Reproductive and teratologic effects of low-frequency electromagnetic fields: A review of in vivo and in vitro studies using animal models

In order to evaluate the reproductive risks of low-frequency electromagneti c fields (EMF), it is important to include epidemiological and animal studi es in the evaluation, as well as the appropriate basic science information in developmental biology and teratology. This review presents a critical re view of in vivo animal studies and in vitro tests, as well as the biologica l plausibility of the allegations of reproductive risks, in vitro or in viv o studies in nonhuman species can be used to study mechanisms and the effec ts that have been suggested by human investigations. Only well designed who le-animal teratology studies ave appropriate when the epidemiologists and c linical teratologists are uncertain about the environmental risks. Even the inference of teratogenesis cannot be drawn from culture experiments, becau se the investigator is not in a position to know whether any of his observa tions will be manifested in living organisms at term. Other aspects of repr oductive failure such as abortion, infertility, stillbirth, and prematurity , cannot be addressed by in vitro or culture experiments. in fact, they are very difficult to design and interpret in nonprimate in vivo models. The b iological plausibility some of the basic mechanisms involved in reproductiv e pathology were evaluated, concentrating primarily on the mechanisms invol ved in the production of birth defects. The studies dealing with mutagenesi s, cell death and cell proliferation using in vitro systems do not indicate that EMFs 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 eff ect, deleterious or not, at very high exposures. The animal and in vitro st udies dealing with the reproductive effects of EMF exposure are extensive. There are >70 EMF research projects that deal with some aspect of reproduct ion and growth. Unfortunately, a large proportion of the embryology studies used the chick embryo and evaluated the presence or absence of teratogenes is after 48-52 h of development. This is not a stage of development at whic h an investigator could determine whether teratogenesis occurred. The prese nce of clinically relevant teratogenesis can only be determined at the end of the gestational period. The chick embryo studies are also of little assi stance to the epidemiologist or clinician in determining whether EMF repres ents a hazard to the human embryo, and the results are, in any event, incon sistent. On the other hand, the studies involving nonhuman mammalian organi sms dealing with fetal growth, congenital malformations, embryonic loss, an d neurobehavioral development were predominantly negative and are therefore not supportive of the hypothesis that low-frequency EMF exposures result i n reproductive toxicity. (C) 1999 Wiley-Liss, Inc.