Journal Highlights SwRI Electromagnetic Field Studies
A special issue of Bioelectromagnetics consists solely of peer-reviewed papers documenting Institute studies of the effects of 60-Hz electric and magnetic fields on baboons
by Walter R. Rogers, Ph.D.
A special issue of the journal Bioelectromagnetics has been published that contains 10 peer-reviewed papers describing the results of a series of experiments completed at Southwest Research Institute (SwRI). It is unusual for a scientific journal to publish such an issue. However, in an accompanying comment, Editor-in-Chief Dr. Ben Greenebaum notes the special nature of this work, done with nonhuman primates, and the unique opportunity to present the experiments as an integrated set. The following is a summary of findings reported in the scientific papers.
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| Dr. Walt Rogers, staff scientist in the Biosciences and Bioengineering Department at SwRI, is a nationally recognized expert on 60-Hz bioeffects. During his 22 years at the Institute he has also conducted major investigations of cigarette smoking and cardiovascular disease in baboons. He currently serves on a key panel sponsored by the National Academy of Science that reviews the results of the national 60-Hz bioeffects research program. |
The focus of the studies, which were initiated in the late 1970s and early 1980s, was to use the nonhuman primate as a surrogate for the human in experiments designed to examine the effects of 60-Hz electric and magnetic fields associated with powerlines and electrical appliances. The work was funded jointly by the United States Department of Energy and Japan's Central Research Institute of the Electric Power Industry.
Previous research with rodents had suggested that 60-Hz electric fields probably had no serious effects, although subtle, temporary effects on behavior, and therefore possibly on the brain, did occur. The goal of the program conducted at SwRI was to see if the conclusions drawn from experiments with rats held true in the primate. In general, the results of the behavioral studies of baboons exposed to electric fields were consistent with what had been reported in rodents, strengthening the argument that such field exposure does not adversely affect humans.
One possible exception to the conclusion that 60-Hz electric fields produced no important effects in rodents was the observation that electric field exposure prevented the normal night-time rise in melatonin, a hormone produced by the brain. Thus the SwRI program, which focused on behavior as an indicator of the ability of exposed animals to function normally, also included studies of melatonin. At the time this program began, the issue of whether exposure to electric and/or magnetic fields was associated with a slight increase in leukemia was not a major concern, so the SwRI program was not designed to examine this question. However, because of increasing interest in magnetic field bioeffects, the latter portion of the program studied the effects of combined 60-Hz electric and magnetic field exposure.
Dr. Jack Orr and Jeffrey H. Lucas of SwRI were major contributors to the program. Orr provided critical expertise in operant and computer methods and served as project manager for the latter third of the program. Lucas was the facility engineer, handling all aspects of design and operation of what was the largest such exposure facility in the world. The structure included two exposure areas, each with its own transformer to produce high voltage electric power. In most experiments, one end of the facility was used for the experimental group and the other for the control group.
Preliminary Experiments
In one early project conducted by Orr, six baboons were trained to push one button when an electric field was present. Responses on a second button indicated no field was present, as was the case on half of the test trials. Correct responses of either type earned food rewards. Then the subjects were systematically exposed to different electric field intensities and allowed to offer their answers concerning field absence or presence. The average electric field detection threshold for baboons was 12 kV/m, a value somewhat higher than that of the rat (8 kV/m) and somewhat less than that of the human (15 kV/m).
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| Mean serum melatonin concentrations (picograms/milliliter) were not affected in three electromagnetic field-exposed (30 kV/m and 0.5 Gauss) and three sham-exposed baboons during an exposure period of six weeks. Exposure consisted of regularly-scheduled daytime electromagnetic fields, without the presence of transients. The error bars represent the standard error of the mean (SEM). |
Knowing what electric field intensity can be perceived is important, because the perception of an unusual stimulus can alter behavior (an indirect effect), even if the agent producing the stimulus produces no physiological effects (a direct effect) other than those mediated by perception. A direct effect on brain function would be of more significance than an indirect effect mediated by perception. Incidentally, an electric field of 12 kV/m is much stronger than the fields found in most homes and offices, where fields generally are less than 0.5 kV/m, except close to electrical appliances. At a distance of a few inches, an appliance such as an electric blanket or shaver can have an electric field of 1 kV/m.
At the same time, the author conducted a set of experiments designed to determine if electric field exposure was aversive to baboons. If field exposure was painful or uncomfortable, the resulting stress could lead, indirectly, to adverse consequences. The baboons were trained that pushing a button would turn off the electric field and produce a food reward. The six baboons responded well. However, when the only consequence of responding was to turn off the electric field, subjects did not bother to respond at the same rate, even with electric field intensities of as much as 66 kV/m. Instead, they exhibited "extinction," the gradual cessation of responding that occurs when the reward for an operant task no longer is provided.
The large size of the baboon, relative to that of the rat, makes it a much better model of the human. However, because the baboon is about half the height of an adult human, the effect of an electric field of 66 kV/m corresponds roughly to that experienced by a human in an electric field of 33 kV/m. A field of 33 kV/m is three to four times stronger than any electric field associated with power transmission, distribution, or use in conventional settings. Therefore, the safety factor in these studies was three- or four-fold.
Operant Behavior
Knowing that electric fields were detectable but not aversive, a series of experiments at 30 kV/m and 60 kV/m was conducted by Orr using operant behavior as the endpoints. Operant behavior refers to animals responding, typically by pushing a button, to earn food rewards. The first two series of experiments involved use of operant methods. The effects of electric field exposure on the ability to perform two previously learned operant tasks was examined in experiments involving six-week pre-exposure, exposure, and post-exposure periods.
The only effect observed in two experiments at 30 kV/m and one at 60 kV/m was a temporary reduction in operant responding on the first day of exposure. The subjects did not push buttons for the first few hours of exposure. Once they resumed responding, they functioned normally. However, because of the initial "work stoppage" effect, the amount of responding done on the first day of exposure was less than normal. The sudden introduction of an unusual stimulus, at a level 2.5 or 5.0 times its detection threshold, can temporarily interfere with operant responding. That is why most operant experiments are done in a Skinner box, an enclosure that isolates the subject from irrelevant cues in the external environment. An indirect effect mediated through perceptual and behavioral processes is less likely to indicate a hazard than is a direct effect on brain function, as might be produced, for example, by a sedative chemical.
Social Behavior
Operant behavior is used extensively in the laboratory, but it involves artificial, learned behaviors. A complementary approach to behavior is the use of natural behavior, such as the social interactions displayed by a group of primates living together. The friendships and rivalries of eight young adult baboons living in groups were systematically studied by many hours of careful observation.
Once again, initiation of electric field exposure produced temporary changes in behavior. The effects were most apparent on the first day of exposure, and then the subjects resumed their normal behavior. In these experiments, the smallest temporal unit was a week, so when the data were analyzed, changes appeared primarily in the first week of exposure. The same type of effects were seen in three experiments.
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| Dr. Jack Orr, assistant director of Biosciences in the Biosciences and Bioengineering Department, inspects the electromagnetic field exposure facility constructed at SwRI. The curved screen over the individual and social group cages produced homogeneous vertical electric fields, while the red conductors wrapped around the exposure area produced horizontal electric fields. |
Electric and Magnetic Fields
In two additional operant and social behavior experiments, the effects of exposure to combined 60-Hz electric fields and 60-Hz magnetic fields were examined. The first experiment used 30 kV/m and 500 milliGauss (mG), and the second experiment used 60 kV/m and 1000 mG. The magnetic fields associated with most powerlines are less than 500 mG; equal or greater field strengths are found within a few inches of many electrical appliances. In these experiments, a more complex operant task was used to assess whether electric and magnetic field exposure affected short-term memory. The work stoppage effect observed with electric fields alone was less pronounced when a magnetic field also was present. There was no sign that short-term memory was affected.
In these two experiments, the magnitude of the temporary changes in social behavior also was reduced or absent when a magnetic field was present.
The possibility of an interaction between electric and magnetic fields was not expected, and further research is required to examine the possibility that 60-Hz magnetic fields exert an influence on neurobehavioral processes.
Health
In general, the subjects in these short-term experiments showed no adverse changes in their health. Body weight, growth, blood chemistry, etc., the kinds of variables measured in a general human checkup, all remained within normal ranges. However, the possibility of change in immune system function was noted in one small experiment. The results from other published experiments on immune system function are equivocal: some report effects while others do not.
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| A dramatically different outcome occurred during one experiment consisting of 21 days of exposure to 60-Hz electromagnetic fields. Irregularly-scheduled day and night exposure, with transients accompanying electric field onset and offset, resulted in serum melatonin concentrations almost completely suppressed relative to mean values observed during three pre-exposure samplings. |
Melatonin
Rodent studies indicated that exposure to electric fields might inhibit the function of the pineal gland, the part of the brain that manufactures the hormone melatonin. If such an effect occurred, it could be significant. Melatonin affects many important biological processes, including circadian rhythms (sleep), reproduction, mood, the immune system, and defenses against cancer. The studies with baboons showed clearly that one kind of exposure did not affect melatonin production in baboons, but a second kind of exposure might reduce melatonin.
In preparation for these studies, groups of three field-exposed and three sham-exposed subjects each were fitted with a venous cannula so blood samples could be taken automatically, without pain or stress, during the day or night.
In three experiments directed by the author, all using regularly-scheduled, day-time electric and magnetic field exposure produced without any transients (noise in the electric field), there was no effect on night-time serum melatonin concentration. However, a small experiment with two baboons showed profound suppression of melatonin production. The exposure paradigm in this experiment was different from that of the three main experiments: the pilot experiment used irregularly-scheduled, day and night exposure, and there were transients associated with electric field onset and offset.
Some engineering and physical science investigators believe the high frequency noise of transients is more likely to produce effects than a pure 60-Hz signal. When the three main experiments were completed, the transients were removed. However, it is possible that the electrical engineer's noise is the relevant biological signal. Biological investigators suggest that time of exposure, and variability in exposure, might be particularly important. Organisms adapt rapidly to regular events, whereas irregular events can continue to produce stress. Real world exposure to electric and magnetic fields is extremely irregular, and transients are common. As is so often the case in science, further research is required.
Conclusions
Although there is considerable experimental evidence to show that exposure to extremely low frequency electric and magnetic fields can affect biological functions in the laboratory, there is no evidence supporting the view that exposure to electric and magnetic fields associated with electric power is a major danger. The consequences of any effect could be beneficial or adverse, depending on the situation. The unproved possibility that field exposure might affect melatonin, for example, is certainly worthy of additional study. Bioelectromagnetics is the official journal of the Bioelectromagnetics Society, the Society for Physical Regulation in Biology and Medicine, and the European Bioelectromagnetics Association. Published bimonthly, it specializes in reporting original data on biological effects and applications of electromagnetic fields that range in frequency from zero hertz (static fields) to the terahertz undulations of visible light.
Papers Comprising the Special Issue
Published in the Spring 1996 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Joe Fohn.
