A neurobiological basis for ELF guidelines.
It is well understood that electric currents applied directly to the body can stimulate peripheral nerve and muscle tissue; such effects can be fatal if breathing is inhibited or ventricular fibrillation is induced. Exposure to extremely low frequency electric and magnetic fields will also induce electric fields and currents within the body, but these are almost always much lower than those that can stimulate peripheral nerve tissue. Guidance on exposure to such fields is based on the avoidance of acute effects in the central nervous system. This paper reviews the physiological processes involved in nerve cell excitability in the peripheral and central nervous system, and the experimental evidence for physiologically weak electric field effects. It is concluded that the integrative properties of the synapses and neural networks of the central nervous system render cognitive function sensitive to the effects of physiologically weak electric fields, below the threshold for peripheral nerve stimulation. However, the only direct evidence of these weak field interactions within the central nervous system is the induction of phosphenes in humans--the perception of faint flickering light in the periphery of the visual field, by magnetic field exposure. Other tissues are potentially sensitive to induced electric fields through effects on voltage-gated ion channels, but the sensitivity of these ion channels is likely to be lower than those of nerve and muscle cells specialized for rapid electrical signaling. In addition, such tissues lack the integrative properties of synapses and neuronal networks that render the central nervous system potentially more vulnerable.
Saunders
Richard D
RD
Health Protection Agency, Centre for Radiation, Chemical and Environmental Hazards Radiation Protection Division, Chilton, Didcot, Oxfordshire, UK. rick.saunders@hpa.org.uk
Jefferys
John G R
JG
D000818:Animals; D001822:Body Burden; D002490:Central Nervous System / Q000502:physiology* / Q000528:radiation effects*; D003198:Computer Simulation; D004560:Electricity; D004574:Electromagnetic Fields; D004781:Environmental Exposure / Q000032:analysis / Q000592:standards; D006801:Humans; D008954:Models, Biological; D008959:Models, Neurological; D009446:Neurobiology / Q000379:methods / Q000592:standards; D017933:Peripheral Nervous System / Q000502:physiology* / Q000528:radiation effects*; D017410:Practice Guidelines as Topic; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000379:methods / Q000592:standards; D011835:Radiation Protection / Q000379:methods / Q000592:standards; D011846:Radio Waves; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity