Occupational ELF-EMF exposure
Just as the comfort of our modern homes requires the use of multiple electric household appliances, the economic competitiveness of companies, industries and the technical progress of medicine also require a growing number of electric devices.
Note: Around these devices and apparatuses, fields of various frequencies can be measured, like static fields, 50/60 Hz fields, RF fields...
See sources of electric and magnetic fields in hospitals, in factories and in transportation.
EMF in hospitals
In the medical field, Nuclear Magnetic Resonance (NMR), a medical imaging technique, generates significant, but mainly continuous, magnetic fields (up to 10T in typical systems), which are associated with fields in the range of radio frequencies. See further information on these fields in a thematic file on static fields.
Another very promising example is the application of electromagnetic fields to stimulate bone fracture repairs and to treat pseudo osteoarthritides or chronic pain (Ellis, 1993). However, these fields do not have the same characteristics of fields at the industrial frequency.
Magnetic fields are also used in treating certain forms of depression. The patient receives painless transcranial magnetic stimulations that have no dangerous side effects.
EMF in factories
Several professions are particularly exposed to electric and magnetic fields (e.g. arc welders, personnel responsible for power line maintenance, electricians, sub-stations operators).
Measurements performed in various occupations indicate a significant daily variability of exposure according to the task carried out: the relatively low averaged values are associated with high peaks at certain periods of the day.
For example, the measurements performed for assemblers of power lines indicate a minimal exposure of 0.05 µT, with a median value of 0.15 µT and maximal values of 304 µT (Sahl, 1994).
Here is a document on electromagnetical fields of welding equipment (pdf 9.5Mo).
EMF in trains
Most Belgian electrified railways, except high speed trains, work on direct current. Thus, electrical lines (catenaries) supplying trains, generate direct electric and magnetic fields.
In trains (direct fields in Belgium) and HST (alternating fields), passengers are exposed to magnetic fields from the power supply cable. People living in the vicinity are also exposed to magnetic fields from this overhead cable.
Lorsque nous voyageons en train, nous pouvons nous trouver dans des CE statiques de l’ordre de 300 V/m (Source : ICNIRP). Le CM statique est de l’ordre de 40 µT. Des valeurs maximales de 120 µT ont été mesurées dans les locomotives alimentées en courant continu (tension de 3 kV DC comme en Belgique, mesures réalisées dans des trains russes et italiens).
Documents & Links
- Exposure at work (pdf 99 Ko) - Value of the magnetic induction (µT) met in professional and medical conditions
- Electromagnetical fields of welding equipment (pdf) - Document presented in the International workshop organized by VITO nv, April 6 2006. Workshop Handbook available in English (pdf 9.5Mo)
- Hydroquébec : Champs électriques et magnétiques, Sources et intensité
- <a href="http://www.icnirp.org/en/frequencies/static-magnetic-fields-