Static Magnetic Fields

Man made static magnetic fields are generated whenever direct current (DC) is use, such as in some electric trains, electroplating operations, and medical imaging devices such as Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Imaging (NMR). 

Strong static magnetic fields have been linked to slight increases in blood pressure, interference with the operation of cardiac pacemakers, and movement of implanted ferrometallic medical implants.

There are no OSHA Standards on Static Magnetic Field exposure, however the ACGIH has published Threshold Limit Values (TLVs) for static magnetic field exposure:

Routine occupational exposure should not exceed 2 Tesla (T) in the general work environment but can have ceiling values of 8T for workers with special training who are operating in a controlled work environment.

Special training involves making workers aware of transient sensory effects that can result from rapid motion in static magnetic fields with flux densities greater than 2T. 

A controlled work environment is one in which forces exerted by static magnetic fields on metallic objects do not create potentially hazardous projectiles.

Exposure to the limbs of workers in the general work area should not exceed 20T. 

Workers with implanted ferrometallic or electronic devices should not be exposed to static magnetic fields exceeding 0.5mT.

Projects to install high powered magnets must take the surrounding areas into consideration (both horizontally and vertically) and take care to locate the magnet so that no area accessible by the general public would be subjected to magnetic field strengths of more than 0.1mT.  This is often referred to as the 1 gauss line (1mT=10G).

GT EHS conducts magnetic field surveys on new installations of electromagnets and on request. 

Sub Radio-Frequency Magnetic Fields

In this context a sub-radiofrequency magnetic field (Sub-RF) refers to a field with a frequency range at 30kHz (kilohertz) and below. 

The 1 to 300 Hz portion of this range is referred to as the extremely low frequency (ELF) range.  Non-static electromagnetic fields can be found around high voltage electrical lines and even around in-home electrical wiring.  

Some evidence suggests that these fields can cause cancer, however, to date, neither IARC or ACGIH lists non-static electrical fields as carcinogens.

OSHA does not have a standard for exposure to non-static magnetic fields, but the ACGIH does have TLVs, which vary according to the frequency range of the field.   Please refer to ACGIH TLVs and BEIs- most recent version, for more information on this subject. 

Like static fields, non-static magnetic fields are also capable of interfering with the function of implanted medical devices, which makes it especially important for owners of these devices to understand the hazards before they start to work.

Any concerns about sub-RF magnetic fields should be directed to the EHS chemical safety group (404-894-4635)