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Effects of Electromagnetic Fields on Organs and Tissues
Pages 67-84

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From page 67... ... NERVOUS SYSTEM The effects of radiation on nervous tissues have been a subject of active investigation since changes in animal behavior and nerve electrical properties were first reported in the Soviet Union during the 1950s and 1960s.i RF radiation is reported to affect isolated nerve preparations, the central nervous system, brain chemistry and histology, and the blood-brain barrier. In studies with in vitro nerve preparations, changes have been observed in the firing rates of Aplysia neurons and in the refractory period of isolated frog sciatic nerves exposed to 2.45-GHz microwaves at SAR values exceeding 5 W/kg.2 3' 4 Those effects were very likely associated with heating of the nerve preparations, in that much higher SAR values have not been found to produce changes in the electrical properties of isolated nerves when the temperature was controlled.5 6 Studies on isolated heart preparations have provided evidence of bradycardia as a result of exposure to RF radiation at nonthermal power densities,7 although some of the reported effects might have been artifacts caused by currents induced in the recording electrodes or by nonphysiological conditions in the bathing medium. Read the entire page →
From page 68... ... Changes in cerebral blood flow rate, rather than direct changes in permeability to tracer molecules, might also be incorrectly interpreted as changes in the properties of the blood-brain barrier. Effects of pulsed and sinusoidal ELF fields on the electrical activity of the nervous system have also been studied extensively.22, 23 In general, only high-intensity sinusoidal electric fields or rapidly pulsed magnetic fields induce sufficient current density in tissue (around 0.1-1.0 A/m2 or higher) Read the entire page →
From page 69... ... A visual phenomenon associated with exposure to ELF fields that has been studied for nearly a century is the induction of a flickering illumination known as phosphenes. Time-varying magnetic fields with either pulsed or sinusoidal waveforms and frequencies below 100 Hz have been shown to produce phosphenes when the time rate of change of the field exceeds I.3 T/sec.30 The frequency most likely to produce magnetophosphenes with sinusoidal fields is 20 Hz; the threshold flux density for eliciting the visual effect is ~ mT.3i A similar frequency dependence has been observed for electrophosphenes produced by placing electrodes in contact with the forehead near the eyes.32 The locus of the effect is in the retina, and available evidence suggests that induced currents in the retina elicit visual responses similar to those resulting from photic stimulation.30 Changes in visually evoked potential (VEP) Read the entire page →
From page 70... ... Those findings indicate that RF heating alters the complex interactions of the hypothalamic, pituitary, adrenal, and thyroid systems that are important in the maintenance of homeostasis.~9 It is noteworthy that a 2-yr exposure of rats to nonthermogenic pulsed 2.45-GHz microwaves did not produce detectable endocrine alterations.37 Studies on the possible endocrine effects of ELF electric and magnetic fields have yielded inconsistent results.22 Increases, decreases, and no change in plasma steroid hormones have been reported. Results of studies with dogs and rats suggest that the threshold 60-Hz electric field required to produce changes in blood concentrations of corticosterone or testosterone is in excess of 10 kV/m.3840 Results of experiments with monkeys exposed to 60-Hz electric and magnetic fields at intensities typical of those in the vicinity of high-voltage transmission lines indicated that a decrease in neurotransm~tter concentrations occurs during chronic exposure.4i However, there were no other observations of behavioral or physiological changes in the exposed animals. Read the entire page →
From page 71... ... It appears from available information that the threshold SAR for altering lymphocyte responses to mitogens exceeds 4 W/kg with both pulsed and CW microwaves.4749 Thermogenic levels of exposure have been found to decrease natural killer cell activity and to activate macrophages.50, 52 The changes observed in components of the immune system at RF power densities that produce tissue heating are consistent with the expected effects of increased release of steroid hormones into the circulation.) 52, 53 In one study involving a 2-yr exposure of rats to a nonthermal level of pulsed 2.45-GHz microwaves (SAR, 0.4 W/kg) Read the entire page →
From page 72... ... significant cardiovascular and hematologic alterations are high. - r 7 cardiovascular indexes were not affected by exposure to 60-Hz, 100-kV/m fields.67 Acute human exposures to ELF electric fields up to 200 kV/m and magnetic fields up to 5 mT have also failed to show any consistent hematologic or cardiovascular effects.68 69 ANIMAL CARCINOGENESIS A few studies have investigated the carcinogenic potential of microwave radiation in whole animals. Read the entire page →
From page 73... ... Beneficial effects of induced hyperthermia have been observed after treatment with microwave radiation.77 78 Lung sarcoma cells injected into Balb/C mice demonstrated temporary regression after exposure to 2.45-GHz radiation. After radiation exposure was stopped, tumor volumes increased and lung metastases exceeded those in untreated animals.77 Sarcoma cells were implanted on 73 Read the entire page →
From page 74... ... They also reported an increased tumor response in rats exposed to the 50-Hz field alone. CONCLUSIONS - OVery few studies have been performed on the responses of organs and tissues to electromagnetic fields in the low-frequency or ultra-high-frequency ranges used by GWEN transmitters, but it is possible to conclude from the analysis presented here that effects of RF radiation are unlikely to occur at the power densities and absorbed energies associated with GWEN fields. Read the entire page →
From page 75... ... Some physiologic effects of ELF fields that might result from low induced current in tissue, such as alterations in pineal melaton~n concentration, have not been shown to pose a direct risk to human health. In sum, studies on physiologic effects of ELF fields have yielded little evidence that exposure to the low-frequency fields from GWEN antennae in areas of most likely public access would represent a health risk. Read the entire page →
From page 76... ... Pp. 339-423 in Handbook of Biological Effects of Electromagnetic Fields, C Read the entire page →
From page 77... ... Pp. 345-378 in Biological Effects and Dosimet~y of Static and ELF Electromagnetic Fields, M Read the entire page →
From page 78... ... Pp. 132-146 in Biological Effects of Extremely Low Frequency Electromagnetic Fields, R Read the entire page →
From page 79... ... Pp. 105-~12 in Biological Effects of Static and Extremely Low Frequent y Magnetic Fields, J Read the entire page →
From page 80... ... 1990. Marked rapid alterations in nocturnal pineal serotonin metabolism in mice and rats exposed to weak intermittent magnetic fields. Read the entire page →
From page 81... ... 1983. Reduced mitogenic stimulation of human lymphocytes by extremely low frequency electromagnetic fields. Read the entire page →
From page 82... ... Pp. 525-537 in Biological Effects and Dosimetry of Static and ELF Electromagnetic Fields, M Read the entire page →
From page 83... ... 1982. Accelerated development of spontaneous and benzopyrene-induced skin cancer in mice exposed to 2,450-MHz microwave radiation. Read the entire page →

From page 67...

... NERVOUS SYSTEM The effects of radiation on nervous tissues have been a subject of active investigation since changes in animal behavior and nerve electrical properties were first reported in the Soviet Union during the 1950s and 1960s.i RF radiation is reported to affect isolated nerve preparations, the central nervous system, brain chemistry and histology, and the blood-brain barrier. In studies with in vitro nerve preparations, changes have been observed in the firing rates of Aplysia neurons and in the refractory period of isolated frog sciatic nerves exposed to 2.45-GHz microwaves at SAR values exceeding 5 W/kg.2 3' 4 Those effects were very likely associated with heating of the nerve preparations, in that much higher SAR values have not been found to produce changes in the electrical properties of isolated nerves when the temperature was controlled.5 6 Studies on isolated heart preparations have provided evidence of bradycardia as a result of exposure to RF radiation at nonthermal power densities,7 although some of the reported effects might have been artifacts caused by currents induced in the recording electrodes or by nonphysiological conditions in the bathing medium.

Effects of Electromagnetic Fields on Organs and Tissues Pages 67-84

Effects of Electromagnetic Fields on Organs and Tissues
Pages 67-84