EM Fields is an independent consultancy based in UK and operating internationally,
providing advice and measurements on public and occupational exposure
to electromagnetic fields and  RF radiation.

1 What are the known effects of exposure to EMF?

At low frequencies (below 100 kHz) the risk is from voltages and currents flowing in the body
as a result of exposure to electric and magnetic fields. It’s the same effect as electric shock  –
although it’s effectively impossible to be killed by EMF, it is possible in some industrial situations
to feel peripheral nerve stimulation or see “lights in the eyes” as a result of current flow in the
retina. These effects require very high levels of exposure indeed, well above public safety limits.

Like any electrical system, the human nervous system has a limited bandwidth, and above about
100 kHz it becomes increasingly unable to be affected by EMF. At higher frequencies (above 10 MHz)
the effects of exposure are thermal – you get hot if exposed to very high levels – and safety limits are
set to avoid any risk of heating.

Between 100 kHz and 10 MHz both effects can occur, but in fact there are not that many sources of
exposure in this “intermediate” frequency range (although there are a few).

This shift from electrical to thermal effects is why a current in your body of 5 mA at 50 Hz can kill you,
but 300 mA in your arm at 50 MHz can be felt as a slight warming.

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