The kind of effect electromagnetic fields have on people depends primarily on the frequency, intensity and other factors, such as the waveform of the source.

Electromagnetic fields may cause:

• Direct effects resulting from an interaction of fields with the body, they may be thermal or nonthermal
• Indirect effects due to the presence of an object in an electromagnetic field that may be a risk to safety or health.

Direct effects can be further divided into:

• non-thermal effects from 0 Hz to 10 MHz
• thermal effects from 100 kHz to 300 GHz

Article 3 of Directive 2013/35/EU defines  values exposure limit (VLE) for both thermal and nonthermal effects. In particular, VLE for thermal effects, which could cause major health damage, must always be observed in the workplace.

VLE are defined in terms of quantities found within the body that cannot be measured directly or simply calculated. For this reason, the concept of Levels Action (LA) is introduced, which are set in terms of external field magnitudes therefore easily detectable by measurements or calculations.
If the LAs are not exceeded, it can be assumed that the exposures are in accordance with the VLE and no further assessment is needed.

With the entry into force of Directive 2013/35/EU, obligations are introduced for the employer who, in sectors subject to exposure to electromagnetic fields, must provide periodic measurements to assess that LAs are not exceeded, inform and train personnel on electromagnetic fields, and finally equip professionally exposed workers with personal protective equipment.