Biological effects of magnetic fields: laboratory studies

There is now a reasonable battery of evidence from a large number of laboratories, that exposure to extremely low frequency magnetic and electric fields (EMF) produces biological responses in animals. Many of the observed effects appear to be directly or indirectly associated with the neural or neuroendocrine systems. Such effects include increased neuronal excitability, chemical and hormonal changes in the nervous system, altered behavioral responses, some of which are related to sensing the presence of the field, and changes in endogenous biological rhythms. Bone growth and fracture repair clearly show evidence of effects by exposure to magnetic fields of sufficient intensity. Additional indices of general physiological status appear relatively unaffected by exposure, although effects have occasionally been described in reproduction and development and immune system function. A major focus of ongoing research in the laboratory is to determine whether the epidemiological-based suggested association between magnetic field exposure and risk of cancer can be supported in studies using animal models. Three major challenges exist for ongoing laboratory research: (1) knowledge about the mechanisms underlying observed bioeffects is incomplete, (2) understanding of the physical aspects of exposure and the dose that produce biological responses is not currently available, and (3) health consequences resulting from EMF exposure are primarily speculative. There is presently no clear and convincing evidence from animal or cellular studies that demonstrates deleterious effects of EMF. There are, however, some studies, though largely unreplicated, that are suggestive of potential health impacts. From the perspective of laboratory studies, this presentation will discuss biological responses to extremely low frequency magnetic field exposures.