Static Magnetic Fields

[Western Radiation Services <westrad@nimrod.com.au>]

Diane Elmer asked about health effects of static magnetic fields of up to 4
Gauss in a disused MRI room.

Static magnetic fields interact with ionic currents, as a result of the
Lorentz forces exerted on moving charge carriers, to produce an electric
field. Estimated maximum values generated across the human aorta resulting
from the flow of blood in a static magnetic field range from about 7 to 14
mV per Tesla. (1 Tesla = 10,000 Gauss). Studies on human volunteers have
shown no measurable effects of chronic exposure to static magnetic fields up
tp 0.15 Tesla. Some studies have shown a slight effect on heart rates at 2
Tesla acute exposure.

There is a possible effect on computer video displays, which can mean a
slight offset of the picture to one side of the screen, but this will depend
on the position of the display in the field;s polarity. It is possible that
it may affect floppy discs if they are continually used in the field by
corrupting data or even complete loss of disc data.

A good reference for magnetic field health effects is "Electromagnetic
Fields and the Risk of Cancer" published by the National Radiological
Protection Board of the UK. The document can be obtained by contacting
<anna.thomas@nrpb.org.uk>.

Bill Chandler
Western Radiation Services
Perth, Western Australia
westrad@nimrod.com.au 

At the 1-4 Gauss range, there is no concern for human health