Constant electric field
This type of field is related to electrostatic charge. It is caused by a separation of charge and facilitated or even enabled by synthetic materials. For instance, a separation of charge occurs when you walk over a carpeted floor. This produces a potential difference between you and the environment. A discharge occurs in a flash-like manner as soon as you touch a grounded object or another person.
Constant magnetic field
Constant magnetic fields can originate from radiators, steel reinforcements of ceilings, coils of a sprung mattress or from metal bed bases. This distorts the homogenous earth’s magnetic field, producing a negative effect on the human body.
Alternating electric field
This type of field is present around all electric lines, cables, switches and sockets to which voltage is applied, i.e. after switching the circuit on, this field is present 24 hours a day. This is the normal state of the mains. Of course, all live connecting and extension cables also emit such an alternating electric field. The human body absorbs this alternating field so that there is a voltage up between the person and the ground. This so-called coupling voltage can be detected by means of special equipment and can be in a range from a few millivolts up to several volts. Only coupling voltage values below 20 millivolts (mV) are tolerable. The reason why this value is recommended as a biological limit value for permanent exposure is that the cell voltage of the human body lies between 30 and 70 mV.
Alternating electromagnetic field
This type of field builds up only when a current flows through a wire. The magnitude of this field depends on the amount of the current. Stranded cables and wires considerably attenuate these fields because they partly neutralise each other. Overhead lines and flat webbed house wires, however, have a contrary effect due to their large conductor spacing.
According to VDE specification 0848, a permanent magnetic flow density of 5000 nanotesla (nT) is tolerable for human beings. In this case, the electro-biological reference value is 20 nT. Hundreds of electro-biological studies revealed that the first reversible dysfunctions in humans already occur from 30 nanotesla upward.