Do magnetic fields cause increased risk of childhood leukemia via melatonin disruption?

Melatonin Levels and Low-Frequency Magnetic Fields in Humans and Rats: New Insights From a Bayesian Logistic Regression

The present analysis revisits the impact of extremely low-frequency magnetic fields (ELF-MF) on melatonin (MLT) levels in human and rat subjects using both a parametric and non-parametric approach. In this analysis, we use 62 studies from review articles. The parametric approach consists of a Bayesian logistic regression (LR) analysis and the non-parametric approach consists of a Support Vector analysis, both of which are robust against spurious/false results. Both approaches reveal a unique well-ordered pattern, and show that human and rat studies are consistent with each other once the MF strength is restricted to cover the same range (with B ≲ 50 μT). In addition, the data reveal that chronic exposure (longer than ∼22 days) to ELF-MF appears to decrease MLT levels only when the MF strength is below a threshold of ~30 μT ( log B thr [ μ T ] = 1 . 4 - 0 . 4 + 0 . 7 ), i.e., when the man-made ELF-MF intensity is below that of the static geomagnetic field. Studies reporting an association between ELF-MF and changes to MLT levels and the opposite (no association with ELF-MF) can be reconciled under a single framework. Bioelectromagnetics. 2019;40:539-552. © 2019 Bioelectromagnetics Society.

Role of designed Bio-Geometrical forms in antagonizing neurobehavioral burden of Wi-Fi radiation: Evidence-based experimental study

This study investigated the impact of Wi-Fi signals exposure on cognitive function and its relevant brain biomarkers and the possible role of designed Bio-Geometrical forms in restoring the neurobehavioral alterations resulting from the exposure to the emerging radiation.Rats were assigned into 3 groups; Gp I control group (away from exposure to radiation); Gp II, III were exposed to wireless router signals for 24 h for 6 months and Gp III was protected by a set of designed BioGeometrical shapes. Animals were tested for spatial memory, anxiety and emotionality in addition to the related neurotransmitters (dopamine, serotonin and acetylcholine) in different brain areas. Melatonin, Heat Shock Protein (HSP-70) and acetylcholine esterase (AchE) were also measured in various brain regions and histopathological examination was carried out as well. Wi-Fi radiation exposed group showed elevated anxiety level and impaired spatial memory. Moreover, significant decline in dopamine, serotonin and acetylcholine levels in the investigated brain areas has been recorded. Melatonin levels were decreased in the cortex, striatum and hippocampus while HSP-70 was depleted in the cortex only. Using Bio-Geometrical forms along with Wi-Fi exposure could combat the burden of Wi-Fi radiation. This was evidenced by the recovery of the anxiety level and the improvement of memory task. In addition, the presence of Bio-Geometrical shapes could retrieve dopamine, serotonin and acetylcholine as well as melatonin and HSP-70 levels This study provides solid foundation for the potential use of Bio-Geometrical shapes to modify the insult of Wi-Fi radiation on brain function and structure.

Melatonin: does it have utility in the treatment of haematological neoplasms?

Melatonin, discovered in 1958 in the bovine pineal tissue, is an indoleamine that modulates circadian rhythms and has a wide variety of other functions. Haematological neoplasms are the leading cause of death in children and adolescents throughout the world. Research has demonstrated that melatonin is a low-toxicity protective molecule against experimental haematological neoplasms, but the mechanisms remain poorly defined. Here, we provide an introduction to haematological neoplasms and melatonin, especially as they relate to the actions of melatonin on haematological carcinogenesis. Secondly, we summarize what is known about the mechanisms of action of melatonin in the haematological system, including its pro-apoptotic, pro-oxidative, anti-proliferative and immunomodulatory actions. Thirdly, we discuss the advantages of melatonin in combination with other drugs against haematological malignancy, as well as its other benefits on the haematological system. Finally, we summarize the findings that are contrary to the suppressive effects of melatonin on cancers of haematological origin. We hope that this information will be helpful in the design of studies related to the therapeutic efficacy of melatonin in haematological neoplasms. LINKED ARTICLES: This article is part of a themed section on Recent Developments in Research of Melatonin and its Potential Therapeutic Applications. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.16/issuetoc.

Effect of exposure to extremely low frequency magnetic fields on melatonin levels in calves is seasonally dependent

The question of health effects of extremely low frequency (50/60 Hz) magnetic fields (ELFMF) has been widely discussed, but the mechanisms of interaction of these fields with biological systems for intensities relevant to human and animal exposure are still under question. The melatonin (MLT) hypothesis suggests that exposure to ELFMF might decrease MLT production thereby promoting cancerogenesis. So far, most studies of MLT secretion under exposure to ELFMF reported negative or inconsistent results. Here, we measured salivary MLT in 1–2 months old cattle calves exposed to 50 Hz-MF in the hundreds of nT-range. We found an inhibitory effect of the ELFMF upon MLT secretion in winter (in accordance with the MLT hypothesis). In contrast, in summer, MLT concentration was increased by ELFMF exposure (contrary to the MLT hypothesis). The inhibitory effect in winter was much stronger than the positive effect in summer. We hypothesize that this season-dependent effect upon MLT synthesis might by mediated by an effect of ELFMF upon the serotonin metabolism and conclude that future tests of ELFMF effects should also measure serotonin levels and consider association with the seasonal effects (photoperiod or temperature) during the exposure.

Occupational EMF exposure from radar at X and Ku frequency band and plasma catecholamine levels

Workers in certain occupations such as the military may be exposed to technical radiofrequency radiation exposure above current limits, which may pose a health risk. The present investigation intended to find the effect of chronic electromagnetic field (EMF) exposure from radar on plasma catecholamines in the military workforce. In the study, 166 male personnel selected randomly were categorized into three groups: control (n = 68), exposure group-I (X-band, 8-12 GHz, n = 40), and exposure group-II (Ku-band, 12.5-18 GHz, n = 58). The three clusters were further divided into two groups according to their years of service (YOS) (up to 9 years and ≥10 years) to study the effect of years of radar exposure. Enzyme immunoassay was employed to assess catecholamine concentrations. EMF levels were recorded at different occupational distances from radar. Significant adrenaline diminution was registered in exposure group-II with no significant difference in exposure group-I when both groups were weighed against control. Nor-adrenaline and dopamine levels did not vary significantly in both exposure groups when compared to controls. Exposure in terms of YOS also did not yield any significant alteration in any of the catecholamines and in any of the exposure groups when compared with their respective control groups. The shift from baseline catecholamine values due to stress has immense significance for health and well-being. Their continual alteration may prove harmful in due course. Suitable follow-up studies are needed to further strengthen these preliminary observations and for now, exposures should be limited as much as possible with essential safeguards.

Effect of occupational EMF exposure from radar at two different frequency bands on plasma melatonin and serotonin levels

OBJECTIVE

To delineate the effect of chronic electromagnetic field (EMF) exposure from radar on plasma melatonin and serotonin levels in occupationally exposed military personnel.

SUBJECTS AND METHODS

A total of 166 male military personnel participated in the study out of which only 155 joined for blood draw. They were divided into three sets: Control group (n = 68), exposure group I (n = 40) exposed to 8-12 GHz and exposure group II (n = 58) working with radar at 12.5-18 GHz frequency. The three groups were further split into two groups according to their years of service (up to 10 years and > 10 years) in order to investigate the effect of years of exposure from radar. Melatonin and serotonin levels were estimated by enzyme immunoassay in fasting blood samples collected from 06:00-07:00 h. EMF measurements were recorded at different locations using Satimo EME Guard 'Personal Exposure Meter' and Narda 'Broad Band Field Meter'.

RESULTS

The group I exposed population registered a minor though not significant decrease in plasma melatonin concentration while the other group II exposed population registered statistically significant decline in melatonin concentration when compared with controls. Highly significant increase in plasma serotonin levels was found in exposure group II when compared to control whereas marginal non-significant rise was also registered in exposure group I in comparison to control. Exposure in terms of length of service up to 10 years did not produce any significant effect in the indoleamine levels in both the exposure groups when they were compared with their respective control groups. Whereas, length of service greater than 10 years was observed to decrease and increase respectively the melatonin and serotonin concentration significantly in exposure group II but not in exposure group I. However, correlation test did not yield any significant association between years of service and melatonin or serotonin levels respectively in both the exposure sets I and II. No significant association was observed between melatonin and serotonin levels as well.

CONCLUSION

The study showed the EMF ability to influence plasma melatonin and serotonin concentration in radar workers, significantly in 12.5-18 GHz range with service period greater than 10 years.

Health Implications of Electromagnetic Fields, Mechanisms of Action, and Research Needs

Electromagnetic fields (EMF) have been implicated to influence a range of bodily functions. Given their ubiquitous nature, widespread applications, and capability to produce deleterious effects, conclusive investigations of the health risks are critical. Accordingly, this paper has been constructed to weigh the bioeffects, possible biointeraction mechanisms, and research areas in bioelectromagnetics seeking immediate attention. The several gaps in the existing knowledge do not permit one to reach a concrete conclusion but possibility for harmful effects cannot be underestimated in absence of consistent findings and causal mechanisms. Several studies with appropriate methodologies reflect the capacity of electromagnetic radiations to cause adverse health effects and there are several credible mechanisms that can account for the observed effects. Hence, need of the hour is to activate comprehensive well-coordinated blind scientific investigations, overcoming all limitations and demerits of previous investigations especially replication studies to concretize the earlier findings. Furthermore, appropriate exposure assessment is crucial for identification of dose-response relation if any, and the elucidation of biological interaction mechanism. For the time being, the public should follow the precautionary principle and limit their exposure as much as possible.

Influence of electric, magnetic, and electromagnetic fields on the circadian system: current stage of knowledge

One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields.

Association of geomagnetic disturbances and suicides in Japan, 1999-2010

OBJECTIVES

Previous studies have shown a positive relationship between geomagnetic disturbances and an increased incidence of suicide. The Japanese suicide rate is the ninth highest in the world, but there have been no reports examining the relationship between geomagnetic disturbance and the number of suicides, and, therefore, this paper examines this relationship.

METHODS

The number of Japanese suicides per month from January 1999 to December 2010 was obtained, and it was found that a total of 262,596 males and 102,539 females committed suicide during this period. To adjust the other factors which affect the number of suicides, a multiple linear regression analysis with backward elimination was carried out, with the monthly number of suicides as the response variable and the monthly mean K index value, monthly mean number of sunspots, monthly mean unemployment rate, proportion of elderly people (%), monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly mean day length (h) as the explanatory variables.

RESULTS

In the multiple linear regression analysis for males, the monthly mean K index value was associated with the monthly number of suicides, but in females, the monthly mean K index value was not associated with the monthly number of suicides.

CONCLUSION

In this study, we generated a hypothesis that geomagnetic disturbances may trigger male suicides.

Electromagnetic field-induced converse cell growth during a long-term observation

PURPOSE

Professional and public concern about the potential adverse effects of man-made electromagnetic fields (EMF) on the human body has dramatically expanded in recent years. Despite numerous attempts to investigate this issue, the long-standing challenge of reproducibility surrounding alternating EMF effects on human health remains unresolved. Our chief aim was to investigate a plausible mechanism for this phenomenon.

MATERIALS AND METHODS

Growth of cultured human cancer cells, DU145 and Jurkat, exposed to power frequency magnetic field (MF) (60 Hz, 1 mT) for 3 days, was determined using a 2-(4-Iodophenyl)- 3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium (WST-1) assay and a trypan blue exclusion assay. This experiment was repeated at incubators long-term monitoring period up to 5.3 years. A periodogram analysis was performed to investigate periodic patterns in the MF and sham effects on cell growth.

RESULTS

Unlike conventional assumptions, the MF effect on growth in both cell types was promotive or suppressive in a period-dependent manner. The converse cell growth induced by the MF was consistent in incubators, with little variation.

CONCLUSIONS

Spatiotemporal evidence suggests that the period-dependent converse cell growth by the MF may contribute to the poor reproducibility and explain the adverse effects observed in previous experimental and epidemiological investigations. Additionally, the novel approach of this study may be applied to design features required to experimentally determine the effects of EMF on living organisms in a convincing manner.

Increased vascular permeability in the circumventricular organs of adult rat brain due to stimulation by extremely low frequency magnetic fields

It has been demonstrated that the exposure of biological systems to magnetic fields (MFs) can produce several beneficial effects: tissue recovery in chronic wounds, re-establishment of blood circulation after tissue ischemia or in necrotic tissues, improvement after epileptic episodes, angiogenesis, etc. In the current study, the effects of extremely low frequency (ELF) MF on the capillaries of some circumventricular organs (CVOs) are demonstrated; a vasodilator effect is reported as well as an increase in their permeability to non-liposoluble substances. For this study, 96 Wistar male rats (250 g body mass) were used and divided into three groups of 32 rats each: a control group (no treatment); a sham ELF-MF group; and an experimental group subjected to ELF-MF (120 Hz harmonic waves and 0.66 mT, root mean square) by the use of Helmholtz coils. All animals were administered colloidal carbon (CC) intravenously to study, through optical and transmission electron microscopy, the capillary permeability in CVOs and the blood-brain barrier (BBB) in brain areas. An increase in capillary permeability to CC was detected in the ELF-MF-exposed group as well as a significant increase in vascular area (capillary vasodilation); none of these effects were observed in individuals of the control and sham ELF-MF groups. It is important to investigate the mechanisms involved in the phenomena reported here in order to explain the effects of ELF-MF on brain vasculature.

Is newborn melatonin production influenced by magnetic fields produced by incubators?

BACKGROUND

During permanence in most incubators, newborns are very close to the electric engine, which represents a source of electromagnetic fields (EMF). Previous studies demonstrated a decrease in melatonin production in adults and animals exposed to EMF.

AIMS

To assess melatonin production in a group of newborns exposed to EMF, and to evaluate whether removing the babies from the source of MF can affect melatonin production.

STUDY DESIGN AND SUBJECTS

We have recruited 28 babies (study group), who had spent at least 48 h in incubator where we had previously assessed the presence of significant EMF. We have measured their mean 6-hydroxy-melatonin-sulfate (6OHMS) urine excretion at the end of their permanence in the incubators, and compared it with their mean 6OHMS excretion after having been put in cribs, where EMF are below the detectable limit (<0.1mG). We have also measured urine 6OHMS twice, with an interval of 48h, in a control group of 27 babies who were not exposed to EMF during both samples.

RESULTS

Mean 6OHMS/cr values were respectively 5.34±4.6 and 7.68±5.1ng/mg (p=0.026) when babies were exposed to EMF in incubators, and after having been put in the crib. In the control group, mean 6OHMS/cr values in the first and in the second sample were respectively 5.91±5.41 vs 6.17±3.94ng/mg (p=0.679).

CONCLUSIONS

The transitory increase in melatonin production soon after removing newborns from incubators demonstrates a possible influence of EMF on melatonin production in newborns. Further studies are needed to confirm these data.

Effects of power frequency electromagnetic fields on melatonin and sleep in the rat

Background

Studies investigating the effect of power frequency (50–60 Hz) electromagnetic fields (EMF) on melatonin synthesis in rats have been inconsistent with several showing suppression of melatonin synthesis, others showing no effect and a few actually demonstrating small increases. Scant research has focused on the ensuing sleep patterns of EMF exposed rats. The present study was designed to examine the effects of extremely low power frequency electromagnetic fields (EMF) on the production of melatonin and the subsequent sleep structure in rats.

Methods

Eighteen male Sprague-Dawley rats were exposed to a 1000 milligauss (mG) magnetic field for 1 month. Urine was collected for the final 3 days of the exposure period for analysis of 6-sulphatoxymelatonin, the major catabolic product of melatonin found in urine. Subsequent sleep was analyzed over a 24-hour period.

Results

Melatonin production was mildly increased in exposed animals. Although there were no statistically significant changes in sleep structure, exposed animals showed slight decreases in REM (rapid eye movement) sleep as compared to sham (non-exposed) animals.

Conclusions

Power frequency magnetic fields induced a marginally statistically significant increase in melatonin levels in exposed rats compared to control. Subsequent sleep analysis indicated little effect on the sleep architecture of rats, at least not within the first day after 1 month's continuous exposure. Varying results in the literature are discussed and future research suggested.

Does magnetoreception mediate biological effects of power-frequency magnetic fields?

The question of possible biological effects of power-frequency magnetic fields (PF-MF) remains controversial, notably because no valid mechanism of interaction could be proposed so far for intensities relevant to human and animal exposure (e.g. such as near high-tension power lines). In rodents, however, a few consistent effects of weak PF-MF have been reported. These are, notably, influence on spatial memory and partial inhibition of melatonin secretion under long-lasting exposure. Recent developments in study of magnetoreception in mammals justify reviving the hypothesis previously proposed of the intervention of the magnetic sense in melatonin disruption by PF-MF. We revisit this hypothesis and revise and extend it with respect to current knowledge and, particularly, with respect to reported effects on spatial memory. Proposals are made for experimental testing of the hypothesis. We argue that these tests may provide further insight into mechanisms of biological interactions of PF-MF and also, into mechanisms of magnetoreception per se.

Pathophysiology of microwave radiation: effect on rat brain

The study aims to investigate the effect of 2.45 GHz microwave radiation on Wistar rats. Rats of 35 days old with 130 ± 10 g body weight were selected for this study. Animals were divided into two groups: sham exposed and experimental (six animals each). Animals were exposed for 2 h a day for 45 days at 2.45 GHz frequency (power density, 0.21 mW/cm(2)). The whole body specific absorption rate was estimated to be 0.14 W/kg. Exposure took place in a ventilated plexiglas cage and kept in an anechoic chamber under a horn antenna. After completion of the exposure period, rats were killed, and pineal gland and whole brain tissues were isolated for the estimation of melatonin, creatine kinase, caspase 3, and calcium ion concentration. Experiments were performed in a blind manner and repeated. A significant decrease (P < 0.05) was recorded in the level of pineal melatonin of exposed group as compared with sham exposed. A significant increase (P < 0.05) in creatine kinase, caspase 3, and calcium ion concentration was observed in whole brain of exposed group of animals as compared to sham exposed. One-way analysis of variance method was adopted for statistical analysis. The study concludes that a reduction in melatonin or an increase in caspase-3, creatine kinase, and calcium ion may cause significant damage in brain due to chronic exposure of these radiations. These biomarkers clearly indicate possible health implications of such exposures.

A precautionary public health protection strategy for the possible risk of childhood leukaemia from exposure to power frequency magnetic fields

Background

Epidemiological evidence showing a consistent association between the risk of childhood leukaemia and exposure to power frequency magnetic fields has been accumulating. This debate considers the additional precautionary intervention needed to manage this risk, when it exceeds the protection afforded by the exposure guidelines as recommended by the International Commission on Non-Ionizing Radiation Protection.

Methods

The Bradford-Hill Criteria are guidelines for evaluating the scientific evidence that low frequency magnetic fields cause childhood leukaemia. The criteria are used for assessing the strength of scientific evidence and here have been applied to considering the strength of evidence that exposures to extremely low frequency magnetic fields may increase the risk of childhood leukaemia. The applicability of precaution is considered using the risk management framework outlined in a European Commission (EC) communication on the Precautionary Principle. That communication advises that measures should be proportionate, non-discriminatory, consistent with similar measures already taken, based on an examination of the benefits and costs of action and inaction, and subject to review in the light of new scientific findings.

Results

The main evidence for a risk is an epidemiological association observed in several studies and meta-analyses; however, the number of highly exposed children is small and the association could be due to a combination of selection bias, confounding and chance. Corroborating experimental evidence is limited insofar as there is no clear indication of harm at the field levels implicated; however, the aetiology of childhood leukaemia is poorly understood. Taking a precautionary approach suggests that low-cost intervention to reduce exposure is appropriate. This assumes that if the risk is real, its impact is likely to be small. It also recognises the consequential cost of any major intervention. The recommendation is controversial in that other interpretations of the data are possible, and low-cost intervention may not fully alleviate the risk.

Conclusions

The debate shows how the EC risk management framework can be used to apply the Precautionary Principle to small and uncertain public health risks. However, despite the need for evidence-based policy making, many of the decisions remain value driven and therefore subjective.

Heavy metal exposure in patients suffering from electromagnetic hypersensitivity

BACKGROUND

Risks from electromagnetic devices are of considerable concern. Electrohypersensitive (EHS) persons attribute a variety of rather unspecific symptoms to the exposure to electromagnetic fields. The pathophysiology of EHS is unknown and therapy remains a challenge.

OBJECTIVES

Heavy metal load has been discussed as a potential factor in the symptomatology of EHS patients. The main objective of the study was to test the hypothesis of a link between EHS and heavy metal exposure.

METHODS

We measured lead, mercury and cadmium concentrations in the blood of 132 patients (n=42 males and n=90 females) and 101 controls (n=34 males and n=67 females).

RESULTS

Our results show that heavy metal load is of no concern in most cases of EHS but might play a role in exceptional cases.

CONCLUSIONS

The data do not support the general advice to heavy metal detoxification in EHS.

Does evening exposure to mobile phone radiation affect subsequent melatonin production?

PURPOSE

To test whether exposure to the emissions from a digital mobile phone handset prior to sleep alters the secretion of melatonin.

MATERIALS AND METHODS

In a double-blind cross-over design, 55 adult volunteers were both actively exposed or sham-exposed (in random order on successive Sunday nights) to mobile phone emissions for 30 min (0.25 W average power). Urine collection occurred immediately prior to retiring to bed and on rising the next morning. Melatonin output was estimated from principal metabolite concentrations (6-sulphatoxymelatonin (aMT6s) via radioimmunoassay), urine volumes and creatinine concentrations.

RESULTS

Total melatonin metabolite output (concentration x urine volume) was unchanged between the two exposure conditions (active 14.1+/-1.1 microg; sham 14.6+/-1.3 microg). The pre- and post-bedtime outputs considered separately were also not significantly different, although the pre-bedtime value was less for active versus sham exposure. When melatonin metabolite output was estimated from the ratio of aMT6s to creatinine concentrations, the pre-bedtime value was significantly less (p = 0.037) for active compared to sham. Examination of individual responses is suggestive of a small group of 'responders'.

CONCLUSIONS

Total nighttime melatonin output is unchanged by mobile phone handset emissions, but there could be an effect on melatonin onset time.

Cellular effects of extremely low frequency (ELF) electromagnetic fields

PURPOSE

The major areas of research that have characterised investigation of the impact of extremely low frequency (ELF) electromagnetic fields on living systems in the past 50 years are discussed. In particular, selected studies examining the role of these fields in cancer, their effects on immune and nerve cells, and the positive influence of these ELF fields on bone and nerve cells, wound healing and ischemia/reperfusion injury are explored.

CONCLUSIONS

The literature indicates that there is still no general agreement on the exact biological detrimental effects of ELF fields, on the physical mechanisms that may be behind these effects or on the extent to which these effects may be harmful to humans. Nonetheless, the majority of the in vitro experimental results indicate that ELF fields induce numerous types of changes in cells. Whether or not the perturbations observed at the cellular level can be directly extrapolated to negative effects in humans is still unknown. However, the myriad of effects that ELF fields have on biological systems should not be ignored when evaluating risk to humans from these fields and, consequently, in passing appropriate legislation to safeguard both the general public and professionally-exposed workers. With regard to the positive effects of these fields, the possibility of testing further their efficacy in therapeutic protocols should also not be overlooked.

Campos magnéticos de frequência extremamente baixa e efeitos na saúde: revisão da literatura

A partir da publicação, em 1979, dos resultados de um estudo que apontava para o aumento do risco de leucemia em crianças associado à exposição a campos magnéticos, o interesse pelo tema vem aumentando, e diversos estudos foram publicados. O objetivo desta revisão é apresentar os diferentes métodos utilizados na avaliação da exposição aos campos magnéticos de frequência extremamente baixa, bem como as dificuldades enfrentadas na quantificação dessa exposição, além de relatar os resultados de estudos epidemiológicos publicados nos últimos 10 anos. A falta de um modelo fisiopatológico que explique uma possível influência dos campos magnéticos na saúde e a dificuldade para quantificar a exposição têm sido os maiores obstáculos da pesquisa na área. Leucemia e tumores do sistema nervoso central têm sido os efeitos mais estudados. Leucemia em crianças é o desfecho mais consistentemente associado à exposição a campos magnéticos. Estudos mais recentes apontam a associação entre esclerose lateral amiotrófica e campos magnéticos.

Can disturbances in the atmospheric electric field created by powerline corona ions disrupt melatonin production in the pineal gland?

Recent epidemiological studies have reported an increased risk of leukemia in adults and children near overhead high voltage powerlines at distances beyond the measured range of the direct electric and magnetic fields. Corona ions are emitted by powerlines, forming a plume that is carried away from the line by the wind. The plume generates highly variable disturbances in the atmospheric electric field of tens to a few hundred V/m on time scales from seconds to minutes. Such disturbances can be seen up to several hundred meters from powerlines. It is hypothesized that these random disturbances result in the disruption of nocturnal melatonin synthesis and related circadian rhythms, in turn leading to increased risk of a number of adverse health effects including leukemia. In support of the hypothesis, it is noted that melatonin is highly protective of oxidative damage to the human hemopoietic system. A review of electric field studies provides evidence that (i) diurnal variation in the natural atmospheric electric field may itself act as a weak Zeitgeber; (ii) melatonin disruption by electric fields occurs in rats; (iii) in humans, disturbances in circadian rhythms have been observed with artificial fields as low at 2.5 V/m. Specific suggestions are made to test the aspects of the hypothesis.

Electromagnetic fields (EMF): Do they play a role in children's environmental health (CEH)?

Possible adverse health effects of exposure to electric, magnetic and electromagnetic fields (EMF), and especially the question of whether there exists a special vulnerability of children, have been a much discussed topic during the last two decades. Static fields produce health effects only in very rare and exceptional circumstances at extremely high field intensities. As for low-frequency EMF, the results of epidemiological research with respect to childhood leukaemia prompted the International Agency for Research on Cancer (IARC) in 2001 to classify these fields as "possibly carcinogenic to humans". Current hypotheses on the mechanism of such action are presented. The effect, if existent, appears to be not very important in relation to established other causes of childhood leukaemia. High-frequency EMF, as used in mobile and wireless communication (mobile telephony according to the GSM and UMTS standard, cordless DECT phones, wireless local area networks (WLAN), Bluetooth) and since many decades also in radio and television technology, are practically omnipresent. At high intensities, the generation of heat is the principal effect. Current guidelines, limits and regulations prevent any such effect. Mobile phone calls may, in certain circumstances, lead to local exposures close to limit values. Base stations typically produce exposures lower by 2-5 magnitudes. The discussion centres on the so-called non-thermal effects, which are supposedly occurring at field intensities, which are by orders of magnitude lower than those responsible for thermal effects. The reproducibility of these effects is usually poor, and no physiologic or pathogenic mechanism, so far, has been found to explain the alleged effects. Equally, epidemiologic studies have not furnished clear and reproducible data as arguments for negative health effects. Final results of the INTERPHONE study on the risk of brain tumours, acoustic neurinoma and parotid gland tumours associated with the use of mobile phones will be soon available. Preliminary results do not seem to indicate a substantial increase in risk. There are presently no scientific data supporting the concept of a special vulnerability of children and adolescents to high-frequency EMF, even if the usual caveats (developing organisms and structures may be more vulnerable, decades of life to come) are considered. The concept of precautionary measures adapted to such concerns is critically discussed.

How dangerous are mobile phones, transmission masts, and electricity pylons?

Electrical power and mobile communications deliver enormous benefit to society, but there are concerns whether the electric and magnetic field (EMF) emissions associated with the delivery of this benefit are linked to cancer or other health hazards. This article reviews the strength of the available epidemiological and laboratory evidence and notes that this falls short of what is normally required to establish a causal link. However, because of scientific uncertainty a cautious approach is often advocated, but here, too, there may be a tendency to judge these risks more harshly than those in other areas with similar strength of evidence.