WHO – static fields

WHO produced a monographs on static fields, Environmental Health Criteria no 232, in 2006, and an accompanying factsheet, number 299 2006.  See also WHO's conclusions on ELF fields.

Environmental Heath Criteria 232

Key extracts from the summary are:

"1.1.7  Health risk assessment

Static electric fields

There are no studies on exposure to static electric fields from which any conclusions on chronic or delayed effects can be made.  IARC (IARC, 2002) noted there was insufficient evidence to determine the carcinogenicity of static electric fields.

Few studies of the acute effects of static electric field effects have been carried out.  On the whole, the results suggest that the only adverse acute effects are associated with direct perception of fields and discomfort from microshocks.

Static magnetic fields

The available evidence from epidemiological and laboratory studies is not sufficient to draw any conclusions with regard to chronic and delayed effects.  IARC (IARC, 2002) concluded that there was inadequate evidence in humans for the carcinogenicity of static magnetic fields, and no relevant data available from experimental animals.  Their carcinogenicity to humans is therefore not at present classifiable.

Short-term exposure to static magnetic fields in the tesla range and associated field gradients induce a number of acute effects.

Cardiovascular responses, such as changes in blood pressure and heart rate, have been occasionally observed in human volunteer and animal studies.  However, these were within the range of normal physiology for exposure to static magnetic fields up to 8 T.

Although not experimentally verified, it is important to note that calculations suggest three possible effects of induced flow potentials.  These include minor changes in heartbeat (which may be considered to have no health consequences), the induction of ectopic heartbeats (which may be more physiologically significant), and an increase in the likelihood of re-entrant arrhythmia (possibly leading to ventricular fibrillation).  The first two effects are thought to have thresholds in excess of 8 T, and threshold values for the third are difficult to assess at present because of modelling complexity.  Some 5 - 10 per 10,000 people are particularly susceptible to re-entrant arrhythmia, and the risk to such people may be increased by exposure to static magnetic fields and gradient fields.

The limitations of the available data are such, however, that it is not possible to put them all together to draw firm conclusions about the effects of static magnetic fields on the endpoints considered above.

Physical movement within a static field gradient induced sensations of vertigo and nausea, and sometimes phosphenes and a metallic taste in the mouth, for static fields in excess of about 2 - 4 T.  Although only transient, such effects may adversely affect people.  Together with possible effects on eye-hand coordination, the optimal performance of workers executing delicate procedures (e.g. surgeons) could be reduced, with a concomitant impact on safety.

Effects on other physiological responses have been reported, but it is difficult to reach any firm conclusion without independent replication."

Factsheet 299

The key section on health reads:

"HEALTH EFFECTS
For static magnetic fields, acute effects are only likely to occur when there is movement in the field, such as motion of a person or internal body movement, such as blood flow or heart beat. A person moving within a field above 2 T can experience sensations of vertigo and nausea, and sometimes a metallic taste in the mouth and perceptions of light flashes. Although only temporary, such effects may have a safety impact for workers executing delicate procedures (such as surgeons performing operations within MRI units).

Static magnetic fields exert forces on moving charges in the blood, such as ions, generating electrical fields and currents around the heart and major blood vessels that can slightly impede the flow of blood. Possible effects 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). However, these types of acute effects are only likely within fields in excess of 8 T.

It is not possible to determine whether there are any long-term health consequences even from exposure in the millitesla range because, to date, there are no well-conducted epidemiological or long-term animal studies. Thus the carcinogenicity of static magnetic fields to humans is not at present classifiable (IARC, 2002)."