Thyroid morphology and wet organ weight changes in rats exposed to different low intensity 0.5 Hz magnetic fields and pre-experimental caging conditions

In eight separate experiments, 48 adult female rats were caged in groups of 3 or 4 individuals under normal lighting conditions for 120–140 days. They were then exposed in pairs to one of 6 different variation intensities (0.001 to 10 G, i.e., 10^–7 T to 10^–3 T) of a 0.5 Hz rotating magnetic field (RMF) or to one of 3 sham field positions for 10 days while under constant 45 lux illumination. Post-mortem examination and histological analyses demonstrated that RMF-exposed rats show no significant changes in thyroid follicle numbers, perifollicular mast cell numbers, wet adrenal and pituitary weights, body weight changes, or water consumption either between intensity groups or relative to sham field controls. Significant interactions existed for thyroid and spleen weights between exposure intensities and preexposure caging conditions for the 10^–5 T to 10^–6 T groups; the effect was not linearly related with field intensity. Rats that had been maintained in the 4/cage situation showed significantly lighter body weights and more thyroid follicles; the significant alterations in thyroid, adrenal and spleen weights were related to body weight.     

Large granular lymphocytic (LGL) leukemia in rats exposed to intermittent 60 Hz magnetic fields

An animal model for large granular lymphocytic (LGL) leukemia in male Fischer 344 rats was utilized to determine whether magnetic field exposure can be shown to influence the progression of leukemia. We previously reported that exposure to continuous 60 Hz, 1 mT magnetic fields did not significantly alter the clinical progression of LGL leukemia in young male rats following injection of spleen cells from donor leukemic rats. Results presented here extend those studies with the following objectives: (a) to replicate the previous study of continuous 60 Hz magnetic field exposures, but using fewer LGL cells in the inoculum, and (b) to determine if intermittent 60 Hz magnetic fields can alter the clinical progression of leukemia. Rats were randomly assigned to four treatment groups (18/group) as follows: (1) 1 mT (10 G) continuous field, (2) 1 mT intermittent field (off/on at 3 min intervals), (3) ambient controls ( < 0.1 microT), and (4) positive control (5 Gy whole body irradiation from cobalt-60 four days prior to initiation of exposure). All rats were injected intraperitoneally with 2.2 x 10(6) fresh, viable LGL leukemic spleen cells at the beginning of the study. The fields were activated for 20 h per day, 7 days per week, and all exposure conditions were superimposed over the natural ambient magnetic field. The rats were weighed and palpated for splenomegaly weekly. Splenomegaly developed 9-11 weeks after transplantation of the leukemia cells. Hematological evaluations were performed at 6, 8, 10, 12, 14, and 16 weeks of exposure. Peripheral blood hemoglobin concentration, red blood cells, and packed cell volume declined, and total white blood cells and LGL cells increased dramatically in all treatment groups after onset of leukemia. Although the positive control group showed different body weight curves and developed signs of leukemia earlier than other groups, differences were not detected between exposure groups and ambient controls. Furthermore, there were no overall effects of magnetic fields on splenomegaly or survival in exposed animals. In addition, no significant and/or consistent differences were detected in hematological parameters between the magnetic field exposed and the ambient control groups.     

Effects of prooxidants on human serum exposed to 50 Hz magnetic fields

The purpose of this article is to evaluate magnetic field effects (50 Hz, different magnetic intensities) on the chemiluminescence intensity of human serum. We find that 1 and 2 h of exposure increased the chemiluminescence emission. The addition to the serum of prooxidants FeCl(2) and H(2)O(2) in different concentrations increased the chemiluminescence intensity even more.     

Elevated sister chromatid exchange frequencies in dividing human peripheral blood lymphocytes exposed to 50 Hz magnetic fields

The in vitro cytomolecular technique, sister chromatid exchange (SCE), was applied to test the clastogenic potentiality of extremely low frequency (ELF) electromagnetic fields (EMFs) on human peripheral blood lymphocytes (HPBLs). SCE frequencies were scored in dividing peripheral blood lymphocytes (PBLs) from six healthy male blood donors in two rounds of experiments, R1 and R2, to determine reproducibility. Lymphocyte cultures in the eight experiments conducted in each round were exposed to 50 Hz sinusoidal (continuous or pulsed) or square (continuous or pulsed) MFs at field strengths of 1 microT or 1 mT for 72 h. A significant increase in the number of SCEs/cell in the grouped experimental conditions compared to the controls was observed in both rounds. The highest SCE frequency in R1 was 10.03 for a square continuous field, and 10.39 for a square continuous field was the second highest frequency in R2. DNA crosslinking at the replication fork is proposed as a model which could explain the mechanistic link between ELF EMF exposure and increased SCE frequency.     

Nocturnal melatonin levels in human volunteers exposed to intermittent 60 Hz magnetic fields

Two double-blind laboratory-based studies were performed to determine whether a suppression of nocturnal melatonin similar to that observed in rodents occurs when humans are exposed to magnetic fields at night. In study 1, 33 men were exposed to sham, 10 mG, or 200 mG intermittent, circularly polarized magnetic fields from 2300 to 0700 h under controlled environmental and exposure test conditions. Overall, exposure had no effect on melatonin levels. Men with preexisting low levels of melatonin, however, showed significantly greater suppression of melatonin when they were exposed to light and also when they were exposed to the 200 mG magnetic-field condition. Study 2 directly tested the hypothesis that low-melatonin subjects show enhanced sensitivity when exposed to light and to 200 mG magnetic fields. After preexposure screening, each of 40 men slept in the exposure facility on two nights. On one night, the men were sham exposed. On the other night, they were exposed to the 200 mG field condition used previously. Again, exposure had no overall effect on melatonin levels. The original finding of enhanced sensitivity in low-melatonin subjects was not replicated in this study. We conclude that the intermittent exposure conditions used in these two studies were not effective in altering nocturnal melatonin release patterns in human volunteers. Further research is underway with regard to exposure parameters, hormonal and immune system measures, and individual differences. © 1996 Wiley-Liss, Inc.     

Heart rate variability and physiological arousal in men exposed to 60 Hz magnetic fields

In previous research, intermittent exposure to sinusoidal 60 Hz magnetic fields at a resultant flux density of 28.3 microT was found to alter heart rate variability (HRV) in men during night sleep. When the 24 men in the present study were exposed under similar conditions, HRV was not altered. The previous studies included the hourly collection of blood samples via an indwelling venous catheter, while the present study did not. This may account for the observed differences in results. Further research is needed to determine if field exposure interacts with physiological arousal mechanisms to alter autonomic nervous system control over cardiac rhythms.     

Clinical progression of transplanted large granular lymphocytic leukemia in Fischer 344 rats exposed to 60 Hz magnetic fields

The purpose of this study was to determine if 60 Hz magnetic fields can alter the clinical progression of leukemia in an animal model. Large granular lymphocytic (LGL) leukemia cells from spleens of leukemic rats were transplanted into young male Fischer 344 rats, producing signs of leukemia in approximately 2–3 months. The animals were randomly assigned to 4 treatment groups (108/group) as follows: 1) 10 G (1.0 mT) linearly polarized 60 Hz magnetic fields, 2) sham exposed [null energized unit with residual 20 mG (2 μT) fields], 3) ambient controls [<1 mG (0.1 μT)], and 4) positive controls (a single 5 Gy whole body exposure to ⁶⁰Co 4 days prior to initiation of exposure). All rats were injected intraperitoneally (ip) with 2.2 × 10⁷ LGL leukemic cells at the initiation of exposure or sham exposure. The magnetic fields were activated for 20 h/day, 7 days/week, allowing time for animal care. The experimental fields were in addition to natural ambient magnetic fields. Eighteen rats from each treatment group were bled, killed, and evaluated at 5, 6, 7, 8, 9, and 11 weeks of exposure. Peripheral blood hematological endpoints, changes in spleen growth, and LGL cell infiltration into the spleen and liver were measured to evaluate the leukemia progression. No significant or consistent differences were detected between the magnetic field exposed groups and the ambient control group, although the clinical progress of leukemia was enhanced in the positive control animals. These data indicate that exposure to sinusoidal, linearly polarized 60 Hz, 10 G magnetic fields did not significantly alter the clinical progression of LGL leukemia. Furthermore, the data are in general agreement with previous results of a companion repeated‐bleeding study in which animals were exposed for 18 weeks. Bioelectromagnetics 20:48–56, 1999. © 1999 Wiley‐Liss, Inc.     

Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields

Two experiments were carried out to assess the effects of electric and magnetic fields (EMF) on blood thyroxine (T4) in dairy cattle. In experiment 1, 16 lactating pregnant Holstein cows were exposed to 10 kV/m, 30 microTesla (microT) EMF. The animals were divided into two groups of eight animals each. Each group was exposed to EMF according to one of two treatment sequences of three periods of 28 days each. Sequence 1 was EMF OFF-ON-OFF and sequence 2 was EMF ON-OFF-ON. During the last day of each treatment period, blood samples were collected every 4 h for 24 h to estimate T4 plasma concentrations. In experiment 2, 16 nonlactating, nonpregnant, multiparous Holsteins were exposed to 10 kV/m, 30 microT EMF. The animals were divided into two groups of eight animals each. Each group was exposed to EMF according to one of the two treatment sequences described above, except that each period amounted to the number of days corresponding to one estrous cycle. During treatment, blood samples were collected every other day for T4 analysis. In both experiments, the light cycle emulated a short photoperiod (8 h light/16 h dark). During the ON periods, the animals were exposed to EMF for 16 h, 8 h of the light period plus the first 8 h of during the dark period. In experiment 1, exposed animals did not have any change in T4 plasma concentrations due to treatment (P = .0968), but, the time of sample collection revealed a significant difference (P = .0012). In experiment 2, the effect of period (P = .0009) and the treatment by days interaction (P = .0003) were statistically significant. We conclude that a worst case scenario exposure of dairy cattle to 10 kV/m, 30 microT EMF influences, in a moderate fashion, the blood levels of thyroxine.     

Thymus mast cell numbers following perinatal and adult exposures to low intensity 0.5 Hz magnetic fields

In a factorial design, 40 male 200-day-old rats that had been exposed from 2.5 days before to 2.5 days after birth to either 0.5 Hz rotating magnetic fields (RMFs) between 10^–3T to 10^–6T or to sham fields and maintained after weaning in one of two typical caging conditions were exposed as adults to either one of three 0.5 Hz RMF intensities (10^–6T, 10^–7T or 10^–8T) or to sham fields or to colony room control conditions. The numbers of mast cells (MCs/mm²) were determined for thymus tissues stained with thionin and toluidine blue. Thymuses from adult rats that had been perinatally exposed to the RMF displayed a marginally significant 20% to 35% elevation in MC numbers relative to sham-field controls. However the adult exposures did not sïgnificantlÿ affect the MC numbers. The two postweaning caging conditions, a non-magnetic field comparator variable, induced a significant 35% difference in MC numbers. The absence of sïgnificant perinatal by adult RMF exposure interactions indicated that early magnetic field exposure did not alter adult thymus responsivity to weaker but more natural intensity levels.     

Absence of genotoxicity in human blood cells exposed to 50 Hz magnetic fields as assessed by comet assay, chromosome aberration, micronucleus, and sister chromatid exchange analyses

In the past, epidemiological studies indicated a possible correlation between the exposure to ELF fields and cancer. Public concern over possible hazards associated with exposure to extremely low frequency magnetic fields (ELFMFs) stimulated an increased scientific research effort. More recent research and laboratory studies, however, have not been able to definitively confirm the correlation suggested by epidemiological studies. The aim of this study was to evaluate the effects of 50 Hz magnetic fields in human blood cells exposed in vitro, using several methodological approaches for the detection of genotoxicity. Whole blood samples obtained from five donors were exposed for 2 h to 50 Hz, 1 mT uniform magnetic field generated by a Helmholtz coil system. Comet assay, sister chromatid exchanges (SCE), chromosome aberrations (CA), and micronucleus (MN) tests were used to assess DNA damage, one hallmark of malignant cell transformation. The effects of a combined exposure with X-rays were also evaluated. Results obtained do not show any significant difference between ELFMFs exposed and unexposed samples. Moreover, no synergistic effect with ionizing radiation has been observed. A slight but significant decrease of cell proliferation was evident in ELFMFs treated samples and samples subjected to the combined exposure.     

Epidermal ornithine decarboxylase and polyamines in mice exposed to 50 Hz magnetic fields and UV radiation

We studied the influence of magnetic fields (MFs) and simulated solar radiation (SSR) on ornithine decarboxylase (ODC) and polyamines in mouse epidermis. Chronic exposure to combined MF and SSR did not cause persistent effects on ODC activity or polyamines compared to the animals exposed only to UV, although the same MF treatment was previously found to accelerate skin tumor development. In an acute 24-h experiment, an elevation of putrescine and down-regulation of ODC activity was observed in the animals exposed to a 100-μT MF. No effect was seen 24 h after a single 2-MED (minimal erythemal dose) exposure to SSR. The results indicate that acute exposure to 50 Hz MF does exert distinctive biological effects on epidermal polyamine synthesis. Bioelectromagnetics 19:388–391, 1998. © 1998 Wiley-Liss, Inc.     

Behavioral changes in adult rats exposed to ELF magnetic fields

In two experiments, male rats that had been exposed to an ELF (0.5 Hz), 3–50 gauss rotating magnetic field (RMF) for 21–30 days, displayed significantly (p < 0.05) greater ambulatory behavior (activity) than the control group in an open field test, when removed from the RMF. In a third experiment rats were exposed to a different RMF apparatus (3–30 gauss), and tested in a different open field for longer duration. Again the RMF-exposed group displayed greater activity (p < 0.10) than the control group.

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Zusammenfassung In zwei Untersuchungen zeigten männliche Ratten,die einem ELF (0,5 Hz) 3–50 Gauss rotierenden magnetischen Feld (RMF) für 21–30 Tage ausgesetzt wurden, in einem Open-Field Test signifikant (p < 0,05) mehr Bewegungsaktivität als die Kontrollgruppe,nachdem sie von dem RMF entfernt wurden. In einer dritten Untersuchung wurden Ratten in einem anderen RMF Gerät gehalten und in einem anderen Open-Field für längere Zeit getestet. Wieder zeigte die Gruppe, die dem RMF ausgesetzt war, mehr Bewegungsaktivität (p < 0,10) als die Kontrollgruppe.

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Resume Lors de deux essais, on a placé des rats mâles dans un champ magnétique tournant (CMT) de 3 à 50 gauss et des très basse fréquence (FTB) (0,5 Hz). Après 21 à 30 jours de ce traitement, on les a remis dans des conditions normales. Leur activité (marche) était plus élevée que celle d'un groupe de contrôle et cela de façon significative (p < 0,05). Dans un troisième essai, d'autres rats furent placés dans un autre appareil (3 à 30 gauss) et examinés ensuite dans un autre champ ouvert sur une plus longue période. Le groupe traité a déployé dans ce cas également une plus grande activité qu'un groupe de contrôle (p < 0,10).

     

Analysis of induced currents in a rat exposed to 50 Hz linearly and circularly polarized magnetic fields

This paper presents a numerical analysis of currents induced in a rat by linearly and circularly polarized magnetic fields of 50 Hz. Special focus was placed on pineal gland and retina of rats since these organs were often associated with the changes of melatonin synthesis and concentration. Induced currents in two MRI-based rat models with resolutions of up to 0.125 mm(3) were calculated by using the impedance method. We characterized the induced currents by amplitude and polarization. Calculated induced current densities were extremely small, i.e., < 30 microA/m(2) for both linearly and circularly polarized magnetic fields of 1.41 microT (peak). There were no significant differences in amplitude nor polarization of induced currents in the pineal gland between the linearly and the circularly polarized magnetic fields when the polarization was in a vertical plane. In contrast, the magnetic fields rotating in the horizontal plane produced most circularly polarized currents both in the pineal gland and in the retina.     

Differential modulation of natural and adaptive immunity in fischer rats exposed for 6 weeks to 60 Hz linear sinusoidal continuous-wave magnetic fields

Two separate, independent experiments were conducted to evaluate the effect of 60 Hz linearly polarized, sinusoidal, continuous-wave magnetic fields (MFs) on immune system performances in rats born and raised under these fields. Each experiment lasted for 6 weeks. A total of 96 animals, divided into groups of eight animals each, was exposed for 20 h/day to MFs of different intensities, i.e., sham (<0.02 μT) and 2, 20, 200, and 2000 μT. Another group of animals, which was housed in a separate room, served as cage controls (CC). These animals were exposed to ambient MFs of <0.02 μT. The following immune responses were evaluated in both experiments: total T and B cells; CD4⁺ and CD8⁺ subpopulation and natural killer (NK) cell activity in splenic lymphocytes; hydrogen peroxide (H₂O₂), nitrous oxide (NO), and tumor necrosis factor (TNF) production by peritoneal macrophages. Our results show that a 6 week exposure to MFs induced a significant decrease in the number of CD5⁺, CD4⁺, and CD8⁺ populations. These changes were even more significant in rats that were exposed to fields of 2000 μT. A lower, although significant, decrease in the CD5⁺ population was also observed in animals that were exposed to fields of 200 μT. Linear regression analysis demonstrated a dose effect with MF intensity. B lymphocyte (Ig⁺ cell) populations also showed a 12% decrease (P < .05) in the groups that were exposed to fields of 20 and 200 μT. However, these results were not significant, and no relation with MF intensities could be demonstrated. In contrast, evaluation of splenic NK cell activity revealed a 50% increase (P < .05) in animals that were exposed to fields of 2000 μT. No significant results were obtained from the evaluation of TNF activity and NO secretion in peritoneal macrophages. Phorbol 12-myristate 13-acetate (PMA)-stimulated and net H₂O₂ productions for a minor subpopulation of peritoneal cells showed positive dose-response correlations by linear regression analysis. Taken together, our results suggest that an in vivo exposure of rats for 6 weeks to 60 Hz MFs can induce significant immunological perturbations on effector cells of both natural and adaptive immunity in a dose-dependent fashion. © 1996 Wiley-Liss, Inc.     

Biologic effects of prolonged exposure to ELF electromagnetic fields in rats: II. 50 Hz magnetic fields

To provide possible laboratory support to health risk evaluation associated with long-term, low-intensity magnetic field exposure, 256 male albino rats and an equal number of control animals (initial age 12 weeks) were exposed 22 h/day to a 50 Hz magnetic flux density of 5 μmT for 32 weeks (a total of about 5000 h). Hematology was studied from blood samples before exposure to the field and at 12 week intervals. Morphology and histology of liver, heart, mesenteric lymph nodes, and testes as well as brain neurotransmitters were assessed at the end of the exposure period. In two identical sets of experiments, no significant differences in the investigated variables were found between exposed and sham-exposed animals. It is concluded that continuous exposure to a 50 Hz magnetic field of 5 μT from week 12 to week 44, which makes up ?70% of the life span of the rat before sacrifice, does not cause changes in growth rate, in the morphology and histology of liver, heart, mesenteric lymph nodes, testes, and bone marrow, in hematology and hematochemistry, or in the neurotransmitters dopamine and serotonin. © 1995 Wiley-Liss, Inc.     

DEXA analysis on the bones of rats exposed in utero and neonatally to static and 50 Hz electric fields

Effects of the electromagnetic fields on living bodies, bones in particular, are among the relevant issues of contemporary life. In this study, we report the influences of 50 Hz and 0 Hz (static) electric fields (EF), on intact rat bones, as evaluated by dual energy X-ray absorbtion (DEXA) measurements on bone content and density when these animals (n = 27) are continuously exposed in utero and neonatally to EFs (10 kV/m) 14 days before and 14 days after their birth, for 28 days in total. Differences between 50 Hz EF and static EF groups are found to be significant (95% confidence level) for total bone mineral content (BMC), TBMC (P = .002). Differences between 50 Hz and control groups are found to be significant for total bone mineral density (BMD), TBMD (P = .002), lumbar BMC, LBMC (P = .023), and TBMC (P = .001). Differences between static EF and control groups are found to be significant for femoral BMD, FBMD (P = .009), TBMD (P = .002), LBMC (P = .001), and TBMC (P = .001). Note that TBMC parameters are jointly significant for all differences between the three groups of test animals. These results have shown that both static and 50 Hz EFs influence the early development of rat bones. However, the influence of static EFs is more pronounced than that of the 50 Hz field.     

Blood melatonin and prolactin concentrations in dairy cows exposed to 60 Hz electric and magnetic fields during 8 h photoperiods

Two experiments were conducted to test the hypothesis that electric and magnetic field (EMF) exposure may result in endocrine responses similar to those observed in animals exposed to long days. In the first experiment, 16 lactating, pregnant Holstein cows were assigned to two replicates according to a crossover design with treatment switchback. All animals were confined to wooden metabolic cages and maintained under short day photoperiods (8 h light/16 h dark). Treated animals were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 microT (EMF) for 16 h/day for 4 weeks. In a second, similar experiment, 16 nonlactating, nonpregnant Holstein cows subjected to short days were exposed to EMF, using a similar protocol, for periods corresponding to the duration of one estrous cycle. In the first experiment, circulating MLT concentrations during the light period showed a small numerical decrease during EMF exposure (P < .05). Least-square means for the 8 h light period were 9.9 versus 12.4 pg/ml, SE = 1.3. Melatonin concentrations during the dark period were not affected by the treatment. A similar trend was observed in the second experiment, where MLT concentrations during the light period tended to be lower (8.8 pg/ml vs. 16.3 pg/ml, P < .06) in the EMF exposed group, and no effects were observed during the dark period. Plasma prolactin (PRL) was increased in the EMF exposed group (16.6 vs. 12.7 ng/ml, P < .02) in the first experiment. In the second experiment, the overall PRL concentrations found were lower, and the mean plasma PRL concentration was not affected by treatment. These experiments provide evidence that EMF exposure may modify the response of dairy cows to photoperiod.     

Oxidative DNA damage in rats exposed to extremely low frequency electro magnetic fields

Extremely low frequency (ELF) electromagnetic field (EMF) is thought to prolong the life of free radicals and can act as a promoter or co-promoter of cancer. 8-hydroxy-2'-deoxyguanosine (8OHdG) is one of the predominant forms of radical-induced lesions to DNA and is a potential tool to asses the cancer risk. We examined the effects of extremely low frequency electro magnetic field (ELF-EMF) (50 Hz, 0.97 mT) on 8OHdG levels in DNA and thiobarbituric acid reactive substances (TBARS) in plasma. To examine the possible time-dependent changes resulting from magnetic field, 8OHdG and TBARS were quantitated at 50 and 100 days. Our results showed that the exposure to ELF-EMF induced oxidative DNA damage and lipid peroxidation (LPO). The 8OHdG levels of exposed group (4.39+/-0.88 and 5.29+/-1.16 8OHdG/dG.10(5), respectively) were significantly higher than sham group at 50 and 100 days (3.02+/-0.63 and 3.46+/-0.38 8OHdG/dG.10(5)) (p<0.001, p<0.001). The higher TBARS levels were also detected in the exposure group both on 50 and 100 days (p<0.001, p<0.001). In addition, the extent of DNA damage and LPO would depend on the exposure time (p<0.05 and p<0.05). Our data may have important implications for the long-term exposure to ELF-EMF which may cause oxidative DNA damage.     

核磁共振磁场照射对子代大鼠海马突触形态的影响

研究观察了孕期磁共振磁场照射对子代大鼠海马突触超微结构的影响。SD孕鼠妊娠第12-18d给予0．35T核磁共振(magnetic resonance imaging,MRI)磁场照射。测量1、2和5月龄雌性仔鼠海马CAl区和齿状回的突触结构参数,用立体计量学方法进行定量测定。结果显示,磁场照射可引起2月龄子代大鼠海马CAl区突触间隙增宽．齿状回突触活性区长度变短、突触界面曲率和活性区面密度减小;5月龄子代大鼠CAl区突触间隙增宽,突触后致密物变薄,突触界面曲率减小,齿状回突触间隙增宽。结果提示,妊娠期接受MRI磁场照射可引起海马突触超微结构的改变。对这些结构变化与行为损害之间的关系进行了讨论。     

Effect of 50 Hz, 0.2 mT magnetic fields on RBC properties and heart functions of albino rats

In this work the effect of sinusoidal 50 Hz, 0.2 mT magnetic fields on the red blood cells (RBCs) and heart functions of Albino rats were investigated. Twenty-four male Albino rats were equally divided into four groups, A, B, C, and D. Animals from groups B were continuously exposed to the magnetic field for 15 days; and groups C and D, for 30 days. Group A was used as control. Animals from group D were kept after exposure to the magnetic field for a period of 45 days for delayed effect studies. The osmotic fragility and shape of RBCs' membrane and hemoglobin (Hb) structure tests were carried out for all groups. The dielectric relaxation of Hb molecules was measured in the frequency range of 0.1-10 MHz and the dielectric increment (Deltaepsilon), relaxation time (tau), molecular radius (r), and Cole-Cole parameter (alpha) were calculated for all groups. The ECG was measured for all animals before and after exposure to the magnetic field. The results indicated that exposure of the animals to 50 Hz, 0.2 mT magnetic fields resulted in the decrease of RBCs membrane elasticity and permeability and changes in the molecular structure of Hb. The ECG of the exposed animals was considerably altered. The data also indicated that there was no sign of repair in the newly generated RBCs structure and the ECG after removing the animals from the magnetic field, which indicates that the blood generating system was severely injured. The injuries in the heart of the animals were attributed to the loss of some physiological functions of the RBCs as a result of exposures of the rats to the magnetic field.