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Clinical proton NMR imaging uses magnetic field strengths in the range 0.1 to 0.5 T. In addition to the large static magnetic field, patients are exposed to magnetic field gradients during imaging and under extreme conditions, such as power failure or quenching, the field may collapse precipitously. A potential source of hazard to patients under these conditions is the induction of thoracic currents which may trigger ventricular fibrillation. In the present experiments, a 0.16 T resistive magnet with a time constant of 60 ms, powered by a programmable power supply, was used to examine any possible effects of static and changing magnetic field on the ECG and arterial blood pressure of anesthetized rats and guinea pigs. Animals were exposed to the following field conditions: static fields of 0.16 T; sine, triangular, and square wave modulated fields from 0.1 to 2 Hz; rapid field switches in excess of 2.0 T/s for 25 ms timed to occur at different stages of the cardiac cycle, including the vulnerable period during ventricular repolarization; and AC fields of 50 Hz. No change was observed in the blood pressure, heart rate, or ECG under any of the field conditions examined.

This paper gives current densities measured in homogeneous grounded human models exposed to vertical, 60-Hz electric fields. The methods used for these measurements were validated by measuring the current densities induced in a grounded hemisphere and in a grounded prolate hemispheroid; agreement between measurement and theory was good. For an unperturbed field strength of 10 kV/m, current densities measured in the human chest were in the range 125-300 nA/cm2. A strong horizontal current-density enhancement was observed in the axillae, with peak values of about 400 nA/cm2. The vertical current density in the arms, when held downward, was in the opposite direction to that in the chest. Current densities in the abdomen, pelvis, and legs were a strong function of whether the body was grounded through one or both feet. With one foot grounded, the horizontal current density in the lower pelvic region, just above the crotch, was 770 nA/cm2. This value was the largest of those measured in the head, arms, or torso of the human model. Scaling factors derived from these data and similar data for animals will provide a quantitative basis for comparing animal and human exposure to 60-Hz electric fields. In addition, current-density data given in this paper can be directly extrapolated to higher frequencies, at least to 1 MHz. These extrapolated data may be useful to individuals and groups involved in the determination of safety standards for the lower radiofrequency region.

Electromagnetic fields are a ubiquitous part of man's environment. Natural sources of energy have been present, and possibly have contributed to the processes of the evolution of living forms. In very recent time, however, exploitation of the properties of the electromagnetic spectrum, has added variables in intensity, frequency, modulation frequency, and alterations in contributions of electrical and magnetic components. Biological impact has been little studied and poorly defined. Animal carcinogenesis studies and human epidemiological data indicate that exposure to nonionizing radiation can play a role in cancer causation. Numerous effects at the physiological and biochemical level have been reported; many are of such a nature that a relationship to the causation of neoplastic transformation can rationally be hypothesized. Many bioeffects of electromagnetic fields can be adequately and economically explained in terms of heat effects alone. However, observations of frequency-, pulse form or modulation-, and intensity-specificity as well as effects opposite to that known for temperature-rise, imply direct interaction of radiant energy with biomolecules. The possibility of such direct interaction has been shown in quantum mechanical models.

The hygienic norms for radiofrequency electromagnetic fields in this country are based on a large number of experimental and industrial studies performed in separate countries and jointly on the CMEA side. Up to 1983 they comprised the widest frequency range in the world - from 60 kHz, 300 GHz, protecting in the best way man. However, these hygienic norms are not perfect: they have steplike frequency dependence, do not include exposure (except at the length of wave under 1 m - microwave range; there are no norms for frequency under 60 kHz, for magnetic field from 1.5 to 30 MHz and from 50-300 MHz do not concern modulated electromagnetic fields and for their combination with other factors of the environment--noise, vibration, overheated microclimate, some toxic substances etc. Therefore, on the side of CMEA two new standards are under preparation, which include the quantity equivalent dose effect in the microwave range--200 W h/cm2, and also report the exposure of the other ranges. This is an advance in the principles of the hygienic standardization, facilitate the hygiene evaluation and are prepared for implementation in our country for the next 2-3 years.

Myelopoiesis and distribution of white blood cells in peripheral blood in 210 guinea pigs related to the duration and induction of an applied magnetic field were studied. Exposure to a static magnetic field of induction 0.05 T and 0.3 T each day for 7 weeks at 1 h per day led to a decrease of basophilic and polychromatophilic erythroblasts, an increase in the percentage of cells of the granulopoietic (neutrophilic myelocytes, eosinophilic metamyelocytes, band neutrophils, band basophils, segmented eosinophils) and lymphopoietic system, a slight increase in plasma cells and decrease in the percentage of megakaryocytes in bone-marrow. In the peripheral blood the percentage of lymphocytes was increased. The observed changes were independent on the duration of magnetic field action within the magnetic induction value.

The neurophysiologic effects of combined 60-Hz electric (E) and magnetic (B) fields, of magnitudes comparable to those produced by high-voltage powerlines, were investigated in 10 monkeys (Macaca nemestrina). Six animals (experimental group) were each exposed to three different levels of E and B fields: 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G. Field exposures were preceded and followed by sham exposures, during which factors of field generation were present (e.g., heat, vibration, noise, etc.) without E and B fields. Each of the five segments (i.e., the three exposure segments and the initial and final sham exposure segments) lasted 3 weeks. Animals were exposed for 18 h/day (fields on at 1600 h, off at 1000 h). Four other animals (external control group) were given sham exposure for the entire 15-week period. Auditory, visual, and somatosensory evoked potentials were recorded twice a week, during the daily 6-h field-off period. E- and B-field exposure had no effect on the early or mid-latency evoked potential components, suggesting that exposure at these levels has no effect on peripheral or central sensory afferent pathways. However, there was a statistically significant decrease in the amplitudes of late components of the somatosensory evoked potential during the 10kV/m and 0.3 G, and 30 kV/m and 0.9 G exposure levels. This result is possibly related to the opiate antagonist effect of electromagnetic field exposure reported by others.

With an increase in the strength of the ultrahigh frequency field the sensitivity of the hypophyseal-adrenal system increases and activity of the anticoagulatory blood system decreases. Functional changes in these systems repeatedly exposed to ultrahigh frequency effects can be considered as adaptive reactions with a delayed resistance at a flux density of 50--80 Mwt/cm2.

Video display terminals (VDTs) are in widespread use and can be found in practically every modern office. Assessment of possible health effects of electromagnetic emissions from these devices is necessary. The intensity of the magnetic field and the frequency spectrum of the emissions at extremely low frequencies (ELF) (5-500 Hz) were measured for a few VDTs and compared with the background field intensities and emissions from other devices. The emissions in the frequency range investigated are of such low intensities that they are very unlikely to have any biological effects, let alone represent a health hazard.

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.

To study possible medical effects of high radiofrequency radiation (RF), 113 Swedish men and women were studied by means of a structured interview and rating of subjective symptoms. A test session was included in order to examine coordination and muscular function of the hands. A neurological test concerning two-point discrimination (2-PD) was also done. As referents, 23 women, sewing machine operators and assembly workers, were chosen, interviewed and likewise tested. Exposure measurements were taken of the RF fields around the welding machines. The present Swedish ceiling value of 250 W/m2 for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, both for electric and magnetic fields, were found near machines used in factories for ready-made clothing, which gave a high exposure to the hands. Irritative eye symptoms were reported by 23% of the men and 40% of the women. A group of 27 persons was selected for a clinical eye examination and checked by photographs, and nine persons had modest conjunctivitis. A high prevalence of numbness in hands, especially among women, was found. A significantly impaired 2-PD was found in the exposed women as compared to the referent group. The pregnancy outcome for 305 female plastic welders during 1974-1984 did not show any significant differences with the Swedish average concerning malformation or prenatal mortality.

Pacemaker function was tested in two electricity substation workers exposed to high tension electric fields. High intensity electric fields induced reversion to the interference mode, producing in one case competitive rhythm and in the other inappropriately slow pacing which resulted in asymptomatic pauses of up to 2.5 s. A suit designed to shield the body from the effects of high intensity electric fields was tried and proved to be effective in protecting the pacemaker, allowing it to function normally in the substations.

We exposed pigtailed macaques (Macaca nemestrina) to electric (E) and magnetic (B) fields at strengths of 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G for three 21 day segments. These three exposure segments were preceded and followed by 21 day sham exposure segments. Additional animals received only sham exposure for five 21 day segments. Detailed description of the exposure chamber and field generation apparatus is given. We evaluated measures of animal well-being, including weight, blood chemistry, blood cell counts, and performance on a simple motor task, and performed postmortem examinations. Reliable and consistent results were obtained throughout data collection. None of the measures evaluated was significantly affected by E- and B-field exposures. Data obtained during actual exposure segments were not distinguishable from those obtained during the initial and final sham exposure segments, nor were they different from data obtained from the sham-exposed animals. Thus, field exposure had no apparent effects on general health or performance.

In this document, the 1974 Inter-Society Commission for Heart Disease Resources (ICHD) report, Implantable Cardiac Pacemakers, has been revised and updated to emphasize the increased complexity of present-day pacing, to propose realistic guidelines for various aspects of pacing practice, and to identify the resources needed for delivery of this important mode of health care. The first section of the report describes the several types of pacemakers currently available, how they function, and how and to what purpose they may be modified through noninvasive programming. Recommendations are given for a modified and updated version of the widely accepted ICHD code for identification of pacing modes. The emphasis of the second section of the report is on physical and personnel resources. Matters considered in some depth include the training and qualification of the various medical, technical, and paramedical specialists involved in an implantation procedure; requirements for, and methods of achieving, short- and long-term surveillance of pacemaker patients; and the role of the hospital, the manufacturers, and the FDA in this new era of complex dual-chamber, multiprogrammable pacemakers.

To explore the association between occupation and the occurrence of brain tumor, an epidemiologic study was conducted using data from the death certificates of 951 adult white male Maryland residents who died of brain tumor during the period 1969 through 1982. Compared with the controls, men employed in electricity-related occupations, such as electrician, electric or electronic engineer, and utility company serviceman, were found to experience a significantly higher proportion of primary brain tumors. An increase in the odds ratio for brain tumor was found to be positively related to electromagnetic (EM) field exposure levels. Furthermore, the mean age at death was found to be significantly younger among cases in the presumed high EM-exposure group. These findings suggest that EM exposure may be associated with the pathogenesis of brain tumors, particularly in the promoting stage.

Physiological examinations of 63 subjects were performed as well as clinical, functional, paraclinical, etc. examinations of 82 subjects working under the effect of wide-band modulated electromagnetic fields in HFA of telephone exchanges. Some physiological changes were found as regards the level of blood pressure and auditory threshold. Though the intensity of EMF were within the allowable limits, changes in the neuro-vegetological state, genital sphere, were found in some of the examined workers as well as in immunologic reactivity and some paraclinical indices, described to develop under electromagnetic effect, attributed to the specificity of EMF-wide-band, modulated.

Luminous phenomena and anomalous physical forces have been hypothesized to be generated by focal tectonic strain fields that precede earthquakes. If these geophysical processes exist, then their spatial and temporal density should be greatest during periods of protracted, localized UFO reports; they might be used as dosimetric indicators. Contemporary epidemiological data concerning the health risks of power frequency electromagnetic fields and radon gas levels (expected correlates of certain tectonic strain fields), suggest that increased incidence (odds ratios greater 1:3) of brain tumors and leukemia should be evident within "flap" areas. In addition the frequency of variants of temporal lobe lability, psychological depression and posttraumatic stress should be significantly elevated. UFO field investigators, because they have repeated, intermittent close proximity to these fields, are considered to be a particularly high risk population for these disorders.

People living in the industrial society of today are unavoidably exposed to low-energy electromagnetic (EM) radiation. The potential risk to human health of such exposure has received much study. In this regard, numerous epidemiological studies have linked exposure to low-energy EM fields to increased cancer risk. We investigated the ability of low-energy 60-Hz EM fields to alter the activity of ornithine decarboxylase (ODC) in a number of established cell lines. The activity of ODC, the controlling enzyme in polyamine biosynthesis, has been shown to be elevated in growing cells or tissues and during the process of tumor promotion. A 1-h exposure to a 60-Hz EM field of an intensity of 10 mV/cm produced a 5-fold increase in ODC activity in human lymphoma CEM cells and a 2- to 3-fold increase in mouse myeloma cells (P3) relative to the unexposed cultures. Depending upon the cell type, ODC activity increased during the 1-h exposure period and remained elevated for several hours after the field exposure ended. In another series of experiments, fields of an intensity as low as 0.1 mV/cm for a 1-h period produced a 30% increase in the activity of ODC in Reuber H35 hepatoma cells grown in monolayer culture. In the H35 cells, continuous exposure to the 60-Hz EM field (10 mV/cm) for periods of 2 and 3 h resulted in either no increase in ODC activity (2 h) or a decrease in enzyme activity (3 h) compared to the unexposed control cultures. The data is discussed in relation to possible molecular mechanisms of field-cell interaction, the importance of the exposure intervals altering cellular ODC activity and the potential ability of 60-Hz EM fields to serve as a tumor promoting stimulus.

The possibility that chromosome alterations take place in personnel exposed to electromagnetic radiation in radar centres has been studied. The study was carried out "blind" on short-term cultures of peripheral blood, some 450 metaphases being analysed for each case. No aberrations were found in either radar operators or controls and there was no statistically significant difference between them.

The present study used exercise testing to examine the effects of 60-Hz electric and magnetic field exposure. Eleven males, 21-29 years, were tested during four experimental sessions (counterbalanced order and double-blind design). These included either 45-min exercise (50% of VO2 max) or no-exercise periods followed by either real field (9-kV/m, 16-A/m) or sham exposure for 2 h in a 60-Hz human exposure facility. Exercise produced a decrease in plasma volume and increases (p less than 0.05) in lactic acid, cortisol, growth hormone and testosterone levels, but these were not different under real and sham field conditions during the 2-h recovery periods. During no-exercise sessions, cardiac interbeat interval was increased (p less than 0.05), i.e., heart rate was slower, when subjects were exposed to real fields. Our results suggest that future studies should focus on evaluation of the effects of 60-Hz fields on the entire process of exercise-induced activation and recovery.

Fertilized eggs of Gallus domesticus were exposed continuously during their 21-day incubation period to either 50- or 60-Hz sinusoidal electric fields at an average intensity of 10 Vrms/m. The exposure apparatus was housed in an environmental room maintained at 37 degrees C and 55-60% relative humidity (RH). Within 1.5 days after hatching, the chickens were removed from the apparatus and tested. The test consisted of examining the effect of 50- or 60-Hz electromagnetic fields at 15.9 Vrms/m and 73 nTrms (in a local geomagnetic field of 38 microT, 85 degrees N) on efflux of calcium ions from the chicken brain. For eggs exposed to 60-Hz electric fields during incubation, the chicken brains demonstrated a significant response to 50-Hz fields but not to 60-Hz fields, in agreement with the results from commercially incubated eggs [Blackman et al., 1985a]. In contrast, the brains from chicks exposed during incubation to 50-Hz fields were not affected by either 50- or 60-Hz fields. These results demonstrate that exposure of a developing organism to ambient power-line-frequency electric fields at levels typically found inside buildings can alter the response of brain tissue to field-induced calcium-ion efflux. The physiological significance of this finding has yet to be established.

The inhibited pacemaker (VVI or AAI) has become the most popular in recent years because of its ability to combine a physiological advantage with economical current consumption in cases with spontaneous activity. One of its disadvantages is its sensitivity to external electromagnetic interference. Though today's pacemakers possess effective protection against most interference signals there may be instances in which patients are subjected to uncomfortable or even life-threatening situations. This is the case of "amplitude modulated" or "pulsed" fields with modulation frequencies in the physiological range. Fields of that sort have been found in the vicinity of a welder, an electric steel plant, and in medical practice where therapeutic currents were applied. Even touch-actuated switches may influence a demand pacemaker. However, these situations may be overcome by a device within the pacemaker for simple time analysis which can be carried out with few components. If electromagnetic fields of diathermy equipment are applied, today's pacemakers may react with intolerably high or low rates. They should, therefore, be avoided.

In a previous study we found an increased rate of chromosomal aberrations in substation workers. To follow up this finding we in this study present data from 38 employees of electric power companies; 19 of the subjects worked with the repair and maintenance of circuit breakers and disconnectors in 400 kV-substations. The other 19 served as controls and were only exposed to normal environmental electromagnetic fields. Coded blood samples were sent to a laboratory for determination of the rate of chromosomal aberrations (CA), sister chromatid exchanges (SCE), and cells with micronuclei (MN). Compared to the control group the exposed men displayed a statistically significant increase in CA and cells with MN. No increase was found in the frequency of SCE. Since "in vitro" studies of lymphocytes exposed to transient electric currents (spark discharges) produced similar results the increase in chromosomal damage in substation workers may be associated with exposure to transient electric currents during work.

The literature data are used to analyze the hygienic situation when man is exposed to constant electrical and low frequency electromagnetic radiations. The spectral characteristics and intensities of electrical fields near and on the surface of the Earth generated by natural sources of electromagnetic radiations (electrical quasi-static fields, atmospheric electricity, thunderstorm charges, electromagnetic radiation emitted by the sun and galaxies) are given. They can be employed to determine man's adaptive capabilities to the frequencies described during acute and chronic irradiation. The mechanisms of biological effects of the exposures are discussed. The methods for calculating the safety levels based on the USSR radiation safety standards and the "competing frequencies" procedure proposed can be applied to the design of electrotechnical devices and evaluation of integral hazard of constant electrical and electromagnetic fields of low frequencies.

The effects of exposure to clinical magnetic resonance imaging (MRI) on analgesia induced by the mu opiate agonist, fentanyl, was examined in mice. During the dark period, adult male mice were exposed for 23.2 min to the time-varying (0.6 T/sec) magnetic field (TVMF) component of the MRI procedure. Following this exposure, the analgesic potency of fentanyl citrate (0.1 mg/kg) was determined at 5, 10, 15, and 30 min post-injection, using a thermal test stimulus (hot-plate 50 degrees C). Exposure to the magnetic-field gradients attenuated the fentanyl-induced analgesia in a manner comparable to that previously observed with morphine. These results indicate that the time-varying magnetic fields associated with MRI have significant inhibitory effects on the analgesic effects of specific mu-opiate-directed ligands.

55 women occupationally exposed to lasting electromagnetic radiation at 27--30 MHz frequency and 101 persons from control group were examined with reference to the status of lens transparency. No statistically significant differences between the frequency of lens opacity in the exposed and control group were found. No dependence of opacity on duration of employment was found, either. An increase in lens opacity was proportional to age both in the exposed and control group.