Occupational Medicine 1996;46:17-19
© 1996 Society of Occupational Medicine
Estimated Exposure to Static Magnetic Fields for the Staffs of NMR-Units
Department of Occupational Medicine, Sahlgrenska University Hospital Göteborg, Sweden
Exposure of the staffs to static magnetic fields of NMR-units, was investigated at two departments for chemical analysis (static field strength of the systems 11.7 and 4.7 Tesla) and two for clinical imaging (0.5 and 0.02 Tesla). The exposure time was estimated by personal interviews. The magnetic flux density was highly dependent on distance to the magnet, and the magnetic fields in normal work with the NMR-units were, during most working time, lower than 1 milliTesla (mT), which is far below the whole-body limit recommended by the American Conference of Governmental and Industrial Hygienists (60 mT), the British National Radiation Protection Board (200 mT), or the International Commission on Non-Ionizing Radiation Protection (200 mT). During short periods, when changing samples or assisting anxious patients, the fields may be strong (100–150 mT). The recommended ceiling values (2–5 Tesla) are, however, not exceeded.
Received 16 November 1994
Accepted 11 April 1995
Correspondence and reprint requests to: L. Barregård, Department of Occupational Medicine, Sahlgrenska University Hospital, St Sigfridsg 85, S-412 66 Göteborg, Sweden.