Electromagnetic fields are present everywhere in our environment. Electric fields are produced by natural sources such as the local build-up of electric charges in the atmosphere associated with thunderstorms while the earth's magnetic field is used by birds and fish for navigation. Human-made sources include medical equipment using static fields (e.g. MRI), electric appliances using low frequency electric and magnetic fields (50/60 Hz), and various wireless, telecommunications and broadcasting equipment using high radiofrequency electromagnetic fields (100kHz-300 GHz).

When properly used, electromagnetic fields greatly improve our quality of life, health and well-being. However, above certain levels, these fields can be harmful to health and affect the human body in different ways depending on their frequency. Therefore, countries have set standards to limit exposure to electromagnetic fields, either for specific frequencies and applications, or over the whole electromagnetic field spectrum.