Power Frequency Magnetic Fields Research Articles

Everyday exposure to power frequency magnetic fields and associations with non-specific physical symptoms

The aim of this study was to investigate the association between exposure to extremely low frequency magnetic fields (ELF MF), or power frequency fields, and non-specific physical symptoms (NSPS). In a cross-sectional study, personal exposure to ELF MF was measured for 99 adults selected in and around Amsterdam, the Netherlands in 2009–2010. They were scored on 16 NSPS. As a cut-off point for the individual 24-h time weighted average exposure the 80-percentile (0.09 μT) was chosen. As only one man scored “moderately high” on the somatisation scale against nine women, we decided to proceed analyses only with the 48 women. The crude odds ratio (OR) for women was 8.50 (CI 95%: 1.73–46.75), suggesting that for women environmental exposure to ELF MF is associated with an increased score on NSPS. As this is an exploratory cross-sectional study in a relatively small sample, no conclusions regarding causality can be drawn.

Power frequency magnetic fields induced reactive oxygen species-related autophagy in mouse embryonic fibroblasts

Power frequency magnetic fields (PFMF) have been reported to affect several cellular functions, such as cell proliferation and apoptosis. In this study, we investigated the effects of PFMF on mouse embryonic fibroblasts (MEF) autophagy. After cells were exposed to 50Hz PFMF at 2mT for 0.5h, 2h, 6h, 12h, and 24h, we observed a significant increase in autophagic markers at 6h, including (i) higher microtubule-associated protein 1 light chain 3-II (LC3-II), (ii) the increased formation of GFP-LC3 puncta, and (iii) increased numbers of autophagic vacuoles under transmission electron microscope. Moreover, we provide convincing evidence using chloroquine (CQ) that the increase of autophagic markers was the result of enhanced autophagic flux and not the suppression of lysosomal function. In a search for molecular mechanisms underlying PFMF-mediated autophagy, we observe that the autophagic process involved reactive oxygen species (ROS) and was independent of the mammalian target of rapamycin (mTOR) signaling pathway.

An Experimental Study of Simplified Model for Air-Core Reactors

With the development of electric power system, Power-frequency Magnetic Field (MF) has become a matter of concern recently. In order to speed up the computation and modeling process, the small-scale experimental technique and simplified model for air-core reactors are introduced as a novel way to assess the MF of air-core reactors in this paper. Firstly, the scaling rules of the parameters for air-core reactors are summarized. Then, the scaling rules modification is put forward to reduce the error. Thirdly, three simplified models were established for air-core reactors, including one loop model, two loops model and three loops model. It is concluded after that the two loops model in configuration 2 can be considered as the optimal simplified model.

Assessment of Magnetic Field Mitigation and Electrical Environmental Effects for Commercially Operating 154kV Transmission Lines with Passive Loop

Power frequency magnetic field is still a critical problem for new construction of overhead power transmission lines in Korea because most people have been concerned about possibly carcinogenic effects of it. Although reference level of power frequency(60Hz) magnetic field has been set to 200uT in ICNIRP guidelines published in 2010, Korean government has no intention of adjusting 83.3uT specified by law in 2006 to this new reference level in consideration of people’s concerns for the time being. Regardless of the current regulated magnetic field value, electric utility company has been trying to reduce magnetic field in the residential area in the vicinity of overhead power transmission lines to take into account of public concerns on the long-term effect of magnetic fields. In an effort to reduce magnetic field, engineering side has made considerable efforts to develop passive loop based, cost-effective mitigation technique of power frequency magnetic field more than ten years. In order to verify developed power frequency magnetic field mitigation technique based on passive loop, a horizontal type of passive loop was designed and installed for commercially operating 154kV overhead power transmission line for the first time in Korea. The measurement results before and after the installation of passive loop showed that magnetic field could be reduced to about 20%. The electrical environmental effects such as AN, RI and TVI were assessed before and after the installation of passive loop and these values were complied with the requirements specified by electric utility. It has been confirmed from the field test results that passive loop could be commercially and cost-effectively utilized to mitigate power frequency magnetic field.

Survey of residential power-frequency magnetic fields in Melbourne, Australia.

Pooled analyses of epidemiological studies have reported an association between prolonged residential exposure to power-frequency magnetic fields of >0.4 μT and an increased risk in childhood leukaemia. In order to compare residential magnetic fields in Australia with those in other countries, a survey was conducted in 296 randomly selected homes in Melbourne. Magnetic fields were assessed by performing spot measurements throughout the house and 24-h measurements in rooms where children spend large amounts of time. Children's exposure in Australia was generally comparable with that in other countries with average fields of 0.05-0.06 μT (95 % CI 0.05-0.06 μT). Prolonged exposure of >0.4 μT was shown in ∼2 % of the homes (95 % CI 0.2-3.6 %) mainly being due to close proximity of the house to transmission lines. Based on the results of this survey, the public health impact of a causal association between residential magnetic fields and childhood leukaemia is expected to be small.

Magnetic field shielding optimization in underground power cable duct banks

In this paper, an optimization process, based on a genetic algorithm, is presented for the minimization of the cost (including losses) of ferromagnetic and conductive shields. The purpose of these shields is to maintain the power frequency magnetic field generated by underground power cable duct banks below a certain threshold, without limiting the ampacity of the mitigated cable. Both horizontal and reverse-U shielding geometries are tested through their application to a case study composed of 9 (3×3) ducts where two balanced in-phase three-phase circuits are arranged in three configurations: vertical, horizontal and triangular. The area to be shielded is located above ground surface at one side of the trench axis, where dwellings are usually present. The associated electromagnetic-thermal problem is solved in the optimization process by means of the finite element method. The most suitable solutions are identified, by highlighting the key features of each shield (material and geometry). Further scenarios, such as the addition of a third three-phase circuit in the shielded duct bank, are also analyzed.

Temporal variability of daily personal magnetic field exposure metrics in pregnant women

Recent epidemiology studies of power-frequency magnetic fields and reproductive health have characterized exposures using data collected from personal exposure monitors over a single day, possibly resulting in exposure misclassification due to temporal variability in daily personal magnetic field exposure metrics, but relevant data in adults are limited. We assessed the temporal variability of daily central tendency (time-weighted average, median) and peak (upper percentiles, maximum) personal magnetic field exposure metrics over 7 consecutive days in 100 pregnant women. When exposure was modeled as a continuous variable, central tendency metrics had substantial reliability, whereas peak metrics had fair (maximum) to moderate (upper percentiles) reliability. The predictive ability of a single-day metric to accurately classify participants into exposure categories based on a weeklong metric depended on the selected exposure threshold, with sensitivity decreasing with increasing exposure threshold. Consistent with the continuous measures analysis, sensitivity was higher for central tendency metrics than for peak metrics. If there is interest in peak metrics, more than 1 day of measurement is needed over the window of disease susceptibility to minimize measurement error, but 1 day may be sufficient for central tendency metrics.

Magnetic energy harvesting properties of piezofiber bimorph/NdFeB composites

The magnetic energy harvesting properties of piezoelectric bimorph/magnet composite are studied in this Letter. The devices are fabricated with NdFeB magnets and piezofiber (d33 mode), whose magnetoelectric (ME) coefficient reaches 526 V/cm·Oe (RMS) at the resonant frequency (27.3 Hz), and the maximum power density of which is 38.8 mW/cm3 at 9.78 Oe. Factors influencing the magnetoelectric property of the piezoelectric/magnet composite are discussed, which might guide further enhancement of its energy harvesting ability. This particular ME composite possesses far better energy harvesting abilities than magnetostrictive/piezoelectric composites, able to scavenge energy from power-frequency magnetic fields to support wireless sensor network.

Weak power frequency magnetic field acting similarly to EGF stimulation, induces acute activations of the EGFR sensitive actin cytoskeleton motility in human amniotic cells.

In this article, we have examined the motility-related effects of weak power frequency magnetic fields (MFs) on the epidermal growth factor receptor (EGFR)-sensitive motility mechanism, including the F-actin cytoskeleton, growth of invasive protrusions and the levels of signal molecules in human amniotic epithelial (FL) cells. Without extracellular EGF stimulation, the field stimulated a large growth of new protrusions, especially filopodia and lamellipodia, an increased population of vinculin-associated focal adhesions. And, an obvious reduction of stress fiber content in cell centers was found, corresponding to larger cell surface areas and decreased efficiency of actin assembly of FL cells in vitro, which was associated with a decrease in overall F-actin content and special distributions. These effects were also associated with changes in protein content or distribution patterns of the EGFR downstream motility-related signaling molecules. All of these effects are similar to those following epidermal growth factor (EGF) stimulation of the cells and are time dependent. These results suggest that power frequency MF exposure acutely affects the migration/motility-related actin cytoskeleton reorganization that is regulated by the EGFR-cytoskeleton signaling pathway. Therefore, upon the MF exposure, cells are likely altered to be ready to transfer into a state of migration in response to the stimuli.

A pilot neighborhood study towards establishing a benchmark for reducing electromagnetic field levels within single family residential dwellings

Electromagnetic fields (EMF) permeate the built environment in different forms and come from a number of sources including electrical wiring and devices, wireless communication, ‘energy-efficient’ lighting, and appliances. It can be present in the indoor environment directly from indoor sources, or can be transmitted through building materials from outside sources. Scientists have identified it as an indoor environmental pollutant or toxin that has ubiquitously plagued developed nations causing a variety of adverse health effects such as sick-building syndrome symptoms, asthma, diabetes, multiple sclerosis, leukemia, electro-hypersensitivity (EHS), behavior disorders, and more. There is currently no international consensus on guidelines and exposure limits. This paper presents the results of 29 EMF field audits in single family residential dwellings located within an urban neighborhood in Toronto (Canada). The following EMF spectra were evaluated: radio frequency, power frequency electric fields, power frequency magnetic fields and high frequency voltage transients. The field audits were conducted in order to provide initial baseline statistics to be used in future studies and in order to be compared to a low-cost EMF reduction design incorporated within the Renovation2050 research house — located within the test neighborhood. The results show the low-cost reduction strategy to be effective, on average reducing exposure by 80% for high-intensity EMF metrics. Research of this nature has not been conducted with relation to the built environment and can be used to spark an industry movement to design for low-exposure to EMF in a residential context.

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.

Canceling the Power Frequency Magnetic and Electric Fields of Power Lines

Methods are presented for the cancellation of the power line's power frequency magnetic and electric fields at pre-specified points close to the line corridor. For canceling the magnetic field, the method is based on the use of three auxiliary conductors constituting two mitigating loops. The mitigating conductors' configuration should be geometrically similar to the arrangement of the 3-phase power line's active conductors, with respect to the point at which a zero total magnetic field is required. It will be shown that a considerable field reduction at locations beyond the pre-specified point of zero field is also achieved. The scaling factor relating the power conductors' and the mitigating conductors' geometrical dimensions has a strong effect on the modified field distribution. A procedure is suggested for the optimal selections of the scaling factor for canceling the magnetic field, taking into account both the mitigation effectiveness and the cost of the mitigating conductors. A similar procedure can be used for canceling the electric field at a pre-specified point. It is based on using three auxiliary conductors of geometric mean radii and locations geometrically similar to the power line conductors. They should carry electric charges proportional to those on the active conductors, but of opposite signs. The proportionality factor is equal to the geometrical scaling factor. In the case of a 750kV line, the three voltages required to supply the auxiliary conductors were found to be almost in phase, but of different magnitudes.

Uncertainty evaluation in the measurement of power frequency electric and magnetic fields from AC overhead power lines

Measurements of power frequency electric and magnetic fields from alternating current power lines are carried out in order to evaluate the exposure levels of the human body on the general public. For any electromagnetic field measurement, it is necessary to define the sources of measurement uncertainty and determine the total measurement uncertainty. This paper is concerned with the problems of measurement uncertainty estimation, as the measurement uncertainty budget calculation techniques recommended in standardising documents and research studies are barely described. In this work the total uncertainty of power frequency field measurements near power lines in various measurement sites is assessed by considering not only all available equipment data, but also contributions that depend on the measurement procedures, environmental conditions and characteristics of the field source, which are considered to increase the error of measurement. A detailed application example for power frequency field measurements is presented here by accredited laboratory.

Investigation of transcriptional responses of juvenile mouse bone marrow to power frequency magnetic fields

To seek alterations in gene transcription in bone marrow cells following in vivo exposure of juvenile mice to power frequency magnetic fields, young (21–24-day old) C57BL/6 mice were exposed to a 100μT 50Hz magnetic field for 2h. Transcription was analysed by three methods, High Coverage Expression Profiling (HiCEP), Illumina microarrays and quantitative real-time polymerase chain reaction (QRT-PCR). A pilot HiCEP experiment with 6 exposed (E) and 6 non-exposed (NE) mice identified four candidate responsive transcripts (two unknown transcripts (AK152075 and F10-NED), phosphatidylinositol binding clathrin assembly protein (Picalm) and exportin 7 (Xpo7)). A larger experiment compared 19 E and 15 NE mice using two independent QRT-PCR assays and repeated microarray assays. No significant field-dependent changes were seen, although Picalm showed a trend to significance in one QRT-PCR assay (E/NE=0.91; P=0.06). However, the study was underpowered to detect an effect of this magnitude (52% power at P=0.05). These data indicate the current experimental constraints in detecting small changes in transcription that may occur in response to magnetic fields. These constraints result from technical limitations in the accuracy of assays and biological variation, which together were sufficient to account statistically for the number of differentially expressed transcripts identified in the pilot experiment.

Susceptibility of magnetic information storage to power frequency magnetic fields

The potential for loss of magnetically stored information in the presence of power frequency magnetic fields is described in terms of fundamental physical mechanisms. Three important mechanisms are identified: (1) short term erasure when external fields are high enough to be a significant fraction of the demagnetizing field, (2) long term thermal degradation when external fields exceed a magnetic field associated with the acceleration of the natural thermal degradation process to an unacceptable level, and (3) concentration of magnetic flux by recording equipment, leading to erasure, augmented thermal degradation or corruption of the recording process. Quantitative expressions are developed for evaluation of the first two mechanisms in terms of fundamental magnetic properties of the recording medium, and a 3-D finite element simulation is used to quantitatively assess the third mechanism for a modern recording head. The first two mechanisms typically require field levels much larger than ordinary power frequency fields, but the third mechanism can lead to local fields large enough to bring the prior mechanisms into play. Results are put in the context of prior published standards and descriptions.

Effective Combination of Soft Magnetic Materials for Magnetic Shielding

This study proposes an effective method in the arrangement of layers of high permeability materials for shielding power frequency magnetic field. The side of a neutral ground reactor was blocked with one or two layers of grain-oriented electrical steel (GO), nonoriented electrical steel (NGO), and permalloy (PC). In a weak magnetic field, PC showed the highest shielding performance, whereas GO was the best in a strong magnetic field. NGO had a lower shielding performance than GO, but was better than PC in a very strong magnetic field. When shielding with two layers directly adjacent to each other, the performance level of GO/PC combination (GO is closer to the field source) was between that of GO/GO and PC/PC combinations. When the two layers were slightly separated, on the other hand, GO/PC was most effective in a wide range of magnetic fields. These results are due to the shunt effect of high permeability materials and change of rank of permeability with magnetic field strength between different magnetic materials. Closely adjacent layers act as one body under the regime of shunt mechanism of magnetic shielding. Once the layers are separated, the GO sheet effectively reduces the strong magnetic field first, and then the PC sheet effectively shields the weakened field.

A comparison of magnetic fields inside and outside high-voltage urban 110-kV power substations with the exposure recommendations of the Ukrainian regulatory authorities

The aim of this study was to carry out theoretical investigations of power frequency magnetic fields (MFs), produced inside and outside the domain of urban 110-kV power substations and to establish a correspondence between the levels of the fields and the specified population limits as defined by Ukrainian regulations. The fields produced by high-voltage substations were studied based on the application of the numerical finite element methodology. The investigations have shown that magnetic flux density values calculated inside and outside the considered 110-kV power substations do not reach the exposure limits specified by the Ukrainian regulations (1750 μT) and by international guidelines (ICNIRP 2010). Inside the domain of the substation, the maximum value of MFs was found under the 10-kV busbars and it equalled 420 μT.

Could the geomagnetic field be an effect modifier for studies of power-frequency magnetic fields and childhood leukaemia?

Epidemiological studies find an association between power-frequency magnetic fields and childhood leukaemia. One candidate mechanism for a causal link is effects of magnetic fields on biological reactions involving free radicals. This mechanism predicts effects from variations in static, as well as alternating, magnetic fields, and therefore different consequences at different locations on the earth’s surface due to variations in geomagnetic field. Testing this directly is problematic. Instead, we investigate whether geomagnetic field appears to be an effect modifier in studies of alternating magnetic fields. We find some, but rather limited and not statistically significant, evidence for this, and discuss the implications.

Investigation of occupational exposure to power frequency electromagnetic fields in workers of power grid

To measure and assess the levels of occupational exposure to power frequency electromagnetic fields in workers of power grid. PMM8053 electromagnetic fields measuring system with EHP-50 probe was used to measure the levels of electromagnetic fields at working place. Personal dosimeters (EMDEX LITE) were utilized to measure the individual exposure levels of power frequency magnetic field. The results were evaluated with the limitation criteria of GBZ2.2 and ICNIRP. In the 500 kV ultra high voltage substation, the intensity at 90% measure points of power electric field was more than 5 kV/m. The magnetic field intensity in the areas nearby reactors and capacitors was often higher than 100 µT, even several hundreds µT. The mean daily exposure levels of workers in power grid were between 0.04 and 5.0 µT, and the exposure levels of 70% workers were higher than 0.4 µT. In the areas of ultra high voltage and nearby the reactors and capacitors are the key control points for occupational health in power grid. There is acute health risk of workers exposed to high accumulative exposure levels.

Influence of 50 Hz-1 mT magnetic field on human median nerve

In this study, human median nerve was exposed to power frequency magnetic fields in order to provide clarification for possibly changeable nerve conduction mechanism. The nerve was exposed to 50 Hz magnetic field by utilizing a special Helmholtz applicator. The experiments were carried out with six healthy human-volunteers. Median motor distal amplitude/proximal amplitude ratios were recorded from adult human median nerve pre-exposure, during, and post-exposure to a 50 Hz, 1 mT magnetic field. The result of 18 measurements shows that median motor distal amplitude/proximal amplitude ratio significantly decreases in pre-exposure state as compare to post exposure of which. The results of this study may be useful for some nerve rehabilitation, excitation, and stimulation in more effective/safe physical therapy. Additionally, 50 Hz, 1 mT sinusoidal magnetic field should not be recognizing as safe for conduction mechanism on a nerve. These mechanisms would be cleared by new advanced engineering models in other future works.