What are electromagnetic fields?
Electric and magnetic ﬁ elds are all around us – for example, natural electric ﬁ elds in thunderstorms cause lightning to leap across the sky, and man made electric ﬁ elds are found in the ﬂuorescent lamps that light our streets. Magnetic ﬁ elds are also well known to us; the Earth’s magnetic ﬁ eld causes a compass needle to point North and helps many birds and ﬁ sh to navigate. These electric and magnetic ﬁ elds are linked because whenever an electric current ﬂ ows in an electric ﬁ eld, then a magnetic ﬁeld is generated.Together They form an electromagnetic ﬁ eld, or EMF. An example of this Is found in our homes, in hi-ﬁ systems, where an electric ﬁeld, or voltage, drives a varying electric current which produces a varying magnetic ﬁeld that causes the speaker cone to vibrate and reproduce sounds.
Electromagnetic ﬁ elds can be described as a series of waves that oscillate at a particular frequency and have a certain distance between one wave and the next – the wavelength.EMFs have a very wide range of frequencies, extending from lowfrequency electricity supply lines with wavelengths of some hundreds of metres, through the radio and
visible light frequencies, to very high-frequency medical X-rays with wavelengths measured in trillionths of a metre.
The electromagnetic spectrum is a continuous range of frequencies that are measured in hertz (Hz), as explained in box 1. This continuous spectrum is divided according to the use that is made of various parts – for example, the infrared range that is used for TV remote controls, the microwave range used for cooking, and radio-frequency (RF) waves that carry radio and television signals. At the extra-low frequencies (ELF) are the power
lines and pylons of the electricity grid that supplies electricity to homes and factories. These different parts of the electromagnetic spectrum are marked in diagram 1 together with some of their applications.Radio frequencies and microwaves are of particular interest when we come to consider the possible effects of EMFs on human health.
EMF: The benefits and concerns
Some of the non-ionising ﬁ elds we encounter in daily life result from the deliberate use of
EMF to achieve particular beneﬁ ts. They are used extensively in medicine for diagnosis and treatment, for example in magnetic resonance scanners to study the brain and in irradiation for bone repair and cancer treatment. A major indirect source of non-ionising EMFs is the electricity supply grid that we depend on to light buildings and streets, to power our kitchens and televisions, and to run the lifts, trains, computers and industrial machinery that our society needs. Power stations send electricity through overhead and underground cables and substations to our cities, factories and homes – a vital network of
ﬂ owing electric current that generates EMFs all around us.The fastest growing source of exposure to EMFs is communications, in particular mobile telephony. Although television and radio antennae have been with us for a long time, more recently, the massive growth in mobile telephony is a major success story in which the European GSM standard leads the world. The mobile telephony sector has increased employment in the EU; it has improved personal security, in particular for the young; emergency services are faster; business is more eﬃ cient; and it helps fulﬁ l our individual need to communicate when and where we want to, by speech, text message, email, and more recently with images.
A cause for concern?Exposure to non-ionising electromagnetic ﬁ elds is unavoidable in today’s society and thisexposure is growing mainly because of mobile telephones which are held close to the head, and also to the high density of mobile telephone antennae in our towns and cities. Therefore, the question as to whether or not they can damage
our health is an important one. The eﬀ ects of long-term exposure to low-intensity EMF are not at all well known – and it is exposure to this type of ﬁ elds that is growing.The diﬃ culties in evaluating the eﬀ ects of long-term low-level exposure to potential environmental hazards are not new; for example, the low concentrations of chemical and biological
agricultural residues that get into the food chain have been active research areas for many years. A major problem in this research is that the eﬀ ects can be cumulative; they build up in the body over time. This means that research into the hazards they pose is long-term and painstaking – and it is further complicated when the longterm research is overtaken by new technologies. Much of this research is into the ‘genotoxicity’ of ELF and RF-EMF from electricity power lines and mobile telephones respectively. A genotoxin is an agent that can damage DNA and possibly lead to cancer. So far, no convincing links between exposure to low-level EMFs and damage to health have been found. Awareness of the possible risks of mobile telephones has raised public concern, which has been echoed by the European Parliament. In addition, the spread of antennae through our towns is raising objections, not just for aesthetic reasons but also because of fears about their potential harmful eﬀ ects. While industry has done much to limit the exposure to EMF from telephones and antennae, public fears are delaying the deployment of next-generation
mobile telephone systems.