This is a very complex question related to the control of the interaction between the electromagnetic fields that for their nature have different frequencies varying from a few oscillations per second (50 hertz in the alternating current) to some hundreds of billions and an extraordinary complex human being. A human being as well as any other material body in presence of an electromagnetic field interacts with it by absorbing energy. In this case the quantity of energy is definitely not sufficient to determine ionization phenomena, that is alterations of the molecules electric charges (as it occurs on the contrary with either ultraviolet x, alpha, beta or gamma rays), but it is sufficient to cause effects to cellular level. So many variables have to be considered that it is very difficult to measure the real quantity of energy absorbed by a human being in a given condition. As a matter of fact is often more prudent and comfortable to protect people who are exposed to the fields independently of a careful evaluation of the energy quantity that can be absorbed. According to some Swedish studies the electromagnetic fields can either foster or accelerate some genetic mutations that is they act as a catalyst for phenomena of molecular nature that in turn may lead to genetic mutations. The authorities of the Germany Federal Republic have recently decided to start a national research aimed at verifying the events described above. According to many researchers if these events would be confirmed the sanitary risk would be so high that it would justify either a protection action or a direct protection of people particularly submitted to it.