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Forty two workers underwent examinations under clinical conditions. The workers were affected by the magnetic field of intensities ranging between 112-190 Gauss, depending on the workplace. They underwent internal, ophthalmological, psychological, psychiatric and analytical examinations and the health status of those exposed was compared to that of twenty controls. Most subjects, mainly those of long length of employment in e-m fields exposure, exhibited nonspecific abdominal pains, general weakness, insomnia, increased thirst and conjunctivitis.

Using radioautography, the influence of the industrial frequency electromagnetic field (50 cps) (EMF i/f), with the tension of 50 and 150 kv/m was studied, on the synthesis of collagen and non-collagen proteins in cultured fibroblast-like human embryo cells in the presence and absense in the medium of adrenaline and of cyclic adenosine monophosphate (cAMP). The EMF depresses protein proportionally to its intesity and duration. The specific function of fibroblasts -- the synthesis of collagen -- is subject to this influence to a great extent. The preliminary administration of adrenaline or cAMP prevented the above changes. The cyclic AMP exerted a much stronger protective effect.

A residential neighborhood in Buffalo, NY, was surveyed with a magnetic field meter to evaluate whether or not spot measurements are reliable predictors of the 60-Hz fields at street corners and residences. The results of repeated measurements over 7 days at 33 street corners in this neighborhood indicate that day-to-day variation in power line magnetic fields is negligible (intraclass correlation coefficient = 0.94). Multivariate linear regression analysis of the data indicates that transmission lines and thick, three-phase primary wires near the field measurement site are strong predictors and account for the majority of the ambient magnetic field variance between locations (multiple correlation coefficient squared = 0.60; F ratio = 22.2, P less than .001). Magnetic fields measured at the front sidewalk were highly correlated with fields at the front doorsteps of 45 homes in this neighborhood (gamma = 0.81). These results suggest that ambient power line magnetic field levels at urban residences can be reliably characterized on a one-time site inspection using a hand-held magnetic field meter and a simple wiring classification system.

Roots of Pisum sativum L. were chronically exposed in aqueous inorganic nutrient medium to 60-Hz electric fields between 140 and 490 V/m (growth medium conductivity approximately 0.08 S/m). The growth rate, meristematic mitotic index, and growth rate recovery of the roots were determined. At 140 V/m there was no perturbation in growth rate or mitotic index. At 430 V/m the growth rate and the mitotic index were reduced. The mitotic index had a maximum depression (approximately 55% of control), which occurred at 4 h. The depression in growth rate was immediate and constant over time. When roots were exposed to an electric field at 430 V/m for 2 days, the growth rate was depressed by about 40%. When the field was terminated, the growth rate steadily increased and was almost normal after 5 days. At 490 V/m root growth rate was almost completely arrested. According to these results, there is a narrow range of induced membrane potentials that span the range from slightly altered to almost completely arrested growth rates.

Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposures to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system.

We attempt here to outline the different sources of interference and the methods of interference detection and protection with their advantages and disadvantages. A proposal is made as to how a better interference suppression could be established. A comparison of 16 pacemakers from ten manufacturers tested with different interference sources revealed a great variety, which does not allow one to generalize the problem of interference. As an example, an electric steel furnace with its magnetic field is described and how its influence on pacemakers can be estimated. Rules are given as to how pacemaker patients may be treated by electrotherapy. A test procedure for characterizing the specific interference behavior is proposed.

To investigate possibilities of magnetic resonance imaging at high magnetic fields in humans, a whole-body magnet with a magnetic field density of 4 T was developed. Due to the few data that are available at present on biological effects and side effects of such high fields, a reproduction experiment with NMRI mice was performed using a crossover design. The mice were allowed to mate during a 7-day period within the field or after their stay in the field. The number of pregnant mice and foetuses were recorded and compared to the controls. Another group was held within the magnetic field during the whole period of pregnancy until day 18, one day before delivery. In all groups, development of the foetuses was studied. Additionally, haematological parameters of the males and females were estimated and necroscopy was performed. Brains, lungs and optical nerves were investigated using pathohistological techniques. It could be shown that in case of mating within the magnetic field, the number of pregnant mice was considerably reduced. This effect was, however, completely reversible if mating occurred after the stay in the field. Malformations, retardations or an increased number of resorptions were never found. The haematological parameters were, in general, not changed. Necroscopy as well as pathohistological investigations showed no pathological alterations. Therefore, it appears that whereas high magnetic fields reduce the activity of mating behaviour, they do not exert any influence on physiological parameters.

The standard Ames Salmonella test (TA 100) was used to detect the mutagenicity of radiation from a video display terminal. The Ames test is a sensitive assay that detects the ability of a chemical to damage deoxyribonucleic acid. It has also been employed to detect the mutagenicity of electromagnetic radiation. An extremely short distance (62 mm) from a video display terminal and an extremely high electrostatic field strength (250 kv/m) was employed. No mutagenic response was found in this test system.

Evidence from animal experiments and human studies suggests that electromagnetic fields may be human leukemogens. Epidemiological studies of leukemia in occupational groups and in the general populations are reviewed. The results are inconsistent. In the few studies showing an association between exposure to electromagnetic fields and the risk of leukemia, the temporal relationship between exposure and effect was not established, the observed associations were weak, the dose-response relationships were based on qualitative levels of exposure without regard to the duration of exposure or secondary sources of exposure, and the risk ratios were probably biased due to the population selection procedures used and misclassification of exposure. The proportionate mortality or cancer incidence ratios are unreliable estimates of relative risk. Further epidemiological research is needed to establish an association between exposure to electromagnetic fields and the risk of leukemia.

The biological effects of the interaction of stationary magnetic fields (SMF) with man and other animals have been reviewed. The lowest detectable limit of interaction between higher animals and a SMF is 80 to 100 G. The recommended limit on an extended-period basis for whole-body or head exposure is 200 G. Higher limits of magnetic-field exposure for limited periods of time are contained within this report.

The chronic exposure of guinea pigs to the magnetic field of induction 0.005 T and 0.3 T cause the morphological changes of spleen and functional disturbances of liver (the histochemical analysis indicate on greater amount of glycogen in hepatocytes). Everyday 1-hour exposure determined the drop in ceruloplasmin activity and an unchanged iron content in the serum of tested animals.

The authors present the results of medical examinations of 444 workers from an aluminum electrolysis plants with occupational exposure to fluorides, polycyclic aromatic hydrocarbons, carbon dioxide, aluminum dust and electromagnetic fields. The concentration of fluorides and polycyclic aromatic hydrocarbons exceeded the accepted levels. Nervous system changes, probably caused by occupational harmful factors, were demonstrated in 123 workers, with neurotic syndromes in 89. Slight pyramidal and cerebellar changes were observed in the remaining 39 workers. In 71 cases EEG investigations were done and 10 were abnormal, including 9 with seizure activity, and one with diffuse changes. The authors stress great difficulties in evaluating the combined action of toxic and physical factors on the nervous system.

Under the conditions of the present study, magnetic fields ranging from 200 to 2000 Gauss strength have no toxic or histopathological effects on rats. The in vivo study and the histopathological results show no alterations of the vascular tissues, except for a nonpathological congestion of the spleen, and no intravascular thrombosis related to the experimental conditions. An unexpected observation was that the increase in body and organ weight of young rats was significantly greater in the groups exposed to magnetic fields. Therefore, no undesirable effects should be expected when magnetic fields within the prescribed safety limits of 200 to 2000 Gauss are applied to human subjects for several hours.

In vivo and in vitro studies of the clastogenic effects of power frequency electric fields and transient electric currents have been performed. For the in vivo investigation peripheral lymphocytes from twenty switchyard workers were screened for chromosome anomalies. The rates of chromatid and chromosome breaks were found to be significantly increased compared to the rates in 17 controls. Exposure of human peripheral lymphocytes, in vitro, to a 50-Hz current with 1 mA/cm2 current density did not induce any chromosome damage. Exposure to ten 3 mus-long spark discharge pulses with a peak field strength in the samples of 3.5 kV/cm, however, resulted in chromosome breaks at a frequency similar to that induced in lymphocytes in vitro by ionizing radiation at 0.75 Gy. The biological significance of chromosomal damage induced in somatic cells is discussed.

Sixteen monkeys were used in a study to determine the effects, or noneffects, of exposure to a steady magnetic field of 2 T (20 000 G). Arterial and venous blood samples were taken before, immediately after, and several weeks following the test. Blood gas analyses were made of arterial samples, and hemotologic cell data and Technicon SMAC analyses were made of venous samples. Differential and absolute white blood cell counts of segmented neutrophils and lymphocytes were considerably changed during the test, even for monkeys which were not exposed to the magnetic field. These changes have also been observed in monkeys whose environment and daily routine are modified appreciably. Eight of the 16 monkeys were tested twice: first, in the magnet with the magnet turned on, and second, two months later, in the magnet, but with the magnet turned off. A large superconducting magnet (0.63 m i. d. and 1.85 m long warm-air bore) was used, which accommodated two monkeys at one time. Paired-t tests of 45 blood parameters showed no significant differences between the two tests. Exposure to a gradient field compared with exposure to a uniform magnetic field showed no significant differences.

Papers dealing with biological effects of electromagnetic fields are reviewed. The data indicate that certain biological changes are caused by exposure to electromagnetic fields. There is at present, however, no evidence of specific causal mechanisms.

Female DBA/2 mice at 8 weeks of age were implanted with P388 leukemia cells in groups of ten mice and exposed to a 60-Hz 1.4-microT, 200-microT, or 500-microT magnetic field 2-3 hours after the implant for 6 hours daily, 5 days/week until all the exposed P388-treated and nontreated mice died. Parallel exposed groups of non-P388-treated mice and P388-treated mice exposed at 0 microT were included for study. No statistically significant differences (P greater than .05) in survival, spleen weight, or body weight resulted between P388-treated or nontreated mice from exposure to the magnetic field. No effect on the incidence or progression of P388 leukemia was apparent.

Three groups of six male Balb/c mice, subjected to 30 MHz continuous wave NMR exposure in a static magnetic field of 7.05 K Gauss for one hour, were each compared to another group of ten unexposed mice with respect to chromatid and chromosomal aberrations. The exposed groups were sacrificed at two hours, 24 hours and 48 hours following NMR exposure respectively. Control mice were sacrificed 24 hours after sham-exposure. All groups had approximately 0.02 apparent aberrations per cell. These apparent aberrations were in the form of metacentric chromosomes, possibly resulting from a union of chromosomes at their centromeres or possibly simply chromosomes in association. The results are consistent with earlier in vitro findings that NMR exposure causes no adverse cytogenetic effects.

Modern man is constantly exposed to many forms of electromagnetic radiation, both ionizing and non-ionizing. Although many uses of electromagnetic radiation artfully administered serve man well, injudicious exposure carries a potential for harm. Various types of electromagnetic radiation and possible hazards from them are discussed.

Exposure to extremely-low-frequency (ELF) electric or magnetic fields has been postulated as a potentially contributing factor in depression. Epidemiologic studies have yielded positive correlations between magnetic- and/or electric-field strengths in local environments and the incidence of depression-related suicide. Chronic exposure to ELF electric or magnetic fields can disrupt normal circadian rhythms in rat pineal serotonin-N-acetyltransferase activity as well as in serotonin and melatonin concentrations. Such disruptions in the circadian rhythmicity of pineal melatonin secretion have been associated with certain depressive disorders in human beings. In the rat, ELF fields may interfere with tonic aspects of neuronal input to the pineal gland, giving rise to what may be termed "functional pinealectomy." If long-term exposure to ELF fields causes pineal dysfunction in human beings as it does in the rat, such dysfunction may contribute to the onset of depression or may exacerbate existing depressive disorders.

The biophysical model described in this paper has been used as basis for the preparation of the German standards which determine and define limits of exposure to electric or magnetic fields below several MHz, including 50/60 Hz. The electric field strength within the tissue is considered decisive for the biological effect in the low frequency range. Threshold values of field strengths and current densities including biological effects are compared. It is possible to establish "safe", "dangerous" and "hazardous" current density curves as a function of frequency. To define exposure limits, the field strength or current density causing injury should be reduced by a factor exceeding 100 in order to avoid well established biological effects. The electric and magnetic field strengths in the human environment are correlated with the corresponding electric current density induced in the human body. This enables "safe", "dangerous" and "hazardous" levels of current density in the human body to be correlated with the external electric or magnetic field strength. Additionally to the direct field effects indirect effects must be considered. In the second part of this paper data on touch voltages and currents are summarized and evaluated with regard to their health risk. Furthermore, as an example for indirect effects the interference of electric and magnetic fields with pacemakers is considered.

Presented is a summarization of past and current literature that establishes a workable guideline for the treatment of the pacemaker wearer in the dental office. This guideline gives the practicing dentist a procedure for the management of such a patient.

Experiments were conducted to further investigate the effect of 60-Hz cyclotron-resonance exposures on rats performing on a multiple FR-DRL schedule. The previously reported temporary loss of DRL baseline response, when measured as a function of A.C. magnetic intensity, was found to have a threshold. Utilizing the component of A.C. magnetic intensity parallel to the D.C. field, we report this threshold as (0.27 +/- 0.10) x 10(-4) Trms.