What are EMFs?

Other sources of EMFs

Other sources of EMFs

The EMF helpline can provide information on the electric and magnetic fields associated with the UK electricity industry. These are 50 Hz electric and magnetic fields produced by equipment such as overhead electricity lines, substations, and cables. There are other frequencies of EMF and other sources of 50 Hz fields, but we do not provide guidance on those at this helpline.


This site covers power-frequency EMFs only and does not cover radiofrequency or mobile phone issues.

Some of the differences between power-frequency (50 Hz) fields and radiofrequency fields are given in the table below.

Power-frequency EMFs  Radiofrequency EMFs  
The operating frequency is 50 hertz.  The frequency is hundreds of kilohertz upwards, all the way up to tens of gigahertz (millions, or even tens of millions, times higher than power frequencies).
They are produced by mains electricity e.g., overhead lines, substations, electricity in the home, appliances. They are produced by many different technologies e.g., broadcast TV and radio, mobile phones, wi-fi etc.
The electric and magnetic fields are separate phenomena – you can have one without the other. The electric and magnetic fields are coupled together as radiation.
They can induce currents in the body but do not cause significant heating. They can cause heating in the body.
They tend to be relatively straightforward waveforms (a sine wave with only a few harmonics). The modulations used to transmit signals mean the waveforms are highly complex.


Railway and other electric transport

Railways and other electrified transport systems produce power-frequency EMFs that are similar in many ways to those produced by the power system, however we do not specifically cover EMF issues relating to railways or other electric transport on this website or on the EMF helpline.