Static Electric Fields
Characteristics of the field and its use
Static electric fields are constant fields, which do not change in intensity or direction over time, in contrast to low and high frequency alternating fields. Hence, static electric fields have a frequency of 0 Hz. They exert a force on charges or charged particles.
The strength of a static electric field is expressed in volts per meter (V/m). The strength of the natural electric field in the atmosphere varies from about 100 V/m in fair weather to several thousand V/m under thunderclouds. Other sources of static electric fields are charge separation as a result of friction or static electric currents from varied technologies. In the home, charge potentials of several kilovolts can be accumulated while walking on non-conducting carpets, generating local fields of up to 500 kV/m. High voltage DC power lines can produce static electric fields of up to 20 kV/m and more. Inside DC operated electric trains, static electric fields of up to 300 V/m can be found.
Effects of static electric fields on the body and health implications
Static electric fields do not penetrate the human body because of its high conductivity. The electric field induces a surface electric charge, which, if sufficiently large, may be perceived through its interaction with body hair and through other phenomena such as spark discharges (microshocks). The perception threshold in people depends on various factors and can range between 10 - 45 kV/ m. Furthermore, very high electric fields, such as from HVDC lines, can charge particles in the air, including polluted particles. There was a hypothesis that charged particles might be better absorbed by the lung than uncharged ones and so, raise people’s exposure to air pollution. Current knowledge, however, suggests that an increased health risk from such charging of particles is very unlikely.
Overall, the limited number of animal and human laboratory studies that have investigated the effects of exposure to static electric fields, have not provided evidence of adverse health effects.
The only established health effect is possible stress resulting from prolonged exposure to microshocks. National authorities may implement programs that protect both the public and workers from any untoward effects of static and that avoid discomfort from electric discharge to tissues of the body.