Biological effects of power frequency electric and magnetic fields

The purpose of this study was to reproduce and extend an earlier investigation of the effects of human exposure to combined, 60-Hz electric and magnetic fields. This paper presents the neurobehavioral results. Thirty men participated in one training session and four testing sessions. Subjects were randomly assigned to two groups. The 18 subjects in Group I were exposed (9 kV/m, 20 microT) and sham exposed in two counterbalanced orders. In Group II, half of 12 subjects were exposed (9 kV/m, 20 microT) every session, and the remaining half were sham exposed every session. The study was doubly blinded. Measures of cardiac interbeat interval, event-related brain potentials, and performance were obtained before, during, and after exposures. As in the earlier study, exposure to the combined field resulted in a statistically significant slowing of heart rate, in changes in late components of event-related brain potentials, and in decreased errors on a choice reaction-time task. In addition, field effects on several other measures approached statistical significance. The physiological measures obtained during exposure indicated that effects were greatest soon after the field was switched on, and again when it was switched off. The data indicate that changes in exposure level may be more important than duration of exposure for producing effects in human beings.

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A replication study of human exposure to 60‐Hz fields: Effects on neurobehavioral measures

Cook

Graham

Cohen

et al. 1992

Bioelectromagnetics

111

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Dose response study of human exposure to 60 Hz electric and magnetic fields

Graham

Cook

Cohen

et al. 1994

Bioelectromagnetics

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This human exposure study examined the relationship between field strength and biological response and tested whether the exposure levels at which the greatest effects occur differ for different endpoints. Three matched groups of 18 men each participated in two 6 h exposure test sessions. All subjects were sham exposed in one session. In the other session, each group of subjects was exposed at a different level of combined electric and magnetic field strength (low group:6 kV/m, 10 microT; medium group:9 kV/m, 20 microT; and high group: 12 kV/m, 30 microT). The study was performed double blind, with exposure order counterbalanced. Significant slowing of heart rate, as well as alternations in the latency and amplitude of event-related brain potential measures derived from the electro encephalogram (EEG), occurred in the group exposed to the 9 kV/m, 20 microT combined field (medium group). Exposure at the other field strength levels had no influence on cardiac measures and differential effects on EEG activity. Significant decrements in reaction time and in performance accuracy on a time estimation task were observed only in the low group. These results provide support for the hypothesis that humans may be more responsive to some combinations or levels of field strength than to others and that such differences in responsivity may depend, in part, on the endpoint of interest.

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Influence of Electromagnetic Fields on Bone Mass and Growth in Developing Rats: A Morphometric, Densitometric, and Histomorphometric Study

et al. 1997

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The effect of electromagnetic fields on bone is debated. In an experimental study of this effect, we compared two lots of growing female rates (both lots n = 15, age 3 weeks, average weight 23.2 +/- 3.3 g), one of which was exposed to a 3-mT, 100-Hz, Helmholtz-type electromagnetic field for 24 hours a day for 30 days, and the other of which served as the control. Bone development and bone mass were evaluated by morphometry, densitometry, and histomorphometry. The rats were killed at 30 days and weighed. The right femurs were dissected, measured, and weighed; bone densitometry was used to determine femoral bone mineral content (BMC) and density (BMD), and histomorphometry of the nondecalcified bone was used to determine trabecular bone volume (Cn-BV-TV%), number (Tb-N mm) and thickness (Tb-Th microm), intertrabecular space (Tb-Sp microm) and growth cartilage thickness (Gc-Th microm). In the rats exposed to the electromagnetic field, BMC and BMD (P = 0.019 and P = 0.002, respectively) and Cn-BV-TV, Tb-N, Tb-Th (P = 0.005, P = 0.036, and P = 0.027, respectively) all were decreased, whereas Tb-Sp was increased (P = 0.002). There were no significant differences in initial and final body weight, or in final femur weight, femur length, and GC-Th. These findings indicate that electromagnetic fields of the type used here reduced bone formation and increased bone resorption without affecting bone development in rats.

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Biological effects of power frequency electric and magnetic fields

Cited by 28 publications

References 75 publications

A replication study of human exposure to 60‐Hz fields: Effects on neurobehavioral measures

A replication study of human exposure to 60‐Hz fields: Effects on neurobehavioral measures

Dose response study of human exposure to 60 Hz electric and magnetic fields

Influence of Electromagnetic Fields on Bone Mass and Growth in Developing Rats: A Morphometric, Densitometric, and Histomorphometric Study

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