Preface<br >Electric and magnetic fields can affect biological systems in ways that are<br >not yet fully appreciated. Of particular interest during the past decade have<br >been the possible effects of extremely low frequency (ELF) electromagnetic<br >fields on humans. The debate concerning possible health consequences from<br >the increasing worldwide exposure to ELF electromagnetic fields has<br >waxed and waned， and has often been driven by epidemiological studies<br >in an area in which few relevant laboratory data have been available.<br >Beneficial effects of ELF field exposure， such as enhanced bone fracture<br >healing， have been reported and are now well documented in the literature.<br >Public attention， however， has focused on the less well documented<br >detrimental effects and associated uncertainties. As one result of the re-<br >cent public awareness of the ELF question， the quality of epidemiological<br >studies and laboratory research has improved. In the past few years， much<br >insight into ELF bioeffects and their possible mechanisms has been gained.<br > This book is not intended， however， as a general treatment of the sub-<br >ject of ELF bioeffects. In particular， it does not address questions related<br >to risk assessment or possible hazards of what we term ELF exposure.<br >We have elected， rather， to focus on that which seems to be the central<br > scientific issue emerging from current ELF research in epidemiology and<br > in the laboratory; namely， can ELF electromagnetic fields interact with<br > biological systems in such a way as to increase cancer risk? We examine<br > how cancer risk might be related to two reproducible biological effects of<br > ELF exposure: effects on the pineal gland and circadian biology， and ef-<br > fects on calcium homeostasis in cells. Because we are concerned with the<br > possible biological mechanisms of carcinogenesis， epidemiological studies<br > are only briefly reviewed.<br > To accommodate a broad readership， introductory chapters on the var-<br > ious disciplines relevant to later sections follow the background material<br >Vll<br >