DC Magnetic Field Health Concerns

A review of available literature and research regarding possible human health risks associated with exposure to DC (Static) magnetic fields, reveals limited concern except in very high DC field environments.

The International Commission on Non-Ionizing Radiation Protection. "Guidelines on limits of Exposure to Static Magnetic Fields". Health Physics 66: 100-106 (1994) states the following:

• People become nauseous, develop taste in mouth, vertigo, and magnetophosphenes (flickering sensation in the eyes) at 4 T (40 G)
• Pacemakers can malfunction @ at 3.1 G (this is from a German report for an unspecified model of pacemaker, most pacemakers specify higher fields to malfunction)
• Circadian rhythms are affected by merely rotating Earth's 1/2 G dc field
• Pacemaker warnings usually start at 5 G with manufacturers warning at 10 G
• Precautions for users of metallic prostheses at 30 G
• Precautions for metal tools at 30 G
• Overexposures are unlikely, but fields which could be hazardous to pacemaker users or cause problems for prostheses and tool users are much more likely to be found.

The majority of concerns, both for possible health risk and safety, seem to be centered around NMR and MRI imaging systems and/or similar devices, which utilize very powerful DC magnets. Manufactures of such equipment usually provide guidelines for establishing a "5 G line" around the devices and caution that persons with pacemakers or other implanted medical devices, should stay clear of the 5 G line. An "attractive force hazard" also exists wherein nearby metallic objects can be "drawn" toward the powerful magnets and in some instances at dangerous or even fatal velocity and force. Such attractive force hazards typically include:

• Tools & compressed gas cylinders
• Prosthetic implants made of magnetizable materials (this can include machined stainless steel)
• Jewelry and some watches
• Credit cards & badges (beginning at ~10 G)

NMR and MRI manufactures also urge users of prostheses which contain metal be checked before entering areas where DC magnetic field levels exceed 30G.