation Protection set exposure limits to protect the public from all known established risks of exposure to ELF MFs.

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The US Food and Drug Administration (FDA) recently published a review examining the possible effect of radiofrequency electromagnetic fields (RF EMF) on tumorigenesis.  The review examined 37 in vivo and 69 epidemiological papers published between 2008 and 2018 and also reviewed the National Toxicology Program (NTP) 2018 reports on RF exposure to rats and mice. The review concluded that, based on the evidence from the in vivo studies, including the NTP study, that there is no clear evidence that RF EMF has any effect on tumorigenesis. The review also reported a number of limitations from the in vivo studies including lack of animal temperature assessment and issues with the methods, sample handling and sample evaluation. The review further states that due to the limitations of the in vivo studies they cannot be used to draw conclusions on the impact of low powered RF EMF on humans. Further, the review discussed some of the inherent limitations in epidemiological studies including accurate exposure assessment and recall bias. Based on the epidemiological evidence the FDA review concluded there was no causal association between RF EMF exposure and tumorigenesis. 

Review of Published Literature between 2008 and 2018 of Relevance to Radiofrequency Radiation and Cancer

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This review by the FDA contributes to our understanding of the evidence of RF EMF exposure and health. It demonstrates the importance of considering the totality of evidence and understanding that methodological limitations affect the outcomes of scientific reviews. The timing of this review is particular topical as there is currently some heightened public concern regarding RF EMF and health with a particular focus on the roll out of the 5G telecommunications network. Other health agencies such as the World Health Organisation and the International Commission on Non-ionizing Radiation Protection have previously considered the possible health effects of RF EMF exposure and have reached conclusions similar to those in the FDA review. In Australia, the ARPANSA RF exposure standard sets limits to protect the public and workers from any harmful exposure to RF EMF. This standard is based on scientific research that shows the levels at which harmful effects occur and it sets limits, based on international guidelines, well below these harmful levels. The standard is designed to protect people of all ages and health status against all known adverse health effects from exposure to RF EMF.

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This study examined the effects radiofrequency electromagnetic fields (RF EMF) had on mice sperm. Mice received a whole-body RF exposure at 905 MHz with a specific absorption rate (SAR) of 2.2 W/Kg 12 hours a day for 1, 3 or 5 weeks. The study reported statistically significant decreases in sperm vitality and motility. Further, the study reported statistically significant increases in sperm mitochondrial reactive oxygen species and oxidative DNA damage. There were no changes reported in the fertility of the RF EMF treated mice. The authors concluded that sustained whole-body RF EMF is capable of inducing oxidative damage in sperm DNA.

Whole-body exposures to radiofrequency-electromagnetic energy can cause DNA damage in mouse spermatozoa via an oxidative mechanism

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This study exposed mice to very high levels of RF EMF. The public whole-body average SAR limit is 0.08 W/kg. This means the study exposed these mice to RF EMF that was over 27 times higher than the human public exposure limit. The study did not investigate the effect of heat stress or measure the temperature of the exposed mice. Another study investigating the effect of heat stress on fertility of mice reported similar results on sperm (Pérez‐Crespo et al, 2008). This indicates that the reported results likely occurred as a result of heating rather than being a sub-thermal effect. The ARPANSA radiofrequency exposure standard RPS3 gives limits for exposure that protect against any known biological effects. The only established effect of exposure is heating of biological tissue. The limits set for both public and occupational exposure are many times below the level where any measurable heating occurs, ensuring a large degree of conservatism within the standard.

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This population-based case-control study compared mobile phone use with the incidence of thyroid cancer diagnosed between 2010 and 2011 in Connecticut. The study included 440 cases of histologically confirmed incident thyroid cancers and 460 controls, with genotyping information for 823 single nucleotide polymorphisms (SNPs) in 176 DNA genes. All participants, including cases and controls, were interviewed using a standardized questionnaire to collect information on mobile phone use and the responses were used to classify cases and controls as users or non-users. Blood samples were provided for DNA analysis. The authors reported that the study found a statistically significant association between cell phone use and thyroid cancer for certain SNPs, implying a genetic susceptibility to thyroid cancer due to mobile phone use.

Genetic susceptibility may modify the association between cell phone use and thyroid cancer: A population-based case-control study in Connecticut

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This study built upon a previous study by the same authors (Lou et al, 2019) that found no association between mobile phone use and thyroid cancer in the same study group. One of the advantages of using a study group within the period 2010-2011 was that it is much easier to separate mobile phone users from non-mobile phone users. A disadvantage of using this study group was that the exposure data had to be gathered through surveying the participants. The information required was from a point in the distant past where recall bias may effect some of the results. The control group consisted of a higher proportion of males to females than the case group. This may have significant implications on the reliability of the results due to the higher occurrence of thyroid cancer in of woman. Further, mobile phones were not the only exposures to radio waves during the time of exposure assessment. A good example of this was the widespread use of cordless phones which are used in the same manner (held to the head) and have a similar level of exposure.

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The French Agency for Food, Environmental and Occupational Health & Safety (ANSES) produced a report assessing the risks associated with the use of Light Emitting Diodes (LEDs). The report also provided recommendations aimed at better protection of human health and the environment. LED lighting can be found in all aspects of modern society including personal devices with visual displays (e.g. phones and tablets), toys, car lights and outdoor and house lighting systems. The ANSES assessed evidence of whether the blue light content and temporal light modulation (flickering) properties of LEDs could increase the risk of potential health effects of this lighting source. The opinion focused on the major risks to human health and biodiversity of fauna and flora. 

The report concluded that there was some evidence that LEDs, particularly types rich in blue light, may affect both circadian rhythm and diseases of the eye. However, this evidence is not strong enough to calculate the level of risk. Little research has been done on the effects of modulation and there is limited evidence of symptoms such as migraines and epileptic attacks. The research on biodiversity was limited and relied on studies of all artificial lighting, not specifically LEDs. There was some evidence that lighting could affect biodiversity, however, it was not clear to what extent lighting is associated with any reported effects, with other important confounding factors such as pollution, habitat reduction, climate change and environmental overexploitation needing to be considered.

ANSES opinion on the potential risk of LEDs on the health of humans and fauna and flora

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While there is research showing potential health effects of exposure to LED lighting, it is not clear if the impacts are from the effect of exposure to the light or other factors. This is particularly evident with the potential impact of blue light on the circadian rhythm. Research indicates that blue light exposure from phones and tablets in the evening can affect sleep quality; however, it is not clear if this is a result of the activity being carried out or the blue light exposure. The Scientific Committee on Health, Environmental and Emerging Risks (SCHEER, 2018) had recently reviewed the evidence on the effects of LEDs on human health. ARAPNSA also reviewed the SCHEER opinion as part of our radiation literature survey in 2018. SCHEER concluded that the available scientific research does not support an association between LEDs and a health risk to the eye or skin. However, in common with the ANSES report, disruption to circadian rhythm was identified as a potential effect. Distraction and other optical phenomena (e.g. phantom array effect) from LEDs incorporating temporal light modulation was also identified as an indirect risk factor for harm in both the ANSES and SCHEER reports.

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This was a retrospective cohort study that examined the association between ultraviolet radiation (UVR) and basal cell carcinoma (BCC) The study followed 63,912 white cancer-free US radiologic technologists with known ultraviolet exposure (irradiance at up to 5 residential locations) for 5–22 years. 2151 technologists reported incident primary BCC within the study period. The authors reported that the absolute risk of BCC increased with increased cumulative UVR exposure. The authors also reported that the relative risk showed substantial variation with time after exposure and age at exposure, so that risk is highest for the period 10–14 years after UVR exposure and for those exposed under the age of 25. Some limitations described by the authors in the study included that the BCC incidence was self-reported, however, a large number of these were verified through medical records. Also, residency used for exposure assessment was self-reported. Assumptions were made that this cohort of workers spent a large proportion of their time indoors due to their profession and could not take into account individual behaviour such as excessive outdoor activity and UVR exposure received on holidays.

US study adds weight to increased risk of basal cell skin cancer from exposure to solar UV radiation

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Despite some of the limitations described by the authors, this study added to the body of evidence that UVR exposure is a causal factor in the development of BCC. Evidence for the association between UVR exposure and the development of other skin cancer types such as squamous cell carcinoma and melanoma has been clearer in the body of scientific evidence. This large study strengthens the evidence of an increase in BBC with increasing cumulative UVR exposure. The results support the advice from both ARPANSA and Cancer Council Australia about limiting UV exposure and applying sun protection measures.

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This meta-analysis examined 225 studies consisting of human, cellular and animal experiments specifically focussing on genetic damage from exposure to radiofrequency (RF) electromagnetic energy. The meta-analysis assessed the quality of the studies by the presence or absence of four different parameters; blinding, adequately described dosimetry, positive controls and sham-exposed controls. The authors compared the reported results of each study against the assessed level of quality of these factors within the study. It was reported that studies with a high degree of quality in these parameters reported fewer, if any, effects from exposure to radio waves. Further, the authors observed that studies that reported no significant change in genetic damage of cells exposed to RF incorporated more quality control parameters into their experiments. Conversely, studies that reported increased damage in cells exposed to RF used fewer quality control parameters. The authors concluded that the use of quality control measures within experimental design are extremely important in order to provide a meaningful evaluation of any potential health risk from RF exposure.

Comprehensive Review of Quality of Publications and Meta-analysis of Genetic Damage in Mammalian Cells Exposed to Non-Ionizing Radiofrequency Fields

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This meta-analysis demonstrates the importance of evaluating evidence based on the quality of the methods used in studies while considering the reported biological and health effects.  This underlying principle of evidence evaluation to assess its strength is particularly topical with the current roll-out of the next generation of mobile telecommunications technology, 5G. Exposure to RF remains one of the most high profile public health concerns and also one of the most highly researched environmental agents in biomedical research. ARPANSA’s RF exposure standard sets limits based on the body of scientific evidence available and is designed to protect against the known harmful effects of RF exposure. The study by Vijayalaxmi and Prihoda TJ demonstrates the considerations the scientific community make when assessing the evidence for harm from exposure to RF. ARPANSA and other bodies such as the World Health Organisation and the International Commission on Non-ionzing Radiation Protection consider all studies in the assessment of their health advice concerning RF exposure. There is also an ARPANSA factsheet about how we assess scientific evidence (link). Based on evaluations for these organisations, and consistent with the conclusions of Vijayalaxmi et al, there is no established evidence of harmful effects from exposure to low-level RF exposure below the limits in the ARPANSA standard.

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This survey that examined the occurrence of eye injuries caused by hand held lasers in Canada. Questionnaires developed by Health Canada were sent to optometrists and ophthalmologists surveying the cases of eye injuries from hand held lasers. Responses from the survey indicated that there were 318 eye injuries caused by hand held lasers between 2014 and 2017. Of these injuries, 77 were minor to severe cases of vision loss and 59 were classified as retinal damage. There was a higher prevalence of eye injuries for males (82.5%) than females (14.0%). Injuries were also reported to occur more often due to the actions of another person (67.6%) rather than self-exposure (26.1%). The authors concluded that the results provided insights into the potential prevalence of injuries from exposures to handheld laser devices in Canada. However, these results were not nationally representative due to the low survey response rate (23.1% and 12.7% for optometrists and ophthalmologists, respectively) and other unknown factors. These included potential over-reporting by duplication from the two responding professional groups, eye injuries from other causes and reported exposures not leading to injuries.

Survey of reported eye injuries from handheld laser devices in Canada

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In Australia, all hand held laser pointers available to the public are restricted to an accessible emission limit (AEL) of a Class 2 laser. This means they must have a power output of less than 1 milliwatt (mW). Lasers with an output below this limit are considered a low hazard. Unfortunately, Australian studies have shown that handheld laser pointers available to the public are not always labelled correctly and may emit energy at harmful levels. In one study, the majority of laser pointers tested failed to meet the output restriction with outputs well above 1 mW. (Wheatley, 2013). ARPANSA provides advice on laser safety on its website to promote risk awareness and assist in responsible use of handheld laser products (link).