Health Hazards Of Weak Electromagnetic Fields?

For the past several decades, public and scientific debates have continued over a shifting range of issues about possible adverse health effects of nonionizing electromagnetic fields. Electromagnetic fields are surely hazardous, at some level of exposure. However, the well-established hazards (such as shock and burn) are obvious, mundane, and easily avoided. Various exposure standards and engineering codes offer effective protection against them. More controversial is the possibility of hazard at lower levels of exposure. Hazards have been alleged by some critics to be associated with: low-level microwave or radiofrequency radiation, and electric and/or magnetic fields associated with video display terminals (VDTs), household appliances, neighborhood distribution lines, and high voltage power transmission lines. These critics cite diverse laboratory and epidemiologic studies to support their claims of subtle hazard. I describe the scientific background of one such issue: the possibility of increased cancer risk from exposure to 50-60 Hz electric or magnetic fields. I argue that the evidence for any such hazard is weak, and much of the problem arises from scientific ambiguity, which is a common feature of risk assessment.