Electric fields are generated by electric charges or by time-varying magnetic fields. Magnetic fields are generated by moving electric charges or by time-varying electric fields, such as those near a wire conducting alternating current. When the electric and magnetic fields are coupled, they are jointly called 'electromagnetic fields'. On this website, the term 'electromagnetic fields' (EMF) is used as an abbreviation for electric, magnetic or electromagnetic fields with frequencies from 0 to 300 gigahertz. EMF are strongest near the conductor or device that generates them (the source) and weaken with increasing distance to the source. Apart from human-made sources, EMF are also generated in nature, for example as a result of lightning or the flow of conducting materials in the earth's core.
The effects of EMF on the body depend on their frequency and strength. Fields with relatively low frequencies, such as those generated by power lines , can stimulate nerves or sensory organs when they are strong enough. Fields with relatively high frequencies, such as those generated by mobile phone masts , can lead to excessive heating of the body if they are strong enough. Scientific organisations have defined exposure limits for EMF, below which such effects do not occur. Such exposure limits can be implemented in legislation by national or international authorities. Scientists have also conducted research to answer the question whether exposure to EMF weaker than the present exposure limits can have health effects in humans or affect animals or plants in the environment.
Exposure of the general population to low frequency EMF arises mainly from electrical appliances in and around the home and to a lesser degrees from electrical facilities such as power lines. Exposure of the general population to radiofrequency EMF arises mainly from mobile phone use and to a lesser degree from transmitters such as mobile phone masts. EMF exposure in the workplace can sometimes be higher than exposure outside work. For example, particularly strong EMF can occur near welding equipment, induction heaters and radar installations. Exposure of hospital patients to EMF can be even higher than that of workers, for example when undergoing an MRI-scan. In that case the medical benefits outweigh the potential risks of EMF exposure.
More details about the main research topics on EMF within RIVM can be found on the following webpages: