Effects of static fields

This site is principally concerned with the alternating fields produced by 50 and 60 Hz power systems.  But there are some places where power systems operate with DC - direct current - which produces static fields.  So we provide a summary here of the effects that static fields can have.

Effects of high static magnetic fields

According to basic physics, effects of static magnetic fields on the human body, which is essentially non-magnetic, are only likely to occur if there is movement of a charge relative to the field.  This could be movement of the whole person through the field, or movement of charge within the body, such as flow of blood through a blood vessel.

A person moving within a field can experience sensations of vertigo and nausea, and sometimes a metallic taste in the mouth and perceptions of light flashes. This can occur in fields greater than about 2 T.

Static magnetic fields exert forces on moving charges in the blood.  These forces can then interact in such a way as to impede slightly the flow of blood. The possible consequences of this range from minor changes in heartbeat to an increase in the risk of abnormal heart rhythms (arrhythmia) that might be life-threatening (such as ventricular fibrillation). These effects are likely only in fields in excess of 8 T.

Effects of high static electric fields

The only identified effects of static electric fields are microshocks.  See more details on AC microshocks - the sensations are similar.

Effects of lower static fields

The epidemiological evidence that suggests effects of EMFs on, for example, childhood leukaemia is specific to alternating fields at 50 and 60 Hz and has no direct relevance to static fields.

There have been epidemiological studies of workers exposed to static magnetic fields.  They have not identified any health effects, but they have not been of particularly high quality, so equally, they cannot be used to rule out any effects definitively.  Accordingly, the classification of static magnetic fields to humans by IARC and WHO is "not classifiable".

There have been a few studies of the health of people living near DC power lines, from America in the early 1980s.  Overall, these do not suggest any health risks, but they are not particularly strong studies.

Human beings have evolved in the earth's static magnetic field.  This makes it unlikely that static fields of a similar magnitude would be harmful.

Effects of static fields on studies of AC fields

It's possible, becausde of the way some mechanisms work, that the earth's static magnetic field could affect the findings of epidemiological studies of AC fields.  This has been investigated, but without very clear findings either way.

See also:

  • what the expert review bodies say about the effects of static fields:

WHO   |   IARC   |   ICNIRP   |   HPA