Electromagnetic fields occur where electricity is used or consumed.

Electromagnetic fields

Electromagnetic fields are characterised by the following:

• they are invisible;
• humans are not able to perceive them;
• they occur where there is electricity;
• they propagate at the speed of light;
• they are both electric and magnetic.

The electric and magnetic fields are interrelated, but they are two different aspects of the same phenomenon. Wherever electricity moves, both an electric field and a magnetic field are generated. It is necessary to differentiate between the two in the working environment, because their mechanism of action is different and different limit values have been set for both.

Figure. The electric and magnetic fields are perpendicular to each other in the electromagnetic field

Tabel. Erinevused ja sarnasused elektri- ja magnetvälja vahel

Electric field	Magnetic field
unit of measurement in volts per metre (V/m)	unit of measure Tesla (T)
relatively easy to screen	passes almost everything, difficult to shield
spreads in the room by means of a magnetic field	spreads in the room by means of an electric field
the field strength decreases when moving away from the source	the field strength decreases when moving away from the source
occurs when the device is energised (the device does not have to be in operating mode)	occurs during power consumption (when the device is switched on)
the peculiarity of the spread	the peculiarity of the spread

Unlike static electric or magnetic fields, most electromagnetic fields in the working environment are in constant change (make several oscillations per second).

Time-varying electromagnetic fields are generally divided into three regions:

1. low frequency;
2. middle frequency; and
3. high frequency.

The change in time is measured in hertz (Hz), 1Hz = 1 oscillation per second. In the case of a device that emits electromagnetic fields, it is important to know the frequency of the field it generates, because different frequencies have different limit values (some frequencies affect a person more effectively than others).

Health effects

The current limit values protect workers against two main health effects:

• a thermal effect in which body tissues overheat, which is manifested by whole-body or local heat stress;
• nervous system stimulation.

Other biological effects have also been identified in science, but as scientists do not yet have a clear understanding and consensus on the mechanism of action of these effects, they have not yet been included in the limit values.

Also, occupational exposure limit values only apply to acute, short-term effects (up to one working day). Due to limited scientific understanding of long-term and repeated exposure, these effects have not been reflected in the regulation.

Nervous system stimulation

The alternating electromagnetic field creates a weak current in the human body, which also results in the ability to cause harmful biological effects. The current generated in the human body can stimulate nerves or muscles in an irritating way.

Thermal effect

High-power radio frequency radiation is a source of thermal energy, the exposure to which has all the consequences of heating biological organisms: burns, temporary or permanent changes in reproductive capacity, cataracts and death. Although a person can feel the heat on the skin, it is not enough to perceive the danger situation – thermoreceptors are located in the skin and cannot perceive when the internal organs of the body are heated by radio radiation. The strength of the electric current generated in the body also depends on the position of the body in relation to the radiation source (at what angle it enters the body).

The effect of the electromagnetic field to the body mainly depends on the strength of the electromagnetic field, the distance from the radiation source and the exposure time. With regard to exposure to electromagnetic fields, the risk groups are considered to be persons wearing an active or passive medical implant and pregnant women. Persons at risk are advised to choose work areas and tasks where they are not exposed to large electromagnetic fields (such as welding work).

Although industrial equipment sold in Europe must comply with European safety standards, including those applied to electromagnetic fields, experience has shown that certain equipment may have so-called leakage electromagnetic fields, which have a regional or whole-body effect on workers. Therefore, it is important to periodically monitor and maintain equipment that uses high electromagnetic fields, and special attention should be paid if pregnant women or women of childbearing age should work near them.

Prevention

By regulating the factors on the extent of which the worker's exposure to electromagnetic fields depends, it is possible to significantly reduce the dose. It is important to protect workers in the areas where they spend the most time. Because a person does not sense electromagnetic fields, the worker can receive a large part of the exposure from sources and places that are not necessary for the work process. It is therefore important to take measurements to identify 'hot spots' in the workplace and to train workers in safe work practices. Unnecessary exposure to electromagnetic fields must be eliminated. Equipment and places with a high radiated power must be marked with safety signs.

Options for reducing exposure to electromagnetic fields

• Remove the radiation source – turn it off or replace it with an alternative, safer solution.
• Move workers away from the radiation source – the strength of the electromagnetic field decreases in correlation with the square of the distance; for larger sources, a place should be found that is away from most workers. Similarly, the choice of workplaces for workers must take into account the proximity of high-current electrical cables or equipment. Equipment that generates high levels of leakage radiation (e.g. induction and dielectric heaters) should be operated remotely whenever possible. Shield a radiation source – build a screen made of reflective or absorbent material to protect workers. Cables and other radiating parts of the device can be shielded. There may be leakage radiation in the case of radio and middle frequency electromagnetic fields, which should also be taken into account.
• Protect workers – choice of shielding clothing (but does not protect against low-frequency magnetic fields). For example, aprons are available for pregnant women to protect the foetus from radio frequency radiation.
• Given the rapid growth of electromagnetic fields in the living and working environment, and given the limited research based on their effects, it is not yet possible to draw definitive conclusions on safety. The European Union therefore recommends applying the precautionary principle and minimising electromagnetic fields where possible.