International Commission on Non-Ionizing Radiation Protection (ICNIRP). Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz)

Advances in Residential Design Related to the Influence of Geomagnetism

Since the origin of the Modern Movement, there has been a basic commitment to improving housing conditions and the well-being of occupants, especially given the prediction that 2/3 of humanity will reside in cities by 2050. Moreover, a compact model of the city with tall buildings and urban densification at this scale will be generated. Continuous constructive and technological advances have developed solid foundations on safety, energy efficiency, habitability, and sustainability in housing design. However, studies on improving the quality of life in these areas continue to be a challenge for architects and engineers. This paper seeks to contribute health-related information to the study of residential design, specifically the influence of the geomagnetic field on its occupants. After compiling information on the effects of geomagnetic fields from different medical studies over 23 years, a case study of a 16-story high-rise building is presented, with the goal of proposing architectural design recommendations for long-term occupation in the same place. The purpose of the present work is three-fold: first, to characterize the geomagnetic field variability of buildings; second, to identify the causes and possible related mechanisms; and third, to define architectural criteria on the arrangement of uses and constructive elements for housing.

Influence of tissue conductivity on foetal exposure to extremely low frequency magnetic fields at 50 Hz using stochastic dosimetry

Human exposure to extremely low frequency magnetic fields (ELF-MF) at 50 Hz is still a topic of great interest due to the possible correlation with childhood leukaemia. The estimation of induced electric fields in human tissues exposed to electromagnetic fields (EMFs) strictly depends on several variables which include the dielectric properties of the tissues. In this paper, the influence of the conductivity assignment to foetal tissues at different gestational ages on the estimation of the induced electric field due to ELF-MF exposure at 50 Hz has been quantified by means of a stochastic approach using polynomial chaos theory. The range of variation in conductivity values for each foetal tissue at each stage of pregnancy have been defined through three empirical approaches and the induced electric field in each tissue has been modelled through stochastic dosimetry. The main results suggest that both the peak and median induced electric fields in foetal fat vary by more than 8% at all gestational ages. On the contrary, the electric field induced in foetal brain does not seem to be significantly affected by conductivity data changes. The maximum exposure levels, in terms of the induced electric field found in each specific tissue, were found to be significantly below the basic restrictions indicated in the ICNIRP Guidelines, 2010.

Workers' exposure to electric fields during the task 'maintenance of an operating device of circuit breaker from a service platform' at 110-kV substations

The objective of the study was to investigate occupational exposure to electric fields during the task 'maintenance of an operating device of circuit breaker from a service platform' at 110-kV substations. The aim was also to compare the results to Directive 2013/35/EU. At 16 substations, 255 electric field measurements were performed. The highest mean value of the electric fields was 9.6 kV⋅m^-1. At 63% of substations the maximum values were over 10.0 kV⋅m^-1, and at 31% of the substations the 75th percentiles were over 10.0 kV⋅m^-1, which is the low action level (AL) according to Directive 2013/35/EU. All measured values were below the high AL (20.0 kV⋅m^-1). In the future, it is important to take into account that the measurements were only taken at Finnish 110-kV substations; therefore, it is not possible to generalize these results to other countries and different types of substations.

Occupational exposure to electromagnetic fields in magnetic resonance environment: basic aspects and review of exposure assessment approaches

The purpose of this review is to make a contribution to build a comprehensive knowledge of the main aspects related to the occupational exposure to electromagnetic fields (EMFs) in magnetic resonance imaging (MRI) environments. Information has been obtained from original research papers published in international peer-reviewed journals in the English language and from documents published by governmental bodies and authorities. An overview of the occupational exposure scenarios to static magnetic fields, motion-induced, time-varying magnetic fields, and gradient and radiofrequency fields is provided, together with a summary of the relevant regulation for limiting exposure. A particular emphasis is on reviewing the main EMF exposure assessment approaches found in the literature. Exposure assessment is carried out either by measuring the unperturbed magnetic fields in the MRI rooms, or by personal monitoring campaigns, or by the use of numerical methods. A general lack of standardization of the procedures and technologies adopted for exposure assessment has emerged, which makes it difficult to perform a direct comparison of results from different studies carried out by applying different assessment strategies. In conclusion, exposure assessment approaches based on data collection and numerical models need to be better defined in order to respond to specific research questions. That would provide for a more complete characterization of the exposure patterns and for identification of the factors determining the exposure variability. Graphical abstract Main approaches adopted in the literature to perform occupational exposure assessment to electromagnetic fields (EMFs) in magnetic resonance imaging (MRI) environments. SMF: static magnetic field; GMF: gradient magnetic fields; RF: radio-frequencies.

Perspectives on setting limits for RF contact currents: a commentary

BACKGROUND

Limits for exposure to radiofrequency (RF) contact currents are specified in the two dominant RF safety standards and guidelines developed by the Institute of Electrical and Electronics Engineers (IEEE) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP). These limits are intended to prevent RF burns when contacting RF energized objects caused by high local tissue current densities. We explain what contact currents are and review some history of the relevant limits with an emphasis on so-called "touch" contacts, i.e., contact between a person and a contact current source during touch via a very small contact area.

RESULTS

Contact current limits were originally set on the basis of controlling the specific absorption rate resulting from the current flowing through regions of small conductive cross section within the body, such as the wrist or ankle. More recently, contact currents have been based on thresholds of perceived heating. In the latest standard from the IEEE developed for NATO, contact currents have been based on two research studies in which thresholds for perception of thermal warmth or thermal pain have been measured. Importantly, these studies maximized conductive contact between the subject and the contact current source. This factor was found to dominate the response to heating wherein high resistance contact, such as from dry skin, can result in local heating many times that from a highly conductive contact. Other factors such as electrode size and shape, frequency of the current and the physical force associated with contact are found to introduce uncertainty in threshold values when comparing data across multiple studies.

CONCLUSIONS

Relying on studies in which the contact current is minimized for a given threshold does not result in conservative protection limits. Future efforts to develop limits on contact currents should include consideration of (1) the basis for the limits (perception, pain, tissue damage); (2) understanding of the practical conditions of real world exposure for contact currents such as contact resistance, size and shape of the contact electrode and applied force at the point of contact; (3) consistency of how contact currents are applied in research studies across different researchers; (4) effects of frequency.

RKIP-Mediated NF-κB Signaling is involved in ELF-MF-mediated improvement in AD rat

In a previous study, we reported the positive effects of extremely low frequency electromagnetic field (ELF-MF) exposure on Alzheimer's disease (AD) rats; however, the underlying mechanism remains unclear. In addition, we found that Raf-1 kinase inhibitor protein (RKIP) was downregulated by microwave exposure in the rat hippocampus. Our hypothesis was that RKIP-mediated NF-κB pathway signaling is involved in the effect of ELF-MF on the AD rat. In this study, D-galactose intraperitoneal (50 mg/kg/d for 42 d) and Aβ_25-35 hippocampal (5 μL/unilateral, bilateral, single-dose) injection were implemented to establish an AD rat model. Animals were exposed to 50 Hz and 400 µT ELF-MF for 60 continuous days. The spatial memory ability of the rat was then tested using the Morris water maze. Protein expression and interaction were detected by western blotting and co-immunoprecipitation for RKIP-mediated NF-κB pathway factors. The results showed that ELF-MF exposure partially improved the cognitive disorder, upregulated the levels of RKIP, TAK1, and the RKIP/TAK1 interaction, but downregulated p-IKK levels in AD rats. These results indicated that RKIP-mediated NF-κB pathway signaling plays an important role in the ELF-MF exposure-mediated improvements in the AD rat. Our study suggested that ELF-MF exposure might have a potential therapeutic value for AD. Further in depth studies are required in the future.

Numerical assessment of low-frequency dosimetry from sampled magnetic fields

Low-frequency dosimetry is commonly assessed by evaluating the electric field in the human body using the scalar potential finite difference method. This method is effective only when the sources of the magnetic field are completely known and the magnetic vector potential can be analytically computed. The aim of the paper is to present a rigorous method to characterize the source term when only the magnetic flux density is available at discrete points, e.g. in case of field measurements. The method is based on the solution of the discrete magnetic curl equation. The system is restricted to the independent set of magnetic fluxes and circulations of magnetic vector potential using the topological information of the computational mesh. The solenoidality of the magnetic flux density is preserved using a divergence-free interpolator based on vector radial basis functions. The analysis of a benchmark problem shows that the complexity of the proposed algorithm is linearly dependent on the number of elements with a controllable accuracy. The method proposed in this paper also proves to be useful and effective when applied to a real world scenario, where the magnetic flux density is measured in proximity of a power transformer. A 8 million voxel body model is then used for the numerical dosimetric analysis. The complete assessment is completed in less than 5 min, that is more than acceptable for these problems.

In silico modelling of influence from low or intermediate frequency magnetic fields on users of wearable insulin pumps

PURPOSE

The aim was to model the effects of exposure to a low or intermediate frequency electromagnetic field (LIF-EMF), characterized by the electric field induced in the body, in order to evaluate how the type of insulin needle and the way it is injected influences the exposed user of a wearable insulin pump.

MATERIAL AND METHODS

Numerical models of exposure scenarios (sources of LIF-EMF, with a dominant magnetic component: 50Hz-1MHz; the insulin needle type; the way it is injected and insulin pump user) were worked out. The influence of the insulin needle on the user's safety (the ratio of the induced electric field in tissues surrounding the needle and tissues of a person without an injection, both exposed identically) were calculated.

RESULTS

The effects of LIF-EMF exposure in insulin pump users were found to be up to approximately 7-times higher, varying with statistically significance (p < .05) with the material of the needle, the way it is injected and the polarization of the affecting magnetic field.

CONCLUSIONS

When steel insulin needles is used, the assessment of user's EMF exposure should be carried out using magnetic field limits at least 5-times lower than given in general international requirements.

Exposure Assessment and Biomonitoring of Workers in Magnetic Resonance Environment: An Exploratory Study

Magnetic resonance imaging (MRI) has evolved rapidly over the past few decades as one of the most flexible tools in medical research and diagnostic imaging. MRI facilities are important sources of multiple exposure to electromagnetic fields for both patients and health-care staff, due to the presence of electromagnetic fields of multiple frequency ranges, different temporal variations, and field strengths. Due to the increasing use and technological advancements of MRI systems, clearer insights into exposure assessment and a better understanding of possible harmful effects due to long-term exposures are highly needed. In the present exploratory study, exposure assessment and biomonitoring of MRI workers at the Radio-diagnostics Unit of the National Cancer Institute of Naples "Pascale Foundation" (Naples, Italy) have been carried out. In particular, exposure to the MRI static magnetic field (SMF) has been evaluated by means of personal monitoring, while an application tool has been developed to provide an estimate of motion-induced, time-varying electric fields. Measurement results have highlighted a high day-to-day and worker-to-worker variability of the exposure to the SMF, which strongly depends on the characteristics of the environment and on personal behaviors, and the developed application tool can be adopted as an easy-to-use tool for rapid and qualitative evaluation of motion-induced, time-varying electric field exposure. Regarding biomonitoring, the 24 workers of the Radio-diagnostics Unit were enrolled to evaluate both spontaneous and mitomycin C-induced chromosomal fragility in human peripheral blood lymphocytes, by means of the cytokinesis-block micronucleus assay. The study subjects were 12 MRI workers, representative of different professional categories, as the exposed group, and 12 workers with no MRI exposure history, as the reference group. The results show a high worker-to-worker variability for both field exposure assessment and biomonitoring, as well as several critical issues and practicalities to be faced with in this type of investigations. The procedures for risk assessment and biomonitoring proposed here can be used to inform future research in this field, which will require a refinement of exposure assessment methods and an enlargement of the number of subjects enrolled in the biomonitoring study to gain robust statistics and reliable results.

Stochastic Dosimetry for the Assessment of Children Exposure to Uniform 50 Hz Magnetic Field with Uncertain Orientation

This study focused on the evaluation of the exposure of children aging from five to fourteen years to 50 Hz homogenous magnetic field uncertain orientation using stochastic dosimetry. Surrogate models allowed assessing how the variation of the orientation of the magnetic field influenced the induced electric field in each tissue of the central nervous system (CNS) and in the peripheral nervous system (PNS) of children. Results showed that the electric field induced in CNS and PNS tissues of children were within the ICNIRP basic restrictions for general public and that no significant difference was found in the level of exposure of children of different ages when considering 10000 possible orientations of the magnetic field. A "mean stochastic model," useful to estimate the level of exposure in each tissue of a representative child in the range of age from five to fourteen years, was developed. In conclusion, this study was useful to deepen knowledge about the ELF-MF exposure, including the evaluation of variable and uncertain conditions, thus representing a step towards a more realistic characterization of the exposure to EMF.

Behavioral testing of mice exposed to intermediate frequency magnetic fields indicates mild memory impairment

Human exposure to intermediate frequency magnetic fields (MF) is increasing due to applications like electronic article surveillance systems and induction heating cooking hobs. However, limited data is available on their possible health effects. The present study assessed behavioral and histopathological consequences of exposing mice to 7.5 kHz MF at 12 or 120 μT for 5 weeks. No effects were observed on body weight, spontaneous activity, motor coordination, level of anxiety or aggression. In the Morris swim task, mice in the 120 μT group showed less steep learning curve than the other groups, but did not differ from controls in their search bias in the probe test. The passive avoidance task indicated a clear impairment of memory over 48 h in the 120 μT group. No effects on astroglial activation or neurogenesis were observed in the hippocampus. The mRNA expression of brain-derived neurotrophic factor did not change but expression of the proinflammatory cytokine tumor necrosis factor alpha mRNA was significantly increased in the 120 μT group. These findings suggest that 7.5 kHz MF exposure may lead to mild learning and memory impairment, possibly through an inflammatory reaction in the hippocampus.

OCCUPATIONAL EXPOSURE OF NMR SPECTROMETRISTS TO STATIC AND RADIOFREQUENCY FIELDS

Occupational exposure to static and radiofrequency fields emitted by nuclear magnetic resonance spectrometers was assessed through systematic field metering during operation of 19 devices in nine research centers. Whereas no measurable levels of radiofrequency radiation were registered outside the spectrometers, significant exposure to static field was detected, with maximum values recorded at the user's hand (B = 683.00 mT) and head-thorax (B = 135.70 mT) during spectrometer manipulation. All values were well below the exposure limits set by the European standard for workers protection against the effects of acute field exposure only. As for potential effects of chronic exposure, waiting for more complete knowledge, adoption of technical and operational strategies for exposure minimizing is advisable. In this respect, the data revealed that compared with standard magnetic shielding, ultrashield technology allows a 20-65-fold reduction of the field strength received by the operator.

Effects of A 60 Hz Magnetic Field of Up to 50 milliTesla on Human Tremor and EEG: A Pilot Study

Humans are surrounded by sources of daily exposure to power-frequency (60 Hz in North America) magnetic fields (MFs). Such time-varying MFs induce electric fields and currents in living structures which possibly lead to biological effects. The present pilot study examined possible extremely low frequency (ELF) MF effects on human neuromotor control in general, and physiological postural tremor and electroencephalography (EEG) in particular. Since the EEG cortical mu-rhythm (8–12 Hz) from the primary motor cortex and physiological tremor are related, it was hypothesized that a 60 Hz MF exposure focused on this cortical region could acutely modulate human physiological tremor. Ten healthy volunteers (age: 23.8 ± 4 SD) were fitted with a MRI-compatible EEG cap while exposed to 11 MF conditions (60 Hz, 0 to 50 mT_rms, 5 mT_rms increments). Simultaneously, physiological tremor (recorded from the contralateral index finger) and EEG (from associated motor and somatosensory brain regions) were measured. Results showed no significant main effect of MF exposure conditions on any of the analyzed physiological tremor characteristics. In terms of EEG, no significant effects of the MF were observed for C1, C3, C5 and CP1 electrodes. However, a significant main effect was found for CP3 and CP5 electrodes, both suggesting a decreased mu-rhythm spectral power with increasing MF flux density. This is however not confirmed by Bonferroni corrected pairwise comparisons. Considering both EEG and tremor findings, no effect of the MF exposure on human motor control was observed. However, MF exposure had a subtle effect on the mu-rhythm amplitude in the brain region involved in tactile perception. Current findings are to be considered with caution due to the small size of this pilot work, but they provide preliminary insights to international agencies establishing guidelines regarding electromagnetic field exposure with new experimental data acquired in humans exposed to high mT-range MFs.

IEI-EMF provocation case studies: A novel approach to testing sensitive individuals

The etiology of Idiopathic Environmental Intolerance attributed to Electromagnetic Fields (IEI-EMF) is controversial. While the majority of studies have indicated that there is no relationship between EMF exposure and symptoms reported by IEI-EMF sufferers, concerns about methodological issues have been raised. Addressing these concerns, the present experiment was designed as a series of individual case studies to determine whether there is a relationship between radiofrequency-electromagnetic field (RF-EMF) exposure and an IEI-EMF individual's self-reported symptoms. Three participants aged 44-64 were tested during a series of sham and active exposure trials (2 open-label trials; 12 randomized, double-blind, counterbalanced trials), where symptom severity and exposure detection were scored using 100 mm visual analogue scales. The RF-EMF exposure was a 902-928 MHz spread spectrum digitally modulated signal with an average radiated power output of 1 W (0.3 W/m² incident power density at the participant). In the double-blind trials, no significant difference in symptom severity or exposure detection was found for any of the participants between the two conditions. Belief of exposure strongly predicted symptom severity score for all participants. Despite accounting for several possible limitations, the present experiment failed to show a relationship between RF-EMF exposure and an IEI-EMF individual's symptoms. Bioelectromagnetics. 39:132-143, 2018. © 2017 Wiley Periodicals, Inc.

Cellular Response to ELF-MF and Heat: Evidence for a Common Involvement of Heat Shock Proteins?

It has been shown that magnetic fields in the extremely low frequency range (ELF-MF) can act as a stressor in various in vivo or in vitro systems, at flux density levels below those inducing excitation of nerve and muscle cells, which are setting the limits used by most generally accepted exposure guidelines, such as the ones published by the International Commission on Non-Ionizing Radiation Protection. In response to a variety of physiological and environmental factors, including heat, cells activate an ancient signaling pathway leading to the transient expression of heat shock proteins (HSPs), which exhibit sophisticated protection mechanisms. A number of studies suggest that also ELF-MF exposure can activate the cellular stress response and cause increased HSPs expression, both on the mRNA and the protein levels. In this review, we provide some of the presently available data on cellular responses, especially regarding HSP expression, due to single and combined exposure to ELF-MF and heat, with the aim to compare the induced effects and to detect possible common modes of action. Some evidence suggest that MF and heat can act as costressors inducing a kind of thermotolerance in cell cultures and in organisms. The MF exposure might produce a potentiated or synergistic biological response such as an increase in HSPs expression, in combination with a well-defined stress, and in turn exert beneficial effects during certain circumstances.

Occupational exposure in MR facilities due to movements in the static magnetic field

PURPOSE

The exposure of operators moving in the static field of magnetic resonance (MR) facilities was assessed through measurements of the magnetic flux density, which is experienced as variable in time because of the movement. Collected data were processed to allow the comparison with most recent and authoritative safety standards.

METHODS

Measurements of the experienced magnetic flux density B were performed using a probe worn by volunteers moving in MR environments. A total of 55 datasets were acquired nearby a 1.5 T, 3 T, and 7 T whole body scanners. Three different metrics were applied: the maximum intensity of B, to be compared with 2013/35/EU Directive exposure limit values for static fields; the maximum variation of the vector B on every 3s-interval, for comparison with the ICNIRP-2014 basic restriction aimed at preventing vertigo effects; two weighted-peak indices (for "sensory" and "health" effects: SENS-WP, HLTH-WP), assessing compliance with ICNIRP-2014 and EU Directive recommendations intended to prevent stimulation effects.

RESULTS

Peak values of |B| were greater than 2 T in nine of the 55 datasets. All the datasets at 1.5 T and 3 T were compliant with the limit for vertigo effects, whereas six datasets at 7 T turned out to be noncompliant. At 7 T, all 36 datasets were noncompliant for the SENS-WP index and 26 datasets even for the HLTH-WP one.

CONCLUSIONS

Results demonstrate that compliance with EU Directive limits for static fields does not guarantee compliance with ICNIRP-2014 reference levels and clearly show that movements in the static field could be the key component of the occupational exposure to EMF in MR facilities.

Equivalent magnetic vector potential model for low-frequency magnetic exposure assessment

In this paper, a novel source model based on a magnetic vector potential for the assessment of induced electric field strength in a human body exposed to the low-frequency (LF) magnetic field of an electrical appliance is presented. The construction of the vector potential model requires only a single-component magnetic field to be measured close to the appliance under test, hence relieving considerable practical measurement effort-the radial basis functions (RBFs) are adopted for the interpolation of discrete measurements; the magnetic vector potential model can then be directly constructed by summing a set of simple algebraic functions of RBF parameters. The vector potentials are then incorporated into numerical calculations as the equivalent source for evaluations of the induced electric field in the human body model. The accuracy and effectiveness of the proposed model are demonstrated by comparing the induced electric field in a human model to that of the full-wave simulation. This study presents a simple and effective approach for modelling the LF magnetic source. The result of this study could simplify the compliance test procedure for assessing an electrical appliance regarding LF magnetic exposure.

Power frequency magnetic field promotes a more malignant phenotype in neuroblastoma cells via redox-related mechanisms

In accordance with the classification of the International Agency for Research on Cancer, extremely low frequency magnetic fields (ELF-MF) are suspected to promote malignant progression by providing survival advantage to cancer cells through the activation of critical cytoprotective pathways. Among these, the major antioxidative and detoxification defence systems might be targeted by ELF-MF by conferring cells significant resistance against clinically-relevant cytotoxic agents. We investigated whether the hyperproliferation that is induced in SH-SY5Y human neuroblastoma cells by a 50 Hz, 1 mT ELF magnetic field was supported by improved defence towards reactive oxygen species (ROS) and xenobiotics, as well as by reduced vulnerability against both H2O2 and anti-tumor ROS-generating drug doxorubicin. ELF-MF induced a proliferative and survival advantage by activating key redox-responsive antioxidative and detoxification cytoprotective pathways that are associated with a more aggressive behavior of neuroblastoma cells. This was coupled with the upregulation of the major sirtuins, as well as with increased signaling activity of the erythroid 2-related nuclear transcription factor 2 (NRF2). Interestingly, we also showed that the exposure to 50 Hz MF as low as 100 µT may still be able to alter behavior and responses of cancer cells to clinically-relevant drugs.

Use of Rod Compactors for High Voltage Overhead Power Lines Magnetic Field Mitigation

In the last decades, strengthening the high voltage transmission system through the installation of new overhead power lines has become critical, especially in highly developed areas. Present laws concerning the human exposure to electric and magnetic fields introduce constraints to be considered in both new line construction and existing systems. In the paper, a technique for passive magnetic field mitigation in areas close to overhead power lines is introduced, fully modelled and discussed through a parametric analysis. The investigated solution, which basically consists in approaching line conductors along the span making use of rod insulators, is applicable on both existing and under-design overhead lines as an alternative to other mitigating actions. Making use of a 3-dimensional representation, the procedure computes both positions of phase conductors and forces acting on insulators, towers, conductors and compactors, with the aim of evaluating the additional mechanical stress introduced by the compactors. Finally, a real case study is reported to demonstrate and quantify the benefits in terms of ground magnetic field reduction achievable by applying the proposed solution, in comparison to a traditional configuration. Furthermore, using compactors to passively reduce the magnetic field is simple to be applied, minimally invasive and quite inexpensive as regards to alternative mitigating actions.

Human exposure to pulsed fields in the frequency range from 6 to 100 GHz

Restrictions on human exposure to electromagnetic waves at frequencies higher than 3-10 GHz are defined in terms of the incident power density to prevent excessive temperature rise in superficial tissue. However, international standards and guidelines differ in their definitions of how the power density is interpreted for brief exposures. This study investigated how the temperature rise was affected by exposure duration at frequencies higher than 6 GHz. Far-field exposure of the human face to pulses shorter than 10 s at frequencies from 6 to 100 GHz was modelled using the finite-difference time-domain method. The bioheat transfer equation was used for thermal modelling. We investigated the effects of frequency, polarization, exposure duration, and depth below the skin surface on the temperature rise. The results indicated limitations in the current human exposure guidelines and showed that radiant exposure, i.e. energy absorption per unit area, can be used to limit temperature rise for pulsed exposure. The data are useful for the development of human exposure guidelines at frequencies higher than 6 GHz.

Effects of intermediate frequency magnetic fields on male fertility indicators in mice

Human exposure to intermediate frequency (IF) fields is increasing due to new applications such as electronic article surveillance systems, wireless power transfer and induction heating cookers. However, limited data is available on effects of IF magnetic fields (MF) on male fertility function. This study was conducted to assess possible effects on fertility indicators from exposure to IF MF. Male C57BL/6J mice were exposed continuously for 5 weeks to 7.5kHz MF at 12 and 120μT. Sperm cells from cauda epididymis were analysed for motility, total sperm counts, and head abnormalities. Motile sperm cells were classified as progressive or non-progressive. Testicular spermatid heads were counted as well. The body weight development and reproductive tissue weights were not affected. No exposure-related differences were observed in sperm counts or sperm head abnormalities. Proportion of non-motile cells was significantly decreased in the 120µT group, and a corresponding increase was seen in the percentage of motile cells (significant in non-progressive motile cells). In conclusion, no adverse effects on fertility indicators were observed. Increased sperm motility is an interesting finding that needs to be confirmed in further studies.

Modelling of induced electric fields based on incompletely known magnetic fields

Determining the induced electric fields in the human body is a fundamental problem in bioelectromagnetics that is important for both evaluation of safety of electromagnetic fields and medical applications. However, existing techniques for numerical modelling of induced electric fields require detailed information about the sources of the magnetic field, which may be unknown or difficult to model in realistic scenarios. Here, we show how induced electric fields can accurately be determined in the case where the magnetic fields are known only approximately, e.g. based on field measurements. The robustness of our approach is shown in numerical simulations for both idealized and realistic scenarios featuring a personalized MRI-based head model. The approach allows for modelling of the induced electric fields in biological bodies directly based on real-world magnetic field measurements.

Index extraction for electromagnetic field evaluation of high power wireless charging system

This paper presents the precise dosimetry for highly resonant wireless power transfer (HR-WPT) system using an anatomically realistic human voxel model. The dosimetry for the HR-WPT system designed to operate at 13.56 MHz frequency, which one of the ISM band frequency band, is conducted in the various distances between the human model and the system, and in the condition of alignment and misalignment between transmitting and receiving circuits. The specific absorption rates in the human body are computed by the two-step approach; in the first step, the field generated by the HR-WPT system is calculated and in the second step the specific absorption rates are computed with the scattered field finite-difference time-domain method regarding the fields obtained in the first step as the incident fields. The safety compliance for non-uniform field exposure from the HR-WPT system is discussed with the international safety guidelines. Furthermore, the coupling factor concept is employed to relax the maximum allowable transmitting power. Coupling factors derived from the dosimetry results are presented. In this calculation, the external magnetic field from the HR-WPT system can be relaxed by approximately four times using coupling factor in the worst exposure scenario.

New conducted electrical weapons: Electrical safety relative to relevant standards

INTRODUCTION

We have previously published about TASER^® conducted electrical weapons (CEW) compliance with international standards. CEWs deliver electrical pulses that can inhibit a person's neuromuscular control or temporarily incapacitate. An eXperimental Rotating-Field (XRF) waveform CEW and the X2 CEW are new 2-shot electrical weapon models designed to target a precise amount of delivered charge per pulse. They both can deploy 1 or 2 dart pairs, delivered by 2 separate cartridges. Additionally, the XRF controls delivery of incapacitating pulses over 4 field vectors, in a rotating sequence. As in our previous study, we were motivated by the need to understand the cardiac safety profile of these new CEWs. The goal of this paper is to analyze the nominal electrical outputs of TASER XRF and X2 CEWs in reference to provisions of all relevant international standards that specify safety requirements for electrical medical devices and electrical fences. Although these standards do not specifically mention CEWs, they are the closest electrical safety standards and hence give very relevant guidance.

METHODS

The outputs of several TASER XRF and X2 CEWs were measured under normal operating conditions. The measurements were compared against manufacturer specifications. CEWs electrical output parameters were reviewed against relevant safety requirements of UL 69, IEC 60335-2-76 Ed 2.1, IEC 60479-1, IEC 60479-2, AS/NZS 60479.1, AS/NZS 60479.2, IEC 60601-1 and BS EN 60601-1.

RESULTS AND CONCLUSION

Our study confirmed that the nominal electrical outputs of TASER XRF and X2 CEWs lie within safety bounds specified by relevant standards.

The Weighted Peak Method in the Time Domain Compared With Alternative Methods for Assessing LF Electric and Magnetic Fields

Directive 2013/35/EU of the European Parliament and Council recommends the weighted peak method for assessing non-thermal effects of low frequency (LF) electric and magnetic fields. This article shows that this method is very practical and user friendly and is absolutely reliable to lead to correct results when applied in the time domain. The method can be used without limitations for any field profile and emulates the underlying physical and biological effects significantly better than all other presently known methods. For this reason, this method is described and recommended in many technical standards for assessing the non-thermal effects of electromagnetic fields and is recognized by the international scientific community. The disadvantages of competing methods are demonstrated. Some technical aspects of real measurement systems are also examined.

Estimates of peak electric fields induced by Transcranial magnetic stimulation in pregnant women as patients using an FEM full-body model

Transcranial magnetic stimulation (TMS) for treatment of depression during pregnancy is an appealing alternative to fetus-threatening drugs. However, no studies to date have been performed that evaluate the safety of TMS for a pregnant mother patient and her fetus. A full-body FEM model of a pregnant woman with about 100 tissue parts has been developed specifically for the present study. This model allows accurate computations of induced electric field in every tissue given different locations of a shape-eight coil, a biphasic pulse, common TMS pulse durations, and using different values of the TMS intensity measured in SMT (Standard Motor Threshold) units. Our simulation results estimate the maximum peak values of the electric field in the fetal area for every fetal tissue separately and for the TMS intensity of one SMT unit.

New conducted electrical weapons: Thoracic cage shielding effects

INTRODUCTION

The TASER^® conducted electrical weapon (CEW) delivers electrical pulses that can temporarily incapacitate subjects. For existing CEW models, we have previously presented the distribution of currents in tissues posterior to the sternum and their likelihood of triggering cardiac arrhythmias. New models, the eXperimental Rotating-Field (XRF) waveform CEW (in development) and the X2 CEW (released) have not been investigated. Both the XRF and X2 CEWs target a precise amount of delivered charge per pulse, 64 μC and 62 μC, respectively. The goal of this study was to numerically model the thoracic cage attenuation of currents and electric fields delivered by the new CEWs and to find whether the heart is shielded from the induction of any dangerous arrhythmias.

METHODS AND RESULTS

Finite element modeling (FEM) was used to approximate the current density and electric field strength in tissues around the thoracic cage. FEM boundary conditions were set to correspond to output waveforms of the new CEWs, the XRF and the X2. We analyzed a CEW dart deployment scenario that had both darts located over the anterior aspect of the sternum. We found that the sternum and thoracic cage provided significant attenuation of currents and electrical fields.

CONCLUSION

The sternum and the thoracic cage significantly attenuated currents and electric fields delivered by XRF and X2 CEWs. These tissues `shielded' the heart against potentially dangerous cardiac arrhythmias. The shorter durations and reduced amount of charged delivered by the XRF and the X2 CEWs resulted in increased cardiac safety margins.

Effects of extremely low frequency electromagnetic fields on in-vitro cellular cultures HeLa and CHO

This paper presents the cellular proliferation effects of the exposure to extremely low frequency electromagnetic fields (ELF-EMF) on in-vitro cellular cultures HeLa and CHO. Through the magnetic stimulation system (MSS) the cells were exposed to magnetic fields with sinusoidal waveform at 50 Hz; initially for 40 minutes at intensities of 0.4 mT, 1.4 mT, 2.13 mT, 2.49 mT and 2.53 mT in parallel and perpendicular directions to the culture plates. Subsequently, the repetitive electromagnetic field (rEMF) was applied to 2.49 mT in parallel direction (for 40 minutes every twelve hours during 4 days) with which the highest cellular proliferation rate was obtained at 66.6 %. The results show a greater effect on proliferation in radiated cell lines, particularly in the application of rEMF a greater effect of ELF-EMF was observed in the proliferation rate of HeLa cells than in CHO cells, in contrast to the respective control cells. These results supported by other studies serve as a reference in the search for alternatives for the treatment of cervical cancer and the maintenance and preservation of cell lines.

Human exposure to power frequency magnetic fields up to 7.6 mT: An integrated EEG/fMRI study

We assessed the effects of power-line frequency (60 Hz in North America) magnetic fields (MF) in humans using simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Twenty-five participants were enrolled in a pseudo-double-blind experiment involving "real" or "sham" exposure to sinusoidal 60 Hz MF exposures delivered using the gradient coil of an MRI scanner following two conditions: (i) 10 s exposures at 3 mT (10 repetitions); (ii) 2 s exposures at 7.6 mT (100 repetitions). Occipital EEG spectral power was computed in the alpha range (8-12 Hz, reportedly the most sensitive to MF exposure in the literature) with/without exposure. Brain functional activation was studied using fMRI blood oxygen level-dependent (BOLD, inversely correlated with EEG alpha power) maps. No significant effects were detected on occipital EEG alpha power during or post-exposure for any exposure condition. Consistent with EEG results, no effects were observed on fMRI BOLD maps in any brain region. Our results suggest that acute exposure (2-10 s) to 60 Hz MF from 3 to 7.6 mT (30,000 to 76,000 times higher than average public exposure levels for 60 Hz MF) does not induce detectable changes in EEG or BOLD signals. Combined with previous findings in which effects were observed on the BOLD signal after 1 h exposure to 3 mT, 60 Hz MF, this suggests that MF exposure in the low mT range (<10 mT) might require prolonged durations of exposure to induce detectable effects. Bioelectromagnetics. 38:425-435, 2017. © 2017 Wiley Periodicals, Inc.

Noninvasive Deep Brain Stimulation via Temporally Interfering Electric Fields

We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice.

Spectral analysis to assess exposure to extremely low frequency magnetic fields in cars

A type of contamination that has been little studied in cars comes from the extremely low frequency (ELF) magnetic fields generated by the vehicle's electrical devices and the magnetized metal in the tyres. The magnetic fields in cars are frequently analysed with broadband meters sensitive to a frequency range above 30Hz. This has the disadvantage that they neither detect the magnetic field of the spinning tyres nor give any information on the spectral components, which makes it impossible to adequately assess exposure. The objective of the present study was to perform spectral analyses of ELF magnetic fields in cars, to identify their frequencies, and to assess exposure based on the ICNIRP regulatory guidelines. To do this, a meter and a spectrum analyser sensitive to magnetic fields in the 5Hz-2kHz frequency range were used. Spectra were acquired for different seats, heights, and speeds, and spatially averaged exposure coefficients were calculated. The results indicated that the main emissions were detected in the 5-100Hz range, where the wheel rotation frequencies and their harmonics are found. The intensity of the rest of the emissions were negligible in comparison. The exposure quotient increases with speed, and is approximately twice as great at foot level as at head level. The magnetic field levels are lower than the reference levels (the maximum represents 3% of the ICNIRP standard), but higher than those found in residential environments and than the cut-off threshold used by the IARC to classify ELF magnetic fields in Group 2B.

Measurements of intermediate-frequency electric and magnetic fields in households

Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely-low-frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate-frequency (IF) range (300Hz to 1MHz) as well as potential effects of IF fields on the human body remains limited, although the range of household appliances with electrical components working in the IF range has grown significantly (e.g., induction cookers and compact fluorescent lighting). In this study, an extensive measurement survey was performed on the levels of electric and magnetic fields in the IF range typically present in residences as well as emitted by a wide range of household appliances under real-life circumstances. Using spot measurements, residential IF field levels were found to be generally low, while the use of certain appliances at close distance (20cm) may result in a relatively high exposure. Overall, appliance emissions contained either harmonic signals, with fundamental frequencies between 6kHz and 300kHz, which were sometimes accompanied by regions in the IF spectrum of rather noisy, elevated field strengths, or much more capricious spectra, dominated by 50Hz harmonics emanating far in the IF domain. The maximum peak field strengths recorded at 20cm were 41.5V/m and 2.7A/m, both from induction cookers. Finally, none of the appliance emissions in the IF range exceeded the exposure summation rules recommended by the International Commission on Non-Ionizing Radiation Protection guidelines and the International Electrotechnical Commission (IEC 62233) standard at 20cm and beyond (maximum exposure quotients EQ_E 1.0 and _EQ_H 0.13).

The effects of human height and mass on the calculated induced electric fields at 50 Hz for comparison with the EMF Directive 2013/35/EU

A worker's height and mass can significantly affect the way in which incident low frequency electric and magnetic fields are absorbed in the body. To investigate this, several anatomically realistic human models were produced for heights between 1.56 and 1.96 m and masses between 33 and 113 kg. The human models were derived from the MAXWEL surface-based phantom, the model previously used in the EMF Directive 2013/35/EU Practical Guide to demonstrate how induced electric fields in the body are calculated. Computer simulations were carried out to calculate the low frequency EMF directive exposure limit value (ELV) quantities, i.e. the induced electric fields, in these human model variations from exposure to external 50 Hz magnetic and electric fields. The computational work showed that simple relationships relating the human model's height/weight with the induced electric fields in tissue types such as bone, fat, muscle, brain, spinal cord and retina could be developed. Calculations of parameters that affected absorption and fields required to produce the EMF Directive ELVs were carried out and compared with the action levels (ALs). It was found that the ALs generally provided a conservative estimate of the ELVs for the various human models and exposure situations studied.

Time constants for temperature elevation in human models exposed to dipole antennas and beams in the frequency range from 1 to 30 GHz

This study computes the time constants of the temperature elevations in human head and body models exposed to simulated radiation from dipole antennas, electromagnetic beams, and plane waves. The frequency range considered is from 1 to 30 GHz. The specific absorption rate distributions in the human models are first computed using the finite-difference time-domain method for the electromagnetics. The temperature elevation is then calculated by solving the bioheat transfer equation. The computational results show that the thermal time constants (defined as the time required to reach 63% of the steady state temperature elevation) decrease with the elevation in radiation frequency. For frequencies higher than 4 GHz, the computed thermal time constants are smaller than the averaging time prescribed in the ICNIRP guidelines, but larger than the averaging time in the IEEE standard. Significant differences between the different head models are observed at frequencies higher than 10 GHz, which is attributable to the heat diffusion from the power absorbed in the pinna. The time constants for beam exposures become large with the increase in beam diameter. The thermal time constant in the brain is larger than that in the superficial tissues at high frequencies, because the brain temperature elevation is caused by the heat conduction of energy absorbed in the superficial tissue. The thermal time constant is minimized with an ideal beam with a minimum investigated diameter of 10 mm; this minimal time constant is approximately 30 s and is almost independent of the radiation frequency, which is supported by analytic methods. In addition, the relation between the time constant, as defined in this paper, and 'averaging time' as it appears in the exposure limits is discussed, especially for short intense pulses. Similar to the laser guidelines, provisions should be included in the limits to limit the fluence for such pulses.

Computation of Pacemakers Immunity to 50 Hz Electric Field: Induced Voltages 10 Times Greater in Unipolar Than in Bipolar Detection Mode

Thisstudy aims to compute 50 Hz electric field interferences on pacemakers for diverse lead configurations and implantation positions. Induced phenomena in a surface-based virtual human model (standing male grounded with arms closed, 2 mm resolution) are computed for vertical exposure using CST EM^® 3D software, with and without an implanted pacemaker. Induced interference voltages occurring on the pacemaker during exposure are computed and the results are discussed. The bipolar mode covers 99% of the implanted pacing leads in the USA and Europe, according to statistics. The tip-to-ring distance of a lead may influence up to 46% of the induced voltage. In bipolar sensing mode, right ventricle implantation has a 41% higher induced voltage than right atrium implantation. The induced voltage is in average 10 times greater in unipolar mode than in bipolar mode, when implanted in the right atrium or right ventricle. The electric field threshold of interference for a bipolar sensing mode in the worst case setting is 7.24 kV·m⁻¹, and 10 times higher for nominal settings. These calculations will be completed by an in vitro study.

Effects of Single and Repeated Exposure to a 50-Hz 2-mT Electromagnetic Field on Primary Cultured Hippocampal Neurons

The prevalence of domestic and industrial electrical appliances has raised concerns about the health risk of extremely low-frequency magnetic fields (ELF-MFs). At present, the effects of ELF-MFs on the central nervous system are still highly controversial, and few studies have investigated its effects on cultured neurons. Here, we evaluated the biological effects of different patterns of ELF-MF exposure on primary cultured hippocampal neurons in terms of viability, apoptosis, genomic instability, and oxidative stress. The results showed that repeated exposure to 50-Hz 2-mT ELF-MF for 8 h per day after different times in culture decreased the viability and increased the production of intracellular reactive oxidative species in hippocampal neurons. The mechanism was potentially related to the up-regulation of Nox2 expression. Moreover, none of the repeated exposure patterns had significant effects on DNA damage, apoptosis, or autophagy, which suggested that ELF-MF exposure has no severe biological consequences in cultured hippocampal neurons.

Characterizing and Mapping of Exposure to Radiofrequency Electromagnetic Fields (20-3,000 Mhz) in Chengdu, China

With radiofrequency exposure caused by electronic applications increasing, some members of the public are worrying about potential health risks. In this paper, methods of performing large-scale radiofrequency exposure evaluation are described. All studied sites were divided into three categories: commercial-area, residential-urban, and residential-rural. Then a series of site investigations were conducted on a car-mounted system in the years 2014 and 2015, aiming to characterize electric field exposure from 12 different radiofrequency sources. The results indicate that the studied environment is safe as indicated by exposure below guidelines and standards. The highest exposure measured in the 2 y of monitoring was from an FM source, 316.23 mV m. Telecommunication sources dominate exposure, contributing the most power density (65-90%). Meanwhile, intergroup differences are discussed and summarized. The spatial distributions of FM and GSM1800 exposure are demonstrated on a map. This study describes an approach for the assessment of the spatiotemporal pattern of radiofrequency exposures in Chengdu and facilitates the identification of any sources causing exposure above relevant guidelines and standards.

An Electromagnetic Sensor for the Autonomous Running of Visually Impaired and Blind Athletes (Part I: The Fixed Infrastructure)

Sport is one of the best ways to promote the social integration of people affected by physical disability, because it helps them to increase their self-esteem by facing difficulties and overcoming their disabilities. Nowadays, a large number of sports can be easily played by visually impaired and blind athletes without any special supports, but, there are some disciplines that require the presence of a sighted guide. In this work, the attention will be focused on marathons, during which athletes with visual disorders have to be linked to the sighted guide by means of a non-stretchable elbow tether, with an evident reduction of their performance and autonomy. In this context, this paper presents a fixed electromagnetic infrastructure to equip a standard running racetrack in order to help a blind athlete to safely run without the presence of a sighted guide. The athlete runs inside an invisible hallway, just wearing a light and a comfortable sensor unit. The patented system has been homemade, designed, realized and finally tested by a blind Paralympic marathon champion with encouraging results and interesting suggestions for technical improvements. In this paper (Part I), the transmitting unit, whose main task is to generate the two magnetic fields that delimit the safe hallway, is presented and discussed.

Human Exposure to Electromagnetic Fields from Parallel Wireless Power Transfer Systems

The scenario of multiple wireless power transfer (WPT) systems working closely, synchronously or asynchronously with phase difference often occurs in power supply for household appliances and electric vehicles in parking lots. Magnetic field leakage from the WPT systems is also varied due to unpredictable asynchronous working conditions. In this study, the magnetic field leakage from parallel WPT systems working with phase difference is predicted, and the induced electric field and specific absorption rate (SAR) in a human body standing in the vicinity are also evaluated. Computational results are compared with the restrictions prescribed in the regulations established to limit human exposure to time-varying electromagnetic fields (EMFs). The results show that the middle region between the two WPT coils is safer for the two WPT systems working in-phase, and the peripheral regions are safer around the WPT systems working anti-phase. Thin metallic plates larger than the WPT coils can shield the magnetic field leakage well, while smaller ones may worsen the situation. The orientation of the human body will influence the maximum magnitude of induced electric field and its distribution within the human body. The induced electric field centralizes in the trunk, groin, and genitals with only one exception: when the human body is standing right at the middle of the two WPT coils working in-phase, the induced electric field focuses on lower limbs. The SAR value in the lungs always seems to be greater than in other organs, while the value in the liver is minimal. Human exposure to EMFs meets the guidelines of the International Committee on Non-Ionizing Radiation Protection (ICNIRP), specifically reference levels with respect to magnetic field and basic restrictions on induced electric fields and SAR, as the charging power is lower than 3.1 kW and 55.5 kW, respectively. These results are positive with respect to the safe applications of parallel WPT systems working simultaneously.

Effect of Lepidium meyenii (maca) on testicular function of mice with chemically and physically induced subfertility

The aim of this study was to evaluate the effect of Lepidium meyenii (maca) in chemically and physically subfertile mice. After 35 days, the following groups of mice were evaluated: control, sham, chemical subfertility, chemical subfertility-maca-supplemented, physical subfertility, physical subfertility-maca-supplemented and maca-supplemented only. Motility (32.36% ± 5.34%) and sperm count (44.4 ± 5.37 × 10(6) /ml) in the chemically and physically subfertile mice (11.81% ± 4.06%, 17.34 ± 13.07 × 10(6) /ml) decreased compared to the control (75.53% ± 2.97% and 57.4 ± 19.6 10(6) /ml) and sham (53.5% ± 7.86% and 58.4 ± 14.10 10(6) /ml). Maca was able to reverse the deleterious effect of motility (76.36 ± 1.97) as well as sperm count (53.5 ± 9.18 × 10(6) /ml) on chemical subfertility. In contrast, maca did not reverse the effects of induced physical subfertility nor motility (18.78% ± 14.41%) or sperm count (20.17 ± 11.20 × 10(6) /ml). The percentage of sperm DNA fragmentation in the physically subfertile mice increased (11.1% ± 19.29%) compared to the control (0.84% ± 0.85%). However, in the physically subfertile group, maca decreased sperm DNA fragmentation (2.29% ± 2.30%) closer to the sham (1.04% ± 0.62%) and the control (0.84% ± 0.85%). The group supplemented only with maca showed 0.54% ± 0.50% of spermatozoa with DNA fragmentation. Yet, the differences observed were statistically not significant. In conclusion, it appears that maca activates the cytochrome P450 system after chemically induced subfertility. However, it does not reverse the low mitochondrial membrane potential in spermatozoa compromised in the physical subfertility group.

Non-conductive and miniature fiber-optic imaging system for real-time detection of neuronal activity in time-varying electromagnetic fields

Establishing an appropriate threshold value for neuronal modulation by time-varying electromagnetic field (EMF) exposure is important for developing international guidelines to protect against the potential health effects, and to design a variety of medical devices. However, it is technically difficult to achieve real-time detection of neuronal activity under repetitive and long-term exposure to EMF. For this purpose, we developed a non-conductive, miniature, and flexible fiber-optic imaging system that does not affect the electromagnetic noise, induction heating, or vibration in a high-intensity and repetitive time-varying EMF exposure. Using the proposed system, we succeeded at real-time detection of spontaneous Ca²⁺ oscillations in single neuronal and glial cells, as well as synchronized bursting activities of multiple neuronal networks at a micrometer-scale and millisecond-order spatiotemporal resolution during long-term EMF exposure (sinusoidal wave, 20kHz, 8.6mT, >30min). The results indicated that short-term (<5min) exposure-related neuronal modulation was not detectable; however, long-term (15-30min) exposure was observed to depress neuronal activities. In addition, the simultaneous and real-time recording of neuronal activity and the environmental temperature revealed that the neuronal modulation was accompanied by a 0.5-1°C rise in the temperature of the culture medium induced by the heat generation of exposure coils. These findings suggest that our real-time imaging system can be used for precise evaluation of the threshold values and clarification of the mechanisms of neuronal modulation induced by time-varying EMF exposure.

Evaluation of exposure to (ultra) high static magnetic fields during activities around human MRI scanners

OBJECTIVE

To assess the individual exposure to the static magnetic field (SMF) and the motion-induced time-varying magnetic field (TVMF) generated by activities in an inhomogeneous SMF near high and ultra-high field magnetic resonance imaging (MRI) scanners. The study provides information on the level of exposure to high and ultra-high field MRI scanners during research activities.

MATERIALS AND METHODS

A three-axis Hall magnetometer was used to determine the SMF and TVMF around human 3- and 7-Tesla (T) MRI systems. The 7-T MRI scanner used in this study was passively shielded and the 3-T scanner was actively shielded and both were from the same manufacturer. The results were compared with the exposure restrictions given by the International Commission on Non-Ionizing Radiation Protection (ICNIRP).

RESULTS

The recorded exposure was highly variable between individuals, although they followed the same instructions for moving near the scanners. Maximum exposure values of B = 2057 mT and dB/dt = 4347 mT/s for the 3-T scanner and B = 2890 mT, dB/dt = 3900 mT/s for 7 T were recorded. No correlation was found between reporting the MRI-related sensory effects and exceeding the reference values.

CONCLUSIONS

According to the results of our single-center study with five subjects, violation of the ICNIRP restrictions for max B in MRI research environments was quite unlikely at 3 and 7 T. Occasions of exceeding the dB/dt limit at 3 and 7 T were almost similar (30% of 60 exposure scenarios) and highly variable among the individuals.

Inconsistency of a recently proposed method for assessing magnetic field exposure for protection against peripheral nerve stimulation in occupational situations

A non-binding guide to practical implementation of European Directive 2013/35/EU concerning the limitation of occupational exposure against electromagnetic fields has been published recently. With regard to exposure assessment this guide proposes practically applicable assessment methods for non-uniform and non-sinusoidal environmental electric and magnetic fields, respectively. For non-sinusoidal magnetic fields in the low frequency range this guide proposes a time domain assessment (TDA) method, claimed to reduce the overestimation of exposure inherent to other assessment methods while being based on fundamental physiological principles regarding nerve stimulation. In the present paper we demonstrate that the proposed TDA method is not consistent with the obvious underlying principles of directive 2013/35/EU. Based on practically relevant waveforms and general considerations it can be shown that external magnetic fields may be deemed compliant by the TDA method although the underlying exposure limit values defined in 2013/35/EU may be exceeded. We therefore strongly recommend that the TDA method is removed from the guide for implementing 2013/35/EU as soon as possible.