Short-term effects

There are two physiological phenomena resulting from exposure to electromagnetic fields that are readily reproducible and for which causal links are well established. These are both related to the induction of currents in biological tissues, which exhibit differing electrical conductivity properties depending on the type of tissue. At low frequencies (<10 MHz) the induced currents can result in electro-stimulation of nerves. At higher frequencies (>100 kHz) the power absorbed results in local heating of the tissue.

Physiological phenomena resulting from exposure to electromagnetic fields at different frequencies

The most consistent effects of exposure to electromagnetic fields at frequencies up to 100 Hz are the appearance of visual phosphenes (resulting from electro-stimulation of the retina) and a minor reduction in heart rate during or immediately after exposure. There is no evidence that these transient effects are associated with any long-term health risk. Other effects that have been reported include headaches and nausea.

Studies have demonstrated that in the range from 100 kHz to 10 MHz, the dominant effect of exposure to a high-intensity electromagnetic field changes from nerve and muscle stimulation to tissue heating. At 100 kHz the primary sensation is nerve tingling; at 10 MHz it is warmth on the skin. In this frequency range, therefore, basic health protection criteria are intended to avoid stimulation of excitable tissues and heating effects. At frequencies in the range from 10 MHz to 300 GHz, heating is the major effect of absorption of electromagnetic energy.

Long-term effects

A wide range of other health effects have been linked to electromagnetic field exposure, but the available data are generally sparse and often contradictory. Thus, the evidence for most of these claimed effects is considered (by ICNIRP and similar organizations) to be too weak and/or incomplete to justify the specification of corresponding exposure limits. That means that the guidelines and directives "relates to the direct risks to the health and safety of workers due to known short-term adverse effects in the human body caused by induced electric or magnetic fields, by energy absorption and by contact currents” and “does not address long-term effects”.