Magnetic Fields In Humans Research Articles

Low-frequency electromagnetic fields increase oxidative stress in tobacco plants

Increasing interest on biological effects of electromagnetic radiation, particularly extremely-low-frequency electromagnetic fields (ELFEMFs) has been observed. Although harmful effects of magnetic fields in humans remain to be demonstrated, it has been proposed that oxidative stress may represent one of the causes of ELF- EMFs adverse effects. We investigated the influence of ELF-EMFs on enzyme activity in tobacco plants under oxidative stress. Nicotiana tabacum (L.) seedlings of the Xanthi variety were continuously exposed to 2.0 mT and 60 Hz frequency ELF-EMFs for 24, 48, 72, and 96 h. The biochemical endpoints measured involved leaf and root extracts ascorbate peroxidase (APX) and catalase (CAT) activities, which were increased in leaf extracts after 48, 72, and 96 h of magnetic field exposure, whereas APX and CAT activities in root extracts increased after 48 and 72 h and 48, 72, and 96 h of continuous exposure to magnetic fields. In contrast, ELF-EMF exposure for 24 h did not alter APX and CAT activities in leaf and root extracts. All treatment regimens were matched with a properly sham-exposed control. These results suggest that ELF-EMFs induce an oxidative stress, which may potentiate the oxidative defense system in tobacco plants

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

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

Personal exposure to static and time-varying magnetic fields during MRI procedures in clinical practice in the UK

Background: Medical diagnosis using Magnetic Resonance Imaging (MRI) is the main source of exposure to high static magnetic fields in humans. Extensive safety protocols have been developed to ensur...

Long-term (up to 20 years) effects of 50-Hz magnetic field exposure on immune system and hematological parameters in healthy men

ObjectivesThe relationship between exposure to 50-Hz magnetic fields and human health is of increasing interest since associations have been found in brain cancer in adults and childhood leukemia. In this study we investigate the possible chronic (up to 20years) effects of exposure to magnetic fields in humans. Design and methodsWe examined the nocturnal profiles of red blood cells, hemoglobin, hematocrit, platelets, mean platelet volume, total white blood cells, lymphocytes, monocytes, eosinophils, basophils, neutrophils, Ig (Immunoglobulin) A, IgM, IgG, CD (cluster of differentiation) 3, CD4, CD8, natural killer cells, B cells, total CD28, CD8+ CD28+, activated T cells, interleukin (IL)-2, IL-6, and IL-2 receptor, in 15 men exposed chronically and daily for a period of 1–20years, in the workplace and at home, to a 50-Hz magnetic field. The weekly geometric mean of individual exposures ranged from 0.1 to 2.6μT. The results are compared to those of 15 unexposed men age-matched, with the same synchronization and physical activity that served as controls (individual exposures ranged from 0.004 to 0.092μT). Blood samples were taken hourly from 20:00h to 08:00h. ResultsExposure over a long period and on a daily basis to magnetic fields resulted in no changes in the levels or patterns of hematological and immune system variables. ConclusionsOur data show that a long-term exposure to 50-Hz magnetic fields does not affect the hematological and immune system functions or their profile in healthy men, at least for the variables studied, and suggest that magnetic fields have no cumulative effects on these functions.

Frequency-specific modulation of population-level frequency tuning in human auditory cortex

BackgroundUnder natural circumstances, attention plays an important role in extracting relevant auditory signals from simultaneously present, irrelevant noises. Excitatory and inhibitory neural activity, enhanced by attentional processes, seems to sharpen frequency tuning, contributing to improved auditory performance especially in noisy environments. In the present study, we investigated auditory magnetic fields in humans that were evoked by pure tones embedded in band-eliminated noises during two different stimulus sequencing conditions (constant vs. random) under auditory focused attention by means of magnetoencephalography (MEG).ResultsIn total, we used identical auditory stimuli between conditions, but presented them in a different order, thereby manipulating the neural processing and the auditory performance of the listeners. Constant stimulus sequencing blocks were characterized by the simultaneous presentation of pure tones of identical frequency with band-eliminated noises, whereas random sequencing blocks were characterized by the simultaneous presentation of pure tones of random frequencies and band-eliminated noises. We demonstrated that auditory evoked neural responses were larger in the constant sequencing compared to the random sequencing condition, particularly when the simultaneously presented noises contained narrow stop-bands.ConclusionThe present study confirmed that population-level frequency tuning in human auditory cortex can be sharpened in a frequency-specific manner. This frequency-specific sharpening may contribute to improved auditory performance during detection and processing of relevant sound inputs characterized by specific frequency distributions in noisy environments.

Effects of continuous masking noise on tone-evoked magnetic fields in humans

Two different types of steep loudness growth have been reported in detail in psychoacoustical studies but have rarely been evaluated by objective methods in humans. One occurs in inner-ear hearing-impaired patients and is known as loudness recruitment. Another similar phenomenon is observed in healthy subjects with concurrent presence of background noise. Concerning the first type, our previous study using magnetoencephalography (MEG) showed that enhancement of the dipole moment of N100m with increase in stimulus intensity was greater in patients than in normal individuals. However, it is unclear whether the enhancement of activity in auditory cortex will also be detected with background noise in healthy subjects. To elucidate the effects of continuous background noise on tone-evoked cortical activity, we measured auditory-evoked magnetic fields (AEFs) from 7 normal-hearing subjects in two different conditions, with and without 55 dB SPL continuous masking white noise (noise/quiet conditions). The stimuli were 200 ms 1-kHz tones delivered monaurally and randomly at 4 different intensities (40–70 dB SPL) with constant 1-s interstimulus intervals. The N100m increased in amplitude and decreased in latency as a function of stimulus intensity in both noise and quiet conditions. The dipole moment of N100m was significantly smaller in the noise than in the quiet condition, showing that continuous background noise suppresses the strength of tone-evoked cortical responses. The mechanisms underlying these two psychoacoustically similar phenomena of rapid loudness growth thus differ.

Reduction of Pain in Reflex Sympathetic Dystrophy (RSD) Associated with Objective Biochemical Changes in Circulating Lymphocytes

In an effort to explain the benefit of therapeutic use of electromagnetic fields (EMF) a systemic effect has been proposed by us. To assess the efficacy of this approach, an objective biochemical approach was developed. Ten patients with Reflex Sympathetic Dystrophy (RSD) were clinically evaluated, and lymphocytes were isolated from their blood samples obtained before and after exposure of the uninvolved limb to an EMF. Utilizing a SpectraCell method that includes radio labeled molecules and protein-free media for culturing the lymphocytes, an elevation of the content of fructose, serine, glycine, and calcium cellular metabolic uptake were found following in the culture to EMF in comparison with non-exposed lymphocytes (p < 0.01). In addition, the pain level was determined by a conventional visual analogue scale (VAS) before and after EMF exposure, evidencing a significant pain relief. Specifically, after exposure to 120 pps semi sinewave, 1500Gauss EMF, generated by a THERAMAG∘ledR device, an improvement in the flexibility of the limb and a reduction in swelling of the affected extremity were detected clinically. These findings are in concert with the new hypothesis that, with relief of pain, lymphocytes are predominately altered in their cell cycle from M phase to S phases associated with increased structuring of intracellular water. A consideration of the basic understanding of the role lymphocytes may be inferred from this preliminary study. An extensive review of the literature on the basic science and therapeutic use of magnetic fields in humans is provided in an attempt to understand the relevance of magnetic therapy of specific pain syndromes.

Effects of sleep on pain-related somatosensory evoked magnetic fields in humans

We investigated the effects of sleep on pain-related somatosensory evoked magnetic fields (SEFs) following painful electrical stimulation to identify the mechanisms generating them in both fast A-beta fibers relating to touch and slow A-delta fibers relating to pain. While the subjects were awake, non-painful and painful electrical stimulations were applied, and while asleep, painful stimulation was applied to the left index finger. During awake, five components (1M–5M) were identified following both non-painful and painful stimulation, but the 4M and 5M at around 70–100 ms and 140–180 ms, respectively, were significantly enhanced following painful stimulation. During sleep, 1M and 2M generated in the primary somatosensory cortex (SI) did not show a significant change, 3M in SI showed a slight but significant amplitude reduction, and 4M and 5M generated in both SI and the secondary somatosensory cortex (SII) were significantly decreased in amplitude or disappeared. The 4M and 5M are complicated components generated in SI and SII ascending through both A-beta fibers and A-delta fibers. They are specifically enhanced by painful stimulation due to an increase of signals ascending through A-delta fibers, and are markedly decreased during sleep, because they much involve cognitive function.

Neural mechanisms for generation of tactile interference effects on somatosensory evoked magnetic fields in humans

Objectives: We examined modification of somatosensory evoked fields following electric middle finger stimulation with interference to the same and surrounding digits in 13 subjects.Methods: During electric middle finger stimulation, concurrent tactile stimulation was applied to the middle finger, to the index and ring fingers, and to the thumb and the little finger, individually.Results: The amplitudes of the N20m and the P30m were significantly reduced by the interference to the middle finger, and to the index and ring fingers. The former interference induced more prominent attenuation than the latter. The amplitudes of the P60m did not show significant changes by any kind of the interference.Conclusions: The N20m and the P30m were attenuated according to the cortical distance between electrically and mechanically activated 3b areas. Pyramidal neurons are interconnected by intrinsic horizontal collaterals, even if their representations are segregated. The activation of the intrinsic collaterals induces direct excitation and indirect inhibition (via inhibitory interneurons) to the target pyramidal neurons. The result indicates that the activation of the intrinsic collaterals inhibits, on balance, the postsynaptic pyramidal targets, thereby generating the attenuation of the N20m and P30m.

A theoretical model based upon mast cells and histamine to explain the recently proclaimed sensitivity to electric and/or magnetic fields in humans

The relationship between exposure to electromagnetic fields (EMFs) and human health is more and more in focus. This is mainly because of the rapid increasing use of such EMFs within our modern society. Exposure to EMFs has been linked to different cancer forms, e.g. leukemia, brain tumors, neurological diseases, such as Alzheimer’s disease, asthma and allergy, and recently to the phenomena of ‘electrosupersensitivity’ and ‘screen dermatitis’. There is an increasing number of reports about cutaneous problems as well as symptoms from internal organs, such as the heart, in people exposed to video display terminals (VDTs). These people suffer from subjective and objective skin and mucosa-related symptoms, such as itch, heat sensation, pain, erythema, papules and pustules. In severe cases, people can not, for instance, use VDTs or artificial light at all, or be close to mobile telephones. Mast cells (MCs), when activated, release a spectrum of mediators, among them histamine, which is involved in a variety of biological effects with clinical relevance, e.g. allergic hypersensitivity, itch, edema, local erythema and many types of dermatoses. From the results of recent studies, it is clear that EMFs affect the MC, and also the dendritic cell, population and may degranulate these cells. The release of inflammatory substances, such as histamine, from MCs in the skin results in a local erythema, edema and sensation of itch and pain, and the release of somatostatin from the dendritic cells may give rise to subjective sensations of on-going inflammation and sensitivity to ordinary light. These are, as mentioned, the common symptoms reported from patients suffering from ‘electrosupersensitivity’/‘screen dermatitis’. MCs are also present in the heart tissue and their localization is of particular relevance to their function. Data from studies made on interactions of EMFs with the cardiac function have demonstrated that highly interesting changes are present in the heart after exposure to EMFs. One could speculate that the cardiac MCs are responsible for these changes due to degranulation after exposure to EMFs. However, it is still not known how, and through which mechanisms, all these different cells are affected by EMFs. In this article, we present a theoretical model, based upon observations on EMFs and their cellular effects, to explain the proclaimed sensitivity to electric and/or magnetic fields in humans.

Theoretical Limits on the Threshold for the Response of Long Cells to Weak Extremely Low Frequency Electric Fields Due to Ionic and Molecular Flux Rectification

Understanding exposure thresholds for the response of biological systems to extremely low frequency (ELF) electric and magnetic fields is a fundamental problem of long-standing interest. We consider a two-state model for voltage-gated channels in the membrane of an isolated elongated cell ( L cell = 1 mm; r cell = 25 μm) and use a previously described process of ionic and molecular flux rectification to set lower bounds for a threshold exposure. A key assumption is that it is the ability of weak physical fields to alter biochemistry that is limiting, not the ability of a small number of molecules to alter biological systems. Moreover, molecular shot noise, not thermal voltage noise, is the basis of threshold estimates. Models with and without stochastic resonance are used, with a long exposure time, t exp = 10 4 s. We also determined the dependence of the threshold on the basal transport rate. By considering both spherical and elongated cells, we find that the lowest bound for the threshold is E min ≈ 9 × 10 −3 V m −1 (9 × 10 −5 V cm −1). Using a conservative value for the loop radius r loop = 0.3 m for induced current, the corresponding lower bound in the human body for a magnetic field exposure is B min ≈ 6 × 10 −4 T (6 G). Unless large, organized, and electrically amplifying multicellular systems such as the ampullae of Lorenzini of elasmobranch fish are involved, these results strongly suggest that the biophysical mechanism of voltage-gated macromolecules in the membranes of cells can be ruled out as a basis of possible effects of weak ELF electric and magnetic fields in humans.

Psychological effects of chronic exposure to 50 Hz magnetic fields in humans living near extra‐high‐voltage transmission lines

Psychological effects of chronic exposure to 50 Hz magnetic fields in humans living near extra‐high‐voltage transmission lines

Psychological effects of chronic exposure to 50 Hz magnetic fields in humans living near extra-high-voltage transmission lines

The validity of several published investigations of the possibility that residential exposures to 50 Hz or 60 Hz electromagnetic fields might cause adverse psychological effects, such as suicide and depression, may have been limited by inadequate controlling for confounders or inadequate measurement of exposures. We investigated the relationships between magnetic field exposure and psychological and mental health variables while controlling for potential confounders and careful characterising individual magnetic field exposures. Five-hundred-and-forty adults living near transmission lines completed neuropsychological tests in major domains of memory and attentional functioning, mental health rating scales and other questionnaires. Magnetic field measurements were taken in each room occupied for at least one hour per day to provide an estimate of total-time-integrated exposure. The data were subjected to joint multivariate multiple regression analysis to test for a linear relation between field exposure and dependent variables, while controlling for effects of possible confounders. Performance on most memory and attention measures was unrelated to exposure, but significant linear dose-response relationships were found between exposure and some psychological and mental health variables. In particular, higher time-integrated exposure was associated with poorer coding-test performance and more adverse psychiatric symptomatology. These associations were found to be independent of participants' beliefs about effects of electromagnetic fields.

Gustatory evoked magnetic fields in humans

Magnetic fields evoked by taste stimuli of the human tongue were measured over the whole head using a helmet-shaped 64 channel magnetoencephalography system in five normal subjects. The stimuli were 10% glucose and 0.3 M NaCl solutions and distilled water. The most prominent peak (N175m) appearing over the bilateral hemispheres had a latency of 150–210 ms. The N175m sources were located using a two-dipole model in a spherical conducting medium based on the individual head dimensions and superimposed on magnetic resonance images. The N175m dipoles due to 10% glucose and 0.3 M NaCl stimuli were located at the operculum and circum-insular areas in both hemispheres, but those due to distilled water could not be located accurately.