T G Cooper
Publication date: September 2002
A non-technical summary of this report is also available.
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) published guidelines on limits of exposure to static magnetic fields in 1994 and on limiting exposure to time-varying electric, magnetic and electromagnetic fields (up to 300 GHz) in 1998. The guidelines advise basic restrictions to provide protection against the established adverse health effects of exposure. Reference levels are also given for practical exposure assessment purposes to determine whether the basic restrictions are likely to be exceeded. Compliance with the reference levels ensures compliance with the relevant basic restrictions, however the reference levels are not limits and if they are exceeded, it does not necessarily follow that the basic restrictions will also be exceeded.
A review is given of occupational exposures to electric and magnetic fields at sub-optical frequencies with regard to the ICNIRP exposure guidelines. Measurements of electric and magnetic field strength, magnetic flux density, power density and contact current are reported that have been obtained in assessments of exposure to the fields produced by electricity generating equipment, resistance welders, induction heaters, plasma discharge equipment, security and access control systems and other miscellaneous devices. The measurements are compared with the reference levels advised by ICNIRP for occupational exposure. Data published previously in NRPB Report R265 are also compared with the reference levels.
Many of the exposure measurements that are reported complied with the relevant reference levels, however a number of devices and applications have been identified where the reference levels or basic restrictions may be approached or exceeded under certain circumstances. In many cases the reference levels were exceeded only at locations of limb or extremity exposure. Reference levels have been found to be exceeded in assessments of exposure to electromagnetic fields produced by the following sources:
Further work may be required in some areas to determine whether occupational exposures exceeding the reference levels are likely to result in non-compliance with the basic restrictions. Analyses of the spatial distributions of magnetic fields produced by resistance welders, radiofrequency identification devices, electronic article surveillance equipment and other security systems would provide valuable information on exposures and would allow compliance with the basic restrictions to be investigated in greater detail. Product standards for some of these devices have been developed by the European Committee for Electrotechnical Standardization (CENELEC) and the standards incorporate protocols for assessing compliance with reference levels and basic restrictions.
Last reviewed: 29 July 2009