Static magnetic fields are normally not suspected of being harmful to humans. Humans have always lived with the Earth's magnetic field, which is about 50 µT (microtesla) at our latitude (directly above a direct-current cable - like the coming Great Belt Power Link - the magnetic field may be approx. 60 µT.) This is the reason why researchers have not given various health effects from this kind of fields nearly as much attention as fields produced by alternating current. The International Agency for Research on Cancer (IARC) (2002) has therefore assessed them to be 'not classifiable as to its carcinogenicity'.
However, relatively strong fields may interfere with, for example, compasses and various equipment incorporating magnetically sensitive parts. They may also interfere with insects and animals navigating by the Earth's magnetic field. Large direct-current fields may affect implanted metal parts such as pacemakers (larger than 0.5 mT), destroy magnetic strips on credit cards or even with much force and speed attract loose metal parts (larger than 3 mT).
In order to prevent people moving around in strong static fields from feeling nauseous and dizzy, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommends exposure limits. The exposure limit is 200 mT averaged over the working day, the maximum being 2 T. For the general public the ICNIRP recommends an exposure limit of 40 mT.
Static electrical fields have not been the subject of much research. The research that has been conducted indicates that the only acute effect is a feeling of discomfort, such as when your hair stands on end, your flesh creeps or when you get small electric shocks. That is what in everyday life is called 'static electricity'. Even less research has been devoted to possible long-term effects.