Introduction

Over the past few years, considerable attention has been given to the potential biologicaleffects of magnetic field (MF). Epidemiological studies have suggested that MF may increase the risk of various types of cancer, including leukemia, brain and breast tumours. The characteristic biological effects of MF appear to be functional changes in the central nervous system, endocrine and immune systems (Ahlbom, 2001).

Electromagnetic fields (EMF) became increasingly a common constituent of the general and workplace environments early in the 20 ^th century, but some lifestyles and occupations are associated with more than the average amount of exposure to EMFs. Many patterns of exposure in the general and workplaceenvironments have been identified with increased intensity and duration of exposure to EMFs. The exaggerated rise on Na rates, K-ATPase, when the organism is subjected to EMF of 60 Hz, results in the increase of stress level on population subjected to this kind of produced radiation, mainly, by theproper home electrics or by workplace environment (Blank et al, 1995). There is conflicting evidence about whether exposure to ELF (define ELF) fields can directly alter the structure of DNA and chromatin. Most reviews have concluded that mutational and neoplastic transformation effects are not expected to happen (NRPB, 1994b; Tenforde, 1996). However, some reports suggest that ELF fields may cause direct effects on the DNA (Lai and Singh, 1997). Even so, the population is not free of the low frequency EMF action, radiated from household appliances (Armario et al, 1990).

During the last decade, many studies indicated the possible relations between different kinds of cancer, like child leukemia, brain tumors, lung cancer, breast cancer and lymphomas, among others and residential exposure to ELF magnetic fields (Balcer and Elizabeth, 1995; Erren, 1997; Loomis et al, 1994). Different epidemiological studies reported the risks of cancer related to exposure to EMF (50/60 Hz) from power lines (NRPB, 1994b; Savitz, 1993; Health, 1996; Stevens and Davis, 1996; Tenford, 1996). Similar studies reported the risk of adverse effects on human reproduction associated to EMF (Chernoff et al, 1992; Brent et al, 1993; Shaw and Croen, 1993; Tenford, 1996). Chernoff et al. (1992) reported significant early pregnancy loss from exposure to residential 50 Hz magnetic fields, but low numbers in the high-exposure group confounded the conclusions of the study. The truth is that, if it won't possible to confirm this correlation, it's not also conclusive the fact of that the electromagnetic waves are harmless when fall on live organisms, between a specific potency and frequency. Several reports have shown that exposure of rodents to ELF magnetic fields reduces the production, secretion or both of melatonin from the pineal gland (Reviewed by Repacholi and Greenebaum , 1999). Exposure of rats for 42 days to circularly polarised magnetic fields (0.02 and 0.1µT) reduced both day-time and night-time melatonin levels by 20-25% (Kato et al, 1991; Bonhomme-Faiver et al, 1998).

The reduction on melatonin secretion and the increased release of ACTH and cortisol suggest that the exposed builds. Dumanshii (1976) presented the first study indicating that environmental exposure to power frequency (50 and 60 Hz), EMF might increase the risk of chronic disease – in this case mortality – from cancer in children. Three years later this study was followed by a report by Milham on the relationship between cancer and occupations with presumed exposure to EMF . These original studies have been followed by a substantial number of subsequent reports on various cancer diseases. To a certain extent these reports have confirmed the original findings, in particular with respect to childhood leukaemia (Health , 1996) . The established mode of interaction between EMF and humans is by means of induced currents, and sufficiently strong fields may result in acute health effects. Nevertheless, the epidemiological research has gradually expanded and has also come to include outcomes other than cancer, for examples neurodegenerative diseases, suicide and depression (Ahlbom, 2001). A study on Alzheimer's disease reported an apparent three-fold increase in risk for magnetic-field exposure (Sobel, 1996). The increase was attributable to a limited number of occupations that typically receive high exposure levels, such as swing machine operators. This author has also reported an association between exposure and amyotrophic lateral sclerosis. A several number of neurodegenerative diseases, including cancer, become difficult to characterize. It is observed that the most difficult thing resides on the impossibility of registering the neurological injuries, cancer and other appeals (De Boer, 1990; Lai and Singh, 1997 ; Lerchl et al , 1997 ; Loescher et al , 1993).

Materials and Methods

Animals

Exposure system

Metabolic Assessment

Statistical analysis

Results

Physical Weight

The results show that the initial body weight average of control group (n=15) was 351.33±0.23g and the final average was 364.23± 0.54 g, while the initial body weight average of exposed group (n=15) was 385.34±1.34g and the final average was 399.45± 0.12g. The fig.1, shows that exposure to electromagnetic radiation did not cause any significant alteration in body weight when compared to the control group.

Figure 1

Figure 1: Determination of body weight, in g, of control animals and exposed animals to electromagnetic (test), before and after 5 exposure days. The results obtained are the average ± standard detour (SD). N=15, p=0.021.

Cortisol concentration

The results showed that the initial concentration of cortisol in the control group (n=15) was 4.33±0.02 pg/ml while in the exposed group (n=15) it was 5.78±0.11 pg/ml> The serum cortisol concentration, after 5 exposure days, in the exposed group, showed an increase of 27% when compared to group A (p=0.004), fig 2. (x10 ^-4 )

Figure 2

Figure 2 : Determination of cortisol serum concentration in pg/ml of control animals and exposed animals to EMF. The results obtained are the average ± standard detour (SD). N=15 p=0.004.

Glucose serum concentration

In relation to glucose serum concentration after the exposure to electromagnetic radiation, results showed that the average of control group (n=15) was 77.66±9.32

Mg/ dL while the average of exposed group (n=15) was 124.16±8.05 and at the exposed group it was observed an increase of 56.23%, when compared to control group, in a significant way (p=0.014), fig.3. (x 10 ^-4 )

Figure 3

Figure 3: Determination of glucose serum concentration in mg/dl of control animals and exposed animals. The results obtained are the average ± standard deviation (SD). N=15 p=0.014.

ACTH level

The Fig. 4 shows that the exposure to electromagnetic radiation causes an increase of more than 33. 06% in ACTH level of group B (n=15) compared to group A. It is observed that the average of control group (n=15) was 45.33±1.66 pg/ ml while the average of exposed group (n=15) was 77.23±5.23 (n=15), presenting a degree of significance of p=0.033.

Figure 4

Figure 4: Determination of ACTH serum concentration in pg/ml of control animals and exposed animals to EMF. The results obtained are the average ± standard deviation (SD). N=15 p=0.033

Discussion

Male normal Guinea pigs were exposed to EMF of 50 Hz, senoidal of 0.207µT, four hours a day for 4 days. The animals were maintained in normal conditions of lighting (day and night), environment temperature varying from 26º to 30º C and with water and food ad libitum. The exposed animals presented lifelong similar to the control animals, as well as the body weight average of exposed group is comparable to control group in this study. The choice of intensity of 0.207µT was because of the necessity in using a higher intensity than in residences and most work-places, the average 50/60 Hz magnetic fields are between 0.1 and 0.3µT (NRPB, 1994b), so that it was used a value ten times higher than the maximum value expected, by the fact of that depending on the distance between the conductors and ground, and magnetic flux densities can average 22µT, depending on the current load in the line (Siomn, 1992) and this value could depend on also the geographic location of the kind of magnetic material near the area.

In our experiment, the animals subjected to EMF did not show any statistical difference in relation to the body weight when compared to the animals of control group that is in agreement with Bonhomme – Fraive's study (1998) which reports that Swiss mice, continuously exposed to ELF of 50Hz and 50µT for 350 days, at different study times, showed no significant difference in body weight between the exposed and unexposed animals. However, Wilson et al (1999) shows that animals exposed to SL (short-light, 8h light: 16h dark) and a steady state 60 Hz magnetic field for 3h/day for 42 days resulted in a statistically significant reduction in body weight, compared to sham-exposed SL animals. Nevertheless, it seems to us that this reduction in body weight is more associated with the absence of light than the exposure to EMF. The reason for measuring the cortisol serum concentration in this experiment was because the cortisol is well known as being a stress indicator (Marti and Armario, 1997 ; Radon et al, 2001).

In our study we observed a statistically significant increase in serum cortisol concentration in the exposed animals when compared to control group, the same occurring with the serum ACTH levels, indicating that the exposure to EMF of 50Hz, in spite of being considered a low frequency, it is capable to stress the organism. This result is

in agreement with Tenforde's study (1996), when exposure of monkeys produced an increase in urinary corticoids which lasted about 6 days, after which the corticoid levels returned to baseline despite continued exposure to the field. Rephrase! In another study, a similar effect on corticoids in rats persisted for 4 months (Dumanshii, 1976). Our results also confirm the Stevens' hypothesis (Stenvens and Davis, 1996) that suggests that field exposure have effects not on melatonin, but also on the reproductive hormones and the immune system. In other way, some reports indicate that acute exposure for one night to a linearly polarized magnetic field at 10µT has no effect on hormonal or immune parameters in healthy male volunteers (Selmaoui et al., 1996b). This result could not be used as a parameter to our studies, because they worked with acute exposure, only one night, while our animals were exposed for five consecutive days, characterizing a chronic exposure or stress. According to Radon, et al (2001), human exposure to EMF does not cause any alteration on cortisol concentration, however, once again, it is difficult to compare with our findings, because we used high frequency EMF and for much shorter time.

In our study the serum glucose concentration also had a significant increase on the exposed group when compared to control group, in accordance with Armario; Martí; De Boer et al (1990); Marti and Armario (1997), which shows that repeated stress is associated with the sensitivity of glucose, inducing hyperglycaemia. Obtained data in this experiment make us to believe that the EMF of 60Hz, in spite of being a low frequency EMF, activates the hypothalamic-hipophyse-adrenal axis with consequent increase on cortisol and glucose characteristic of immune depressed patient. In spite of the obtained data confirm our point of view and many published papers', we believe that many experiments are still necessary, with the purpose of explaining which frequency, intensity, exposure time and other parameters involved with the EMF, to protect us from harms that life can cause to us (Selmaoui et al, 1997 ; Simon et al ,1992 ; Welker et al ,1983 ; Wilson et al , 1981 ; Wilson et al , 1999 ; Yellon, 1996). Not convincing!

Acknowledgments