Extremely Low Frequency Electric and Magnetic Fields

Powerlines, electrical wiring and common appliances (electric blankets, televisions, hair-dryers, computers, etc) all produce extremely low frequency (ELF) electric and magnetic fields.

• What are ELF electric and magnetic fields?

ELF electric and magnetic fields occupy the lower part of the electromagnetic spectrum (PDF 382kb) in the frequency range 0-3000 Hz. ELF electric and magnetic fields result from electrically charged particles. Charged particles in motion are referred to as the electric current and the force that makes the charges move is the electric potential or voltage. The electric field is produced by the voltage whereas the magnetic field is produced by the current. The properties of ELF electric and magnetic fields are described in detail in the World Health Organization’s Environmental Health Criteria 35 Extremely Low Frequency Fields.

• How are ELF electric and magnetic fields measured?

Measurements of ELF electric and magnetic fields are performed in order to characterise emissions from sources and exposure of persons or experimental subjects. The strength of the electric field is measured in units of volts per metre (V/m). The strength of the magnetic field is measured in units of amperes per metre (A/m) but is usually expressed in terms of the magnetic flux density measured in units of tesla (T) or microtesla (μT). Another unit, which is commonly used to measure the magnetic field is the gauss (G) or milligauss (mG), where 1 G is equivalent to 10-4 T (or 1 mG = 0.1 μT).

• How are people exposed to ELF electric and magnetic fields?

ELF electric and magnetic fields are produced by both natural and artificial sources. Naturally occurring ELF fields are associated with atmospheric processes such as ionospheric currents, thunderstorms and lightning. artificial sources are the dominant sources of ELF fields and are usually associated with the generation, distribution and use of electricity at the frequency of 50 or 60 Hz. Powerlines, electrical wiring and common appliances (electric blankets, televisions, hair-dryers, computers, etc) all produce ELF electric and magnetic fields.

The widespread use of electricity means that people are exposed to ELF electric and magnetic fields in the home, in the environment and in the workplace. Residential exposure to ELF fields depends on many factors, including the distance from local power lines, the number and type of electrical appliances in use in the home, and the configuration and position of household electrical wiring. Electric fields around most household appliances and equipment typically do not exceed 500 V/m and magnetic fields typically do not exceed 150 μT (1500mG). Exposure in the workplace can vary. Workers who maintain transmission and distribution lines, for example, may be exposed to very large electric and magnetic fields. Within generating stations and substations electric fields in excess of 25 kV/m and magnetic fields in excess of 2 mT (20,000 mG) may be found. Office workers are exposed to very much smaller fields when using equipment such as photocopying machines and video display terminals. Typical residential and occupational exposures to ELF electric and magnetic fields are listed by the National Institute of Environmental Health Sciences in the US.

• What are the effects of exposure to ELF electric and magnetic fields?

Current evidence suggests that, apart from stimulation arising from electric charge induced on the surface of the body (eg electric shock) there is no other evidence that exposure to electric fields is a health hazard. Whether exposure to magnetic fields is equally harmless remains an open question. A large number of scientific studies performed on animals and cells have not found a health risk. Some epidemiological studies, however, have suggested a weak link between intense and prolonged exposure to magnetic fields and childhood leukaemia. Health effects related to ELF fields are described further in the ARPANSA fact-sheets Electricity and Health and Magnetic & Electric Fields From Power Lines.

• How can I reduce my risk from exposure to ELF electric and magnetic fields?

The National Health and Medical Research Council issued Interim guidelines on limits of exposure to 50/60 Hz electric and magnetic fields (PDF 365kb) in 1989. These guidelines are aimed at preventing immediate health effects resulting from exposure to these fields. ARPANSA is currently developing a Radiation Protection Standard for ELF fields in the frequency range 0 – 3 kHz.