Static Fields

The World Health Organization (WHO) Environmental Health Criteria (EHC) Programme was initiated in 1973 with the main objective of assessing information on the relationship between exposure to environmental pollutants and human health. Since that time, a number of EHC monographs have been published that provide critical reviews on the effect on human health and the environment of physical, chemical and biological agents. They are intended to assist national and international authorities in making risk assessments and subsequent risk management decisions and represent a thorough evaluation of risks but are not, in any sense, recommendations for regulation or standard setting. These are deemed to be the exclusive responsibility of national and regional governments.

The EHC monographs that have previously addressed possible health effects from exposure to electromagnetic fields (EMFs) are now in the process of being revised. The revised EHC will be published in a set of three monographs spanning the relevant frequency range, 0-300 gigahertz (GHz), namely, static fields (0 Hz), extremely low frequency fields (up to 100 kHz) and radiofrequency fields (100 kHz-300 GHz). HPA staff are contributing to this process, helping to prepare draft documents and participating in EHC Task Group meetings.

The EHC monograph on static fields is the first to be published and can be found on the WHO website at www.who.int/peh-emf/publications/reports/ehcstatic/en/index.html. It reviews sources and human exposure to static electric and magnetic fields, interaction mechanisms, dosimetry, experimental and epidemiological studies, and includes a health risk assessment. Recommendations are made for national authorities regarding the need for guidelines and protective measures. In addition, recommendations are given for further research; these are also listed in a static fields research agenda available on the WHO website from www.who.int/peh-emf/research/agenda/en/index.html.

In brief, people can be exposed to static electric and magnetic fields in a variety of situations. Static electric fields of up to 3 kilovolts per metre (kV m ^-1 ) can occur under thunderclouds, but otherwise lie in the range 1-100 V m ^-1 in fair weather. The geomagnetic field varies over the Earth's surface between about 35 and 70 microtesla (?T). Man-made static electric fields of up to 20 kV m ^-1 can be found under direct current (DC) transmission lines; other sources include some rail systems using DC, and visual display units, the latter generating fields of around 10-20 kV m ^-1. Man-made static magnetic fields are generated wherever DC currents are used; the largest, usually in the range 0.2-3 T, are likely to be experienced by patients during clinical magnetic resonance imaging.

With regard to the health risk assessment, the EHC monograph notes that there are insufficient studies to draw any conclusions with regard to delayed or chronic effects like cancer. For static electric fields, the only adverse acute effects are associated with the direct perception of the fields and discomfort from microshocks. For static magnetic fields in excess of 2-4 T, physical movement in static field gradient will induce sensations of vertigo and nausea that, although transient, may adversely affect people. Together with possible effects on eye-hand co-ordination, the optimal performance of workers executing delicate procedures could be reduced, with a concomitant impact on safety. Other acute effects are less clearly established; cardiovascular responses, such as changes in blood pressure and heart rate, have occasionally been observed in volunteer and animal studies, but lie within the normal range below 8 T.

The HPA welcomes the publication of this extensive and authoritative contribution to the assessment of the health impact of exposure to static electric and magnetic fields.

Reference

World Health Organization (2006). Static Fields. Environmental Health Criteria No. 232.(ISBN 92-4-157232-9)
Copies can be obtained from http://www.who.int/bookorders/ [outside link].

July 2006