Electric field effects in selected biologic systems.

A traditional idea with respect to the interaction of electromagnetic fields and biologic systems is that specific effects can occur only when the incident energy is greater than the energy associated with a temperature that is characteristic of the biologic system (kT). The functioning of the visual system and the effect of ionizing radiation are examples of these interactions. For energies less than kT, the only widely accepted effects are those due to heating. They occur at electric field strengths or incident energy densities that depend on frequency but that generally are quite high. In the case of electrostatic fields (ESFs), an energistic analysis would lead to the conclusion that no biologic effects are possible, except for extremely high ESFs, because an insufficient amount of energy is coupled into the quasistatic biologic system. Indeed, the literature contains only a few reports of ESF-induced effects, which involved snails, fruit flies, moths, and worms. There are, however, an increasing number of reports that describe biologic effects induced by electromagnetic fields at frequencies and intensities that do not induce heating. Thus, in addition to energymediated interactions explainable by classic theory, there appears to be a second group unique to biologic systems. In this group, the electromagnetic field does not supply the energy for a given process but merely furnishes the energy to control or trigger it. The more sensitive the particular system that is affected by the electromagnetic fields, the smaller is the energy required to produce the effect. Since low-level, trigger effects induced by electromagnetic fields do occur in mammalian systems, the question arises whether such effects could be induced by ESFs. In addition to framing the question as a parallel to the observed electromagnetic field effects, the question derives independently from the reports that consider the effect of direct electrical current on biologic systems. A variety of experiments have