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.     

The embryonic and post-embryonic development in two Drosophila species exposed to the static magnetic field of 60 mT

In this study, a static magnetic field influence on development and viability in two different species, Drosophila melanogaster and Drosophila hydei, was investigated. Both species completed development (egg–adult), in and out of the static magnetic field induced by double horseshoe magnet. Treated vials with eggs were placed in the gap between magnetic poles (47 mm) and exposed to the average magnetic induction of 60 mT, while control ones were kept far enough from magnetic field source. We found that exposure to the static magnetic field reduced development time in both species, but statistical significance was found only for D. hydei. Furthermore, we found that the average viability of both Drosophila species exposed to the magnetic field was significantly weaker compared to control ones. These results indicate that 60 mT static magnetic field could be considered as a potential stressor, influencing on different levels the embryonic and post-embryonic development of individuals.     

No effects of DC and 60-Hz AC magnetic fields on the first mitosis of two species of sea urchin embryos

The early divisions of sea urchin eggs was used as a model to study the effects of static and of 60 Hz sinusoidal magnetic fields. Two species were used (Sphaerechinus granularis and Paracentrotus lividus). Eggs were fertilized and exposed in two separate coils to the fields (up to 8 mT). Great care was taken to control the temperature of each sample. No difference was found in the time of the first division that could not be attributed to a temperature difference between samples. Comparison is made with other published data on various species. Bioelectromagnetics 19:494–497, 1998. © 1998 Wiley-Liss, Inc.     

Effect of a 12 HZ and of a 460 HZ pulsed magnetic field on the weight of AKR mice

AKR mice were exposed to a 6 mT, 12 Hz or 460 Hz pulsed magnetic field (PMF) 30 minutes twice a week. The exposure took placein utero and/or during the life span for four consecutive generations. The adult mice exposed to the 460 Hz PMF only after the birth time were lighter than the controls; for the two frequencies the decrease in weight with the ageing was less pronounced than in the controls. When the exposure took placein utero the exposed new-born mice were heavier than the controls. The difference in weight progressively disappeared when the mice were exposed to the 12 Hz PMF, persisted when the mice were exposed to the 460 Hz PMF.     

Lack of an effect of static magnetic field on calcium efflux from isolated chick brains

45Ca2+ efflux from neonatal isolated chick brains was measured. The brains were exposed to uniform or nonuniform static magnetic fields. The field intensity ranged from 200-900 mT. The exposure took place during incubation and/or when efflux was being measured. No difference appeared in the 45Ca2+ efflux between controls and exposed brains.     

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.     

不同强度工频磁场对皮层神经元瞬时外向钾离子通道的影响

人们对电磁辐射越来越关注,但是工频磁场产生的生物效应并不确定.选用1、5、10 mT的工频磁场照射急性分离的小鼠皮层神经元(15 min),应用全细胞膜片钳技术离线记录瞬时外向钾通道电流,研究工频磁场对离子通道的影响.结果显示:工频磁场抑制通道的电流密度,并且1 mT、5 mT及10 mT工频磁场的抑制率分别为(63.0±2.2)%、(55.0±1.7)%和(38.0±1.8)%.工频磁场影响离子通道的激活和失活特性,半数激活电压和半数失活电压变小.不同强度工频磁场对离子通道产生的影响程度不同,其中1 mT工频磁场对通道电流的抑制率最大,5 mT工频磁场对通道的半数激活电压和半数失活电压影响最大,10 mT工频磁场增大了通道的失活斜率因子.研究结果表明,工频磁场影响了细胞膜上离子通道蛋白质构象的变化,进一步影响了离子通道的正常功能.     

Enhancement of the hydrolysis activity of F0F1‐ATPases using 60 Hz magnetic fields

The effects of extremely low frequency (ELF) magnetic fields on membrane F₀F₁‐ATPase activity have been studied. When the F₀F₁‐ATPase was exposed to 60 Hz magnetic fields of different magnetic intensities, 0.3 and 0.5 mT magnetic fields enhanced the hydrolysis activity, whereas 0.1 mT exposure caused no significant changes. Even if the F₀F₁‐ATPase was inhibited by N,N‐dicyclohexylcarbodiimide, its hydrolysis activity was enhanced by a 0.5 mT 60 Hz magnetic field. Moreover, when the chromatophores which were labeled with F‐DHPE were exposed to a 0.5 mT, 60 Hz magnetic field, it was found that the pH of the outer membrane of the chromatophore was unchanged, which suggested that the magnetic fields used in this work did not affect the activity of F0. Taken together, our results show that the effects of magnetic fields on the hydrolysis activity of the membrane F₀F₁‐ATPases were dependent on magnetic intensity and the threshold intensity is between 0.1 and 0.3 mT, and suggested that the F1 part of F₀F₁‐ATPase may be an end‐point affected by magnetic fields. Bioelectromagnetics 30:663–668, 2009. © 2009 Wiley‐Liss, Inc.     

Extremely-Low Frequency Magnetic Field Effects on Sulfate Reducing Bacteria Viability

50?Hz magnetic fields effects on Sulfate Reducing Bacteria (SRB) viability were studied by colony forming units (CFU) counting. We found a 15% decrease of CFU number after magnetic field exposure (B=7.1?mT, f=50?Hz, t=24?min) compared to the control samples. These results are in good agreement with our previous work on other bacterial strains. The magnetic field effects on SRB are relatively large for small magnetic fields. The data correlations have been subjected to a simple physical chemical analysis, yielding surprisingly large estimates for the characteristic magnetic reaction susceptibility, even when the entire bacterium is assumed to be the direct target of interaction of the magnetic ac fields for the exposures in the time range from 3–24?min.     

Noise magnetic fields abolish the gap junction intercellular communication suppression induced by 50 hz magnetic fields

Previously, we have reported that exposure to 50 Hz coherent sinusoidal magnetic fields (MF) for 24 h inhibits gap junction intercellular communication (GJIC) in mammalian cells at an intensity of 0.4 mT and enhances the inhibition effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) at 0.2 mT. In the present study, we further explored the effects of incoherent noise MF on MF-induced GJIC inhibition. GJIC was determined by fluorescence recovery after photobleaching (FRAP) with a laser-scanning confocal microscope. The rate of fluorescence recovery (R) at 10 min after photobleaching was adopted as the functional index of GJIC. The R-value of NIH3T3 cells exposed to 50 Hz sinusoidal MF at 0.4 mT for 24 h was 30.85 +/- 14.70%, while the cells in sham exposure group had an R-value of 46.36 +/- 20.68%, demonstrating that the GJIC of NIH3T3 cells was significantly inhibited by MF exposure (P < .05). However, there were no significant differences in the R-values of the sham exposure, MF-plus-noise MF exposure (R: 49.58 +/- 19.38%), and noise MF exposure groups (R: 46.74 +/- 21.14%) (P > .05), indicating that the superposition of a noise MF alleviated the suppression of GJIC induced by the 50 Hz MF. In addition, although MF at an intensity of 0.2 mT synergistically enhanced TPA-induced GJIC inhibition (R: 24.90 +/- 13.50% vs. 35.82 +/- 17.18%, P < .05), further imposition of a noise MF abolished the synergistic effect of coherent MF (R: 32.51 +/- 18.37%). Overall, the present data clearly showed that although noise MF itself had no effect on GJIC of NIH3T3 cells, its superposition onto a coherent sinusoidal MF at the same intensity abolished MF-induced GJIC suppression. This is the first report showing that noise MF neutralizes 50 Hz MF-induced biological effect by using a signaling component as the test endpoint.     

不同强度工频磁场对神经元延迟整流钾通道特性的影响

工频磁场是人类生活中接触最多的一类磁场,其引起的生物效应与人类健康的关系备受关注．本文选用1 mT、5 mT及10 mT工频磁场照射急性分离的小鼠皮层神经元(15 min),应用全细胞膜片钳技术离线记录通道电流,研究了工频磁场对神经元延迟整流钾通道特性的影响．结果显示,1 mT、5 mT及10 mT 3个强度的工频磁场对I_k均有抑制作用,但随着去极化电压的增加,发现1 mT和5 mT工频磁场的抑制率几乎不变,抑制率分别为(30 ± 4.2)%和(20 ± 2.2)%,而10 mT工频磁场的抑制率增加,最大抑制率为43.4%．另外,1 mT和5 mT工频磁场影响了延迟整流钾通道的激活特性,通道的半数激活电压变大,斜率因子不变．而10 mT工频磁场对通道的激活特性没有影响,半数激活电压和斜率因子均不改变．研究表明,工频磁场可能影响了细胞膜上离子通道蛋白质的结构和功能,并且不同强度工频磁场对通道的影响不同,存在强度窗口效应．     

Enhanced mutagenic effect of a 60 Hz time-varying magnetic field on numbers of azide-induced TA100 revertant colonies

Forty-eight hours exposure to a two Gauss (0.2 mT) rms 60 Hz time varying sinusoidal electromagnetic field increased the number of azide induced TA100 revertant colonies of Salmonella typhimurium 14% as compared with controls in the ambient < 2 milli-Gauss 60 Hz field. In the absence of the electromagnetic field, the numbers of mutant colonies grown within and outside the non-energized coil were nearly identical. Without azide, the number of “spontaneous” mutant colonies forming in the experimental field was not statistically significant from numbers of colonies not exposed to field effects. Experimental temperature variation of 2 °C had little effect on colony formation, and the enhanced production of revertant colonies in the presence of the magnetic field was maintained during continued culture for 5 additional days. © 1994 Wiley-Liss, Inc.     

In vitro effects of 50 Hz magnetic fields on oxidatively damaged rabbit red blood cells

The aim of this study was to investigate the effects of 50 Hz magnetic fields (0.2–0.5 mT) on rabbit red blood cells (RBCs) that were exposed simultaneously to the action of an oxygen radical-generating system, Fe(II)/ascorbate. Previous data obtained in our laboratory showed that the exposure of rabbit erythrocytes or reticulocytes to Fe(II)/ascorbate induces hexokinase inactivation, whereas the other glycolytic enzymes do not show any decay. We also observed depletion of reduced glutathione (GSH) content with a concomitant intracellular and extracellular increase in oxidized glutathione (GSSG) and a decrease in energy charge. In this work we investigated whether 50 Hz magnetic fields could influence the intracellular impairments that occur when erythrocytes or reticulocytes are exposed to this oxidant system, namely, inactivation of hexokinase activity, GSH depletion, a change in energy charge, and hemoglobin oxidation. The results obtained indicate that a 0.5 mT magnetic field had no effect on intact RBCs, whereas it increased the damage in an oxidatively stressed erythrocyte system. In fact, exposure of intact erythrocytes incubated with Fe(II)/ascorbate to a 0.5 mT magnetic field induced a significant further decay in hexokinase activity (about 20%) as well as a twofold increase in methemoglobin production compared with RBCs that were exposed to the oxidant system alone. Although further studies will be needed to determine the physiological implications of these data, the results reported in this study demonstrate that the effects of the magnetic fields investigated are able to potentiate the cellular damage induced in vitro by oxidizing agents. Bioelectromagnetics 18:125–131, 1997. © 1997 Wiley-Liss, Inc.     

Chick embryo development can be irreversibly altered by early exposure to weak extremely-low-frequency magnetic fields

Several reports have shown that weak, extremely-low-frequency (ELF), pulsed magnetic fields (PMFs) can adversely affect the early embryonic development of the chick. In this study, freshly fertilized chicken eggs were exposed during the first 48 h of postlaying incubation to PMFs with 100 Hz repetition rate, 1.0 μT peak-to-peak amplitude, and 500 μs pulse duration. Two different pulse waveforms were used, having rise and fall times of 85 μs (PMF-A) or 2.1 μs (PMF-B). It has been reported that, with 2 day exposure, these fields significantly increase the proportion of developmental abnormalities. In the present study, following exposure, the eggs were allowed to incubate for an additional 9 days in the absence of the PMFs. The embryos were taken out of the eggs and studied blind. Each of the two PMF-exposed groups showed an excess in the percentage of developmental anomalies compared with the respective sham-exposed samples. This excess of anomalies was not significant for the PMF-A-treated embryos (P = 0.173), whereas it was significant for the PMF-B-exposed group (P = 0.007), which showed a particularly high rate of early embryonic death. These results reveal that PMFs can induce irreversible developmental alterations and confirm that the pulse waveform can be a determinant factor in the embryonic response to ELF magnetic fields. The data also validate previous work based on the study of PMFs' effects at day 2 of embryonic development under field exposure. © 1994 Wiley-Liss, Inc.     

Lack of chick embryotoxicity after 20 kHz, 1.1 mT magnetic field exposure

This investigation was undertaken because biological studies to evaluate the effects of intermediate frequency magnetic fields are insufficient. White Leghorn fertile eggs (60/group) were either exposed to a 20 kHz, 1.1 mT(rms) sinusoidal magnetic field or sham‐exposed during the first 2, 7, or 11 days of embryogenesis. Lower dose exposures at 0.011 and 0.11 mT(rms) for 2 days were also conducted to elucidate possible dose–response relationships. Additional eggs given all‐trans‐retinoic acid, a teratogen, were exposed to the 1.1 mT(rms) magnetic field for the same periods to investigate the modification of embryotoxicity. After exposure, embryos were examined for mortality and developmental abnormalities. Developmental stage, number of somite pairs, and other developmental endpoints were also evaluated. Experiments were triplicated and conducted in a blind fashion. No exposure‐related changes were found in any of the endpoints in intact embryos exposed to1.1 mT(rms) or to the lower doses of 0.11 and 0.011 mT(rms) magnetic fields. Retinoic acid administration produced embryotoxic responses, which were embryonic death and developmental abnormalities, in 40–60% of embryos in the sham‐exposed groups. The magnitude of these responses was not changed significantly by the magnetic field exposures. Under the present experimental conditions, exposure to 20 kHz magnetic field up to 1.1 mT(rms) was not embryotoxic in the chick and did not potentiate the embryotoxic action of retinoic acid. Bioelectromagnetics 30:573–582, 2009. © 2009 Wiley‐Liss, Inc.     

Magnetic fields suppress Pseudomonas aeruginosa biofilms and enhance ciprofloxacin activity

Due to the refractory nature of pathogenic microbial biofilms, innovative biofilm eradication strategies are constantly being sought. Thus, this study addresses a novel approach to eradicate Pseudomonas aeruginosa biofilms. Magnetic nanoparticles (MNP), ciprofloxacin (Cipro), and magnetic fields were systematically evaluated in vitro for their relative anti-biofilm contributions. Twenty-four-hour biofilms exposed to aerosolized MNPs, Cipro, or a combination of both, were assessed in the presence or absence of magnetic fields (Static one-sided, Static switched, Oscillating, Static + oscillating) using changes in bacterial metabolism, biofilm biomass, and biofilm imaging. The biofilms exposed to magnetic fields alone exhibited significant metabolic and biomass reductions (p < 0.05). When biofilms were treated with a MNP/Cipro combination, the most significant metabolic and biomass reductions were observed when exposed to static switched magnetic fields (p < 0.05). The exposure of P. aeruginosa biofilms to a static switched magnetic field alone, or co-administration with MNP/Cipro/MNP + Cipro appears to be a promising approach to eradicate biofilms of this bacterium.     

Effects of static magnetic fields on plasma levels of angiotensin II and aldosterone associated with arterial blood pressure in genetically hypertensive rats

Effects of static magnetic fields (SMFs) on development of hypertension were investigated using young male, stroke resistant, spontaneously hypertensive rats (SHRs) beginning at 7 weeks of age. SHRs were randomly assigned to two different exposure groups or an unexposed group. The SHRs in the exposure groups were constantly exposed to two different types of external SMFs of 3.0-10.0 mT or 8.0-25.0 mT for 12 weeks. The SMFs were generated from permanent magnetic plates attached to the rat cage. The blood pressure (BP) of each rat was determined at weekly intervals using indirect tail-cuff method. The SMFs suppressed and retarded the development of hypertension in both exposed groups to a statistically significant extent for several weeks, as compared with an unexposed group. The antipressor effects were related to the extent of reduction in plasma levels of angiotensin II and aldosterone in the SHRs. These results suggest that the SMFs of mT intensities with spatial gradients could be attributable to suppression of early BP elevation via hormonal regulatory system.     

Seed orientation and magnetic field strength have more influence on tomato seed performance than relative humidity and duration of exposure to non-uniform static magnetic fields

Different factors (e.g., light, humidity, and temperature) including exposure to static magnetic fields (SMFs), referred here as critical factors, can significantly affect horticultural seed performance. However, the link between magnetic field parameters and other interdependent factors affecting seed viability is unclear. The importance of these critical factors affecting tomato (Solanum lycopersicum L.) var. MST/32 seed performance was assessed after performing several treatments based on a L₉ (3⁴) (four factors at three levels) orthogonal array (OA) design. The variable factors in the design were magnetic flux density (R₁ = 332.1 ± 37.8 mT; R₂ = 108.7 ± 26.9 mT; and R₃ = 50.6 ± 10.5 mT), exposure time (1, 2, and 24 h), seed orientation (North polarity, South polarity, and control – no magnetic field), and relative humidity (RH) (7.0, 25.5, and 75.5%). After seed moisture content stabilisation at the different chosen RH, seeds were exposed in dark under laboratory conditions to several treatments based on the OA design before performance evaluation. Treatments not employing magnetic field exposure were used as controls. Results indicate that electrolyte leakage rate was reduced by a factor of 1.62 times during seed imbibition when non-uniform SMFs were employed. Higher germination (∼11.0%) was observed in magnetically-exposed seeds than in non-exposed ones, although seedlings emerging from SMF treatments did not show a consistent increase in biomass accumulation. The respective influence of the four critical factors tested on seed performance was ranked (in decreasing order) as seed orientation to external magnetic fields, magnetic field strength, RH, and exposure time. This study suggests a significant effect of non-uniform SMFs on seed performance with respect to RH, and more pronounced effects are observed during seed imbibition rather than during later developmental stages.     

Applied DC magnetic fields cause alterations in the time of cell divisions and developmental abnormalities in early sea urchin embryos

Most work on magnetic field effects focuses on AC fields. The present study demonstrates that exposure to medium-strength (10 mT-0.1 T) static magnetic fields can alter the early embryonic development of two species of sea urchin embryos. Batches of fertilized eggs from two species of urchin were exposed to fields produced by permanent magnets. Samples of the continuous cultures were scored for the timing of the first two cell divisions, time of hatching, and incidence of exogastrulation. It was found that static fields delay the onset of mitosis in both species by an amount dependent on the exposure timing relative to fertilization. The exposure time that caused the maximum effect differed between the two species. Thirty millitesla fields, but not 15 mT fields, caused an eightfold increase in the incidence of exogastrulation in Lytechinus pictus, whereas neither of these fields produced exogastrulation in Strongylocentrotus purpuratus. Bioelectromagnetics 18:255–263, 1997. © 1997 Wiley-Liss, Inc.     

Chronic exposure to a 2 mT static magnetic field affects the morphology,the metabolism and the function of in vitro cultured swine granulosa cells

In recent years, the exposure of organisms to static magnetic fields (SMFs) is continuously increasing. Thus, we investigated the effect of chronic exposure to a 2 mT SMF on in vitro cultured swine granulosa cells (GCs). In particular, the culture expansion (cell viability and doubling time), the cell phenotype (cell morphology and orientation, actin and α-tubulin cytoskeleton), the cell metabolism (intracellular Ca²⁺ concentration [Ca²⁺]_i and mitochondrial activity) and the cell function (endocrine activity) were assessed. It has been found that the exposure to the field did not affect the cell viability, but the doubling time was significantly reduced (p < 0.05) in exposed samples after 72 h of culture. At the same time, the cell length and thickness significantly changed (p < 0.05), while the cell orientation was unaffected. Evident modifications were induced on actin and α-tubulin cytoskeleton after 3 days of exposure and, simultaneously, a change in [Ca²⁺]_i and mitochondrial activity started to become evident. Finally, the SMF exposure of GCs longer than 72 h determined a significant alteration of progesterone and estrogen production (p < 0.05). In conclusion, our results demonstrate that the chronic exposure of swine GCs to a 2 mT SMF exerts a negative effect on cell proliferation, morphology, biochemistry and endocrine function in an in vitro model.