Magnetic fields and cancer

The massive body of epidemiological data searching for a relationship between magnetic field exposure and the incidence and development of cancer tells one that the presumably exposed population has essentially the same health characteristics as the population as a whole. Some comfort may be found in the fact that epidemiology has not revealed any large or unusual associations. But, the cost to society for this work has been substantial, and it would be difficult to justify further use of epidemiology in the study of magnetic field bioeffects. These predominantly negative results are not particularly reassuring, however. It simply underscores the obvious fact that epidemiology does not have the power to detect subtle effects, particularly when study groups with clearly different exposure levels cannot be identified, as is the case for magnetic fields. In fact, if there really were effects, the risk ratios would be understated because of the overlaps in true “exposures” in the arbitrarily chosen populations used in the studies. Laboratory studies should provide the sensitivity that is lacking in epidemiology. In addition, laboratory animals can be (and have been) exposed to huge fields for long periods of time. Certainly, some of the suggested positive effects should be followed up, but overall, results from studies of laboratory animals give little encouragement for the hypothesis that magnetic fields affect the development of cancer. It appears one must admit that, at the present time, one has no direct evidence for an association between magnetic fields and cancer. A very substantial, frontal assault on the question has not been fruitful. In the author´s opinion, the mast promising approach to the subject is to step back and ask a more fundamental question. Are there any biological effects at all of modest levels of power frequency magnetic fields? There are many reports of biological effects of magnetic fields in vitro. Furthermore, it is possible to devise objective criteria for choosing the most promising of these reports for replication and further evaluation. A clear positive conclusion that magnetic fields of modest magnitudes do have biological effects would not have a direct bearing on the cancer question, but it would provide a starting point for fundamental investigations of the mechanisms of interaction between the fields and cells. Eventually, such studies could provide an intelligent basis for a renewed study of health issues, including the question of cancer