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.     

Behavioral sensitivity of rats to extremely-low-frequency magnetic fields

Work in our laboratory has revealed autonomic and/or behavioral sensitivity of mice, rats, and a domestic fowl to extremely-low-frequency (ELF) or nominally static magnetic (B) fields at flux densities between 250 and 1700 μT (rms). To extend our work, an automated exposure and data-acquisition system was used with the technique of conditional suppression to assess behavioral sensitivity to time-varying B fields. Each of five rats was exposed aperiodically to a B field during 3 min warning periods that terminated in a brief electric shock. The difference between rates of lever pressing during B-field warning periods and rates during immediately antecedent, 3 min control periods was analyzed at frequencies of 7, 16, 30, 60, and 65.1 Hz. To produce equivalent induced voltages in the rat at each frequency, graded flux densities were established that ranged from 1900 μT at 7 Hz to 200 μT at 65.1 Hz. Analysis of differences in lever-pressing rates revealed that in a given session of testing the rats would increasingly suppress responding when exposed to a B field, but this trend was independent of frequency. This experiment provides evidence of behavioral sensitivity by a mammal to an ELF magnetic field. © 1994 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.     

Light-dependent and -independent behavioral effects of extremely low frequency magnetic fields in a land snail are consistent with a parametric resonance mechanism

Exposure to extremely low frequency (ELF) magnetic fields has been shown to attenuate endogenous opioid peptide mediated antinociception or “analgaesia” in the terrestrial pulmonate snail, Cepaea nemoralis. Here we examine the roles of light in determining this effect and address the mechanisms associated with mediating the effects of the ELF magnetic fields in both the presence and absence of light. Specifically, we consider whether the magnetic field effects involve an indirect induced electric current mechanism or a direct effect such as a parametric resonance mechanism (PRM). We exposed snails in both the presence and absence of light at three different frequencies (30, 60, and 120 Hz) with static field values (B_DC) and ELF magnetic field amplitude (peak) and direction (B_AC) set according to the predictions of the PRM for Ca²⁺. Analgaesia was induced in snails by injecting them with an enkephalinase inhibitor, which augments endogenous opioid (enkephalin) activity. We found that the magnetic field exposure reduced this opioid-induced analgaesia significantly more if the exposure occurred in the presence rather than the absence of light. However, the percentage reduction in analgaesia in both the presence and absence of light was not dependent on the ELF frequency. This finding suggests that in both the presence and the absence of light the effect of the ELF magnetic field was mediated by a direct magnetic field detection mechanism such as the PRM rather than an induced current mechanism. Bioelectromagnetics 18:284–291, 1997. © 1997 Wiley-Liss, Inc.     

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.     

EFFECTS OF STATIC AND ELF MAGNETIC FIELDS ON FREE-RADICAL PROCESSES IN RAT LIVER AND KIDNEY

The aim of the study was to evaluate the activities of the antioxidant enzymes superoxide dysmutase (SOD, EC. 1.15.1.1), catalase (CAT, EC. 1.11.1.6), and glutathione peroxidase (GSH-Px, EC. 1.11.1.9) and the levels of malonic dialdehyde (MDA), a phospholipid peroxidation product, in the liver and kidneys of male and female rats exposed to static (0.49-T) and extremely low-frequency (50-Hz, 0.018-T) magnetic fields. Extremely low frequency magnetic fields increased all enzyme activities and MDA levels in both the liver and kidneys. In contrast, static magnetic field did not produce changes. The results of the study suggest that ELF magnetic fields affect free-radical processes in the liver and kidney.     

Extremely low frequency (ELF) stray magnetic fields of laboratory equipment: a possible co-exposure conducting experiments on cell cultures

Abstract

Measurements of extremely low frequency (ELF) magnetic fields were conducted in the environment of commercial laboratory equipment in order to evaluate the possible co-exposure during the experimental processes on cell cultures. Three types of device were evaluated: a cell culture CO₂ incubator, a thermostatic water bath and a laboratory shaker table. These devices usually have electric motors, heating wires and electronic control systems, therefore may expose the cell cultures to undesirable ELF stray magnetic fields. Spatial distributions of magnetic field time domain signal waveform and frequency spectral analysis (FFT) were processed. Long- and short-term variation of stray magnetic field was also evaluated under normal use of investigated laboratory devices. The results show that the equipment under test may add a considerable ELF magnetic field to the ambient environmental magnetic field or to the intentional exposure to ELF, RF or other physical/chemical agents. The maximum stray magnetic fields were higher than 3?µT, 20?µT and 75?µT in the CO₂ incubator, in water bath and on the laboratory shaker table, respectively, with high variation of spatial distribution and time domain. Our investigation emphasizes possible confounding factors conducting cell culture studies related to low-level ELF-EMF exposure due to the existing stray magnetic fields in the ambient environment of laboratory equipment.     

Sinusoidal ELF magnetic fields affect acetylcholinesterase activity in cerebellum synaptosomal membranes

The effects of extremely low frequency magnetic fields (ELF‐MF) on acetylcholinesterase (AChE) activity of synaptosomal membranes were investigated. Sinusoidal fields with 50 Hz frequency and different amplitudes caused AChE activity to decrease about 27% with a threshold of about 0.74 mT. The decrease in enzymatic activity was independent of the time of permanence in the field and was completely reversible. Identical results were obtained with exposure to static MF of the same amplitudes. Moreover, the inhibitory effects on enzymatic activity are spread over frequency windows with different maximal values at 60, 200, 350, and 475 Hz. When synaptosomal membranes were solubilized with Triton, ELF‐MF did not affect AChE activity, suggesting the crucial role of the membrane, as well as the lipid linkage of the enzyme, in determining the conditions for inactivation. The results are discussed in order to give an interpretation at molecular level of the macroscopic effects produced by ELF‐MF on biological systems, in particular the alterations of embryo development in many organisms due to acetylcholine accumulation. Bioelectromagnetics 31:270–276, 2010. © 2009 Wiley‐Liss, Inc.     

0.2 T magnetic field inhibits angiogenesis in chick embryo chorioallantoic membrane

Inhibition of angiogenesis is a major target in the fight against cancer and other diseases. Although the effects of static magnetic fields on cancer development and cell growth have been investigated, effects on angiogenesis have received no attention so far. In this study we report the effects on angiogenesis of exposure to 0.2 T static magnetic field. Angiogenesis was analyzed using the chick embryo chorioallantoic membrane assay. Exposure to 0.2 T static magnetic field was achieved by placing the eggs for 3 hr in the isocentre of the magnet of a sectorial magnetic resonance tomograph used in clinical practice. In sham exposed specimens treated with phosphate buffered saline (negative control), no significant vascular reaction was detectable; 3 hr exposure to 0.2 T static magnetic field did not affect the basal pattern of vascularization or chick embryo viability. Prostaglandin E1 and fetal calf serum elicited a strong angiogenic response in sham exposed eggs. This angiogenic response was significantly inhibited by 3 hr exposure to 0.2 T static magnetic field. These findings point to possible use of static magnetic field in inhibiting angiogenesis; this effect could be exploited for treatment of cancer and other diseases where excessive angiogenesis is involved.     

Effects of a 60 Hz magnetic field on photosynthetic CO2 uptake and early growth of radish seedlings

Photosynthetic CO2 uptake rate and early growth parameters of radish Raphanus sativus L. seedlings exposed to an extremely low frequency magnetic field (ELF MF) were investigated. Radish seedlings were exposed to a 60 Hz, 50 microT(rms) (root mean square) sinusoidal magnetic field (MF) and a parallel 48 microT static MF for 6 or 15 d immediately after germination. Control seedlings were exposed to the ambient MF but not the ELF MF. The CO2 uptake rate of ELF MF exposed seedlings on day 5 and later was lower than that of the control seedlings. The dry weight and the cotyledon area of ELF MF exposed seedlings on day 6 and the fresh weight, the dry weight and the leaf area of ELF MF exposed seedlings on day 15 were significantly lower than those of the control seedlings, respectively. In another experiment, radish seedlings were grown without ELF MF exposure for 14 d immediately after germination, and then exposed to the ELF MF for about 2 h, and the photosynthetic CO2 uptake rate was measured during the short-term ELF MF exposure. The CO2 uptake rate of the same seedlings was subsequently measured in the ambient MF (control) without the ELF MF. There was no difference in the CO2 uptake rate of seedlings exposed to the ELF MF or the ambient MF. These results indicate that continuous exposure to 60 Hz, 50 microT(rms) sinusoidal MF with a parallel 48 microT static MF affects the early growth of radish seedlings, but the effect is not so severe that modification of photosynthetic CO2 uptake can observed during short-term MF exposure.     

Exposure to ELF magnetic field tuned to Zn inhibits growth of cancer cells

The effects of ELF alternating magnetic fields tuned to Zn(2+) on the growth of cancer cells with different status of p53 were investigated using a cell proliferation assay. Human cancer cells HeLa (cervix cancer, p53(+/+)), Saos-2 and Saos-2-His-273 (osteosarcoma, p53(-/-) and p53 His-273 mutant, respectively), H1299tTA and H1299tTA-His175 (lung carcinoma, p53(-/-) and p53 His-175 mutant), and normal human fibroblasts VH-10 (p53(+/+)) were used. Exposure parameters were calculated for the first harmonic of Zn(2+) based either on the magnetic parametric resonance (MPR) model of Lednev or the ion parametric resonance (IPR) model of Blanchard and Blackman. ELF exposure was for 72 and 96 h. The vertical alternating field was 20 Hz at amplitudes of either 38.7 or 77.4 microT (peaks, IPR or MPR, respectively). The vertical static magnetic field was 43 microT, and the horizontal static magnetic field was zeroed. Treatments of cells with PRIMA-1 and gamma-rays were used as positive controls. Growth inhibition was observed in cells after exposure to ELF at 38.7 microT. Inhibition of HeLa, VH-10, and Saos-2-His-273 cells was statistically significant, P=0.0003, 0.02, and 0.006, respectively. No consistent ELF effects following exposure 77.4 microT were seen. PRIMA-1 inhibited the growth of all cell lines with the strongest effect in mutant p53-carrying cell line H1299tTA-His175. The effects of gamma-rays were relatively weak, suggesting that the cell proliferation assay under conditions employed in this study is not very sensitive to apoptosis. In conclusion, ELF under conditions of exposure tuned to Zn(2+) according to the IPR model inhibited the growth of cancer and normal cells. No clear relationship of the observed growth inhibition to p53 status was found. Further experiments, using complementary techniques, are required to test whether p53 reactivation by ELF is feasible.     

Synergic effect of retinoic acid and extremely low frequency magnetic field exposure on human neuroblastoma cell line BE(2)C

The aim of the present study was to assess whether exposure to a sinusoidal extremely low frequency magnetic field (ELF‐MF; 50 Hz, 1 mT) can affect proliferation and differentiation in the human neuroblastoma cell line BE(2)C, which is representative of high risk neuroblastomas. Cells were subjected to ELF‐MF exposure in the presence or absence of a neuronal differentiating agent (all‐trans‐retinoic acid, ATRA) for 24–72 h. In each experiment, ELF‐MF‐exposed samples were compared to sham‐exposed samples. Cells exposed to ELF‐MF combined with retinoic treatment showed a decreased cellular proliferation and an increased proportion of G₀/G₁ phase cells compared to cells exposed to either treatment alone. Moreover, ELF‐MF‐ and ATRA‐treated cells showed more differentiated morphological traits (a higher neurite number/cell, an increased neurite length), together with a significant increase of mRNA levels of p21^WAF1/CIP1 and cdk5 genes, both involved in neuronal differentiation. In addition, the expression of cyp19 gene, which is involved both in neuronal differentiation and stress response, was evaluated; cyp19 gene expression was enhanced by ATRA treatment and significantly enhanced further by ELF‐MF exposure combined with ATRA. In conclusion, our data suggest that ELF‐MF exposure can strengthen ATRA effects on neuroblastoma cells. Bioelectromagnetics 31:425–433, 2010. © 2010 Wiley‐Liss, Inc.     

Cleavage and survival of Xenopus embryos exposed to 8 T static magnetic fields in a rotating clinostat

In this study, we examined cleavage and survival of fertilized Xenopus embryos exposed to 8 T static magnetic fields (SMFs). We investigated fertilized Xenopus embryos exposed to magnetic field either in static chamber or in a rotating culture system. Our results showed that the exposure to the strong magnetic field of 8 T changed the third cleavage furrow from the usual horizontal one to a perpendicular one; however, when the direction of gravity was randomized by exposing embryos to magnetic field in a rotating culture system, the third cleavage furrow were formed horizontally, a finding which suggests that the observed distortion of the third cleavage furrow in magnetism-exposed embryos was accomplished by altering gravity effects which were elicited by diamagnetic force due to high gradient magnetic field. Our results also showed that the exposure to the strong magnetic field did not damage survival. These results demonstrate that SMF and altering gravity cause distortion of the third cleavage furrow and show that effects of exposing cleavage embryos to magnetic field were transient and did not affect the post-cleavage development. We also showed that strong magnetic field is not hazardous to the cleavage and blastula-gastrula transition of developing embryonic cells.     

Induction of primary root curvature in radish seedlings in a static magnetic field

Primary roots of radish (Raphanus sativus L.) seedlings were exposed to an inhomogeneous static magnetic field generated by a permanent magnet, during continuous rotation on a 0.06 rpm clinostat, thereby reducing the unilateral influence of gravity. The roots responded tropically to the static magnetic field with the tropism appearing to be negative. These roots responded significantly (P < 0.05) to the south pole of the magnet. The significant tropic response was found for a magnetic flux density of 13-68 mT, for a field gradient of 1.8-14.7 T/m, and for the product of magnetic field and field gradient of 0.023-1.0 T(2)/m. A small, but insignificant, response of the roots to the north pole has also been found.     

Extremely-low-frequency magnetic fields disrupt rhythmic slow activity in rat hippocampal slices

Several studies have indicated that weak, extremely-low-frequency (ELF; 1–100 Hz) magnetic fields affect brain electrical activity and memory processes in man and laboratory animals. Our studies sought to determine whether ELF magnetic fields could couple directly with brain tissue and affect neuronal activity in vitro. We used rat hippocampal slices to study field effects on a specific brain activity known as rhythmic slow activity (RSA), or theta rhythm, which occurs in 7–15 s bursts in the hippocampus during memory functions. RSA, which, in vivo, is a cholinergic activity, is induced in hippocampal slices by perfusion of the tissue with carbachol, a stable analog of acetylcholine. We previously demonstrated that the free radical nitric oxide (NO), synthesized in carbachol-treated hippocampal slices, lengthened and destabilized the intervals between successive RSA episodes. Here, we investigate the possibility that sinusoidal ELF magnetic fields could trigger the NO-dependent perturbation of the rate of occurrence of the RSA episodes. Carbachol-treated slices were exposed for 10 min epochs to 1 or 60 Hz magnetic fields with field intensities of 5.6, 56, or 560 μT (rms), or they were sham exposed. All exposures took place in the presence of an ambient DC field of 45 μT, with an angle of -66° from the horizontal plane. Sinusoidal 1 Hz fields at 56 and 560 μT, but not at 5.6 μT, triggered the irreversible destabilization of RSA intervals. Fields at 60 Hz resulted in similar, but not statistically significant, trends. Fields had no effects on RSA when NO synthesis was pharmacologically inhibited. However, field effects could take place when extracellular NO, diffusing from its cell of origin to the extracellular space, was chelated by hemoglobin. These results suggest that ELF magnetic fields exert a strong influence on NO systems in the brain; therefore, they could modulate the functional state of a variety of neuronal ensembles. © 1996 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.     

Germination of soybean seeds exposed to the static/alternating magnetic field and algal extract

In the present study, the effect of the static and alternating magnetic field applied individually and in combination with an algal extract on the germination of soybean seeds (Glycine max (L.) Merrill) and chlorophyll content was examined. The exposure time of seeds to the static magnetic field was 3, 6, and 12 min, whereas to the alternating magnetic field was 1, 2.5, and 5 min. The static magnetic field was obtained by means of a permanent magnets system while the alternating magnetic field by means of magnetic coils. Algal extract was produced from a freshwater macroalga—Cladophora glomerata using ultrasound homogenizer. In the germination tests, 10% extract was applied to the paper substrate before sowing. This is the first study that compares the germination of soybean seeds exposed to the static and alternating magnetic field. The best effect on the germination and chlorophyll content in seedlings had synergistic action of the static magnetic field on seeds for 3 min applied together with the extract and alternating magnetic field used for 2.5 min. It is not possible to clearly state which magnetic field better stimulated the germination of seeds, but the chlorophyll content in seedlings was much higher for alternating magnetic field.     

A possible involvement of beta-endorphin, substance P, and serotonin in rat analgesia induced by extremely low frequency magnetic field

Most of the research concerning magnetic antinociception was focused on brief exposure less than 1 h. The main purpose of the present study was to determine the effect of extremely low frequency (ELF) magnetic field (MF) repeated exposures on rats in inducing antinociception and to find the effective analgesic "time window." Meanwhile this investigation was to examine the role of central beta-endorphin, substance P, and 5-HT in magnetic analgesia. We found tail flick latencies (TFLs) increased significantly after the rats were exposed to 55.6 Hz, 8.1 mT magnetic field for 4 days, 6 h each day. The analgesic effects seemed to decrease gradually when the rats were exposed daily for another 10 days. Their levels of TFLs decreased within 1 day when the rats were removed after a 4-day exposure. The concentrations of hypothalamus beta-endorphin, substance P, and brainstem serotonin (5-HT) were increased significantly on Day 4. However, no differences were found when rats were exposed for another 10 days, and there were no significant increases when rats were removed after the fourth day of exposure and tested for nociception on Days 5 and 7 with no changes in the biochemical markers at 7 days. These results suggest that the ELF magnetic field has analgesic effect, but only on Days 3 and 4. The effect may be associated with increases in endogenous beta-endorphin, substance P, and 5-HT stimulated by the 55.6 Hz, 8.1 mT magnetic field.     

Experimental studies on extremely low frequency pulsed magnetic field inhibiting sarcoma and enhancing cellular immune functions

The previous observation with an electron microscope showed that extremely low frequency (ELF) pulsed magnetic field (PMF) (with the maximum intensity of 0. 6-2. 0 T, gradient of 10-100 T. M-1, pulse width of 20-200 ms and frequency of 0. 16-1. 34 Hz) inhibited the growth of S-180 sarcoma in mice and enhanced the ability of immune cell's dissolving sarcoma cells. In this study, the DNA contents of nuclei were assayed by using Faulgen Staining method. With an electron microscope and cell stereoscopy technology it was observed that magnetic field affected the sarcoma cell's metabolism, lowered its malignancy, and restrained its rapid and heteromorphic growth. The magnetic field enhanced the cellular immune ability and the reaction of lymphocytes and plasma. Since ELF pulsed magnetic fields can inhibit the growth of sarcomas and enhance the cellular immune ability, it is possible to use it as a new method to treat cancer.     

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.