Hypothesis: The risk of childhood leukemia is related to combinations of power-frequency and static magnetic fields

We present a hypothesis that the risk of childhood leukemia is related to exposure to specific combinations of static and extremely-low-frequency (ELF) magnetic fields. Laboratory data from calcium efflux and diatom mobility experiments were used with the gyromagnetic equation to predict combinations of 60 Hz and static magnetic fields hypothesized to enhance leukemia risk. The laboratory data predicted 19 bands of the static field magnitude with a bandwidth of 9.1 μT that, together with 60 Hz magnetic fields, are expected to have biological activity. We then assessed the association between this exposure metric and childhood leukemia using data from a case-control study in Los Angeles County. ELF and static magnetic fields were measured in the bedrooms of 124 cases determined from a tumor registry and 99 controls drawn from friends and random digit dialing. Among these subjects, 26 cases and 20 controls were exposed to static magnetic fields lying in the predicted bands of biological activity centered at 38.0 μT and 50.6 μT. Although no association was found for childhood leukemia in relation to measured ELF or static magnetic fields alone, an increasing trend of leukemia risk with measured ELF fields was found for subjects within these static field bands (P for trend = 0.041). The odds ratio (OR) was 3.3 [95% confidence interval (CI) = 0.4–30.5] for subjects exposed to static fields within the derived bands and to ELF magnetic field above 0.30 μT (compared to subjects exposed to static fields outside the bands and ELF magnetic fields below 0.07 μT). When the 60 Hz magnetic fields were assessed according to the Wertheimer-Leeper code for wiring configurations, leukemia risks were again greater with the hypothesized exposure conditions (OR = 9.2 for very high current configurations within the static field bands: 95% CI = 1.3–64.6). Although the risk estimates are based on limited magnetic field measurements for a small number of subjects, these findings suggest that the risk of childhood leukemia may be related to the combined effects of the static and ELF magnetic fields. Further tests of the hypothesis are proposed. © 1995 Wiley-Liss, Inc.     

Effects of static magnetic fields at the cellular level

There have been few studies on the effects of static magnetic fields at the cellular level, compared to those of extremely low frequency magnetic fields. Past studies have shown that a static magnetic field alone does not have a lethal effect on the basic properties of cell growth and survival under normal culture conditions, regardless of the magnetic density. Most but not all studies have also suggested that a static magnetic field has no effect on changes in cell growth rate. It has also been shown that cell cycle distribution is not influenced by extremely strong static magnetic fields (up to a maximum of 10 T). A further area of interest is whether static magnetic fields cause DNA damage, which can be evaluated by determination of the frequency of micronucleus formation. The presence or absence of such micronuclei can confirm whether a particular treatment damages cellular DNA. This method has been used to confirm that a static magnetic field alone has no such effect. However, the frequency of micronucleus formation increases significantly when certain treatments (e.g., X-irradiation) are given prior to exposure to a 10 T static magnetic field. It has also been reported that treatment with trace amounts of ferrous ions in the cell culture medium and exposure to a static magnetic field increases DNA damage, which is detected using the comet assay. In addition, many studies have found a strong magnetic field that can induce orientation phenomena in cell culture.     

Influence of low-intensity magnetic fields on the development of satellite muscle cells of a newborn rat in primary culture

The influence of Earth magnetic field shielded down to 0.3 μT and static magnetic field (60–160 μT) on the proliferation and differentiation of satellite muscle cells in primary culture has been investigated. A stimulatory effect of static magnetic fields on the rate of the formation of massive multinucleate myotubes and an increase in the intracellular calcium concentration ([Ca²⁺] _i ) have been detected for magnetic fields of the microtesla range. On the other hand, it was shown that the reduction of earth magnetic fields to 0.3 μT leads to inhibition of proliferation and differentiation of skeletal muscle cells in primary culture. Since the formation of contractile myotubes during in vitro experiments is similar to the regeneration of skeletal muscle fibers under muscle damage in vivo, it may be concluded that weak magnetic fields have a strong effect on intracellular processes by influencing all phases of muscle fiber formation. It is necessary to take this fact into consideration when forecasting probable complications of skeletal muscle regeneration during long-term exposure of man to low-intensity magnetic fields and also for the potential use of low static magnetic fields as a tool to recover the affected myogenesis.     

Oviposition and development of Drosophila modified by magnetic fields

Drosophila flies placed in a habitat with two lateral boxes demonstrated sensitivity to magnetic fields: Oviposition decreased by exposure to pulsated extremely low frequency (ELF) (100)Hz, 1.76 miliTesla (mT) and sinusosidal fields (50 Hz, 1 mT), while there was no initial effect of exposure to a static magnetic field (4.5 mT). Drosophila eggs treated for 48 h with the above described fields showed that (1) mortality of eggs was lower in controls than in eggs exposed to all tested magnetic fields; (2) mortality of larvae increased when a permanent magnet was used; (3) mortality of pupae was highest when a permanent magnet was used; and (4) general adult viability was highest in controls (67%) and diminished progressively when eggs were exposed to pulsated (55%), sinusoidal (45%), and static (35%) magnetic fields.     

Influence of weak static and 50 Hz magnetic fields on the redox activity of cytochrome-C oxidase

The effects of static and 50 Hz magnetic fields on cytochrome-C oxidase activity were investigated in vitro by strictly controlled, simultaneous polarographic measurements of the enzyme's high- and low-affinity redox reaction. Cytochrome-C oxidase was isolated from beef heart. Control experiments were carried out in the ambient geomagnetic and 50 Hz magnetic fields at respective flux densities of 45 and 1.8 μT. The experimentally applied fields, static and time-varying, were generated by Helmholtz coils at flux densities between 50 μT and 100 mT. Exposures were timed to act either on the combined enzyme-substrate interchange or directly on the enzyme's electron and proton translo-cations. Significant changes as high as 90% of the overall cytochrome-C oxidase activity resulted during exposure (1) to a static magnetic field at 300 μT or 10 mT in the high-affinity range, and (2) to a 50 Hz magnetic field at 10 or 50 mT in the low-affinity range. No changes were observed at other flux densities. After exposure to a change-inducing, static or time-varying field, normal activity returned. © 1993 Wiley-Liss. Inc.     

Exposure classification of MRI workers in epidemiological studies

We estimate that there are about 100,000 workers from different disciplines, such as radiographers, nurses, anesthetists, technicians, engineers, etc., who can be exposed to substantial electromagnetic fields (compared to normal background levels) around magnetic resonance imaging (MRI) scanners. There is a need for well‐designed epidemiological studies of MRI workers but since the exposure from MRI equipment is a very complex mixture of static magnetic fields, switched gradient magnetic fields, and radiofrequency electromagnetic fields (RF EMF), it is necessary to discuss how to assess the exposure in epidemiological studies. As an alternative to the use of job title as a proxy of exposure, we propose an exposure categorization for the different professions working with MRI equipment. Specifically, we propose defining exposure in three categories, depending on whether people are exposed to only the static field, to the static plus switched gradient fields or to the static plus switched gradient plus RF fields, as a basis for exposure assessment in epidemiological studies. Bioelectromagnetics 34:81–84, 2013. © 2012 Wiley Periodicals, Inc.     

Static Magnetic Fields Inhibit Proliferation and Disperse Subcellular Localization of Gamma Complex Protein3 in Cultured C2C12 Myoblast Cells

Magnetic fields may delay the rate of cell cycle progression, and there are reports that magnetic fields induce neurite outgrowth in cultured neuronal cells. To demonstrate whether magnetic field also effects on myoblast cells in cell growth, C2C12 cell lines were cultured and 2000G static magnetic field was applied. After 48 h of incubation, both the WST-1 assay (0.01 < P < 0.025, t-test) and direct cell counting (P < 0.0005, t-test) showed that static magnetic fields inhibit the proliferation of cultured C2C12 cells. Immunocytochemistry for alpha and tubulin gamma complex protein (TUBA and GCP3) was made and applying a static magnetic field-dispersed tubulin GCP3 formation, a intracellular apparatus for tubulin structuring in cell division. This protein expression was not altered by western blot. This study indicates that applying a static magnetic field alters the subcellular localizing of GCP3, and may delay the cell growth in cultured C2C12 myoblast cells.     

Effect of low-intensity magnetic fields on the development of satellite muscle cells of a newborn rat in the primary culture

The influence of Earth magnetic field shielded down to 0.3 microT and static magnetic field (60-160 microT) on the proliferation and differentiation of satellite muscle cells in the primary culture has been investigated. A stimulatory effect of static magnetic fields on the rate of the formation of massive multinucleated myotubes and an increase in the intracellular calcium concentration ([Ca2+]i) have been detected for magnetic fields of the microtesla range. On the other hand, it was shown that the reduction of earth magnetic fields to 0.3 microT leads to the inhibition of proliferation and differentiation of skeletal muscle cells in the primary culture. Since the formation of contractile myotubes during in vitro experiments is similar to the regeneration of skeletal muscle fibers under muscle damage in vivo, it may be concluded that weak magnetic fields have a strong effect on intracellular processes by influencing all phases of muscle fiber formation. It is necessary to take this fact into consideration when forecasting probable complications of skeletal muscle regeneration during long-term exposure of man to low-intensity magnetic fields and also for the potential use of low static magnetic fields as a tool to recover the affected myogenesis.     

No effect of exposure to static and sinusoidal magnetic fields on nitric oxide production by macrophages

The effects of exposure to static (1–100 mT) or sinusoidal (1 Hz, 1.6 mT) magnetic fields on the production of nitric oxide (NO) by murine BCG-activated macrophages were investigated. In these cells, the inducible isoform of NO synthase is present. No significant differences were observed in nitrite levels among exposed, sham-exposed, or control macrophages after exposure for 14 h to static fields of 1, 10, 50, and 100 mT and to sinusoidal 1.6 mT, 1 Hz magnetic fields. © 1996 Wiley-Liss, Inc.     

Interaction of static and extremely low frequency electric and magnetic fields with living systems: health effects and research needs

An international seminar was held June 4-6, 1997, on the biological effects and related health hazards of ambient or environmental static and extremely low frequency (ELF) electric and magnetic fields (0-300 Hz). It was cosponsored by the World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), the German, Japanese, and Swiss governments. Speakers provided overviews of the scientific literature that were discussed by participants of the meeting. Subsequently, expert working groups formulated this report, which evaluates possible health effects from exposure to static and ELF electric and magnetic fields and identifies gaps in knowledge requiring more research to improve health risk assessments. The working groups concluded that, although health hazards exist from exposure to ELF fields at high field strengths, the literature does not establish that health hazards are associated with exposure to low-level fields, including environmental levels. Similarly, exposure to static electric fields at levels currently found in the living and working environment or acute exposure to static magnetic fields at flux densities below 2 T, were not found to have demonstrated adverse health consequences. However, reports of biological effects from low-level ELF-field exposure and chronic exposure to static magnetic fields were identified that need replication and further study for WHO to assess any possible health consequences. Ambient static electric fields have not been reported to cause any direct adverse health effects, and so no further research in this area was deemed necessary.     

Health effects of static magnetic fields--a review of the epidemiological evidence

Potential health effects of static magnetic fields have received far less attention than, for example, power frequency or radiofrequency fields. Static fields are found in certain occupational settings, e.g. in the aluminium and chloralkali industries, in arc-welding processes, and certain railways systems. Magnetic resonance imaging (MRI) for medical diagnosis is another source. This paper summarizes the epidemiological evidence of static magnetic field exposure and long-term health effects. There are only a few epidemiological studies available, and the majority of these have focused on cancer risks. There are some reports on reproductive outcomes, and sporadic studies of other outcomes. Overall, few occupational studies have focused specifically on effects of static magnetic field exposure, and exposure assessment have consequently been poor or non-existent. Results from studies that have estimated static magnetic field exposure have not indicated any increased cancer risks, but they are generally based on small numbers of cases and crude exposure assessment. Control of confounding has been limited, and it is likely that the “healthy worker” effect have influenced the results. A few studies have reported results on reproductive outcomes among aluminium workers and MRI operators, but limitations in study designs prevent conclusions. A problem in epidemiological studies of static magnetic fields is that workers in exposed occupations are also exposed to a wide variety of other potentially harmful agents, including some known carcinogens. In conclusion, the available evidence from epidemiological studies is not sufficient to draw any conclusions about potential health effects of static magnetic field exposure.     

Effect of weak combined low frequency constant and alternative magnetic fields on intrinsic fluorescence of proteins in aqueous solutions]

It was shown that weak combined static (42 microT) and low-frequency variable (40 nT; 3-5 Hz) magnetic fields change the intensity of intrinsic fluorescence of some proteins (cytochrome c, bovine serum albumin, horseradish peroxidase, alkaline phosphatase). The effect can be interpreted as a change in the conformational state of the protein in water environment by the action of weak magnetic fields. The dynamics of the process, the concentration dependence, the binding of proteins to the fluorescence probe 1,8-ANS after treatment with magnetic fields, the frequency dependence of these reactions, and the dependence of the effect on the presence of the static constituent of the magnetic field were studied. It was shown that the changes in the intrinsic fluorescence of some enzymes (horseradish peroxidase, alkaline phosphatase) are related to changes in their functional activity. It was found that the effect is partially transferred via a solvent (water, 0.01 M NaCl) preliminarily treated with magnetic field. In the solvent, changes in its intrinsic fluorescence by the action of weak magnetic fields were also registered.     

Rapporteur report: cellular, animal and epidemiological studies of the effects of static magnetic fields relevant to human health

Three talks were presented in the session on “Cellular, Animal and Epidemiological Studies of the Effects of Static Magnetic Fields Relevant to Human Health”. The first talk presented the in vitro effects of static magnetic fields on cell cultures. The second talk presented the in vivo evidence obtained from animal studies. The final, third talk, presented the evidence obtained from epidemiological studies.

The overall conclusion of the three presentations and the following general discussion was that the scientific evidence available to date is weak and contains large gaps in knowledge either due to the poor quality of published studies or because of the lack of published research on certain health-related topics.

It was emphasized that the rapid development of new technological applications of static magnetic fields (e.g. magnetic levitation trains or magnetic resonance imaging—MRI) results in the human population at large, in certain occupations, and in a selected population of clinical patients being exposed to ever increasing static magnetic field strengths. It is of concern that the knowledge presently available concerning the health effects of these strong static magnetic fields is lagging a long way behind technological development.

In conclusion, it was suggested that there is an urgent need to perform new studies in all research areas (in vitro, in vivo and epidemiology) in order to fill the present gaps in knowledge and provide assurance that this technology will not cause any unwanted and unexpected health side effects.     

Electromagnetic fields in medicine – The state of art

ABSTRACT

Introduction: Intense development of methods belonging to physical medicine has been noted recently. There are treatment methods, which in many cases lead to reduction treatment time and positively influence on quality of life treatment patients. Research implications: The present physical medicine systematically extends their therapeutic possibilities. This above applies to illnesses and injuries of locomotor system, diseases affecting of soft tissues, as well as chronic wounds. The aim of the study: The evidence on this are the results of basic and clinical examinations relating the practical use of electromagnetic fields in medicine. Originality: In this work the authors introduced the procedure using the current knowledge relating to physical characteristic and biological effects of the magnetic fields. In the work the following methods were used: static magnetic fields, spatial magnetic fields, the variable magnetic fields both with laser therapy (magnetolaserotherapy) and variable magnetic fields both with light optical non-laser (magnetoledtherapy) talked.     

In vivo enhancement of chemotherapy with static electric or magnetic fields

We evaluated the ability of both static electric and static magnetic fields to enhance the in vivo action of a chemotherapeutic agent, adriamycin, against transplanted mammary tumors in mice. Female B6C3F1 mice with transplanted mammary adenocarcinoma were divided into four randomized groups and injected with 10 mg/kg adriamycin on day 7 of the study. Three of the groups were then exposed to nonuniform static electric or static magnetic fields. The resulting tumor regression in each group was measured four times during the remaining 13 days of the 20 day study. Two-sided statistical tests revealed all of the static field exposed groups achieved significantly greater (P 相似文献   

Behavioural evidence that magnetic field effects in the land snail,Cepaea nemoralis,might not depend on magnetite or induced electric currents

Although extremely low frequency (ELF) magnetic fields (<300 Hz) appear to exert a variety of biological effects, the magnetic field sensing/transduction mechanism(s) remains to be established. Here, using the inhibitory effects of magnetic fields on endogenous opioid peptide-mediated “analgaesic” response of the land snail. Cepaea nemoralis, we addressed the mechanism(s) of action of ELF magnetic fields. Indirect mechanisms involving both induced electric fields and direct magnetic field detection mechanisms (e.g., magnetite, parametric resonance) were evaluated. Snails were exposed to a static magnetic field (B_DC=78±1 μT) and to a 60 Hz magnetic field (B_AC=299±1 μT peak) with the angle between the static and 60 Hz magnetic fields varied in eight steps between 0° and 90°. At 0° and 90°, the magnetic field reduced opioid-induced analgaesia by approximately 20%, and this inhibition was increased to a maximum of 50% when the angle was between 50° and 70°. Because B_AC was fixed in amplitude, direction, and frequency, any induced electric currents would be constant independent of the B_AC/B_DC angle. Also, an energy transduction mechanism involving magnetite should show greatest sensitivity at 90°. Therefore, the energy transduction mechanism probably does not involve induced electric currents or magnetite. Rather, our results suggest a direct magnetic field detection mechanism consistent with the parametric resonance model proposed by Lednev. © 1996 Wiley-Liss, Inc.     

Time-varying and static magnetic fields act in combination to alter calcium signal transduction in the lymphocyte.

We have tested the hypothesis that extremely low frequency (ELF) time-varying magnetic fields act in combination with static magnetic fields to alter calcium signalling in the lymphocyte. Results indicate that a 60-min exposure of thymic lymphocytes at 37 +/- 0.05 degrees C to a 16 Hz, 421 mG (42.1 microT) magnetic field simultaneously with a colinear static magnetic field of 234 mG (23.4 microT) (a.c./d.c. field intensity ratio = 1.8) inhibits calcium influx triggered by the mitogen Concanavalin A. Significantly, resting lymphocytes do not respond to the fields, thus, only mitogen-activated cells undergoing calcium signalling exhibit a field response. These results indicate that signal transduction involving calcium is an important biological constraint which operates to mediate this field interaction. Additional split field exposures show that the presence of the a.c. field or the d.c. field alone does not produce an effect. This is consistent with a proposed parametric resonance theory of interaction of low intensity magnetic fields with biological systems (L.L. Lednev (1991) Bioelectromagnetics 12, 71-75), which predicts the occurrence of biological effects at specific values for the frequency and field intensity of the ELF and static magnetic fields.     

Myosin Light Chain Modification Depending on Magnetic Fields: II. Experimental

Recent experiments have revealed that Ca²⁺ -calmodulin dependent myosin light chain phosphorylation in a cell-free preparation exhibits unexpectedly high sensitivity to weak magnetic fields. This enzyme system is a well-studied biochemical system, which appears to depend upon ion binding. A previous article in this journal discussed the theoretical background of myosin phosphorylation and the ion-dependent interactions of EMF with soft tissues. Because of the electromagnetic field (EMF) sensitivity of this cell-free system, experiments were designed to test the effect of a pulsed radio frequency (PRF) field, pulsating magnetic fields (TEMF), gradient magnetic fields (Magnabloc), and homogeneous static magnetic fields (in Helmholtz arrangement) designed for clinical application. It is concluded that these various magnetic fields affect this cell-free enzyme system by modulating ion–protein interactions.     

Exposure of welders and other metal workers to ELF magnetic fields

This study assessed exposure to extremely low frequency (ELF) magnetic fields of welders and other metal workers and compared exposure from different welding processes. Exposure to ELF magnetic fields was measured for 50 workers selected from a nationwide cohort of metal workers and 15 nonrandomly selected full-time welders in a shipyard. The measurements were carried out with personal exposure meters during 3 days of work for the metal workers and 1 day of work for the shipyard welders. To record a large dynamic range of ELF magnetic field values, the measurements were carried out with “high/low” pairs of personal exposure meters. Additional measurements of static magnetic fields at fixed positions close to welding installations were done with a Hall-effect fluxmeter. The total time of measurement was 1273 hours. The metal workers reported welding activity for 5.8% of the time, and the median of the work-period mean exposure to ELF magnetic fields was 0.18 μT. DC metal inert or active gas welding (MIG/MAG) was used 80% of the time for welding, and AC manual metal arc welding (MMA) was used 10% of the time. The shipyard welders reported welding activity for 56% of the time, and the median and maximum of the workday mean exposure to ELF magnetic fields was 4.70 and 27.5 μT, respectively. For full-shift welders the average workday mean was 21.2 μT for MMA welders and 2.3 μT for MIG/MAG welders. The average exposure during the effective time of welding was estimated to be 65 μT for the MMA welding process and 7 μT for the MIG/MAG welding process. The time of exposure above 1 μT was found to be a useful measure of the effective time of welding. Large differences in exposure to ELF magnetic fields were found between different groups of welders, depending on the welding process and effective time of welding. MMA (AC) welding caused roughly 10 times higher exposure to ELF magnetic fields compared with MIG/MAG (DC) welding. The measurements of static fields suggest that the combined exposure to static and ELF fields of MIG/MAG (DC) welders and the exposure to ELF fields of MMA (AC) welders are roughly of the same level. Bioelectromagnetics 18:470–477, 1997. © 1997 Wiley-Liss, Inc.