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.     

Permeability changes of connexin32 hemi channels reconstituted in liposomes induced by extremely low frequency, low amplitude magnetic fields

The effect of extremely low frequency and low amplitude magnetic fields on gap junctional permeability was investigated by using reconstituted connexin32 hemi channel in liposomes. Cytochrome c was loaded inside these proteoliposomes and its reduction upon addition of ascorbate in the bulk aqueous phase was adopted as the index of hemi channel permeability. The permeability rate of the hemi channels, expressed as ΔA/min, was dependent on the incubation temperature of proteoliposomes. The effect of exposures to magnetic fields at different frequencies (7, 13 and 18 Hz) and amplitudes (50, 50 and 70 μT, respectively), and at different temperatures (16, 18 and 24 °C) was studied. Only the exposure of proteoliposomes to 18-Hz (B_acpeak and B_dc=70 μT) magnetic field for 60 min at 16±0.4 °C resulted in a significant enhancement of the hemi channel permeability from ΔA/min=0.0007±0.0002 to ΔA/min=0.0010±0.0001 (P=0.030). This enhancement was not found for magnetic field exposures of liposomes kept at the higher temperatures tested. Temperature appears to influence lipid bilayer arrangement in such a way as being capable to mask possible effects induced by the magnetic field. Although the observed effect was very low, it seems to confirm the applicability of our model previously proposed for the interaction of low frequency electromagnetic fields with lipid membrane.     

Human exposure to magnetic fields: A comparative assessment of two dosimeters

Two types of dosimeters for measuring human exposure to 60 Hz magnetic fields were compared. Fifty adults wore the single-axis, wrist model AMEX (average magnetic field exposure system) and the triple axis, hip-pocket or pouch model AMEX-3D meters for 2 days. Ninety-six percent of the tests were accomplished without apparent dosimeter failure. The average root mean square magnetic flux density measurements with the AMEX3D (mean = 0.10 μT, S.D. = 0.07, range = 0.03 ? 0.31) were significantly higher than with the AMEX meter (mean = 0.07 μT, S.D. 0.05, range = 0.02 ? 0.27 μT) (t test, P < 0.01). There was substantial correlation between the AMEX and the AMEX-3D measurements (Pearson's correlation coefficient = 0.65, P < 0.01) but poor concordance (Intraclass correlation coefficient = ? 0.25). These results suggest that there is a wide variation in exposure to extremely low frequency magnetic fields in the population. Magnetic field measurements with the AMEX-3D are nearly always higher than with the AMEX dosimeters. Caution is advised when comparing magnetic field measurements made with different types of dosimeters. © 1994 Wiley-Liss, Inc.     

Influence of pulsed electromagnetic and pulsed vector magnetic potential field on the growth of tumor cells

Aims and Background: Tumor diseases cause 20% of deaths in Europe and they are the second most common cause of death and morbidity after cardiovascular diseases. Thus, tumor cells are target of many therapeutic strategies and tumor research is focused on searching more efficient and specific drugs as well as new therapeutic approaches. One of the areas of tumor research is an issue of external fields. In our work, we tested influence of a pulsed electromagnetic field (PEMF) and a hypothetic field of the pulsed vector magnetic potential (PVMP) on the growth of tumor cells; and further the possible growth inhibition effect of the PVMP. Methods: Both unipolar and bipolar PEMF fields of 5?mT and PVMP fields of 0?mT at frequencies of 15?Hz, 125?Hz and 625?Hz were tested on cancer cell lines derived from various types of tumors: CEM/C2 (acute lymphoblastic leukemia), SU-DHL-4 (B-cell lymphoma), COLO-320DM (colorectal adenocarcinoma), MDA-BM-468 (breast adenocarcinoma), and ZR-75-1 (ductal carcinoma). Cell morphology was observed, proliferation activity using WST assay was measured and simultaneous proportion of live, early apoptotic and dead cells was detected using flow cytometry. Results: A PEMF of 125?Hz and 625?Hz for 24?h–48?h increased proliferation activity in the 2 types of cancer cell lines used, i.e. COLO-320DM and ZR-75-1. In contrast, any of employed methods did not confirm a significant inhibitory effect of hypothetic PVMP field on tumor cells.     

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.     

Mediterranean flour moth Ephestia kuehniella eggs and larvae exposed to a static magnetic field and preference by Trichogramma embryophagum

This study investigated the effect of strong magnetic fields as insecticidal activity on Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) larvae and eggs at different stages of development and their preference by the egg parasitoid, Trichogramma embryophagum Hartig (Hymenoptera: Trichogrammatidae). Eggs ranging in age from 24-h to 48-h and 72-h-old and larvae (1 to 2 days) were exposed to 1.4 Tesla (T) magnetic fields from a DC power supply at 50 Hz for different time periods (3, 6, 12, 24, 48 and 72 h). Twelve hours of exposure at 1.4 T was toxic to 24-h-old eggs of E. kuehniella. The 72-h-old host eggs treated with 1.4 T for 6–72 h were not significantly preferred by T. embryophagum. The magnetic field was toxic to 24-h-old eggs of E. kuehniella exposed to 1.4 T for 12. The treatment of magnetic fields on the 72-h-old host egg with 1.4 T at 6–72 h was not significantly preferred by T. embryophagum. Magnetization of 24-h-old eggs of E. kuehniella for 3 h could be effectively used with T. embryophagum as sterilised host eggs. These eggs were markedly preferred by T. embryophagum. The LT₅₀ and LT₉₉ values of magnetic fields at different egg stages of E. kuehniella, and larvae were measured. A level of 1.4 T at 72 h completely prevented the development of the larvae. There was no significant effect on larval survival at 1.4 T at 48 and 72 h. Increasing magnetic fields exposure times for eggs that were 24-h, 48-h and 72-h-old prevented larval emergence and increased their mortality rate. Consequently, magnetic fields could be used in controlling stored-product pest eggs and larvae of E. kuehniella.     

Augmentation of antibiotic activity by low-frequency electric and electromagnetic fields examining Staphylococcus aureus in broth media

Systemic treatment of biomaterial‐associated bacterial infections with high doses of antibiotics is an established therapeutic concept. The purpose of this in vitro study was to determine the influence of magnetic, electromagnetic, and electric fields on gentamicin‐based, antibiotic therapy. It has been previously reported that these fields are successful in the treatment of bone healing and reducing osteitis in infected tibia‐pseudarthroses. Four separate experimental setups were used to expose bacterial cultures of Staphylococcus aureus both in Mueller‐Hinton broth (MHB) and on Mueller‐Hinton agar (MHA), in the presence of gentamicin, to (1) a low‐frequency magnetic field (MF) 20 Hz, 5 mT; (2) a low‐frequency MF combined with an additional alternating electric field (MF + EF) 20 Hz, 5 mT, 470 mV/cm; (3) a sinusoidal alternating electric field (EF AC) 20 Hz, 470 mV/cm; and (4) a direct current electric field (EF DC) 588 mV/cm. No significant difference between samples and controls was detected on MHA. However, in MHB each of the four fields applied showed a significant growth reduction of planktonically grown Staphylococcus aureus in the presence of gentamicin between 32% and 91% within 24 h of the experiment. The best results were obtained by a direct current EF, decreasing colony‐forming units (CFU)/ml more than 91%. The application of electromagnetic fields in the area of implant and bone infections could offer new perspectives in antibiotic treatment and antimicrobial chemotherapy. Bioelectromagnetics 32:367–377, 2011. © 2011 Wiley‐Liss, Inc.     

EVIDENCE OF SYNCHRONIZATION OF NEURONAL ACTIVITY OF MOLLUSCAN BRAIN GANGLIA INDUCED BY ALTERNATING 50 Hz APPLIED MAGNETIC FIELD

Experimental evidence for the appearance of synchronized bioelectric activity in neurons under applied extremely low frequency (ELF) magnetic fields is shown. We have studied the synchronizing process by recording the intracellular bioelectric activity from pairs of neurons randomly chosen from the brain ganglia of the snail Helix aspersa. The recordings were made in real time under exposure to sinusoidal low frequency (50 Hz) weak (B₀=1–15 mT) magnetic fields. Synchronization was observed in 27% of the pairs tested. A linear dependence of the firing frequency f with the energy density of the applied magnetic field (i.e., f∝B₀²) was presented. The ability of low frequency sinusoidal weak magnetic fields to promote “magnetic synchronization” is exciting and opens new avenues for induced electromagnetic field bioeffects.     

Permeability changes of connexin32 hemi channels reconstituted in liposomes induced by extremely low frequency, low amplitude magnetic fields

The effect of extremely low frequency and low amplitude magnetic fields on gap junctional permeability was investigated by using reconstituted connexin32 hemi channel in liposomes. Cytochrome c was loaded inside these proteoliposomes and its reduction upon addition of ascorbate in the bulk aqueous phase was adopted as the index of hemi channel permeability. The permeability rate of the hemi channels, expressed as DeltaA/min, was dependent on the incubation temperature of proteoliposomes. The effect of exposures to magnetic fields at different frequencies (7, 13 and 18 Hz) and amplitudes (50, 50 and 70 microT, respectively), and at different temperatures (16, 18 and 24 degrees C) was studied. Only the exposure of proteoliposomes to 18-Hz (B(acpeak) and B(dc)=70 microT) magnetic field for 60 min at 16+/-0.4 degrees C resulted in a significant enhancement of the hemi channel permeability from DeltaA/min=0.0007+/-0.0002 to DeltaA/min=0.0010+/-0.0001 (P=0.030). This enhancement was not found for magnetic field exposures of liposomes kept at the higher temperatures tested. Temperature appears to influence lipid bilayer arrangement in such a way as being capable to mask possible effects induced by the magnetic field. Although the observed effect was very low, it seems to confirm the applicability of our model previously proposed for the interaction of low frequency electromagnetic fields with lipid membrane.     

Frequency-dependent alterations in enolase activity in Escherichia coli caused by exposure to electric and magnetic fields

Some neurochemical effects of low-intensity electric and magnetic fields have been shown to be nonlinear functions of exposure parameters. These effects occurred within narrow ranges of frequency and intensity. Previous studies on membrane-associated endpoints in cell culture preparations demonstrated changes in calcium efflux and in acetylcholinesterase activity following exposure to radiofrequency radiation, amplitude modulated (AM) at 16 and at 60 Hz, at a specific absorption rate of 0.05 W/kg. In this study, these modulation frequencies were tested for their influence on the activity of a cytoplasmic enzyme, enolase, which is being tested clinically for detection of neoplasia. Escherichia coli cultures containing a plasmid with a mammalian gene for enolase were exposed for 30 min, and cell extracts were assayed for enolase activity by measuring absorbance at 240 nm. The enolase activity in exposed cultures was compared to the activity in paired control cultures. Exposure to 147 MHz carrier waves at 0.05 W/kg, AM at 16 Hz showed enolase activity enhanced by 62%, and AM at 60 Hz showed enolase activity reduced by 28%. Similarly, exposure to 16 Hz fields alone, at 21.2 V/m_rms (electric) and 97 nT_rms (magnetic), showed enhancement in enolase activity by 59%, whereas exposure to 60 Hz fields alone, at 14.1 V/m_rms (electric) and 65 nT_rms (magnetic), showed reduction in activity by 24%. Sham exposures as well as exposure to continuous-wave 147 MHz radiation at 0.05 W/kg showed no change in enolase activity. Although the underlying basis for these field effects in the cytoplasmic compartment has not been established, differential sensitivities to 16 Hz and to 60 Hz signals provide a clear focus for additional research to determine the responsible mechanism. © 1994 Wiley-Liss, Inc.     

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.     

Investigation of the effects of 50 Hz magnetic fields on platelet aggregation using a modified aggregometer

Purpose: Electromagnetic fields have various effects on intracellular calcium levels, free oxygen radicals and various enzymes. The platelet activation pathway involves an increase in intracellular calcium levels and protein kinase C activation; and free oxygen radicals play a mediating role in this pathway. This study investigated whether 1 mT and 6 mT, 50 Hz magnetic fields had any effects on platelet aggregation.

Materials and Methods: Blood from healthy volunteers was anticoagulated with either citrate or heparin. Each sample was divided in half and assigned to exposure and control groups. Platelet rich plasma samples in the exposure group were exposed to a 1 mT or a 6 mT, 50 Hz magnetic field for 1.5 or 1 h, respectively. The samples from both exposure and control groups were simultaneously evaluated using a modified optical aggregometer. Adenosine-diphosphate, collagen, and epinephrine were used as inducing agents. The slopes of the aggregation curve, the maximum values and the areas under the curves were recorded and compared.

Results: A significant effect was observed only in the 1 mT-citrate group. It was found that magnetic field exposure significantly increased the maximum values and slopes of the collagen-induced aggregations.

Conclusions: It was found that magnetic field exposure has an activating effect on platelet aggregation.     

Effects of 50 Hz magnetic fields on gap junctional intercellular communication.

To explore whether the extremely low frequency (ELF) electromagnetic fields (EMFs) may act as cancer promoters or be synergistic with 12-O-tetradecanoylphorbol-13-acetate (TPA) in cancer promotion, an experiment was conducted on the effects of 50 Hz magnetic fields (MFs) on gap junctional intercellular communication (GJIC) of Chinese hamster lung (CHL) cells. Lucifer dye was loaded into CHL cells by iontophoretic injection, and the number of dye-coupled cells (DCC) 5 min after the injection was adopted as the index of GJIC. The effects of TPA at different concentrations and magnetic fields at different intensities, combined with 5 ng/ml TPA, were studied. The results showed that the suppression of TPA on GJIC was dependent on TPA concentration; the threshold concentration of TPA for CHL cells was between 1 and 5 ng/ml. After exposure to 0.8 mT magnetic field for 24 h, the number of DCC decreased to 6.08 +/- 1.59, whereas the number of DCC in the control group was 9.84 +/- 2.27 (P < .05). When the cells were exposed at 0.2, 0.4, and 0.8 mT for 24 h, combined with 5 ng/ml TPA treatment during the last 1 h, the number of DCC decreased to 5.52 +/- 1.53, 5.00 +/- 1.22, and 4.00 +/- 1.29, respectively, which were significantly lower than the values for the group treated with 5 ng/ml TPA alone (6.38 +/- 1.39). It is suggested that certain intensities of 50 Hz magnetic field might act as cancer promoters, be additive with other promoters in cancer promotion, or both.     

Effects of 50 Hz rotating magnetic field on the viability of Escherichia coli and Staphylococcus aureus

This study presents results of research on the influence of rotating magnetic field (RMF) of the induction of 30?mT and the frequency of 50?Hz on the growth dynamics and cell metabolic activity of E. coli and S. aureus, depending on the exposure time. The studies showed that the RMF caused an increase in the growth and cell metabolic activity of all the analyzed bacterial strains, especially in the time interval t?=?30 to 150?min. However, it was also found that the optical density and cell metabolic activity after exposition to RMF were significantly higher in S. aureus cultures. In turn, the study of growth dynamics, revealed a rapid and a significant decrease in these values from t?=?90?min) in the case of E. coli samples. The obtained results prove that RMF (B?=?30?mT, f?=?50?Hz) has a stimulatory effect on the growth and metabolic activity of E. coli and S. aureus. Furthermore, taking into account the time of exposure, stronger influence of RMF on the viability was observed in S. aureus cultures, which may indicate that this effect depends on the shape of the exposed cells.     

Measurement of the individual exposure to 50 and 16 2/3 Hz magnetic fields within the Bavarian population.

This study investigates the individual magnetic field exposures at 16 2/3 and 50 Hz of 1952 people, selected from the Bavarian population. Personal flux density meters ("Field Watcher FW2A") were worn by the participants for 24 h. Every second, the flux density was recorded for both frequencies and for the three spatial axes (dynamic range per axis: several nT up to 100 microT at 50 Hz, 150 microT at 16 2/3 Hz). For 50 Hz fields, the mean of the 1,952 individual means was 0.101 microT and that of the individual medians was 0.047 microT. High level exposures occurred mainly during working hours. Only 2.4% of the subjects showed individual medians higher than 0.2 microT. About 53% of all volunteers were working on the day of recording. Levels for craftsmen (n = 148; mean individual mean: 0.166 microT) were generally higher than those for office workers (n = 624; mean individual mean: 0.107 microT). Flux densities exceeding 100 microT at 50 Hz were measured in 31 persons. The total time with such extreme exposures amounts to nearly 21 min, less than 0.001% of the total time for all measurements (5.3 years). To our knowledge, this is the first exposure study where 16 2/3 Hz magnetic fields (caused by electrified railways) have additionally been monitored over 24 h. For persons living next to railway lines, the mean individual mean (0.156 microT) and mean individual median (0.102 microT) were calculated. Over all, the mean exposures are only 0.1% of the magnetic flux density limit for 50 Hz (100 microT) and about 0.05% of the limit (300 microT) for 16 2/3 Hz recommended by the International Commission on Non-Ionizing Radiation Protection.     

Effects of prenatal exposure to 50 Hz magnetic fields on development in mice: II. Postnatal development and behavior

To investigate the potential of magnetic fields to act as a behavioral teratogen, pregnant CD1 mice were exposed or sham-exposed for all of gestation to a 50 Hz/20 mT magnetic field. Maturation of offspring was assessed using a range of standard developmental indices (eye opening, pinna detachment, hair coat, tooth eruption, sexual maturity, and weight) and simple reflexive behaviors (air righting, surface righting, forepaw grasp, cliff avoidance, and negative geotaxis). Activity and coordination levels were explored in juvenile and adult mice using an open field arena, a head-dip board, an accelerating Rotarod, and a residential activity wheel. All assessments were carried out without knowledge of exposure condition. Results from 168 sham-exposed mice from 21 litters and from 184 exposed mice from 23 litters were compared using survival analysis techniques and multivariate regression methods. Three possible field-dependent effects were found: Exposed animals performed the air righting reflex earlier (P < 0.01); exposed males (but not females) were significantly lighter in weight (P = 0.008) at 30 days of age; and exposed animals remained on a Rota-rod for less time as juveniles (P = 0.03). Some of these results have not been reported in other studies and may reflect spurious statistical significance, although some effect of magnetic field exposure cannot be ruled out. Overall, these results suggest that prenatal exposure to a 50 Hz magnetic field does not engender any gross impairments in the postnatal development or behavior of mice. This does not preclude such exposure affecting more subtle aspects of behavior. Published 1994 by Wiley-Liss, Inc.     

Effects of Extremely Low-Frequency Magnetic Field on Growth and Differentiation of Human Mesenchymal Stem Cells

Human Mesenchymal Stem Cells (hMSCs) were exposed to a developed extremely low-frequency (ELF) magnetic fields (50?Hz ,20?mT ELF) system to evaluate whether exposure to (ELF) magnetic fields affects growth, metabolism, and differentiation of hMSCs. MTT method was used to determine the growth and metabolism of hMSCs following exposure to ELF magnetic fields. Na⁺/K⁺ concentration and osmolality of extracelluar were measured after exposured culture. Alkaline phosphatase (ALP) assay and Calcium assay, ALP staining, and Alizarin red staining were performed to evaluate the osteogenic differentiation of hMSCs under the ELF magnetic field exposure. In these experiments, the cells were exposed to ELF for up to 23 days. The results showed that exposure to ELF magnetic field could inhibit the growth and metabolism of hMSC, but have no significant effect on differentiation of hMSCs. These results suggested that ELF magnetic field may influence the early development of hMSCs related adult cells.     

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.     

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.