Introduction
This topic covers extremely low frequency (ELF) radiation and static electric and magnetic fields as non-ionizing radiation hazards at work: what they are, where they come from, what they do to health, and how workers are protected.
Extremely low frequency radiation and static fields
- ELF has frequencies up to 300 Hz and a wavelength above 1000 km.
- Static magnetic and electric fields occur where the frequency is zero Hz: the field does not change in time.
- Both belong to the non-ionizing part of the electromagnetic spectrum: the photon energy is far too low to ionize atoms or break chemical bonds, so effects come from induced currents and field forces, not from ionization.
- At these frequencies the electric and magnetic components act almost independently. The electric field is measured in V/m and the magnetic field (flux density) in tesla (T) or microtesla (µT).
Sources
- The ELF region of the electromagnetic spectrum is associated with the generation, distribution and use of electricity.
- Occupational examples: power stations, high-voltage transmission lines and substations, transformers, electrical workshops and welding, electric motors and heavy electrical machinery, electrified railways, and domestic and office appliances (mains frequency is 50 Hz in Europe).
- Static fields arise from direct-current (DC) installations such as DC power lines, electrolysis and some industrial processes, permanent magnets, and the strong superconducting magnets of magnetic resonance imaging (MRI) scanners, which also expose hospital staff.
- Static electric fields occur near charged objects and in dry air where electric charge builds up on surfaces.