Reproduction, Growth and Healing
Studies of the cells and organs of the reproductive system have revealed a general debilitating effect of EMF exposure (25-30). Altered spermatogenesis was reported in rats following exposure to 5000 v/m, 50 Hz, for up to 4.5 months (25). After 1.5 months' exposure, the number of atypical sperm cells was significantly greater in the exposed animals (30.7% vs. 15.9%, p<0.0I); the percentage of pathological forms increased with the duration of exposure and reached 36.8% after 4.5 months. The exposed rats also produced fewer sperm cells and exhibited a higher ratio of living to dead cells; both effects became significant after 3.5 months. Comparison of the parameters of respiration and phosphorylation of testicular mitochondria following 4.5 months' exposure revealed decreased phosphorylatic respiration, speed of phosphorylation of ADP, and respiratory control.
Table 8.5. TRACE ELEMENTS IN RAT TISSUES FOLLOWING EXPOSURE AT 50 HZ
In a study of carbohydrate metabolism in testicular tissue, Udinstev and Khlyin exposed rats continuously (for 24 hr.) or intermittently (6.5 hr./ day, for 5 days) to 200 gauss, 50 Hz (26). In the case of the 24-hour exposure, he observed a brief initial activation of enzyme activity followed by a depression of activity and then a return to normal levels. Intermittent exposure to the field, however, was characterized by a prolonged depression of the activity of several enzymes, including hexokinase, glucose-6-phosphate dehydrogenase, and cytochromoxidase. These changes pointed to a depression in tissue respiration which would be consistent with the authors' previous work that showed a decrease in testosterone production following exposure to the EMF.
Chronic exposure of mice to a 7-KHz pulsed magnetic field produced morphological changes in the testes of rats: the seminal epithelium, ducts and sperm cells were each altered at 30 gauss, but not at 5 gauss (27).
Female rats exhibited estrous-cycle dysfunction and some pathological changes in the uterus and ovaries following exposure to 5 kv/m 50 Hz (28). In males, the EMF caused a decrease sperm count and an increase in the number of dead and atypical spermatozoa. When the exposed animals were mated with unexposed rats, decreased birth rates and increased postnatal mortality were found in the offspring (28). Constant exposure to a 130-140 gauss magnetic field, both DC and so Hz, also produced changes in the estrous-cycle of female rats (29). Disturbances in ovarian morphology and fertility, and alterations in postembryonic development were seen following exposure of female mice to 10-50 µW/cm2, 2.4 GHz (30).
Because the developing organism is particularly sensitive to external influences, several investigators have exposed immature animals to EMFs and studied their impact on growth rate. Rats exposed to an intermittent EMF at 3 GHz, 153 µW/cm2, exhibited a smaller weight gain than the control animals (31). The difference became statistically significant after 4 months' exposure, and it persisted during the subsequent 3 months' exposure.
Noval et al. (32), studied the effect on growth rate of rats of exposure to 0.5-100 v/m, 45 Hz, as compared to the growth rate of control rats maintained under Farady-cage conditions. He found a consistent depression of the body weights of the exposed animals, even for fields as low as 0.5 v/m (Table 8.6). Low-frequency fields-electric and magnetic-also produced growth depression in 25-day-old chicks (33).
Table 8.6. CHANGES IN AVERAGE BODY WEIGHTS OF RATS EXPOSED TO 45-HZ VERTICAL
By the mid-190's, no studies had been done to assess the possible impact on successive generations of animals of the continuous presence of a low-frequency EMF; we therefore undertook such a study (34). Initially, mature male and female mice were split into horizontal, vertical, and control groups. Mice in the horizontal group were allowed to mate, gestate, deliver, and rear their offspring in a horizontal 60-Hz electric field of 10 kv/m. At maturity, randomly selected individuals from the first generation were similarly allowed to mate and rear their offspring while being continuously exposed. Randomly selected individuals from the second generation were then mated to produce the third and final generation. A parallel procedure was followed for the vertical group wherein three generations were produced in a 60 Hz vertical electric field of 15 kv/m, and for the control group wherein three generations were produced in the ambient !laboratory electric field. In the first and second generations, males and females reared i both the horizontal and vertical electric field were significantly smaller than the controls when weighed at 35 days after birth In the third generation, the only group whose body weights were significantly affected were the males exposed to the vertical field. In both the second and third generation, a large mortality rate in the vertical-field mice was seen during the 8-35 day postpartum period. We repeated the multi-generation study at 3 .5 kv/m using an improved exposure system (55) (Fig. 8.2 and 8.3). In the first generation, no consistent effect on body weight attributable to the EMF was seen throughout a 63-day observation period. In both the vertical and horizontal groups, however, infant mortality was increased; in the vertical-control group 48 animals (about 17%) died between birth and weaning. In the vertical-exposed group, if the electric field wasn't a causative factor, a 17% mortality rate should also have been seen. However, that group exhibited a 31% mortality-82 animals died and not the expected 44. Thus, 38 animals, about 16% of those born, failed to live to weaning because of the electric field. A similar result was obtained in the horizontal-exposed group-about 11% of the animals born failed to live to weaning because of the electric field.
Fig. 8.2. Assembly for vertical-field study. The metal plates were grounded in the control assembly.
Fig. 8.3. Cage and water-bottle holder.
In the second generation, no consistent effect on body weight attributable to the field was seen throughout a 108-day observation period. The vertical-exposed group, however, again exhibited a higher mortality; about 6% of the animals alive at weaning failed to live to the final day of observation due to the presence of the electric field. In the third generation, the exposed animals had higher body weights, particularly in the horizontal exposed group. At 49 days after birth, the males and females in each exposed group were significantly heavier than their respective controls. At 119 days after birth only the females in the horizontal-exposed group were significantly heavier, but this was part of a consistent trend for that group. Again we saw an increased mortality in the vertical-exposed group-10% of the weaned animals failed to survive to the end because of low-frequency EMFs were also reported by Grissett (35).
EMFs can alter the growth and development of some tumors. Batkin and Tabrah found that the development of a transplanted neural tumor could be affected by a 12-gauss, 60 Hz EMF (36); they reported a slowing of early tumor growth in the exposed mice. We found that 5 kv/m, 60 Hz, had no material effect on the development of Erhlich ascites tumor in mice; the average length of time between tumor implant and death was not altered by the fields.
The process of wound-healing has been found to be susceptible to EMFs; not surprisingly, the nature of the effect depends on both the exposure conditions and the particular EMFs employed (37-40). One of the first such reports was that of Bassett et al. (37) involving dogs. Electrical circuits, attached to leg bones that had been surgically fractured, produced a pulsed 65-Hz magnetic field at the fracture site. After 28 days, the organization and strength of the repair process as judged by the mechanical strength of the healing callus had increased significantly. We observed an opposite effect on fracture healing in rats exposed to a full-body vertical electric field of 5 kv/m, 50 Hz (38). Midshaft fractures were done on the rats following which half the group was exposed to the field and half was maintained as a control. The rats were housed individually in plastic enclosures maintained in wooden exposure assemblies (see Figures 8.2 and 8.3). The extent of healing was evaluated at 14 days postfracture on the basis of blind scoring of serial microscopic sections. We used a numerical grading system that characterized both the healing process as a whole, and its anatomical components. In two replicate studies, we found a highly significant retardation in fracture healing (Table 8.7); the fractures in the exposed rats exhibited the development normally seen in a 10-day fracture. We found no effect on fracture-healing following exposure at 1 kv/m. The adverse effect of a 60 Hz electric field on fracture healing in the rat was confirmed by Phillips in three replicate studies (39).
Table 8.7. HISTOLOGICAL GRADINGS OF RATS EXPOSED TO 5 kv/m
There is also a report of a beneficial effect of microwave EMFs on healing (40). Under sterile conditions, a linear 5-cm wound down to the dermis was made on the backs of guinea pigs. The wounds were then closed and sutured and the animals were exposed to 4000 ,µW/cm2 and sacrificed up to I1 days after surgery. Microscopically, the wounds from the exposed animals exhibited a more advanced stage of healing, and this was confirmed by mechanical testing data; from 30% to 72% more force was required to re-open the wounds of the animals exposed to the EMF (Table 8.8).
Table 8.8. EFFECT OF EMF EXPOSURE ON THE FORCE REQUlRED TO DISRUPT A SKIN WOUND
