Absence of daytime 50 Hz, 100 μT_rmsmagnetic field or bright light exposure effect on human performance and psychophysiological parameters

Abstract

The purpose of this study was to reproduce and extend two earlier studies of the effects of human exposure to 50 Hz magnetic fields (MF). In a recent paper, we described results of two double-blind investigations performed to examine effects of 100 microT(rms) 50 Hz MF exposure on psychological parameters in the same group of healthy human volunteers. In each exposure session, at 1 week intervals, with sham, continuous, and intermittent (15 s ON/OFF cycles) MF conditions, mood ratings, performance measures, and electrophysiological measures were taken. In the first study, significant amplitude changes were observed in the event-related brain potentials (ERP) recorded during a dichotic listening task. In the second study, latency and reaction time (RT) slowing were seen on a visual discrimination task (P(300) paradigm). Although these results were little related to the number of parameters analysed, they indicate that low level 50 Hz MF might have a slight influence on ERP and RT under specific circumstances of sustained attention. Before concluding that moderately strong MF exposure can influence cognitive function, previous results should be replicated, using the same paradigms with another group of healthy volunteers. In the present study, 18 healthy subjects were exposed to three experimental sessions of 30 min each, given at 1 week intervals. The sessions consisted of continuous 100 microT(rms) 50 Hz MF exposure, sham condition, and bright light (5000 lux) exposure. The study was performed double-blind, with the exposure order counter-balanced. The data on mood, ERP, RT, and other performance measures did not show any differences among the sham exposure, light exposure, and MF exposure conditions. The results of this study do not support the hypothesis that extremely low frequency (ELF) MF exposure affects the brain's electrical activity or cognitive function at field strength (100 microT(rms)) similar to that found in very close proximity of some household and industrial electrical appliances and well in excess of the average MF strength (c. 0.1 microT) found in homes. The sensitivity of the experiment was possibly not sufficient to detect an effect at this relatively low MF, and larger sample sizes would be required in further studies.

Exposure to ELF magnetic and ELF‐modulated radiofrequency fields: The time course of physiological and cognitive effects observed in recent studies (2001–2005)

“…In addition to EEG, performance on a dichotic listening task and visual ERPs were assessed after the exposure period. Although no significant effects were found for any of the measures in Crasson and Legros [2005], the authors acknowledge that this may be due to the difference in MF presentation between the current study and their previous work [Crasson et al, 1999]. For instance, the 2005 study used a continuous presentation of the MF, whereas the 1999 study used an intermittent presentation.…”

“…This observation was also noted by Hamblin and Wood [2002] in their review on mobile phone effects on EEG and sleep variables. Interestingly, this effect was also noted in several ELF studies as well [Cook et al, 2004[Cook et al, , 2005Ghione et al, 2005] suggesting that this observation may be a non-specific response to intermittent stimulation of pulsed fields, as continuously presented ELF fields [Lyskov et al, 1993;Crasson and Legros, 2005] do not tend to elicit the same effect. Alternatively, this also might be specific response to the ELF field exposure as the cw RF used in Huber et al [2002] did not have a significant effect upon the EEG in contrast to the pulse-modulated RF field.…”

“…Conversely, Crasson and Legros [2005] attempted to replicate and extend their previous work [Crasson et al, 1999] Fuller et al [2003] 2000 mT <60 min " epileptiform activity (medial temporal lobe) Marino et al [2004] 60 Hz 100 mT; 2 s exposure " % recurrence over occipital, parietal, central regions Cook et al [2004] Pulsed ELF 200 mT pk-pk ; 15 min " occipital alpha activity (8-13 Hz) Cook et al [2005] Pulsed ELF 200 mT pk-pk ; 15 min # alpha activity in first 5 min of MF exposure Crasson and Legros [2005] 50 Hz, 100 mT rms; 30 min No effect Ghione et al [2005] 50 Hz 40 and 80 mT pk ; 15 min " occipital alpha activity (8-13 Hz)…”

“…Finally, it should be stressed that this post-exposure technique typically examines these effects within seconds of exposure. In Crasson and Legros [2005], electrode placement for the EEG measures was performed immediately post-exposure. As such, it is possible that significant effects were missed during the preparation for the electrophysiology portion of the experiment.…”

Influence mechanism of the natural and technogenic electromagnetic fields on life safety

“…В на-стоящее время всё больше внимания уделя-ется эффектам электромагнитного излучения ниже теплового уровня (10 мВт/см 2 ). В по-следние годы были получены данные о вы-сокой чувствительности организма к слабым магнитным полям [31][32][33].…”