Developmental Toxicology Evaluation of 60-Hz Horizontal Magnetic Fields in Rats

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Abstract
Epidemiological and laboratory studies have indicated various biological effects resulting from exposure to extremely low frequency magnetic fields. The possibility of early embryonic loss and fetal malformations arising from such exposures required investigation. A replicate study, using large numbers of animals, was conducted to determine if 60-Hz magnetic fields would produce developmental toxicity in rats. Systems used previously for electric field exposures were retrofitted to provide magnetic field exposures to small laboratory animals. Large coils, separated from the rat cages, were energized by computer-controlled function generators providing a relatively pure, 1000-μT, 60-Hz, horizontal magnetic field for the high exposure group. Leakage fields to a second system provided a second exposure group with average exposures of 0.61 μT. Ambient fields within a third (control) system were 0.09 μT. Field intensities utilized in this study represent a range of exposures encountered by humans; however, they do not encompass the extremes of human exposure. Mated female rats were exposed for 20 h/day from the day of mating until very near term, 20 days later. Gestational body weight gain was not different in exposed animals when compared with control animals. Evaluation of uterine contents revealed a decrease in the number of fetuses per litter in rats exposed to 1000 μT in replicate A. This decrease, however, did not repeat in replicate B, and significant differences between groups could not be statistically confirmed in combined replicate data. Fetal body weight and incidences of malformations and variations were equivalent among the groups. As tested, 60-Hz magnetic fields of intensities at or below the 1000-μT level would not be classified as either embryotoxic, fetotoxic, or teratogenic in rats.