vitro biologic effects might occur, but evidence of in vivo effects from either electric or magnetic fields has very little support at strengths below those perceived (see following section) by animals. Experiments have also failed to support any mechanism for in vivo effects on reproduction or development.

NEUROBEHAVIORAL EFFECTS

A survey of the literature on the neurobehavioral effects of extremely-low-frequency electric-and magnetic-field exposure revealed that this literature has been reviewed many times. For the purposes of assessment, neurobehavioral effects considered are behavioral, anatomic, and physiologic alterations and chemical changes that may be taken as correlates of behavioral effects. Only those reports published in peer-reviewed journals and with methods adequately described to allow for replication were included in the final evaluation; those reports are summarized in Tables A4-3 through A4-6. Some reports fulfilled these requirements, but others used inappropriate controls or inadequate exposure apparatus. All studies that met the committee's basic requirements are included in the tables; however, only those reports that were repeatable and reliable are discussed herein.

This section is divided into discussions of studies using electric fields and those using magnetic fields or combined electric and magnetic fields. Simple and complex responses are also discussed separately. Simple responses include detection threshold levels (behavioral or physiologic responses) and general activity levels. Complex responses include aversion, avoidance, social behavior, learning, and analgesia.

Electric Fields

Over the past 15 years, several studies using a variety of subjects proved that mammals can detect 60-Hz electric fields as a sensory stimulus. An example that established detection and also determined the approximate threshold level was published by Sagan et al. (1987). Two operant behavioral techniques were used to estimate the minimal field strength necessary for rats to detect the electric field. The investigators found that not only did the rats respond in a way that indicated they detected the fields but also that the rats' performance was correlated accurately with the magnitude of the field. The two behavioral protocols yielded average threshold estimates of 13.3 and 7.9 kV/m rms, which were similar to the thresholds produced by other investigators (between 4 and 10 kV/m) using different behavioral protocols. Although the results clearly showed that rats can detect electric fields, these investigations did not determine the positive or negative effects of electric fields on behavior. Stern and Laties (1989) tested whether 60-Hz electric fields at 90 or 100 kV/m were perceived as an aversive stimulus to rats. In this study, the rats were given the opportunity to turn off the electric



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