Reproductive and teratologic effects of electromagnetic fields

Abstract The reproductive risks of electromagnetic fields (EMF) were evaluated based on an extensive review of the scientific literature pertaining to human epidemiologic studies, secular trend data, in vivo animal studies and in vitro studies, and biologic plausibility. The epidemiologic studies involving the reproductive effects of EMF exposures to human populations have included populations exposed to: (1) video display terminals (VDTs), and (2) power lines and household appliances. The clinical use of diagnostic MRI (magnetic resonance imaging) has been increasing, but there are few reports or studies of pregnant women or individuals of reproductive age who have been exposed to MRI, and whose reproductive performance has been evaluated. The population that has been studied most frequently are women exposed to VDTs, but their EMF exposures are extremely low and frequently are at the level of the ambient EMF in a house or office. The results of epidemiologic studies involving VDTs are generally negataive for the reproductive effects that have been studied. Based on the number of studies, the exposure levels, and the fairly consistent results, it can be argued that VDT epidemiologic studies should no longer be given priority. There have been fewer studies concerned with the reproductive risks of power lines, electric substations, and home appliances. In some publications, positive findings for reproductive risks were reported, but the more consistent findings indicate that EMF, even at these higher exposures, do not generate a measurable increase in reproductive failures in the human population. When compared to other fields of human epidemiology, it is obvious that these studies have many difficulties. Exposures are rarely determined. Studies frequently involve small sample sizes and the investigators rarely have a combined expertise in EMF physics, engineering, and reproductive biology. Because of the allegation that there may be particular windows of frequency, wave shape, and intensity that may be deleterious, it is impossible to disregard low frequency EMF exposures as having no deleterious reproductive effects. Yet the epidemiologic data that are available would point in that direction. Secular trend data analysis of birth defect incidence data indicate that increasing generation of electric power during this century is not associated with a concomitant rise in the incidence of birth defects. There are over 70 EMF research projects dealing with animal and in vitro studies that are concerned with some aspect of reproduction and growth. Unfortunately, a large proportion of the embryology studies utilized the chick embryo and evaluated the presence or absence of teratogenesis after 48 to 52 hours of development. The chick embryo studies were of little assistance to the epidemiologist or clinician in determining whether EMF exposure represents a hazard to the human embryo, and the results were, in any case, inconsistent. Embryo culture or cell culture studies are also of little assistance in determining the human risk of EMF. In vitro or in vivo studies in nonhuman species can be used to study mechanisms and the effects that have been suggested by human investigations. Only well designed whole-animal teratology studies are appropriate when the epidemiologists and clinical teratologists are uncertain about the environmental risks. Other aspects of reproductive failure such as abortion, infertility, stillbirth, and prematurity cannot be addressed by in vitro or culture experiments. In fact, it is very difficult to design and interpret nonprimate in vivo studies. Biologic plausability for teratogenesis can be supported if an agent such as EMF can be demonstrated to be cytotoxic or mutagenic. The studies dealing with mutagenesis, cell death, and cell proliferation using in vitro systems do not indicate that EMF have the potential for deleteriously affecting proliferating and differentiating embryonic cells at the exposures to which populations are usually exposed. Of course, there is no environmental agent that has no effect, deleterious or not, at very high exposures. While there does not appear to be measurable risk of reproductive failure and birth defects from EMF exposures in humans, a modest program of investigation is warranted epidemiologically and in the laboratory to answer some of the issues that have been raised that need clarification. It does not appear that the risk of EMF exposure is significant and, therefore, although preparing conducted research in the area of EMF risks is appropriate, it does not necessitate a massive expenditure of resources.