Electromagnetic field (EMF)
Restrictions on the effects of exposure to EMFs are based upon established health effects and are termed basic restrictions. Depending on the frequency, the physical quantities used to specify the basic restrictions to occupational exposure are as follows:
Time varying electric and magnetic fields
Between 1 Hz and 10 MHz, basic restrictions are provided on Current density to prevent effects on nervous system functions.
Between 100 kHz and 10 GHz, basic restrictions on Specific Absorption Rate (SAR) are provided. This quantity is a measure of how much heat is deposited in body tissues. SAR levels are applied to prevent whole body heat stress and prevent excessive localised tissue heating, at 0.4 W/kg and 10 W/kg respectively.
In the 100 kHz-10 MHz range, restrictions are provided on both Current density at f/100 (f in kHz) and SAR as above.
Between 10 and 300 GHz, basic restrictions are provided on Power density to prevent excessive heating in tissue at or near the body surface. This is restricted to 100 W/m2 .
For more information visit the Public Health England EMF website.
Static magnetic fields
There are few sources of high magnetic field strength on campus. If you are near or work with such a source, it is likely you are aware of its presence. However, those working in close proximity to such a source may arrange for a survey especially if they have any health concerns regarding their exposure. For static magnetic fields, occupational exposure should not exceed the time weighted average for 8 hours of 200 mT. Occupational whole-body exposure should not exceed a magnetic flux density ceiling value of 2T. For limbs only, exposures of 5T can be permitted.
Those fitted with a cardiac pacemaker or ferromagnetic implants should be aware that magnetic fields may not be protected by these limits. The majority of cardiac pacemakers are unlikely to be affected by fields <0.5 mT. Above this threshold, such locations should be avoided.
Areas with magnetic flux densities >3mT should specify with a warning sign to prevent movement or dislodgement of ferromagnetic implants, or hazards from flying metal objects.