A pooled analysis of magnetic fields and childhood leukaemia

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

Epidemiological studies have reported associations between exposure to power frequency magnetic fields and increased risk of certain cancer and noncancer illnesses. For childhood leukemia, a doubling of risk has been associated with exposures above 0.3/0.4 microT. Here, we propose that the melatonin hypothesis, in which power frequency magnetic fields suppress the nocturnal production of melatonin in the pineal gland, accounts for the observed increased risk of childhood leukemia. Such melatonin disruption has been shown in animals, especially with exposure to electric and/or rapid on/off magnetic fields. Equivocal evidence has been obtained from controlled laboratory magnetic field exposures of volunteers, although the exposure conditions are generally atypical of neighborhood exposures. In contrast, support for the hypothesis is found in the body of studies showing magnetic field disruption of melatonin in human populations chronically exposed to both electric and magnetic fields associated with electricity distribution. Further support comes from the observation that melatonin is highly protective of oxidative damage to the human haemopoietic system. Aspects of the hypothesis are amenable to further investigation.

Contact current hypothesis: Summary of results to date

Research conducted over the past 5 years has addressed the hypothesis that the reported association between residential magnetic fields and childhood leukemia may be explained by exposure to contact current. The use of multi-grounded neutrals in electrical distribution and residential electrical wiring systems in the United States results in a voltage on a residence's water line relative to earth that in turn creates a voltage between the water fixtures of a bathtub, sink, or shower and the drain, if the latter is made of conductive material. A bathing child may thus be exposed to contact current upon manual contact with the faucet, spout, or water stream. Dosimetry modeling indicates that modest and realistically anticipated currents (10s of microA) can produce electric fields in bone marrow (100s of mV/m) sufficient to overcome questions of biophysical plausibility. Both measurements in two regions of the United States and computer modeling of typical single-residence US neighborhoods indicate that residences with average magnetic fields in the high tail of the magnetic field distribution are more likely than residences with lower fields to also have higher contact voltage. The association of residential magnetic fields with contact voltage, the dosimetry results, and the indication from a behavioral survey that children tend to engage in behavior that results in exposure all support the hypothesis. Further research is needed to characterize electrical systems in other nations to determine whether contact current exposure occurs and whether it is associated with residential magnetic fields.

Evaluation of Residential Exposure to Intermediate Frequency Magnetic Fields

The authors measured the exposure to intermediate-frequency (IF: 10 kHz to 30 MHz) electromagnetic fields (EMF) in residential environments. They developed a system to acquire and record waveforms of IF magnetic fields (MFs) and set 5 nanotesla (nT) for the trigger level of acquisition. They operated the system near power lines, railroads, and electrical appliances as possible sources of IF-MFs. Most of the maximum values of magnetic flux density and the time derivative for each wave were below the upper limit of the measurable range of our system (i.e., 53 nT and 10 T/s); these values were much lower than the minimum amplitudes that can theoretically induce heating or membrane excitation within biological systems. Moreover, the amplitudes of the IF-MFs were not related to those of extremely low frequency (ELF) MF measured simultaneously, indicating that IF-MFs do not underlie the associations, observed in several epidemiological studies, between residential exposure to ELF-EMF and childhood cancer.

The risk of lymphoma in AKR/J mice does not rise with chronic exposure to 50 Hz magnetic fields (1 microT and 100 microT)

Some epidemiological studies suggest that exposure to 50 or 60 Hz magnetic fields might increase the risk of leukemia, especially in children with a comparable high residential exposure. To investigate this possibility experimentally, the influence of 50 Hz magnetic-field exposure on lymphoma induction was determined in a mouse strain that is genetically predisposed to this disease. The AKR/J mouse genome carries the AK virus, which leads within 1 year to spontaneous development of thymic lymphoblastic lymphoma. Beginning at an age of 4-5 weeks, groups of 160 female mice were sham-exposed or exposed to 50 Hz magnetic fields at 1 or 100 microT for 24 h per day, 7 days per week, for 38 weeks. Animals were checked visually daily and were weighed and palpated weekly. There was no effect of magnetic-field exposure on body weight gain or survival rate, and lymphoma incidence did not differ between exposed and sham-exposed animals. Therefore, these data do not support the hypothesis that chronic exposure to 50 Hz magnetic fields is a significant risk factor for developing hematopoietic malignancy.

Fifty-hertz magnetic fields induce free radical formation in mouse bone marrow-derived promonocytes and macrophages

Our findings show a significant increase of free radical production after exposure to 50 Hz electromagnetic fields at a flux density of 1 mT to mouse bone marrow-derived (MBM) promonocytes and macrophages, indicating the cell-activating capacity of extremely low frequency magnetic fields (ELF-MF). We demonstrate that after exposure to ELF-MF mainly superoxide anion radicals were produced, both in MBM macrophages (33%) and also in their precursor cells (24%). To elucidate whether NADPH- or NADH-oxidase functions are target proteins for MF interaction, the flavoprotein inhibitor diphenyleneiodonium chloride (DPI) was used. MF-induced free radical production was not inhibited by DPI, whereas tetradecanoylphorbolacetate (TPA)-induced free radical production was diminished by about 70%. TPA is known to induce a direct activation of NADPH-oxidase through the PKC pathway. Since DPI lacks an inhibitory effect in MF-exposed MBM cells, we suggest that 50 Hz MF stimulates the NADH-oxidase pathway to produce superoxide anion radicals, but not the NADPH pathway. Furthermore, we showed an oscillation (1-10 days) in superoxide anion radical release in mouse macrophages, indicating a cyclic pattern of NADH-oxidase activity.

Are environmental electromagnetic fields genotoxic?

Long-term exposure to extremely-low-frequency electromagnetic fields (ELF EMFs) greater than 0.4 microT has been linked, by epidemiological studies, to a small elevated risk of childhood leukaemia. Laboratory-based experiments have been claimed to show that ELF EMFs induce a variety of biological responses, although these claims are controversial. Recent experiments by Ivancsits et al. [Mutat. Res. 519 (2002) 1; Int. Arch. Occup. Environ. Health 76 (2003) 431; Mech. Age. Dev. 124 (2003) 847; H.W. Rüdiger, S. Ivancsits, E. Diem, O. Jahn, Genotoxic effects of ELF-EMF on human cells in vitro, Bioelectromagnetics Society 25th Annual Meeting, Maui, USA, 2003] suggest that ELF EMFs are genotoxic, on the basis of observations that intermittent exposures induce single-strand breaks (SSB) and double-strand DNA breaks (DSB) in the DNA of cultured human fibroblasts. The implications of these findings are discussed.

The cancer epidemiology of radiation

Ionizing radiation has been the subject of intense epidemiological investigation. Studies have demonstrated that exposure to moderate-to-high levels can cause most forms of cancer, leukaemia and cancers of the breast, lung and thyroid being particularly sensitive to induction by radiation, especially at young ages at exposure. Predominant among these studies is the Life Span Study of the cohort of survivors of the atomic bombings of Japan in 1945, but substantial evidence is derived from groups exposed for medical reasons, occupationally or environmentally. Notable among these other groups are underground hard rock miners who inhaled radioactive radon gas and its decay products, large numbers of patients irradiated therapeutically and workers who received high doses in the nuclear weapons programme of the former USSR. The degree of carcinogenic risk arising from low levels of exposure is more contentious, but the available evidence points to an increased risk that is approximately proportional to the dose received. Epidemiological investigations of nonionizing radiation have established ultraviolet radiation as a cause of skin cancer. However, the evidence for a carcinogenic effect of other forms of nonionizing radiation, such as those associated with mobile telephones or electricity transmission lines, is not convincing, although the possibility of a link between childhood leukaemia and extremely low-frequency electromagnetic fields cannot be dismissed entirely.

Causes of childhood leukaemia and lymphoma

Childhood cancer is rare comprising less than 1% of all malignancies diagnosed each year in developed countries. Leukaemia is the commonest form of cancer in children accounting for around a third of all childhood cancer, with acute lymphoblastic leukaemia (ALL) being the most prevalent. Biologically specific subtypes of ALL and acute myeloblastic leukaemia (AML), the other major morphological type of childhood leukaemia, are characterised by chromosomal changes. Whilst over 200 genes have been associated with chromosomal translocations, to date, only MLL, TEL, and AML1 have been linked with childhood leukaemia. Interestingly, there is increasing evidence to support the theory that gene rearrangements such as these may originate in utero. As with many other human diseases, both genetic and environmental factors have been implicated in the aetiology of the disease. Although much has been documented with regard to diet, smoking, alcohol consumption and recreational and prescription drug use during pregnancy, there is no consistent evidence to support a link with any of these factors and childhood leukaemia. However, findings from studies investigating prenatal and early life exposures are often based on small numbers of cases as both the type of cancer and exposure are rare. Furthermore, accurate information relating to past exposures can be difficult to obtain and is often reliant on self-reporting. To further our understanding of the aetiology of childhood leukaemia and lymphoma, there are areas which clearly warrant investigation. These include collection of parental dietary folate data combined with genetic analysis of the folate related genes, in utero exposure to DNA topoisomerase II inhibitors, and the possible effects of assisted reproduction technology on disease susceptibility.

Évaluation des effets des champs électromagnétiques sur la santé chez l’homme

During the twentieth century, environmental exposure to electromagnetic fields generated by human activity has increased regularly, at the same time as the quest for electrical energy. Therefore we are all exposed to a complex set of electric and magnetic fields of weak intensity. The levels of exposure of the general population range from 5 to 50 V/m for electric fields and from 0.01 to 0.2 micro T for magnetic fields. Fields in cause are essentially those associated to the use of the electric current (extremely low frequency, ELF: 50 Hz in France, 60 Hz in the United States) and those related to the use of cell phones (radio frequency: 900 and 1,800 MHz). The question of the possible risk on health by exposure to electric and/or magnetic fields became a concern to scientists and is now an important public debate. A number of expertises, led in particular by the WHO, leaning on the careful inspection of scientific publications from numerous countries, conclude that current data do not allow to assert the existence of sanitary effects; however our knowledge of the biologic effects of electromagnetic fields still contains certain gaps which should be filled. Indeed, the numerous epidemiological studies relative to the occurrence of cancer by exposure to electromagnetic fields are conflicting. In every case the increase of the risk, when described, is always weak. The measure of the Relative Risk (RR) which establishes the relation is approximately 2-3. At present, some data concerning the risk of childhood leukemia in the event of exposure of ELF generated in the home indicate that this risk can exist when children are chronically exposed to more than 0.4 micro T (the relative risk is in the order of 2). In the field of radio frequencies, the increasing use of cell phones (38 million users in France) and their antennae - basis are another subject of concern for the effects on health they are susceptible to produce. Large-scale studies, implying numerous countries, carried on at present within the framework of the WHO should bring elements of answer to the unresolved questions.

Spatial epidemiology: current approaches and future challenges

Spatial epidemiology is the description and analysis of geographic variations in disease with respect to demographic, environmental, behavioral, socioeconomic, genetic, and infectious risk factors. We focus on small-area analyses, encompassing disease mapping, geographic correlation studies, disease clusters, and clustering. Advances in geographic information systems, statistical methodology, and availability of high-resolution, geographically referenced health and environmental quality data have created unprecedented new opportunities to investigate environmental and other factors in explaining local geographic variations in disease. They also present new challenges. Problems include the large random component that may predominate disease rates across small areas. Though this can be dealt with appropriately using Bayesian statistics to provide smooth estimates of disease risks, sensitivity to detect areas at high risk is limited when expected numbers of cases are small. Potential biases and confounding, particularly due to socioeconomic factors, and a detailed understanding of data quality are important. Data errors can result in large apparent disease excess in a locality. Disease cluster reports often arise nonsystematically because of media, physician, or public concern. One ready means of investigating such concerns is the replication of analyses in different areas based on routine data, as is done in the United Kingdom through the Small Area Health Statistics Unit (and increasingly in other European countries, e.g., through the European Health and Environment Information System collaboration). In the future, developments in exposure modeling and mapping, enhanced study designs, and new methods of surveillance of large health databases promise to improve our ability to understand the complex relationships of environment to health.

Exposure assessment of ELF magnetic fields in urban environments in Extremadura (Spain)

We present the results of a study of the extremely low frequency (ELF) magnetic fields in urban environments of the Extremadura region (Spain). The study included a spectral analysis, an analysis of the temporal variation, and spot measurements in the streets of four cities. The spectral analysis showed that the main source of magnetic field exposure was that corresponding to the principal power frequency (50 Hz) and its third harmonic. The magnetic flux density measured at one point over 24 h presented rapid fluctuations in short time periods. Smoothing the time series eliminated these fluctuations, showing a temporal evolution associated with the differing levels of power consumption over the course of the day. The values of the spot measurements taken in the streets were all below the ICNIRP reference level, although 30% surpassed 0.2 microT, the value that some epidemiological studies take as the threshold above which there exist risks of effects that could be harmful to health. The values found for the magnetic flux density in these urban settings were generally greater than values reported in the literature for residential areas, and similar to, although in some cases less than those in workplace environments.

Exposure to 900 MHz electromagnetic field induces an unbalance between pro-apoptotic and pro-survival signals in T-lymphoblastoid leukemia CCRF-CEM cells

It has been recently established that low-frequency electromagnetic field (EMFs) exposure induces biological changes and could be associated with increased incidence of cancer, while the issue remains unresolved as to whether high-frequency EMFs can have hazardous effect on health. Epidemiological studies on association between childhood cancers, particularly leukemia and brain cancer, and exposure to low- and high-frequency EMF suggested an etiological role of EMFs in inducing adverse health effects. To investigate whether exposure to high-frequency EMFs could affect in vitro cell survival, we cultured acute T-lymphoblastoid leukemia cells (CCRF-CEM) in the presence of unmodulated 900 MHz EMF, generated by a transverse electromagnetic (TEM) cell, at various exposure times. We evaluated the effects of high-frequency EMF on cell growth rate and apoptosis induction, by cell viability (MTT) test, FACS analysis and DNA ladder, and we investigated pro-apoptotic and pro-survival signaling pathways possibly involved as a function of exposure time by Western blot analysis. At short exposure times (2-12 h), unmodulated 900 MHz EMF induced DNA breaks and early activation of both p53-dependent and -independent apoptotic pathways while longer continuous exposure (24-48 h) determined silencing of pro-apoptotic signals and activation of genes involved in both intracellular (Bcl-2) and extracellular (Ras and Akt1) pro-survival signaling. Overall our results indicate that exposure to 900 MHz continuous wave, after inducing an early self-defense response triggered by DNA damage, could confer to the survivor CCRF-CEM cells a further advantage to survive and proliferate.

Low electromagnetic field (50 Hz) induces differentiation on primary human oral keratinocytes (HOK)

This work concerns the effect of low frequency electromagnetic fields (ELF) on biochemical properties of human oral keratinocytes (HOK). Cells exposed to a 2 mT, 50 Hz, magnetic field, showed by scanning electron microscopy (SEM) modification in shape and morphology; these modifications were also associated with different actin distribution, revealed by phalloidin fluorescence analysis. Moreover, exposed cells had a smaller clonogenic capacity, and decreased cellular growth. Indirect immunofluorescence with fluorescent antibodies against involucrin and beta-catenin, both differentiation and adhesion markers, revealed an increase in involucrin and beta-catenin expression. The advance in differentiation was confirmed by a decrease of expression of epidermal growth factor (EGF) receptor in exposed cells, supporting the idea that exposure to electromagnetic field carries keratinocytes to higher differentiation level. These observations support the hypothesis that 50 Hz electromagnetic fields may modify cell morphology and interfere in differentiation and cellular adhesion of normal keratinocytes.

Importance of addressing National Electrical Code violations that result in unusual exposure to 60 Hz magnetic fields

We evaluated wiring in multifamily developments containing National Electrical Code(R) (NEC(R)) violations as a source of unusual exposure to 60 Hz magnetic fields. Two methods were used in this evaluation: measurement and modeling. We measured the building wiring as a source of magnetic fields in six multifamily developments in Michigan. In this small sample, building wiring proved to be an important source of exposure in four of the six cases. In all four cases with exposure from building wiring, one or more NEC violations were involved. To supplement our measurement efforts, we used computer modeling to compare magnetic field exposure due to building wiring with magnetic field exposure from external power lines. Our calculations showed that where the building wiring has a NEC violation leading to net current loops, the exposure due to wiring is likely to be more important than that from external power lines. Our results support the results obtained in a recent study of the exposure of Californian K-12 students to magnetic fields, where building wiring with one or more NEC violation was found to be the single most important exposure source. If 60 Hz magnetic fields are important to avoid, then improved enforcement of the NEC, as required by law, is perhaps the single most important mitigation policy to adopt. Bioelectromagnetics 25:102-106, 2004.

Residential Proximity to High-Voltage Power Lines and Risk of Childhood Hematological Malignancies

BACKGROUND: Epidemiologic studies of electromagnetic fields and childhood cancers have focused on home exposure. The authors investigated whether residence in districts near high-voltage power lines is associated with childhood hematological malignancies, using small area analysis.

METHODS: Among 50,000 children in a city in Japan, 14 cases aged younger than 15 years were diagnosed with these malignancies in the period from 1992 through 2001. A total of 294 districts constituting this city were classified according to their proximity to high-voltage power lines (either 66 kV or 220 kV). Mantel-Haenszel rate ratio is used to calculate incidence rate ratio and its 95% confidence interval (CI).

RESULTS: Compared to districts of which no area fell within 300 m of high-voltage power lines, districts in which at least 50% of the area fell within 300 m of high-voltage power lines demonstrated an increased risk (incidence rate ratio: 2.2; 95% CI: 0.5-9.0). The association was strengthened for homes in which patients had resided for the longest interval of their lives (incidence rate ratio: 3.4; 95% CI: 0.9-13.2). Point-in-time measurements showed no increase in magnetic field levels for patient homes in districts near the lines.

CONCLUSION: An increased, albeit nonsignificant, risk of childhood hematological malignancies associated with residential proximity to high-voltage power lines warrants further investigations.

Initial interactions in electromagnetic field-induced biosynthesis

Low frequency electromagnetic (EM) fields induce gene expression, and recent insights into physical interactions of EM fields with model systems suggest a mechanism that could initiate this process. The consistently low thresholds at which EM fields stimulate biological processes indicate that they require little energy. Since it has been shown that such weak fields accelerate electron transfer reactions, they could stimulate transcription by interacting with electrons in DNA to destabilize the H-bonds holding the two DNA strands together. Such a mechanism is consistent with the low electron affinity of the bases in previously identified electromagnetic response elements (EMREs) needed for EM field interaction with DNA. It is also in line with both endogenous and in vitro stimulation of biosynthesis by electric fields. The frequency response of several EM sensitive biological systems suggests that EM fields require repetition and are most effective at frequencies that coincide with natural rhythms of the processes affected.

The effect of oscillating low intensity magnetic field on the Na+, K+, Ca++, and Mg++ concentrations in the maternal and fetal circulation of the dually perfused human placental cotyledon

Dual-sided perfusions of the human placental cotyledon in vitro were used to study effects of low intensity magnetic fields (MFs) of 2 mT, 50 Hz (E1, 10 perfusions) and 5 mT, 50 Hz (E2, 10 perfusions). In the control group C (10 experiments) no field was used. Perfusions lasted 180 min each. Increased release of calcium ions from the placental cotyledon was found in the fetal circulation during perfusion when the 2 mT, 50 Hz MF was used. No changes in the release of sodium and magnesium ions were observed compared to the control group. The 5 mT, 50 Hz oscillating MF intensified the release of sodium ions from the perfused cotyledon both to the fetal and maternal circulation up to the 150th min of the experiment. Increased release of magnesium ions was observed only to the fetal circulation between 120 and 180 min and of calcium ions to the fetal circulation between 60 and 180 min. No significant differences in K concentrations were found between the control and MF exposed cotyledons under conditions of these experiments.

Association of residential magnetic fields with contact voltage

The US National Electrical Code's (NEC) requirement to ground a home's electrical service to the residential water line results in a voltage between the water line and earth, V W-E. The voltage may result from ground return current that flows into the earth via the water line or from inductive effects from other sources of magnetic fields, such as transmission lines. This voltage can, in turn, serve as a source for Vbath, the voltage between the water fixtures and conductive drain pipes sunk into the earth beneath a residence. Vbath can be a source of contact current exposure to a child touching a water fixture while bathing. Previous research has suggested that exposure to these currents could be the basis for the association between power-frequency magnetic fields and childhood leukemia. In this study, we assessed the association between measured Vbath and VW-E with the average spot-measured magnetic field, Bavg, in a sample of 191 single-family residences in the Denver metropolitan area. This area was the source of cases and controls for previous studies of electric and magnetic field (EMF) and childhood cancer. The association of both Vbath and VW-E with Bavg had upward trends across magnetic field strata (<0.1 microT (reference); 0.1-<0.3 microT; and > or = 0.3 microT). In addition, VW-E was associated with Vbath. Without further study, these results cannot be applied to multi-dwelling residences or to electrical systems prevalent in other nations. Nonetheless, when combined with the finding that contact current is a far more plausible candidate than the residential magnetic field for mediating biological effects on the basis of comparative dose to bone marrow, these associations indicate that contact current exposure deserves further study.

Evaluation of genotoxic effect of low level 50 Hz magnetic fields on human blood cells using different cytogenetic assays

The question whether extremely low frequency magnetic fields (ELFMFs) may contribute to mutagenesis or carcinogenesis is of current interest. In order to evaluate the possible genotoxic effects of ELFMFs, human blood cells from four donors were exposed in vitro for 48 h to 50 Hz, 1 mT uniform magnetic field generated by a Helmholtz coil system. Comet assay (SCGE), sister chromatid exchanges (SCE), chromosome aberrations (CAs), and micronucleus (MN) test were used to assess the DNA damage. ELF pretreated cells were also irradiated with 1 Gy of X-ray to investigate the possible combined effect of ELFMFs and ionizing radiation. Furthermore, nuclear division index (NDI) and proliferation index (PRI) were evaluated. Results do not evidence any DNA damage induced by ELFMF exposure or any effect on cell proliferation. Data obtained from the combined exposure to ELFMFs and ionizing radiation do not suggest any synergistic or antagonistic effect.

Effects of Electromagnetic Fields on the Immune Systems of Occupationally Exposed Humans and Mice

The authors examined immunological disorders in 6 individuals who had been exposed occupationally to environmental electromagnetic fields. Comparable effects on mice exposed in a similar environment were also investigated. The human subjects had worked 8 hr/day for 5 yr in a laboratory located above electrical transformers and high-tension cables, and in which there were low-frequency electromagnetic fields of 0.2-6.6 microtesla (microT). The 6 control subjects (matched for socioeconomic parameters, sex, and age) had worked away from the immediate vicinity of transformers and high-tension cables. The authors found statistically significantly lower total lymphocyte, CD4, and CD3 counts, and significantly increased natural killer (NK) cells, in exposed subjects vs. controls. Six months after exposure had ceased, total lymphocyte counts had increased, as had CD4, CD3, and CD19 counts (+13%, +28%, +22%, and +17%, respectively), and NK cell counts were decreased by 26% (not significant) in the same human subjects. In the second part of this study, 12 Swiss male mice housed in cages were exposed in the same room in which the human subjects had been exposed (i.e., 5-microT, 50-Hz magnetic field) for 109 days; 12 additional mice were used as unexposed controls. The total lymphocyte, leukocyte, polymorphonuclear neutrophil, CD4, and NK counts of the exposed mice at 109 days were significantly lower than those of controls. In addition, plasma glucose levels (at 30 days) and amylase activity (at 109 days) were significantly lower, whereas plasma sodium and chloride levels were significantly elevated at 109 days. Results from this study suggest that chronic exposure to a 0.2-6.6-microT magnetic field can lead to decreased immunological parameters (total lymphocytes and CD4 counts) in both humans and mice. The increase in some values once exposure was terminated suggests a causal relationship with exposure to electromagnetic fields, as do the changes in mice, particularly the changes in total lymphocyte and CD4 counts.

Evaluation of the nocturnal levels of urinary biogenic amines in men exposed overnight to 50-Hz magnetic field

The aim of this study was to determine whether exposure to magnetic fields might affect human health and to look for possible effects of acute exposure (9 hours) to 50-Hz magnetic fields (10 microT) on the urinary concentration of biogenic amines. Thirty-two young men (20-30 years old) were divided into two groups (sham-exposed and exposed group) of 12 to 16 subjects each. All subjects participated in two 24-hour experiments to evaluate the effects of both continuous and intermittent exposure to magnetic fields. The subjects were exposed to the magnetic field from 2300 to 0800, while lying down. Total urine (from 2300 to 0800) was collected at 0800. The results (expressed as a ratio of biogenic amine excretion to creatinine excretion (nmol/mmol)) did not differ significantly between sham-exposed and exposed men for any of the parameters measured: adrenaline, noradrenaline, dopamine, dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid. These results suggest that nocturnal exposure to either continuous or intermittent 50-Hz magnetic fields of 10 microT does not affect, at least under our experimental conditions, the nocturnal excretion of biogenic amines in healthy young men.

Electromagnetic acceleration of the Belousov–Zhabotinski reaction

Acceleration of the Belousov-Zhabotinski (BZ) reaction, in stirred homogeneous solutions, by low frequency electromagnetic (EM) fields has provided new insights into EM interaction mechanisms. The acceleration varies inversely with the basal reaction rate, indicating that the applied magnetic field and the intrinsic chemical driving forces affect the same electron transfer reaction. The amplitude and frequency dependence of the EM field interactions are also consistent with interaction during electron transfer. A mechanism based on interaction with moving electrons offers a way of explaining the ability of EM fields to stimulate gene expression, in particular the stress response, since electrons have been shown to move in DNA.

Effects of 50 Hz electromagnetic field exposure on apoptosis and differentiation in a neuroblastoma cell line

Experiments were carried out to assess whether a magnetic field of 50 Hz and 1 mT can influence apoptosis and proliferation in the human neuroblastoma cell line LAN-5. TUNEL assays and poly-ADP ribose polymerase (PARP) expression analysis were performed to test apoptosis induction, and the WST-1 assay was used to calculate the proliferation index in a long term exposure. No alterations were found in cellular ability to undergo programmed cell death, but a small increase in the proliferation index was evidenced after 7 days of continuous exposure. Also, a slight and transient increase of B-myb oncogene expression was detected after 5 days of exposure. Combined exposures of cells to EMF and to chemical agents which interfere with proliferation, such as the differentiative agent retinoic acid and the apoptotic inducer camptothecin, showed an antagonistic effect of magnetic fields against the differentiation of the LAN-5 cells and a protective effect towards apoptosis.

Micronucleus induction in cells co-exposed in vitro to 50 Hz magnetic field and benzene, 1,4-benzenediol (hydroquinone) or 1,2,4-benzenetriol☆

The generation, transmission (e.g. power lines, transformers, service wires, and electrical panels), and use (e.g. home appliances, such as electric blankets, shavers, and televisions) of electrical energy is associated with the production of weak electric and magnetic fields (EMF) which oscillate 50 (Europe) or 60 (USA) times per second (power-line frequency), falling in the extremely-low frequency (ELF) region of the electromagnetic spectrum. Epidemiological reports suggest a possible association between exposure to ELF-EMF and an increased risk of cancer (e.g. childhood acute leukaemia). Benzene is an established human leukomogen. This xenobiotic, which is unlikely to be the ultimate carcinogen, is metabolized in the liver to its primary metabolite phenol, which is hydroxylated to hydroquinone (1,4-benzenediol) and 1,2,4-benzenetriol. In this in vitro approach, to test the genotoxic and / or co-genotoxic potency of ELF-EMF, the cytokinesis block micronucleus (MN) method with Jurkat cells has been used. A 50 Hz magnetic field (MF) of 5 mT field strength was applied for different length of time (from 1 to 24 h), either alone or with benzene, 1,4-benzenediol, or 1,2,4-benzenetriol. Our preliminary results show that, after 24 h exposure, the frequency of micronucleated cells in MF-exposed cultures is 1.9 fold higher than in sham-exposed (control) cultures. Benzene exposure does not show any cytogenetic activity, whereas 1,4-benzenediol or 1,2,4-benzenetriol alone significantly affect the number of MN in Jurkat cells, as compared to untreated cultures. Moreover, co-exposure to ELF-MF does not seem to affect the frequency of micronuclei induced by benzene, 1,4-benzenediol, or 1,2,4-benzenetriol.

Possible associations between ELF electromagnetic fields, DNA damage response processes and childhood leukaemia

Epidemiology has shown an association between exposure to extremely low frequency (ELF) electromagnetic fields (EMF) and childhood leukaemia. The causal nature and biological basis of this association are however questionable. Studies with aneuploid cell lines raised the hypothesis that ELF EMF may act as a coleukaemogen by compromising DNA damage response to genotoxic agents such as ionising radiation. We examined this hypothesis using gamma-ray-induced dicentric chromosome exchange in human lymphocytes. The results from 12 h post-gamma-ray exposure to fields of 0.23, 0.47 and 0.7 mT provide no support to the hypothesis. The power of the study was sufficient to exclude an ELF enhancement of chromosomal exchange of 10-15% (2SE).

Magnetic fields and the melatonin hypothesis: a study of workers chronically exposed to 50-Hz magnetic fields

Because epidemiological studies report clinical disorders (mainly neurobehavioral alterations and/or cancer) that may be related to diminished melatonin secretion or to changes in its circadian rhythm in subjects living or working in environments exposed to magnetic fields, research on the effects of these fields in humans is particularly important. In this study, we examine the circadian rhythm of melatonin in 15 men exposed chronically and daily for a period of 1-20 yr, in the workplace and at home, to a 50-Hz magnetic field in search of any cumulative effect from those chronic conditions of exposure. The weekly geometric mean of individual exposures ranged from 0.1 to 2.6 microT. The results are compared with those for 15 unexposed men who served as controls (individual exposures ranged from 0.004 to 0.092 microT). Blood samples were taken hourly from 2000 to 0800. Nighttime urine was also collected and analyzed. This work shows that subjects exposed over a long period (up to 20 yr) and on a daily basis to magnetic fields experienced no changes in their plasma melatonin level, their urinary 6-sulfatoxymelatonin level, or the circadian rhythm of melatonin. Our data strongly suggest that magnetic fields do not have cumulative effects on melatonin secretion in humans and thus clearly rebut the "melatonin hypothesis" that a decrease in plasma melatonin concentration (or a disruption in its secretion) explains the occurrence of clinical disorders or cancers possibly related to magnetic fields.

Childhood leukemia: electric and magnetic fields as possible risk factors

Numerous epidemiologic studies have reported associations between measures of power-line electric or magnetic fields (EMFs) and childhood leukemia. The basis for such associations remains unexplained. In children, acute lymphoblastic leukemia represents approximately three-quarters of all U.S. leukemia types. Some risk factors for childhood leukemia have been established, and others are suspected. Pathogenesis, as investigated in animal models, is consistent with the multistep model of acute leukemia development. Studies of carcinogenicity in animals, however, are overwhelmingly negative and do not support the hypothesis that EMF exposure is a significant risk factor for hematopoietic neoplasia. We may fail to observe effects from EMFs because, from a mechanistic perspective, the effects of EMFs on biology are very weak. Cells and organs function despite many sources of chemical "noise" (e.g., stochastic, temperature, concentration, mechanical, and electrical noise), which exceed the induced EMF "signal" by a large factor. However, the inability to detect EMF effects in bioassay systems may be caused by the choice made for "EMF exposure." "Contact currents" or "contact voltages" have been proposed as a novel exposure metric, because their magnitude is related to measured power-line magnetic fields. A contact current occurs when a person touches two conductive surfaces at different voltages. Modeled analyses support contact currents as a plausible metric because of correlations with residential magnetic fields and opportunity for exposure. The possible role of contact currents as an explanatory variable in the reported associations between EMFs and childhood leukemia will need to be clarified by further measurements, biophysical analyses, bioassay studies, and epidemiology.

Epidemiological research on cancer with a focus on Europe

Cancer has been a growing public health problem throughout the last century. Cancer mortality rates in both sexes combined in the European Union (EU) reached a peak in 1988. Thereafter, they declined by 9.4% in 1998. Likewise, lung cancer rates in the EU for both sexes combined increased by 58% between 1960 and 1988, but declined by 14% in 1998. Over a third of the decline was accounted for by lung cancer alone and approximately half by the combination of tobacco-related neoplasms. About half of the decline in total cancer mortality not attributable to tobacco derived from the steady fall in mortality from gastric cancer. The remaining half, including favourable trends in colorectal, breast, testis and lymphoid neoplasms, can be at least in part attributed to advancements in cancer diagnosis and treatment. The major causes of cancer and hence the most important priorities for research will be reviewed, with a specific focus on European priorities for research.

Absence of genotoxicity in human blood cells exposed to 50 Hz magnetic fields as assessed by comet assay, chromosome aberration, micronucleus, and sister chromatid exchange analyses

In the past, epidemiological studies indicated a possible correlation between the exposure to ELF fields and cancer. Public concern over possible hazards associated with exposure to extremely low frequency magnetic fields (ELFMFs) stimulated an increased scientific research effort. More recent research and laboratory studies, however, have not been able to definitively confirm the correlation suggested by epidemiological studies. The aim of this study was to evaluate the effects of 50 Hz magnetic fields in human blood cells exposed in vitro, using several methodological approaches for the detection of genotoxicity. Whole blood samples obtained from five donors were exposed for 2 h to 50 Hz, 1 mT uniform magnetic field generated by a Helmholtz coil system. Comet assay, sister chromatid exchanges (SCE), chromosome aberrations (CA), and micronucleus (MN) tests were used to assess DNA damage, one hallmark of malignant cell transformation. The effects of a combined exposure with X-rays were also evaluated. Results obtained do not show any significant difference between ELFMFs exposed and unexposed samples. Moreover, no synergistic effect with ionizing radiation has been observed. A slight but significant decrease of cell proliferation was evident in ELFMFs treated samples and samples subjected to the combined exposure.

Electromagnetic radiation

Electromagnetic fields (EMF) are ubiquitous in modern society. It is well known that exposure to strong fields can result in acute effects, such as burns; the mechanisms behind such effects are well established. There is, however, also a concern that long-term exposure to weak fields might have health effects due to an as-yet unknown mechanism. Because of the already widespread exposure, even small health effects could have profound public health implications. Comprehensive research efforts are therefore warranted, and are indeed ongoing. The strongest evidence for health risks is from exposure to fields generated in connection with use of electric power. As for fields used by telecommunications technology, there is still considerably fewer data available and for the time being there is only very weak support for the existence of health effects. However, extensive research activities are ongoing and much more data will be available in the near future. This situation of scientific uncertainty and considerable public concern creates dilemmas for decision makers.

Thermal noise limit on the sensitivity of cellular membranes to power frequency electric and magnetic fields

Several authors have concluded that thermal electromagnetic noise will be of sufficient magnitude to overwhelm electric and/or magnetic fields induced by environmentally generated, power frequency electric and magnetic fields in the membranes of living cells located in the bodies of humans. Yet, there are research reports that indicate that living cells may respond to power frequency electric and/or magnetic field levels well below the limits set by these thermal noise arguments. The purpose of this study is to suggest that published thermal arguments may not make a full accounting of all membrane force fields of thermal origin, and that when such an accounting is made, the net thermal noise fields may be smaller in the power frequency range than previously thought. If this analysis is correct, there may be no thermal noise barrier that precludes the possibility of cellular membranes of human cells responding to environmental levels of power frequency electric or magnetic fields.

Stability of Wertheimer-Leeper wire codes as a measure of exposure to residential magnetic fields over a 9- to 11-year interval

The Wertheimer-Leeper (W-L) wire code is a construct used as a surrogate indicator of residential exposure to electromagnetic fields. However, little is known about how changes in electrical distribution systems affect wire code assignment. The wire code was determined for 150 homes in the Seattle, WA, area twice, 9-11 years apart. For each home, the authors evaluated whether the electrical configuration around the home and the wire code changed between the two time points. The effect of wire code misclassification on observable odds ratios was evaluated, given hypothetical true control distributions and two different dose-response curves. There was an electrical configuration change for 77 (51.3%) homes, which resulted in a wire code change for 29 (19.3%) homes. Eight (5.3%) other homes had a wire code change due to mapping errors or methodological inconsistencies. Misclassification masked the shape of a threshold (nonlinear) dose-response curve and changed the slope of a linear dose-response curve. Although the wire code detected less than half of electrical configuration changes, misclassification of exposure over time may change odds ratios and mask possible dose-response relationships.

Correlation of year-to-year magnetic field exposure metrics among children in a leukemia survival study

The Childhood Leukemia Survival Study is examining the possible association between magnetic field exposure and survival of children with newly diagnosed acute lymphocytic leukemia (ALL). We report the results of serial 24-h personal magnetic field monitoring for 412 US and Canadian children and present the correlations between annual values. The mean time-weighted average (TWA) and geometric mean (GM) were similar for first, second, and third year measurements [TWA: 0.11 microT (n = 412), 0.13 microT (n = 304), and 0.12 microT (n = 134), respectively]. There were no consistent differences in mean TWA or GM based on age or gender. Significantly lower mean TWA and GM were found for children living in rural areas. Higher exposures were noted among children living in urban areas, among apartments dwellers, and those living in rental homes. Measurements taken during summer months and among children residing in the northeast and Canada also tended to be higher. Correlations for most metrics were increased among children who had annual measurements performed during the same season. The metric with the highest year-to-year correlation was the GM. The lowest correlations were found for metrics estimating field intermittency and temporal stability. First to second year GMs were well correlated when taken in the same home (Spearman rank correlation = 0.70), but a lower correlation (0.44) was noted among residentially mobile children. Our findings suggest that summarizing exposure using a single measurement of GM can estimate exposures for residentially stable children, but is not a good predictor of personal exposures among children who change residence during the study interval.

Chronic effects of toxic environmental exposures on children's health

Children have unusual patterns of exposure to environmental chemicals, and they have vulnerabilities that are quite distinct from those of adults. Increasingly, children's exposures to chemicals in the environment are understood to contribute to the causation and exacerbation of certain chronic, disabling diseases in children including asthma, cancer, birth defects, and neurobehavioral dysfunction. The protection of children against environmental toxins is a major challenge to modern society.

Exposure guidelines for low-frequency electric and magnetic fields: report from the Brussels workshop

The EMF Exposure Guidelines Science Workshop was held to evaluate the information base for guidelines for electric and magnetic field exposures at extremely low frequencies, to identify research needs, and to discuss how best to apply scientific knowledge in developing exposure recommendations. Although the existing guideline values are based on electrostimulation of nerve and muscle tissues, guidelines must also consider controversial studies of potential health effects from chronic exposures at environmental levels that are far too weak to cause electrostimulation. The size of the safety factor applied in specifying exposure limits reflects a variety of factors that introduce uncertainties. These include confidence in existing dose-effect relationships, population diversity, the reliability and precision of techniques to control over-exposure, and completeness of the information base, particularly regarding long-term effects. Specific research questions that can change the level of uncertainty meaningfully were identified in these areas: biophysical mechanisms of electrostimulation; the range of thresholds throughout exposed populations; cancer causation in children and adults, including a possible role for contact currents; cognitive, behavioral, and physiological effects on the central nervous system; improved dosimetry; and better understanding of electromagnetic interference with implanted biomedical devices such as pacemakers, defibrillators, and physiological monitors. This report introduces ten papers from the workshop that address these and related topics in detail.

Candidate sites of action for microdosimetry associated with exposure to extremely-low-frequency magnetic fields, electric fields and contact currents

Recent advances enable one to apply numerical techniques to anatomically-correct human models to compute current densities and electric fields in tissue due to exposure to electric fields, magnetic fields, or contact currents. These methods have proved to be informative in estimating exceedance of basic restrictions prescribed by exposure guideline organizations. To date, the analyses have been conducted with a resolution on the order of millimeters. However, these techniques have future roles to play at higher levels of resolution at those sites in target tissues suspected of transducing local electric fields into biological responses. Two specific cases in which high resolution "microdosimetry" would yield value involve (a) residential settings and childhood leukemia and (b) worker exposure and cardiovascular disease. Recent research suggests that residential contact currents on the order of microamperes can produce biologically significant dose (expressed as the local electric field) to the bone marrow of a child. Microdosimetry would focus on pluripotent progenitor cells resident in the marrow compartment, as well as anatomic features that distinguish a child's from an adult's marrow. Laboratory and epidemiologic research has suggested that magnetic field exposure may affect heart rate variability, a measure reflective of autonomic nervous system control of cardiac activity. Given the physical attributes of the central nervous system and the sites that could serve as substrates for field interactions, future microdosimetry addressing heart rate variability effects may be well-advised to focus on the electrically excitable dendritic arborizations of neurons. In both cases, microdosimetry will help shed light on primary interactions in tissue.

Contact voltage measured in residences: implications to the association between magnetic fields and childhood leukemia

We measured magnetic fields and two sources of contact current in 36 homes in Pittsfield, MA. The first source, V(P-W), is the voltage due to current in the grounding wire, which extends from the service panel neutral to the water service line. This voltage can cause contact current to flow upon simultaneous contact with a metallic part of the water system, such as the faucet, and the frame of an appliance, which is connected to the panel neutral through the equipment-grounding conductor. The second is V(W-E), the voltage between the water pipe and earth, attributable to ground currents in the water system and magnetic induction from nearby power lines. In homes with conductive water systems and drains, V(W-E) can produce a voltage between the faucet and drain, which may produce contact current into an individual contacting the faucet while immersed in a bathtub. V(P-W) was not strongly correlated to the magnetic field (both log transformed) (r = 0.28; P < 0.1). On the other hand, V(W-E) was correlated to the residential magnetic field (both log transformed) (r = 0.54; P < 0.001), with the highest voltages occurring in homes near high voltage transmission lines, most likely due to magnetic induction on the grounding system. This correlation, combined with both frequent exposure opportunity for bathing children and substantial dose to bone marrow resulting from contact, lead us to suggest that contact current due to V(W-E) could explain the association between high residential magnetic fields and childhood leukemia.

Health effects relevant to the setting of EMF exposure limits

To date, electric and magnetic exposure limits for frequencies below 100 kHz have been based on vaguely defined neurobiological responses to electric fields induced in tissues in vivo by magnetic fields and on perceptual responses to external electric fields. Advances in tissue dosimetry, risk assessment methods, and biological research on stimulation thresholds and mechanisms are providing new bases for exposure limits. This paper reviews the historical basis for current electric and magnetic exposure limits in preparation for the development of the "next generation" of electric and magnetic occupational and public exposure guidelines. This is followed by an overview of reported neurobiological effects of electric and magnetic stimulation that should be considered in new exposure guidelines. For magnetic fields, there is stronger evidence for setting exposure limits to protect against adverse effects of nerve stimulation than for protecting against visual magnetophosphenes. Magnetophosphenes are not adverse, and the evidence that these perceptual responses of the eye are a precursor or surrogate for other adverse neurologic responses is weak. Rather than relying just on theoretical models to set exposure limits, data from human subjects exposed to pulsed magnetic fields should be used to estimate nerve stimulation thresholds. Such data can provide a solid basis for setting magnetic field exposure limits if uncertainties in the data and inter-individual variability are addressed. Research on sensory perception, spontaneous and evoked potentials, and epidemiologic studies of neuropsychiatric conditions in electric and magnetic exposed populations does not suggest a need for lower exposure limits. However, a report that a 60-mT magnetic field (below the threshold for peripheral nerve stimulation) produces prolonged alterations of brain excitability and "indisposure" of subjects should be investigated in future research.

ELF-EMF, endocrine disruptors, light: what if we apply triage to research?

Triage in medicine is an effective means to maximize health benefits of limited resources. This paper suggests to use triage principles as a means to identify biomedical and epidemiological research priorities. The author applies the following questions to three putative problems which receive different research and funding attention: (a) Does a suspected exposure render many humans at risk? (b) Is a disease frequent, difficult to treat and expensive? and (c) Is a causal link between (a) and (b) biologically plausible? On the basis of answers to (a), (b), and (c) it is concluded that ELF-EMF and childhood leukaemia would not qualify for further urgent investigations and that endocrine disruptors and to-be-identified end-points would not qualify for urgent investigations. Provided that answers to the outlined triage questions can be considered as a practical guide to urgent research investigations, the suggestive link between light, endocrine systems and hormone-dependent cancers should become a higher priority research focus.

Does our electricity distribution system pose a serious risk to public health?

Elevated magnetic field exposures are associated with increased childhood leukaemia risk. A link with breast and other cancers has been postulated via modified melatonin activity. Other illnesses have been linked to electricity distribution, by association or mechanistic considerations. For selected illnesses, this paper estimates the annual number of excess cases that might occur near high-voltage powerlines in the UK. Within 150m of powerlines, magnetic field exposures above 0.1 microT are postulated to result in 9000 excess cases of depression in adults and 60 cases of suicide. Electric field effects can mediate increased exposure to air pollution. Within 400m of powerlines, this may result annually in 200-400 excess cases of lung cancer, 2000-3000 cases of other illnesses associated with air population and 2-6 cases of childhood leukaemia. Seventeen cases of non-melanoma skin cancer might occur by exposure directly under powerlines.

Potential motion related bias in the worn dosimeter measurements of two childhood leukemia studies

Time averaged field measurements produced by a Positron dosimeter worn by study subjects was the primary method of exposure evaluation in two Canadian studies of childhood leukemia and AC magnetic field exposure. Statistically significant but mutually contradictory results obtained in the two studies, done in different locales but under similar study conditions, have not been explained. This report examines operational features of the Positron meter, including an unanticipated sensitivity to wearer motion. If the convalescent cases studied were less active than their healthy controls, as one might expect, then the meter's characteristic responses to motion, particularly as they would affect case-control distributions above and below the different referent group cutpoints used in the two studies, could help to explain both the unexpected inverse risks reported in the larger study and the unusually high risks reported in the smaller study.

Insights into electromagnetic interaction mechanisms

Low frequency (< 300 Hz) electromagnetic (EM) fields induce biological changes that include effects ranging from increased enzyme reaction rates to increased transcript levels for specific genes. The induction of stress gene HSP70 expression by exposure to EM fields provides insight into how EM fields interact with cells and tissues. Insights into the mechanism(s) are also provided by examination of the interaction of EM fields with moving charges and their influence on enzyme reaction rates in cell-free systems. Biological studies with in vitro model systems have focused, in general, on the nature of the signal transduction pathways involved in response to EM fields. It is likely, however, that EM fields also interact directly with electrons in DNA to stimulate biosynthesis. Identification of an EM field-sensitive DNA sequence in the heat shock 70 (HSP70) promoter, points to the application of EM fields in two biomedical applications: cytoprotection and gene therapy. EM field induction of the stress protein hsp70 may also provide a useful biomarker for establishing a science-based safety standard for the design of cell phones and their transmission towers.

Factors confounding cytosolic calcium measurements in Jurkat E6.1 cells during exposure to ELF magnetic fields

Reported changes in the cytosolic calcium concentration ([Ca2+](c)) as a result of exposure to extremely low frequency (ELF) magnetic fields (MF) have been equivocal. In this study, we examine the possibility that some of these differences are attributable to variability associated with the cell cycle, pH of the suspension medium, and response to a calcium agonist. We used a custom designed spectrofluorimeter to measure [Ca2+](c) in Indo 1-AM loaded Jurkat E6.1 cells suspended in conditioned RPMI 1640 medium containing 10% fetal bovine serum. Four exposures were examined: zero static MF (Null), 60 Hz 100 microT(peak) sinusoidal MF (AC), 78 microT static MF (DC), and the combination of the 60 Hz and the 78 microT static MF (AD + DC). A significant decrease in normalized [Ca2+](c) values between 375-495 s for the DC and AC + DC groups was found in comparison to the Null group. However, statistical analysis indicated that cell cycle and quality of the alpha-CD3 monoclonal antibody response were significant covariates, while pH was not a significant covariate. When the effect of these covariates was taken into account, all exposure groups were significantly different from the control. Our results suggest that ELF MF effects may not be seen unless correction is made for biological variability of each cell preparation with respect to cell cycle and [Ca2+](c) response to antigen stimulation.

Biological effects of electromagnetic fields

Nowadays, concerns about hazards from electromagnetic fields represent an alarming source for human lives in technologically developed countries. We are surrounded by electromagnetic fields everywhere we spend our working hours, rest or recreational activities. The aim of this review is to summarize the biological effects due to these fields arising from power and transmission lines, electrical cable splices, electronic devices inside our homes and work-places, distribution networks and associated devices such as cellular telephones and wireless communication tower, etc. Special care has been reserved to study the biological effects of electromagnetic fields on cell lines of the mammalian immune system about which our research group has been working for several years.

Relative contribution of residential and occupational magnetic field exposure over twenty-four hours among people living close to and far from a power line

This study sought to estimate the relative contribution of exposure to 50 Hz magnetic fields experienced at home, at work/school, or elsewhere to the total exposure over 24 hr. Personal exposure meters were carried by 97 adults and children in the Stockholm area. About half of the subjects lived close (<50 m) to a transmission line and half far (>100 m) away. Spot measurements and calculations for the residential exposure were also made. For subjects living<50 m from the line, the exposure at home contributed about 80% of the total magnetic field exposure, measured in mT-hours. Adults living far away experienced only 38% of the total exposure at home, but children still received 55%. Subjects with low time-weighted average (TWA) exposure both at home and at work spent 84% of their time in fields <0.1 microT, and those with high TWA at both locations spent 69% of their time in fields > or = 0.2 microT. This contrast was diluted if only exposure at one location was considered. For spot measurements and calculations of the residential exposure, both sensitivity and specificity was good. However, the intermediate field exposure category (0.1-0.19 microT) showed poor correlation to the 24 hr personal measurements.

Exposure to power frequency magnetic fields suppresses X-ray-induced apoptosis transiently in Ku80-deficient xrs5 cells

In an attempt to determine whether exposure to extremely low frequency (ELF) electromagnetic fields can affect cells, Ku80-deficient cells (xrs5) and Ku80-proficient cells (CHO-K1) were exposed to ELF electromagnetic fields. Cell survival, and the levels of the apoptosis-related genes p21, p53, phospho-p53 (Ser(15)), caspase-3 and the anti-apoptosis gene bcl-2 were determined in xrs5 and CHO-K1 cells following exposure to ELF electromagnetic fields and X-rays. It was found that exposure of xrs5 and CHO-K1 cells to 60 Hz ELF electromagnetic fields had no effect on cell survival, cell cycle distribution and protein expression. Exposure of xrs5 cells to 60 Hz ELF electromagnetic fields for 5 h after irradiation significantly inhibited G(1) cell cycle arrest induced by X-rays (1 Gy) and resulted in elevated bcl-2 expression. A significant decrease in the induction of p53, phospho-p53, caspase-3 and p21 proteins was observed in xrs5 cells when irradiation by X-rays (8 Gy) was followed by exposure to 5 mT ELF magnetic fields. Exposure of xrs5 cells to the ELF electromagnetic fields for 10 h following irradiation significantly decreased X-ray-induced apoptosis from about 1.7% to 0.7%. However, this effect was not found in CHO-K1 cells within 24 h of irradiation by X-rays alone and by X-rays combined with ELF electromagnetic fields. Exposure of xrs5 cells to 60 Hz ELF electromagnetic fields following irradiation can affect cell cycle distribution and transiently suppress apoptosis by decreasing the levels of caspase-3, p21, p53 and phospho-p53 and by increasing bcl-2 expression.

Effect of intermittent and continuous exposure to electromagnetic fields on cultured hippocampal cells

This study was designed to assess the effect of 50 Hz electromagnetic fields (EMFs) on hippocampal cell cultures in the presence or absence of either sodium nitroprusside (SNP, a NO donor) or Fe2+ induced oxidative stress. One week old cultured rat hippocampal cells were exposed to either intermittent EMFs (IEMFs, 50 Hz, 0-5 mT, 1 min ON/OFF cycles, repeated 10 times every 2 h, 6 times/day during 48 h) or continuous EMFs (CEMFs, 50 Hz, 0-5 mT for 48 h). In a second set of experiments, the effect on such EMFs applied in combination with oxidative stress induced by 0.5 microM Fe2+ or SNP was estimated. At the end of both sets of experiments, cell mortality was assessed by lactate dehydrogenase measurements (LDH). Neither type of exposure to EMFs was observed to modify the basal rate of cell mortality. The exposure to CEMFs in presence of either NO or Fe2+ did not induce any significant increase in cell death. However, when cells were exposed to EMFs in the presence of NO, we observed a significant increase in cell death of 11 and 23% (P<0.001) at 2.5 and 5 mT, respectively. This effect had some specificity because IEMFs did not modify the effect of Fe2+ on cell mortality. Although the effects of IEMFs reported in this study were only observed at very high intensities, our model may prove valuable in trying to identify one cellular target of EMFs.